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Misfire


jsjag1990

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I have a 1995 DeVille Concours. Two weeks ago I got gas at a Sam Club, drove across the street to the store, upon returning and starting the car is was stumbling. Hm? Ran perfect before filling up.

Thought bad gas and ran for the past two weeks with gas cleaner and some dryer. Didn't get better.

So I thought it was coils, wires and plugs. Same thing that stopped the misfire two years ago. The car was running fine around town, speeds under 40 MPH. Yesterday I had a chance to run on the freeway and found that when I hit 50 MPH it would miss, sometimes but always going up a hill. Had to get my wife to the airport so I drove on (about a 60 mile round trip). I actually heard a backfire or two. Still I was getting an average of 25 MPG.

Coming home I hit traffic. After the 5th mile the car started to die. It went from 65 MPH to 45. I had to feed more gas to keep it up to speed.

TOday I took the wires and coil towers back and asked for replacements. The wires are original equipment and the coils are made by Wells. Wells makes them for AC Delco. While at the parts store the guy suggests I check the ignition control module. He hooks it up and it shows that it is failing the test. So another $260 for the new control board. Install it and still the same. It surges and you can feel a constant misfire,

I talked with a mechanic I know and he suggested a crank position sensor. I've always suspected a CPS for no-start problems not misfires. Could it me a CPS?

New fuel filter this week.

History of car...

In 2001 previous owner spent $1,000 for plugs, wires and coils.

In 2005 I acquire the car and drive cross country. One thousand miles into the trip I start getting a misfilre. It didn't stop until I got to the east coast and had a chance to replace the plugs, wire and coils (my labor). Misfire ended.

Then two weeks ago it started back again but now the plug,wires and coils won't fix it.

No check engine light

No PCM/ICP/ACP/SIR/TCS codes

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Have you checked the Fuel Pressure Regulator?

One of the problems shortcomings with the 95 is that it is OBD1 and no code is set for a mis fire.

Have you checked each ignition wire with an OHM meter looking for a bad wire?

Check the spark plug wells for oil that could provide a path to ground for the spark.

Have you pulled the plugs and looked for cracks and carbon tracking?

Now one of the terrific things with OBD1 is that you have the ability to turn off and turn on each of the injectors to determine which cylinder is causing your problem. Someone here will post the procedure to do this

Lastly if these things checked out, I would do a compression test to make sure you don't have a valve problem.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Thanks for your reply.

Have not checked the fuel regulator. On the caddie does the sniff for gas test to the vac hose work? To be honest I haven't worked much on this car and can't think where the fuel regulator is located. I know where everything is on my XJ6 that I've had for 10 years.

I've tried two different sets of wires.

Spark plugs are new and the ones that were in had a brown/red tint to them.

Because oil in the wells is something my XJ6 can do I did look for oil but there wasn't anything to write home about.

Turning off each injector has me interested and I would like to do that one.

The lastly issue ....I don't even want to think about. The previous owner had a new engine dumped in and it has about 25,000 on it. I always thought the Northsar engine was bullet proof. The car wasn't backfiring when this happened and I doubt if I have a bent valve.

How do I find out about turning off each injector?

Have you checked the Fuel Pressure Regulator?

One of the problems shortcomings with the 95 is that it is OBD1 and no code is set for a mis fire.

Have you checked each ignition wire with an OHM meter looking for a bad wire?

Check the spark plug wells for oil that could provide a path to ground for the spark.

Have you pulled the plugs and looked for cracks and carbon tracking?

Now one of the terrific things with OBD1 is that you have the ability to turn off and turn on each of the injectors to determine which cylinder is causing your problem. Someone here will post the procedure to do this

Lastly if these things checked out, I would do a compression test to make sure you don't have a valve problem.

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Listen, I have done it over the years, I have assumed that something was good when it was not. Don't assume that your ignition wires are good unless you test them with an OHM meter.

The reason I say to do a compression test, is DIAGNOSTICS, its not guessing, its ELIMINATING potential problems. You might have a sticking, burned valve or a bad valve spring.

Someone will stop by and provide you with the info to turn off/on the injectors

Explain what you mean by this "The car wasn't backfiring when this happened and I doubt if I have a bent valve", when WHAT happened?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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What I mean by wasn't backfiring is this. On the trip down to the airpoert it was running rough and on th big hills, going 55>65 I heard one or two backfires. Several hours later coming home is when it went from running 99% efficient to running like crap there was no backfire before it happened. I dropped a valve once in a car and heard a big backfire beofre dropping the valve.

Wires.....the last time I fixed this problem I used wires from Magnecor (8mms).

This time I bought wires from Advanced Auto that were Autolite Pro. Didn't like them and bought wires online from RockAuot.com. The guy there said that Delphi makes wires for AC Delco and I bought Delphi. The Delphi came with grease already in the boots.

Maybe the grease is the problem?

I can do the compression test but those back holes are a real pain to get to....ouch my aching body. B)

Listen, I have done it over the years, I have assumed that something was good when it was not. Don't assume that your ignition wires are good unless you test them with an OHM meter.

The reason I say to do a compression test, is DIAGNOSTICS, its not guessing, its ELIMINATING potential problems. You might have a sticking, burned valve or a bad valve spring.

Someone will stop by and provide you with the info to turn off/on the injectors

Explain what you mean by this "The car wasn't backfiring when this happened and I doubt if I have a bent valve", when WHAT happened?

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What I mean by wasn't backfiring is this. On the trip down to the airpoert it was running rough and on th big hills, going 55>65 I heard one or two backfires. Several hours later coming home is when it went from running 99% efficient to running like crap there was no backfire before it happened. I dropped a valve once in a car and heard a big backfire beofre dropping the valve.

Wires.....the last time I fixed this problem I used wires from Magnecor (8mms).

This time I bought wires from Advanced Auto that were Autolite Pro. Didn't like them and bought wires online from RockAuot.com. The guy there said that Delphi makes wires for AC Delco and I bought Delphi. The Delphi came with grease already in the boots.

Maybe the grease is the problem?

I can do the compression test but those back holes are a real pain to get to....ouch my aching body. B)

Listen, I have done it over the years, I have assumed that something was good when it was not. Don't assume that your ignition wires are good unless you test them with an OHM meter.

The reason I say to do a compression test, is DIAGNOSTICS, its not guessing, its ELIMINATING potential problems. You might have a sticking, burned valve or a bad valve spring.

Someone will stop by and provide you with the info to turn off/on the injectors

Explain what you mean by this "The car wasn't backfiring when this happened and I doubt if I have a bent valve", when WHAT happened?

You are quite knowledgable, good for you. The grease in the boots is ok, since Delphi put it there, the boots must not be impregnated with grease.

Give some thought that you have a clogged CAT, how is the power, is it laboring badly up hills?

Look at your ignition wires in the pitch dark looking and listening for high voltage leakage. Spritz them with a water spray bottle and see if you get archs.

Look for a wire melted onto something hot, check their routing, see if there is wire to wire shorting

Are the plugs NEW since this mis began?

Test your coils to make sure they are good, using an ohm meter, check the resistance between the towers and in betweeen the secondary and post it, we have a thread for testing coils.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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I was 16 when I did an engine exchange on a 1964 Volvo I owned and several years ago did one on a 1995 XJ6 I owned. I am fairly good with a wrench but not as good at diagnostics.

I did look at the wires in the dark and nothing. I even turned th AC on to put a load on the engine.

Plugged cats. Ouch now there is a few $$$$. I gave that some thought because I was running about with a rough running engine but wouldn't even OBD1 singnal a rich running engine? I never melted a cat but I've always heard that you get a rotten egg smell from them.

When you sit the engine surges. Sometimes it will take a good lunge ahead on a surge. I'm guess that plugged cats would be constant.

Yesterday after the tragic event I installed new wires, coils, plugs and a new Ignition control module. The guy at AutoZone hooked up my old ICM and said it was bad. I wonder if I was sold a $260 pig in a poke? I had no ICM codes on the car. If he didn't have the correct hook up my ICM would have failed the test. Anyhow..none of the new parts made any difference.

Today is raining and can't check the FPR but will check it tomorrow. I keep thinking it is a fuel problem.

I guess if I get the energy I could take everything back to the poit that it rain but a bit rough but wasn't a totalailure to see if it changes. Put my old Magnecour wires on, old ICM, old coils, etc.

What I mean by wasn't backfiring is this. On the trip down to the airpoert it was running rough and on th big hills, going 55>65 I heard one or two backfires. Several hours later coming home is when it went from running 99% efficient to running like crap there was no backfire before it happened. I dropped a valve once in a car and heard a big backfire beofre dropping the valve.

Wires.....the last time I fixed this problem I used wires from Magnecor (8mms).

This time I bought wires from Advanced Auto that were Autolite Pro. Didn't like them and bought wires online from RockAuot.com. The guy there said that Delphi makes wires for AC Delco and I bought Delphi. The Delphi came with grease already in the boots.

Maybe the grease is the problem?

I can do the compression test but those back holes are a real pain to get to....ouch my aching body. B)

Listen, I have done it over the years, I have assumed that something was good when it was not. Don't assume that your ignition wires are good unless you test them with an OHM meter.

The reason I say to do a compression test, is DIAGNOSTICS, its not guessing, its ELIMINATING potential problems. You might have a sticking, burned valve or a bad valve spring.

Someone will stop by and provide you with the info to turn off/on the injectors

Explain what you mean by this "The car wasn't backfiring when this happened and I doubt if I have a bent valve", when WHAT happened?

You are quite knowledgable, good for you. The grease in the boots is ok, since Delphi put it there, the boots must not be impregnated with grease.

Give some thought that you have a clogged CAT, how is the power, is it laboring badly up hills?

Look at your ignition wires in the pitch dark looking and listening for high voltage leakage. Spritz them with a water spray bottle and see if you get archs.

Look for a wire melted onto something hot, check their routing, see if there is wire to wire shorting

Are the plugs NEW since this mis began?

Test your coils to make sure they are good, using an ohm meter, check the resistance between the towers and in betweeen the secondary and post it, we have a thread for testing coils.

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Is the Fuel Pressure Regulator on your car on the fuel rail or in the intake plenum? I think for 93 and 94 the FPR was in the plenum and that it used intake vacuum to regulate fuel flow. When it leaked you could not see it leak. Take a look at your fuel rail and see if you have a FPR on it near the EGR valve. If you do, pull the vacuum hose and smell and look for evidence of fuel. Then leave the hose off, start the engine and check for fuel coming out of the FPR vacuum port while its running while you rev the engine

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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My FPR is on the rail and not a serviceable item. Hm....what were they thinking on that one. You must buy a new rail. Must have been thinking parts sale. :)

I did check for gas squirting out but none. I applied a vac to the FPR itself and it held so it isn't leaking vac. Pulled the hose and couldn't tell if I smelled anything. Bad allergy time of year and clogged sinuses.

I used a Vc gauge on the engine and I am getting about 16 on the pressure gauge and the vac drops to @15 and back up. If I'm not firing on all cylinders would I get much more than 16?

Think I'll go an do some tests with the PCM. I think I can pull voltage Engine Speed in revolutions per minute (rpm)/Ignition 1 Voltage/Front and rear Bank Injector Pulse. Hm, the Octane Level of Fuel may be interesting. I've never ran any tests, only looked at data stuff. I'll need to read how to run the tests.

When idling you can watch the engine moving from being and off balanced firing. The dog bones don't like it!

Is the Fuel Pressure Regulator on your car on the fuel rail or in the intake plenum? I think for 93 and 94 the FPR was in the plenum and that it used intake vacuum to regulate fuel flow. When it leaked you could not see it leak. Take a look at your fuel rail and see if you have a FPR on it near the EGR valve. If you do, pull the vacuum hose and smell and look for evidence of fuel. Then leave the hose off, start the engine and check for fuel coming out of the FPR vacuum port while its running while you rev the engine
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Why would PD42 - Octane Level of Fuel read 0?

Engine revs are going from 800>1000 and back down

Front bank injector pulse width is lower (in the 4.5 range) than the back (5.3 range)

Is the Fuel Pressure Regulator on your car on the fuel rail or in the intake plenum? I think for 93 and 94 the FPR was in the plenum and that it used intake vacuum to regulate fuel flow. When it leaked you could not see it leak. Take a look at your fuel rail and see if you have a FPR on it near the EGR valve. If you do, pull the vacuum hose and smell and look for evidence of fuel. Then leave the hose off, start the engine and check for fuel coming out of the FPR vacuum port while its running while you rev the engine
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The whole thing sounds like a bad load of gas to me.

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Yea I thought so to. My experience with a bad CPS is a no start situation. Weird thing is the parts guy at Advanced Auto, that once worked at a Cadillac dealership (for many years) also suggested a CPS. I asked him, can a CPS cause a misfire and he seems to think so. He said at the shop he worked for, the Northstar had a lot of CPS problems.

I'm finding out that the Northstar engine is a different bird compared to other engines.

I talked with a mechanic I know and he suggested a crank position sensor.

Your symptoms are not that of a CKP sensor.

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My FPR is on the rail and not a serviceable item. Hm....what were they thinking on that one. You must buy a new rail. Must have been thinking parts sale. :)

I did check for gas squirting out but none. I applied a vac to the FPR itself and it held so it isn't leaking vac. Pulled the hose and couldn't tell if I smelled anything. Bad allergy time of year and clogged sinuses.

I used a Vc gauge on the engine and I am getting about 16 on the pressure gauge and the vac drops to @15 and back up. If I'm not firing on all cylinders would I get much more than 16?

Think I'll go an do some tests with the PCM. I think I can pull voltage Engine Speed in revolutions per minute (rpm)/Ignition 1 Voltage/Front and rear Bank Injector Pulse. Hm, the Octane Level of Fuel may be interesting. I've never ran any tests, only looked at data stuff. I'll need to read how to run the tests.

When idling you can watch the engine moving from being and off balanced firing. The dog bones don't like it!

Is the Fuel Pressure Regulator on your car on the fuel rail or in the intake plenum? I think for 93 and 94 the FPR was in the plenum and that it used intake vacuum to regulate fuel flow. When it leaked you could not see it leak. Take a look at your fuel rail and see if you have a FPR on it near the EGR valve. If you do, pull the vacuum hose and smell and look for evidence of fuel. Then leave the hose off, start the engine and check for fuel coming out of the FPR vacuum port while its running while you rev the engine

Your FPR should be serviceable, look at it closely, there should be a snap ring that is compressible to allow the FPR assembly to come out.

An area that we have been sub standard in is checking injectors. We really don't have a definitive test to check injectors. This is an area that interests me. Anyone have any ideas on the subject? Listening to them?, Checking their resistance? replacing them when a determination is made that a specific cylinder is misfiring?

Assuming that there is no mechanical problem here, once a compression test is done, what about injectors? Obviously, if you shut off the #1 injector and there was NO change in the mis, that is your cylinder that has a problem, at that point if compression is GOOD, you must assume its the injector, no?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Funny you should mention injectors.

Today I used my screw driver test on them. That is where you take a long screwdriver, rest it on the injector and put your ear to the handle. On the front bank, one injector was click, click, clicking away fine but the others were very silent. All I heard was swooshing noises.

My Haynes manual says that on the 95 they were not replaceable and the entire rail needed to be replaced. I'll take a closer look. Haynes has been wrong on other cars.

My FPR is on the rail and not a serviceable item. Hm....what were they thinking on that one. You must buy a new rail. Must have been thinking parts sale. :)

I did check for gas squirting out but none. I applied a vac to the FPR itself and it held so it isn't leaking vac. Pulled the hose and couldn't tell if I smelled anything. Bad allergy time of year and clogged sinuses.

I used a Vc gauge on the engine and I am getting about 16 on the pressure gauge and the vac drops to @15 and back up. If I'm not firing on all cylinders would I get much more than 16?

Think I'll go an do some tests with the PCM. I think I can pull voltage Engine Speed in revolutions per minute (rpm)/Ignition 1 Voltage/Front and rear Bank Injector Pulse. Hm, the Octane Level of Fuel may be interesting. I've never ran any tests, only looked at data stuff. I'll need to read how to run the tests.

When idling you can watch the engine moving from being and off balanced firing. The dog bones don't like it!

Is the Fuel Pressure Regulator on your car on the fuel rail or in the intake plenum? I think for 93 and 94 the FPR was in the plenum and that it used intake vacuum to regulate fuel flow. When it leaked you could not see it leak. Take a look at your fuel rail and see if you have a FPR on it near the EGR valve. If you do, pull the vacuum hose and smell and look for evidence of fuel. Then leave the hose off, start the engine and check for fuel coming out of the FPR vacuum port while its running while you rev the engine

Your FPR should be serviceable, look at it closely, there should be a snap ring that is compressible to allow the FPR assembly to come out.

An area that we have been sub standard in is checking injectors. We really don't have a definitive test to check injectors. This is an area that interests me. Anyone have any ideas on the subject? Listening to them?, Checking their resistance? replacing them when a determination is made that a specific cylinder is misfiring?

Assuming that there is no mechanical problem here, once a compression test is done, what about injectors? Obviously, if you shut off the #1 injector and there was NO change in the mis, that is your cylinder that has a problem, at that point if compression is GOOD, you must assume its the injector, no?

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Yea I thought so to. My experience with a bad CPS is a no start situation. Weird thing is the parts guy at Advanced Auto, that once worked at a Cadillac dealership (for many years) also suggested a CPS. I asked him, can a CPS cause a misfire and he seems to think so. He said at the shop he worked for, the Northstar had a lot of CPS problems.

I'm finding out that the Northstar engine is a different bird compared to other engines.

I talked with a mechanic I know and he suggested a crank position sensor.

Your symptoms are not that of a CKP sensor.

GM had a bad supplier from 2000 - early '03. A bad CKP sensor will not cause a misfire. It will cause a stall or perhaps a momentary hiccup. Maybe a no start, but I've not heard of that.

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I tend to agree with you and was rather surprised when the mechanic said it.

Yea I thought so to. My experience with a bad CPS is a no start situation. Weird thing is the parts guy at Advanced Auto, that once worked at a Cadillac dealership (for many years) also suggested a CPS. I asked him, can a CPS cause a misfire and he seems to think so. He said at the shop he worked for, the Northstar had a lot of CPS problems.

I'm finding out that the Northstar engine is a different bird compared to other engines.

I talked with a mechanic I know and he suggested a crank position sensor.

Your symptoms are not that of a CKP sensor.

GM had a bad supplier from 2000 - early '03. A bad CKP sensor will not cause a misfire. It will cause a stall or perhaps a momentary hiccup. Maybe a no start, but I've not heard of that.

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I think you might be on to something with the different sound of the injectors. I would check their resistance, someone here had the correct range for them.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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My FPR is on the rail and not a serviceable item. Hm....what were they thinking on that one. You must buy a new rail. Must have been thinking parts sale. :)

The FPR is under the manifold cover and is serviceable. It snaps out of the fuel rail. There is no vacuum hose on it, just take the cover off, locate the FPR and turn the key to the on position and watch for gas from the FPR nipple. Do not start the engine because it will run wide open with the cover off and could hurt the engine. As far as the Power Balance Check here goes:

Turn on engine and check the codes, after "PCM?" use your fan switch for yes(fan up)/no(fan down), select "Yes", then select "no" until the "pcm override" comes up. Select "yes" then toggle the fan down until "PS04" comes up. Press the "warmer" button until a "1" comes up on the climate control center(this tells you what cylinder you are testing). To maintain the override press "off" button, then select PCM Data "PD11" to view the RPM's in the "information center". Press and hold the "cooler" button to shut off the gas to the cylinder selected. If you noticed an RPM drop then that cylinder is o.k.. If you did not notice a drop then that cylinder is the problem. There could be more than one cylinder causing a problem and you may have to run thru all the cylinders again to get consistant readings. Press the "warmer" button to change cylinders.

What does this tell you? Well you could have a bad coil if the same corresponding cylinders are bad or you could have a clogged/bad injector or plug or plug wire. Bad coils are hard to detect until they finally give out and cause the car to stumble at idle. If the car does not stumble at Idle then this test is no good.

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Thanks Paul, I was not sure if it was attached to the fuel rail or in the intake plenum. Mike

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Thank you for that information.

There was no change when testing #3 and #5 cylinders. This will allow me to proceed with diagnosing the problem.

My FPR is on the rail and not a serviceable item. Hm....what were they thinking on that one. You must buy a new rail. Must have been thinking parts sale. :)

The FPR is under the manifold cover and is serviceable. It snaps out of the fuel rail. There is no vacuum hose on it, just take the cover off, locate the FPR and turn the key to the on position and watch for gas from the FPR nipple. Do not start the engine because it will run wide open with the cover off and could hurt the engine. As far as the Power Balance Check here goes:

Turn on engine and check the codes, after "PCM?" use your fan switch for yes(fan up)/no(fan down), select "Yes", then select "no" until the "pcm override" comes up. Select "yes" then toggle the fan down until "PS04" comes up. Press the "warmer" button until a "1" comes up on the climate control center(this tells you what cylinder you are testing). To maintain the override press "off" button, then select PCM Data "PD11" to view the RPM's in the "information center". Press and hold the "cooler" button to shut off the gas to the cylinder selected. If you noticed an RPM drop then that cylinder is o.k.. If you did not notice a drop then that cylinder is the problem. There could be more than one cylinder causing a problem and you may have to run thru all the cylinders again to get consistant readings. Press the "warmer" button to change cylinders.

What does this tell you? Well you could have a bad coil if the same corresponding cylinders are bad or you could have a clogged/bad injector or plug or plug wire. Bad coils are hard to detect until they finally give out and cause the car to stumble at idle. If the car does not stumble at Idle then this test is no good.

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Thanks Paul, I was not sure if it was attached to the fuel rail or in the intake plenum. Mike

I thought the 95 was just like my 94 Concours. It clips into the plastic retainer that the injectors are held in place with. It also unplugs from the fuel rail.

jsjad1990 you can eliminate the coils as a problem because #3 & #5 are on different coils. If they were bad you would have #2 & #8 causing problems also. I would check the plugs and wires in those cylinders first, switch them out, then check the injectors next. You are almost there.

I miss my 94. I had to park it when it started overheating all the time and started throwing a white exhaust cloud. I never confirmed a pulled head bolt but I am almost certain that is what it is. I started robbing parts off of it for my 97 and so it sits idle in the yard. I would love to work on it again but I do not have time to spend on it. I learned alot from that car. At 163,000 miles it gave me over 100,000 miles of service.

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I made it, car purrs again and it was an odd circumstance.

I am not sure what started the initial problem of a stumbling engine after filling up at a Sams Club. It could have all started out with my ign. control module going bad. I had it tested by two different parts shops and it failed each time. So I guess the $265 spent for a new one was in order.

What ended up happening is something that was out of my control but I will make note of it!

I haven't had an AllData account for a while and the printout information I was using is from years ago when I had the account. The printout that shows which spark plug cables go to which coil tower is wrong. Man how many times I checked and re-checked to make sure I had the wires routed correctly!!!! Just to make sure I wasn't doing a newbie mistake, I had routed my cables probably 4 or more different times using the schematics I had in hand. All that I can think of is that in 2005 I printed off the wrong picture.

I isolated that #3 and #5 were not working. On a lark, I decided to switch those wires around on the coil towers (move #5 to #7 & #7 to #5). Problem solved!!!!!!!!!!! :lol:

Weird that the car ran ok around town with those wires mixed around. It idled ok and up to 50 mph it ran ok.

Often the fix is starring right at you. One time I installed another engine in an XJ6. After installation, after everything was hooked up, the engine would not fire. I looked, looked, looked and looked. The mechanic whose shop I was using looked and could not see why. Finally I found that the bundled 6 ground wires for the injectors had gotten pushed way down when I dumped the engine into the bay. They were way down, out of site and were found while I was shining a flashlight around the engine bay.

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I was about ready to give up. It was the information on how to one by one, shut down an injector that led me to the answer!

Thank you to all who gave their ideas. I need to find a used service manual on this car or even a CD.

My Jag had a weird mis (very small one) that for a year, I couldn't find. When the Cadillac had a problem after filling at Sam's Club, I stopped getting my gas at Sam's. I can report that the Jag problem is now almost imperceptible and seems to be going away.

I now try (sometimes I run 11 miles one way) to get tier one gas and it seems to be working well. Aside from the known stations, one of the mart type stations used to be in our area. Sadly they lost the gas war and they are no longer around town.

http://www.toptiergas.com/retailers.html

Glad you found it!!!
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