running rough
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Cadillac Allante Forum Discussion, running rough in Past Cadillac Vehicle Discussion; My 88 Allante runs very rough when it is first started. Back firing, etc, I've done all of the basics ...
  1. #1
    Moose123 is offline Cadillac Owners Member
    Automobile(s): 1988 Allante
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    running rough

    My 88 Allante runs very rough when it is first started. Back firing, etc, I've done all of the basics including spark
    plugs, oxygen sensors, etc. Any ideas what is going on? thanks

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  3. #2
    carnut is offline Cadillac Owners Master
    Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
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    Re: running rough

    No idea!! Do you know how to enter diagnostics to get fault codes?? Is it backfiring thru the intake or out the exhaust? need alot more help on your end. How old are the plug wires? Is the cap old? Does it run great warm?

  4. #3
    Moose123 is offline Cadillac Owners Member
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    Re: running rough

    Hi carnut: Thanks for the reply. I guess I was a bit vague. Not sure how old the plug wires are but like a dummy, I didn't change them when I did the spark wiires. It does run much better when it is warmed up but you can still feel like a hesitation when accelerating. I think the backfire is through the exhaust, but now that you mention it, I'm not 100% sure. I assume if it is in the intake it would sound more like it is in the engine compartment. I do have the code booklet so I can review that in the morning. I think I need to be more observant of the symptoms.

  5. #4
    c5 rv's Avatar
    c5 rv is offline Cadillac Owners Connoisseur
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    Re: running rough

    Are all the plug wires hooked up correctly?

  6. #5
    Moose123 is offline Cadillac Owners Member
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    Re: running rough

    Good morning. That will be my first order of business...I've been reading my Tech manual and see there are diagnostics for the symptoms I described. Let's see if I'm bright enough to sort through it. I think it's one of those things that if you had someone walk you through it the light would go on- and you'd say Wow, that's amazing!

  7. #6
    Moose123 is offline Cadillac Owners Member
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    Re: running rough

    Good morning Carnut. I ran the onboard diagnostics and I observed the following codes: E052 and E055> E052 Is PCM Memory Reset. I think I know why I got this code...It shows up when the battery has been switched of. This would be due to the "Priority Start" device- no big deal. E055 TPS Misadjusted. I am reading the ECM code diagnostics and can follow the flow diagram. I see the vehicle actually has an automatic adjustment. I'm going to start simple by looking at the vacuum hoses and maybe some deposits on the throtle blade...assuming this is easy to do. ANy tips? And thanks for your support and experience!

  8. #7
    carnut is offline Cadillac Owners Master
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    Re: running rough

    Erase all the codes and wait until newer codes pop up. The TPS is the heart of the fuel delivery system. Misadjusted, the car can run poorly or backfire. Once the TPS is adjusted to spec. disconnect the battery wait a few min. while you clean the primary throttle blade. reconnect it then start the car cold, climate system off. Let it idle for 15 min. then turn on the climate system to AUTO and 75 degrees, then let it idle 15 min again. That will teach the TPS and computer the proper idle speed. As I said, clean the throttle intake while the battery's disconnected. Clean only the primary bore, the smaller of the 2 blades. Use a toothbrush and braklkeen or carb cleaner. Once restarted cold it will run very, very rough until the carb cleaner is burnt off, just disregard this and let it smooth out. Then repost with results.

  9. #8
    Moose123 is offline Cadillac Owners Member
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    Re: running rough

    Thanks Carnut. I look forward to trying this. May not tackle on Monday. I have some previous commitments.

  10. #9
    carnut is offline Cadillac Owners Master
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    Re: running rough

    To be clear, dont shut it off after the first 15 min. just reach in and push the auto button at 75 degrees. What you are doing is learning the idle with compressor off then again learning the idle with a compressors load on the engine. The TPS adjustment can be verified thru on board diagnostics before you do any adjustment to it. Could be the TPS code is an old un erased code. Thats why its best to erase all codes first so you know what codes if any, are current.

  11. #10
    Moose123 is offline Cadillac Owners Member
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    Re: running rough

    Hi Carnut: I'm thinking I may be successful in getting the car running smoother based on your guidance. I erased the codes, cleaned the primary bore and then went through 15 minute cold idle. I started the process with the climate system in "Auto" and then remembered this is pointless since I am showing low refrigerant pressure and the compressor doesn't run. The system is showing ECM Code E052 but that indicates "ECM Memory Reset" which is what i did.

    I took the car out for a spin after the warkm up period and cleaning and it ran very well. No backfire, etc. I am looking forward to firing it up again when it is cold to see if the smooth running is for real.

    I have another question. Why do you clean the primary bore only, and not the secondary. I didn't do it, but I was tempted. Also, if i have low refrigerant pressure does that automatically mean I have a leak? This car sat around in a state of neglect for a while...

    Thanks for your savy guidance.

    Moose

  12. #11
    carnut is offline Cadillac Owners Master
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    Re: running rough

    2 reasons not to clean the larger bore. Main reason is the TPS is attached on the shaft closest to that bore and can be damaged by cleaners, second the secondary bore has nothing to do with air flow read by the ECM. I would still like to know what the TPS reading is after the cleaning. Should be close to zero.

  13. #12
    Moose123 is offline Cadillac Owners Member
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    Re: running rough

    Carnut; I will check it out. Moose

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