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Hi, I have a 1990 deville with 4.5 litre port fuel injection. This car has 190,000 miles and has always run like a top. Maintained properly etc... I recently was driving the car when it suddenly started to studder (misfire) at a level speed. When I put my foot into it it still accelerated very strongly, however, when I came to a stop it stalled. It would restart immeadately and continue to run on acceleration, but misfire or stall when I leveled out the speed. The next day, I checked the fuel pressure suspecting a bad fuel pump or clogged screen. The pressure checked out OK, so I continued on with other basic suspected parts. I added gas dryer to the tank just incase of bad fuel. Then I replaced the distributor cap, rotor (they really needed replacing!) and ignition module. Still having the same problem, I replaced the ignition coil, no luck there either. About a year ago, I replaced the plugs and plug wires, I do not suspect them as I have looked under the hood at night with the engine running for shorts in the wires - none. I have noticed that it seems to make it about 1 1/2 miles down the road before it acts-up, so I am guessing what happens has something to do with the engine being at operating temperature? Yesterday, I thought about the pick-up coil in the distributor, went to a junkyard and found a low mile -wrecked in the rear- 93 deville, pulled the distributor out and replaced mine with it. Still the same problem. I have noticed that the milage sentry goes a little crazy when the car starts acting up, and today noticed the fuel guage first read 9 gallons, then went to low in a flash. Any ideas what this problem could be?

Thanks for any input from experienced Caddilac owners or mechanics! checht

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You have done a lot of diagnostics good for you. Find the PCM and while the car is idling tap in it and see if you can cause a stumble. We have had a few 4.9s especially 92's go wacky like your's, find a replacment or 'known good' PCM and swap it in. Try reseating all PCM connectors and checking grounds as Ranger recommended. You can buy a new PCM (engine control module) at www.rockauto.com for about $90. 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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In adding a redundant ground should it be from the chassis to the engine? Thanks, checht

Yes, that is what a few have done on the 4.9, run a new ground from the starter area to the frame, but anywhere you can run a ground from the engine to the frame will be good. Check your grounds behind the battery also, sometimes acid eats them up.

By the way, have you had your battery load tested?

Try running with a fuel pressure gage connected so that you can see it (with a long hose and tape it to the windshield) so you can see if you are losing fuel pressure when this happens

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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In adding a redundant ground should it be from the chassis to the engine? Thanks, checht

Yes, that is what a few have done on the 4.9, run a new ground from the starter area to the frame, but anywhere you can run a ground from the engine to the frame will be good. Check your grounds behind the battery also, sometimes acid eats them up.

By the way, have you had your battery load tested?

Try running with a fuel pressure gage connected so that you can see it (with a long hose and tape it to the windshield) so you can see if you are losing fuel pressure when this happens

Well, I have checked all my battery and ground connections (unless there are some I don't know about). I found that the positive terminal was a bit corroded, so I cleaned it and put a new bolt in also. I am still having the same problems. I guess the next step is the PCM. Does anyone know if the PCM off a later year (1991 thru 1993 or later) will work with the 4.5L engine? Local junkyards seem to be out of 1990 Caddys!.... JUST A THOUGHT...I would like to eliminate all this computer stuff and convert the engine to a carbureted engine with a HEI distributor, how dependable and simple my mid 70's GM engines were! This car was my brother's car when new, he gave me a manilla envelope with all the work he had done on the car when I bought it from him, it was extensive! This car was never butchered or torn apart, all the work was done by certified mechanics, I just can not afford them. The age of the car does not warrant spending megabucks either! I have the shop manual for this car, the "computer system diagnosis section" seems to be written in a foreign language! Thanks to anyone and everyone out there for help and advice! Any additional info that may be helpful is appreciated! checht

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There is a ground on the engine block close to the starter. It makes sense to replace the stud (8x1.25 mm) and the star washers. This particular ground is known to cause a lot of problems. Check it out even if it looks good.

The saddest thing in life is wasted talent

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In adding a redundant ground should it be from the chassis to the engine? Thanks, checht

Yes, that is what a few have done on the 4.9, run a new ground from the starter area to the frame, but anywhere you can run a ground from the engine to the frame will be good. Check your grounds behind the battery also, sometimes acid eats them up.

By the way, have you had your battery load tested?

Try running with a fuel pressure gage connected so that you can see it (with a long hose and tape it to the windshield) so you can see if you are losing fuel pressure when this happens

Well, I have checked all my battery and ground connections (unless there are some I don't know about). I found that the positive terminal was a bit corroded, so I cleaned it and put a new bolt in also. I am still having the same problems. I guess the next step is the PCM. Does anyone know if the PCM off a later year (1991 thru 1993 or later) will work with the 4.5L engine? Local junkyards seem to be out of 1990 Caddys!.... JUST A THOUGHT...I would like to eliminate all this computer stuff and convert the engine to a carbureted engine with a HEI distributor, how dependable and simple my mid 70's GM engines were! This car was my brother's car when new, he gave me a manilla envelope with all the work he had done on the car when I bought it from him, it was extensive! This car was never butchered or torn apart, all the work was done by certified mechanics, I just can not afford them. The age of the car does not warrant spending megabucks either! I have the shop manual for this car, the "computer system diagnosis section" seems to be written in a foreign language! Thanks to anyone and everyone out there for help and advice! Any additional info that may be helpful is appreciated! checht

Come on.... your car is reliable - it made it 17 years and 190,000 miles before this problem... ;)

Check for codes - and post back. You may get lucky and a code might be stored that will lead you to the trouble. If no relevant codes are stored, I would use Mike's suggestion and duct tape a fuel pressure gage to the windshield and watch the fuel pressure when it starts to act up. It is time for some troubleshooting vs. throwing parts at the problem.

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

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In adding a redundant ground should it be from the chassis to the engine? Thanks, checht

Yes, that is what a few have done on the 4.9, run a new ground from the starter area to the frame, but anywhere you can run a ground from the engine to the frame will be good. Check your grounds behind the battery also, sometimes acid eats them up.

By the way, have you had your battery load tested?

Try running with a fuel pressure gage connected so that you can see it (with a long hose and tape it to the windshield) so you can see if you are losing fuel pressure when this happens

Well, I have checked all my battery and ground connections (unless there are some I don't know about). I found that the positive terminal was a bit corroded, so I cleaned it and put a new bolt in also. I am still having the same problems. I guess the next step is the PCM. Does anyone know if the PCM off a later year (1991 thru 1993 or later) will work with the 4.5L engine? Local junkyards seem to be out of 1990 Caddys!.... JUST A THOUGHT...I would like to eliminate all this computer stuff and convert the engine to a carbureted engine with a HEI distributor, how dependable and simple my mid 70's GM engines were! This car was my brother's car when new, he gave me a manilla envelope with all the work he had done on the car when I bought it from him, it was extensive! This car was never butchered or torn apart, all the work was done by certified mechanics, I just can not afford them. The age of the car does not warrant spending megabucks either! I have the shop manual for this car, the "computer system diagnosis section" seems to be written in a foreign language! Thanks to anyone and everyone out there for help and advice! Any additional info that may be helpful is appreciated! checht

Come on.... your car is reliable - it made it 17 years and 190,000 miles before this problem... ;)

Check for codes - and post back. You may get lucky and a code might be stored that will lead you to the trouble. If no relevant codes are stored, I would use Mike's suggestion and duct tape a fuel pressure gage to the windshield and watch the fuel pressure when it starts to act up. It is time for some troubleshooting vs. throwing parts at the problem.

I am going to follow everyones suggestions, first with the ground wire above the starter, then with the fuel pressure guage taped to the windshield as I attempt to drive it down the road....With the economy as poor as it is, I can not afford a new car at this time! Thanks to everyone participating in my discussion! I will post back when results are available. I will attempt the code thingy too! checht

Edited by checht
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I am going to follow everyones suggestions, first with the ground wire above the starter, then with the fuel pressure guage taped to the windshield as I attempt to drive it down the road....With the economy as poor as it is, I can not afford a new car at this time! Thanks to everyone participating in my discussion! I will post back when results are available. I will attempt the code thingy too! checht

Hi,

My 91 STS 4.9 was doing a lot of similar things mostly when cold and even the dealer couldn't find the cause. They even substituted a new computer to no avail.

After cleaning the battery posts and replacing the bolts, I tried a heavy ground wire from the negative post to the block near the battery and also from the block to the body. This cleared it up.( I actually used my jumper cables for the testing) So I added an extra ground to the engine and put it onto one of the screws for grounds behind the battery. This being a California car, the grounds were not corroded at all but a bit dull so I also cleaned them up. It's run fine since.

Dose you car have several small studs around behind the battery?

Bob B

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In adding a redundant ground should it be from the chassis to the engine? Thanks, checht

Yes, that is what a few have done on the 4.9, run a new ground from the starter area to the frame, but anywhere you can run a ground from the engine to the frame will be good. Check your grounds behind the battery also, sometimes acid eats them up.

By the way, have you had your battery load tested?

Try running with a fuel pressure gage connected so that you can see it (with a long hose and tape it to the windshield) so you can see if you are losing fuel pressure when this happens

Well, I have checked all my battery and ground connections (unless there are some I don't know about). I found that the positive terminal was a bit corroded, so I cleaned it and put a new bolt in also. I am still having the same problems. I guess the next step is the PCM. Does anyone know if the PCM off a later year (1991 thru 1993 or later) will work with the 4.5L engine? Local junkyards seem to be out of 1990 Caddys!.... JUST A THOUGHT...I would like to eliminate all this computer stuff and convert the engine to a carbureted engine with a HEI distributor, how dependable and simple my mid 70's GM engines were! This car was my brother's car when new, he gave me a manilla envelope with all the work he had done on the car when I bought it from him, it was extensive! This car was never butchered or torn apart, all the work was done by certified mechanics, I just can not afford them. The age of the car does not warrant spending megabucks either! I have the shop manual for this car, the "computer system diagnosis section" seems to be written in a foreign language! Thanks to anyone and everyone out there for help and advice! Any additional info that may be helpful is appreciated! checht

Come on.... your car is reliable - it made it 17 years and 190,000 miles before this problem... ;)

Check for codes - and post back. You may get lucky and a code might be stored that will lead you to the trouble. If no relevant codes are stored, I would use Mike's suggestion and duct tape a fuel pressure gage to the windshield and watch the fuel pressure when it starts to act up. It is time for some troubleshooting vs. throwing parts at the problem.

I am going to follow everyones suggestions, first with the ground wire above the starter, then with the fuel pressure guage taped to the windshield as I attempt to drive it down the road....With the economy as poor as it is, I can not afford a new car at this time! Thanks to everyone participating in my discussion! I will post back when results are available. I will attempt the code thingy too! checht

Cool, you will get it, have patience.

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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In adding a redundant ground should it be from the chassis to the engine? Thanks, checht

Yes, that is what a few have done on the 4.9, run a new ground from the starter area to the frame, but anywhere you can run a ground from the engine to the frame will be good. Check your grounds behind the battery also, sometimes acid eats them up.

By the way, have you had your battery load tested?

Try running with a fuel pressure gage connected so that you can see it (with a long hose and tape it to the windshield) so you can see if you are losing fuel pressure when this happens

Well, I have checked all my battery and ground connections (unless there are some I don't know about). I found that the positive terminal was a bit corroded, so I cleaned it and put a new bolt in also. I am still having the same problems. I guess the next step is the PCM. Does anyone know if the PCM off a later year (1991 thru 1993 or later) will work with the 4.5L engine? Local junkyards seem to be out of 1990 Caddys!.... JUST A THOUGHT...I would like to eliminate all this computer stuff and convert the engine to a carbureted engine with a HEI distributor, how dependable and simple my mid 70's GM engines were! This car was my brother's car when new, he gave me a manilla envelope with all the work he had done on the car when I bought it from him, it was extensive! This car was never butchered or torn apart, all the work was done by certified mechanics, I just can not afford them. The age of the car does not warrant spending megabucks either! I have the shop manual for this car, the "computer system diagnosis section" seems to be written in a foreign language! Thanks to anyone and everyone out there for help and advice! Any additional info that may be helpful is appreciated! checht

Come on.... your car is reliable - it made it 17 years and 190,000 miles before this problem... ;)

Check for codes - and post back. You may get lucky and a code might be stored that will lead you to the trouble. If no relevant codes are stored, I would use Mike's suggestion and duct tape a fuel pressure gage to the windshield and watch the fuel pressure when it starts to act up. It is time for some troubleshooting vs. throwing parts at the problem.

I am going to follow everyones suggestions, first with the ground wire above the starter, then with the fuel pressure guage taped to the windshield as I attempt to drive it down the road....With the economy as poor as it is, I can not afford a new car at this time! Thanks to everyone participating in my discussion! I will post back when results are available. I will attempt the code thingy too! checht

Cool, you will get it, have patience.

I have tried the fuel pressure guage taped to the windshield, the results were; a steady fuel pressure of about 40 lbs even when the car stalled. Following suggestions from this discussion board I turned the key on, pressed the 2 proper buttons for a dianostics check (warmer & off). The results were shown as follows; codes E52, E53, and E75 showed up on the fuel data center then a 7.0 followed and stayed on the screen. I went to the website that was given and it says that E52 is PCM memory reset, E53 is distributor signal interrupt, and E75 is intermittent VSS signal. Can someone tell me what all this means please! Thanks, checht.

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I also removed the ground wire from the battery to the engine just above the starter and wire brushed it, there were no star lock washers present, so I added a stainless steel star washer and used silicone grease when reinsatlling the bolt. I ran a 10 guage ground wire from the body stud by the battery to the engine (where the dip stick attaches). I also removed and cleaned all the ground wire terminals I could find and reset them with silicone grease. checht.

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I also removed the ground wire from the battery to the engine just above the starter and wire brushed it, there were no star lock washers present, so I added a stainless steel star washer and used silicone grease when reinsatlling the bolt. I ran a 10 guage ground wire from the body stud by the battery to the engine (where the dip stick attaches). I also removed and cleaned all the ground wire terminals I could find and reset them with silicone grease. checht.

The E53 code is pointing to the problem. A loss of distributor signal will cause sputtering/stalling symptom you describe. Check all the electrical connections to the distributor as well as to the cam sensor in the distributor itself.

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

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If connections related to the distributor are okay, I would just replace the whole thing, the distributor.

I bought a used distributor from the junkyard (with low miles on the car I took it from- it was wrecked in the rear). The distributor has no measuralbe play (except up & down motion, which is normal). I have replaced the cap, rotor, coil & ignition module.

What are the odds that both distributors would have the same problem???? Again, I want to emphazise that the car drives smoothly until it reaches operating temperature! Thinking that there may be a short in the ingnition wire leading to the coil, I jumped it from the battery.....same results! The fuel data center will read 0mpg (as it should)15mpg, all the way up to 70mpg while the car is standing still (foot on brake trans in drive). I am stumped!

checht

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Due to the problem beginning when the engine is hot, check the ECM, try a tap test.

Can you explain the symptoms clearly once again, you lost me on your last post

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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Again, the code E53 is pointing to the problem - a loss of distributor signal. The problem may be in the wiring from the distributor to the ECM - you need to check out the whole circuit. Someone should be able to post a wiring diagram - the 4.9 engine most likely has the same wiring.

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

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Check the ECM.

Can you explain the symptoms clearly once again, you lost me on your last post

1990 Cadillac DeVille 4.5 litre port fuel injection with 194,000 miles. The car was running smoothly until one day while driving it, it started to miss (or stumble) at a level speed. When I came to a stop, or let off the gas it stalled. It would start right up again and run fine during acceleration. Again it would have the same symptoms. I have checked the fuel pressure, changed the ingnition module, cap, coil, rotor, checked and cleaned all ground connections, and added a ground wire from body to engine. HELP!

checht

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Check the ECM.

Can you explain the symptoms clearly once again, you lost me on your last post

1990 Cadillac DeVille 4.5 litre port fuel injection with 194,000 miles. The car was running smoothly until one day while driving it, it started to miss (or stumble) at a level speed. When I came to a stop, or let off the gas it stalled. It would start right up again and run fine during acceleration. Again it would have the same symptoms. I have checked the fuel pressure, changed the ingnition module, cap, coil, rotor, checked and cleaned all ground connections, and added a ground wire from body to engine. HELP!

checht

KHE is correct about the code you need to run that down. If it is not a bad connection between the ECM and the distributor, it could be the ECM itself. Check the ECM for good clean NON-Oxidized grounds and reset the connector at the ECM. While the car is idling, tap on the ECM and see if you can make the car stumble.

You have replaced virtually everything that could cause this, but to me, given problems we have seen here over the years, yours is a classic ECM problem. I have seen the PCM go bad on the 4.9 quite a bit and I am sure that your ECM could be intermittant from vibration or heat. But follow KHE's idea first

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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the engine only does this at operating temperature, I can make it a bout a mile down the road before it acts up.

checht

Its sounding like a classic ECM/PCM problem to me.

Did your new ignition module come with heat sink paste?, if it did make sure you transferred it to the new distributor. It might just have had a heat transfer strip on 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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