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MIke D

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When my injector was leaking there was no visible drip, I had to put a paper towel under the injectors to find the leak. I've found you can also put the tip of your finger under the injector and see if you get any liquid on it. My oil also smelled like fuel.

WARNING: I'm a total car newbie, don't be surprised if I ask a stupid question! Just trying to learn.

Cheers!

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That is a good point and its a good reason to have your OIL analyzed when you have a problem like this. One of the oil tests involves a FLASH test, if fuel is in the OIL, the flash test shows it.

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

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That is a good point and its a good reason to have your OIL analyzed when you have a problem like this. One of the oil tests involves a FLASH test, if fuel is in the OIL, the flash test shows it.

Flash test? Is that like put some OIL in a cup and throw a match at it and look for the flash? HA ha ha.... (actually is is when you heat it up and see at what temp it will ignite?)

I am due for an oil change. I was waiting till i get back to boston to do it. It's better with a lift than on your back in a parking lot.. I'll pull the stick today and see if it smells like gas.

Cop didn't see it, I didn't do it!

93 STS 225,000 Miles

99 STS 111,000 Miles

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Yes, that is exactly what it is, here is Blackstone Labs, they do oil analysis, you can get a free test kit, send your oil in for a battery of tests,

http://www.blackstone-labs.com/

Standard Tests:

Blackstone's standard analysis will tell you what you need to know about the condition of your engine and how it's wearing. The standard analysis costs $22.50 and includes the following:

Spectral Exam: Establishes the levels of wear metals, silicon, and additives present in the oil. Also checks for coolant.

Viscosity: Determines the grade of oil.

Insolubles: Quantifies the percentage of solids present in the oil.

Flash Point: Determines the flash point of the oil. We use the flash point to determine whether any contamination is present in the oil (determined when the flash is lower than the "should be" range).

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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So here is something. When I was cleaning out my trunk I saw that in my old box's for the coils there was a rubber gasket that I was supposed to replace. (it was hidden under the bottom flap of the box on both of them) So I did replace the 2 of them and while it was off I decided to measure the resistance of the two lower tabs and the coil sits on. Starting on the drivers side they went 73.0 72.9 73.1 and 65.4 (furthest one on the passengers side). Now what is it that I am actually measuring? Why would one be way off from the other 3?

Cop didn't see it, I didn't do it!

93 STS 225,000 Miles

99 STS 111,000 Miles

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So here is something. When I was cleaning out my trunk I saw that in my old box's for the coils there was a rubber gasket that I was supposed to replace. (it was hidden under the bottom flap of the box on both of them) So I did replace the 2 of them and while it was off I decided to measure the resistance of the two lower tabs and the coil sits on. Starting on the drivers side they went 73.0 72.9 73.1 and 65.4 (furthest one on the passengers side). Now what is it that I am actually measuring? Why would one be way off from the other 3?

Its funny you say that Mike, when you sent me your OLD coil in the original box, a NEW rubber seal was in the box! When I saw it, I though, oh well he used the OLD seal...Did you use the old seal or no seal? That is the 12 volt feed from the ignition module. If you are getting rain water in there, you could be shorting out the primaries. I am not sure if shorting the primaries could damage the coil, but I would imagine that it could cause you to stumble if the coil is not getting full voltage to trigger the spark..due to the leads grounding out between eachother.

Did you see any moisture?

It might be possible that simple condensation gets into that connection to cause the mis

It also might be possible that the coils resistance causes the voltage to arch at this location if the gasket is missing

Did the stumble/mis go away?

This would make sense since you previously solved this problem then it re-appeared

Can water get into the ignition module through this joint, if its missing the seal, did you notice?

What do you think JimD?

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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So here is something. When I was cleaning out my trunk I saw that in my old box's for the coils there was a rubber gasket that I was supposed to replace. (it was hidden under the bottom flap of the box on both of them) So I did replace the 2 of them and while it was off I decided to measure the resistance of the two lower tabs and the coil sits on. Starting on the drivers side they went 73.0 72.9 73.1 and 65.4 (furthest one on the passengers side). Now what is it that I am actually measuring? Why would one be way off from the other 3?

Its funny you say that Mike, when you sent me your OLD coil in the original box, a NEW rubber seal was in the box! When I saw it, I though, oh well he used the OLD seal...Did you use the old seal or no seal? That is the 12 volt feed from the ignition module. If you are getting rain water in there, you could be shorting out the primaries. I am not sure if shorting the primaries could damage the coil, but I would imagine that it could cause you to stumble if the coil is not getting full voltage to trigger the spark..due to the leads grounding out between eachother.

Did you see any moisture?

It might be possible that simple condensation gets into that connection to cause the mis

It also might be possible that the coils resistance causes the voltage to arch at this location if the gasket is missing

Did the stumble/mis go away?

This would make sense since you previously solved this problem then it re-appeared

Can water get into the ignition module through this joint, if its missing the seal, did you notice?

What do you think JimD?

If there is not a seal installed, it could result in unpredicable/unreliable ignition on damp days and two cylinders will be affected.

I doubt if primary flashover would damage the coil.

Jim

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Very Cool Jim, Thanks

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 had used the OLD seal originally... So I never ran it with NO seal.. There was no moisture either. The old seals were still good too.. not dry or cracked.

What about running some dielectric grease here? Would that solve a moisture situation even though I can't see any...

It did run "better" after just replacing the gaskets but that could just be part of the randomness of the miss. I say "better" because it was missing only at idol and once on acceleration after replacement. We will see first thing tomorrow if it stas this way.

Cop didn't see it, I didn't do it!

93 STS 225,000 Miles

99 STS 111,000 Miles

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Its interesting that when you R&R a coil it seems to run better. I am thinking you might have a questionable connection someplace, not sure if its primary or secondary, but something tells me its the primary connection to the ignition module. I have never taken one apart to know how the coil makes contact to the ignition module, but its a thought.

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 might have found something. The "rail" that the coil's sit on has a big crack in it where I replaced the first coil. (guess it tightened it too much ) I pulled it off. Ran some apoxy on it and let it sit overnight. I am about to go put it back on the car.... In the mean time I went shopping for parts. Long story short I got a used one off ebay for $60. Figure I will try that because it lists for $750 and GMpartsdirect was still $400. The don't "just sell" the carbon fiber piece... Anyways i"ll let you know how my repair goes today and when the new one arrives tomorrow we will see how that one is... Cross your fingers, pray, chant, do what it is that makes wishes come true... I need extra help that this will fix it...

Cop didn't see it, I didn't do it!

93 STS 225,000 Miles

99 STS 111,000 Miles

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My repair did not work... I'm just waiting for the used one now...

Cop didn't see it, I didn't do it!

93 STS 225,000 Miles

99 STS 111,000 Miles

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My repair did not work... I'm just waiting for the used one now...

Are you talking about the ignition module?, it has electrical plugs going into it?

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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Yes, the carbon fiber looking thing below the coils but above the metal plat. It houses the two tabs that the coils sit on...

Cop didn't see it, I didn't do it!

93 STS 225,000 Miles

99 STS 111,000 Miles

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That could be your problem, we spoke about the ignition module a couple of time being the cause of this. My ignition module was replaced about a year before I bought my car. Hopefully you have found your 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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That could be your problem, we spoke about the ignition module a couple of time being the cause of this. My ignition module was replaced about a year before I bought my car. Hopefully you have found your problem

Well now it's back to the original problem of missing when i'm sitting at idle. It's smooth with rpms off idle... i'm heading home this wekend and will be able to do more..

Cop didn't see it, I didn't do it!

93 STS 225,000 Miles

99 STS 111,000 Miles

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SO I just got back from working on my car.. First off I hate the FSM sometimes... my dad and I both think that there are errors in some of the diagnostic trees.. IE does such and such drop more than 5psi in 10 min? if no go to the next number. does it drop 10 psi in 10 min? well if it didn't drop more than 5 then why would it drop more then 10??? ok I feel a little better.

So here is what we did.

Once agian checked every plug, plug valley for Fod, wire, coil and ignition module for defects. None found, yippie!

Then fuel pressure test. With key on and key off after 10 min all values normal. Now we check it running. Good psi at idle, hard acceleration. On slow acceleration it did drop to 33psi... more on that in a minute. We changed the fuel filter, pulled the fuel module and no obvious defects noted. Since we could not find where the diagnostic tree is for the fuel module, we could not test it.

Pulled the fuel rail. cleaned off the end of the injectors with a paper towel just to make sure they are dry.... put new paper towels under them. Turned the key on and no drips noted. Did this a few times with good psi holding and no drips. We re installed the fuel rail and injectors. Do one more psi check and no defects noted.

We checked the pcv's, plastic lines and rubber boots and none were cracked or looking bad. We pulled the vacuum line off the FPR and no gas. Hooked up a vacuum pump up to it and ran the test and the FPR opperated normally...

I'm sure i'm missing more of what we did but it was a busy day and a half. So back to the previous fuel pressure reading on slow acceleration. When I do get the stack backfire it is up hill with a slow acceleration or maintaining my speed. I know that a stack backfire is usually due to a lean mixture. I don't set any codes when this happens. So we think the the Fuel module might not be working properly and can"t suply enough fuel. Not sure if it is getting low voltage or if it is just will not put out enough psi due to being old...

So what do you guys think?? I left the car at my dad's shop for him to work on it when he gets time to read the FSM more... So I can't really do much except guide him to check other things....

Cop didn't see it, I didn't do it!

93 STS 225,000 Miles

99 STS 111,000 Miles

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What is a fuel module?

For some reason, I am thinking that a rich mixture causes the backfire

The next time you have the fuel rail off, change the bottom injector o-rings.

Check your compression, this is beginning to sound like a burned valve to me, someone here (growe?) had a burned valve. Send him a PM and ask what his symptoms were, 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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If I remember my mechanics right...

The only way to get a backfire thru the intake, is if the intake valve is open,

(maybe sticking open momentarily) or the plug fires at the wrong time.

Or a combination of the two.

Otherwise it goes out the exhaust like it is supposed to.

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If I remember my mechanics right...

The only way to get a backfire thru the intake, is if the intake valve is open,

(maybe sticking open momentarily) or the plug fires at the wrong time.

Or a combination of the two.

Otherwise it goes out the exhaust like it is supposed to.

I agree, this is certainly sounding like an intake valve, especially since it was determined that the injectors were not leaking.

A custom compression tester/gage will be needed due to the depth of the spark plug holes, but the next think I would do is test the compression, I think you will find one cylinder that is low.

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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We did not have time to do a compression check. I will pass it along. I'm not sure why it would be that if it does not back fire through the intake EVERY time i get a miss. I just drove 500 miles and it only happened once while it was missing the whole time....

I was also thinking about a pcm? I got a code for the pcm loss of data... I just figured it was when I killed the battery..

A fuel module is comprised of the fuel pump, the strainer, float for the fuel quantity.. The whole assembly that sits in the gas tank.

MD

Cop didn't see it, I didn't do it!

93 STS 225,000 Miles

99 STS 111,000 Miles

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I wouldn't suspect burned valves at this point. 33 psi is on the low side for the fuel pressure. I'd expect at least 10 psi more for proper operation. To me, it sounds like the fuel pump is on its way out and is starving the engine for fuel. When that happens, the engine will buck and/or backfire.

There is a section in the manual to isolate the problem to the fuel pump, or the fuel pressure regulator.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Good point Kevin

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 wouldn't suspect burned valves at this point. 33 psi is on the low side for the fuel pressure. I'd expect at least 10 psi more for proper operation. To me, it sounds like the fuel pump is on its way out and is starving the engine for fuel. When that happens, the engine will buck and/or backfire.

There is a section in the manual to isolate the problem to the fuel pump, or the fuel pressure regulator.

Good call... didn't think of THAT.

If it is running lean...ie starving for fuel... that could cause pre-ignition and make it backfire thru the intake when the intake valve is still partly open.

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