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91 Eldo STILL missing!


bschelle

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My 91 Eldo with 124k miles has a stumble when pulling away from a stop sign and it feels like it is not getting enough gas. It does it under light throttle and as I accelerate it goes away. It does it after it gets to operating temperature. I have replaced the fuel pump and filter, the FPR,BCM,TPS,EGR valve & solenoid,rebuilt injectors,cap,rotor,dist.control module,plugs and wires. Fuel pressure is steady at 42#'s also. The pressure doesn't change when this happens. It feels like a carb with a bad accelerator pump. Also when i take my foot off the gas pedal while going about 45 Mph it stumbles and feels like it is dying for just that moment. Any suggestions?

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Codes?

Check vacuum with a gage. Check fuel pressure while the car is running and at speed tape it to the windshield. When you stumble look at the pressure

Grounds, see Matt and Adallak I think they found a broken ground near the starter that caused stumbles if I recall, Adallak will opine on this

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Also do a search under Marika, she had a bad engine mount that i think caused a bad ground and performance problems. She has a 92 4.9, Mike

Pre-1995 - DTC codes OBD1  >>

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

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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 throttle body and tubes are clean and the pressure check was done with zero results. The pressure was constant throughout the whole time. The ground issue sounds like it may be that. The strange part is that it doesn't do it when the engine is first started and driven in the morning. Once the engine becomes warm it starts to do it! Also "No Codes".

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I was just about to post the opinion that you had dirty injectors until I saw your last post, where it needs to be fully hot to stumble on acceleration. I would check these things:

  • Spark plugs in good condition, gapped properly, and tightened, but not over tightened.
  • Good distributor rotor and cap, and good plug wires. If moving your plug wires changes the behavior at all, change all the plug wires.
  • FPR?
  • Look for vacuum leaks. Check and make sure that your PCV valve is OK, the oil filler cap is seated, the oil dip stick is all the way down, and that there aren't any broken, split or deteriorated vacuum hoses.

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When you changed your ignition module did it come with thermal paste? It is suppose to have thermal paste under it, to shunt away the heat.

Also, have you replaced your COIL? Your coil could be shorting out when its HOT...

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 seem to recall someone (maybe the Guru) once saying that a bad TPS will act just like a bad accelerator pump on a carb.

He indicated that he replaced the TPS, could it be adjusted wrong?

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 cap-rotor-wires-FPR-TPS(adjusted to +.2) are all new and I used the grease for the module in the distributor. The plugs have about 6,000 on them but I will replace them and the coil is old and next on my hit list. After changing the TPS there was no change!

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See this:

http://caddyinfo.ipbhost.com/index.php?sho...ccelerator+pump

I don't think you need to replace the plugs with 6K on them. Are they AC Delco?

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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When you changed your ignition module did it come with thermal paste? It is suppose to have thermal paste under it, to shunt away the heat.

Also, have you replaced your COIL? Your coil could be shorting out when its HOT...

My money is on ignition module. I never installed one, but heard the installation was tricky. Is it an OEM part?

The saddest thing in life is wasted talent

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When you changed your ignition module did it come with thermal paste? It is suppose to have thermal paste under it, to shunt away the heat.

Also, have you replaced your COIL? Your coil could be shorting out when its HOT...

My money is on ignition module. I never installed one, but heard the installation was tricky. Is it an OEM part?

Yes but he commented that he replaced it already.... 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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I did replace the module. I just put in a new coil and no change! Now I heard a rattle when it was idiling. It sounds like something rattleing against the exhaust. I am thinking that maybe the catalytic converter is shot and moving around inside the shell. What do you guys think?

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When you changed your ignition module did it come with thermal paste? It is suppose to have thermal paste under it, to shunt away the heat.

Also, have you replaced your COIL? Your coil could be shorting out when its HOT...

My money is on ignition module. I never installed one, but heard the installation was tricky. Is it an OEM part?

Yes but he commented that he replaced it already.... Mike

I knew , MIke. Nevertheless, he did not say whether it was an OEM part or an aftermarket one. I know people going thru several aftermarket ignition modules on 4.9 engines.

The saddest thing in life is wasted talent

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Oh good Adallak I understand

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 did replace the module. I just put in a new coil and no change! Now I heard a rattle when it was idiling. It sounds like something rattleing against the exhaust. I am thinking that maybe the catalytic converter is shot and moving around inside the shell. What do you guys think?

Bang your cat with a rubber mallet and see if you hear anything rattling inside it.

I had an intermittent rattle that I would hear at 50 mph and it turned out being a heat reflector shield that came loose between my exhaust pipe and body near the cat, that would only rear itself when the wind hit it. :rolleyes:

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The module was from Autozone, it is their Everlast brand. The car runs great at hard throttle driving. When I take off from a stop sign at a moderate speed is when it chortles. Kick it in the a** and it runs great.

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Plugs are A/C, wires are Belden NAPA.]

Did you run the wires in the same path as before? Have you misted the wires at night to see if there is arcing? Any of the wires touching metal? The problem sounds similar to my coil problem, but you said you replaced the coil.

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