Heavy overfueling on cold start - seeking advice
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Cadillac Catera and Cimarron Forum Discussion, Heavy overfueling on cold start - seeking advice in Past Cadillac Vehicle Discussion; Hi chaps, I'm new here and will be posting a picture of my Catera shortly. It is the much troubled ...
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    Pee_beds is offline Cadillac Owners Member
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    Heavy overfueling on cold start - *Sorted*

    Hi chaps, I'm new here and will be posting a picture of my Catera shortly.

    It is the much troubled 1998 model year (this one has been good aside from this though) and it has 174,xxxk on the odometer.

    I love this car but it has an issue with overfueling heavily on cold start and lightly once warmed up.

    Ever since I pulled a spark plug wire to evaluate the severity of the valve cover gasket leak the car has run very rich upon startup but has not issued any DTC's. I used brakeleen and blew dry the plug wire and oil from the spark plug recess before restarting the car. I am suspicious of an O2 sensor but using a scan tool noticed that the IAT reads -40 with the engine off and key in the run position which is very inccurate. However it reads 78 degrees F once the engine is started which is comparable to the ECT which is at 75 and seems warm for a cold start. I don't know how any of this is related to pulling a spark plug wire unless I damaged the wire but the car isn't misfiring and that would surely throw a trouble code.

    It takes three tries before the car starts cold. This is so odd because the car has run so great since I bought it 400 kms ago really taken a turn for the worse here.

    I would appreciate any help you're able to lend. Thanks for reading!

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    investor74 is offline Cadillac Owners Enthusiast
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    Re: Heavy overfueling on cold start - seeking advice

    The O2 sensors don't really come into play until the engine is warm, so that wouldn't affect startup. How do you know it is running rich? Not likely that pulling the spark plug would make it run rich, but it is possible that misfires resulting from removing and replacing the plug wire could cause un-burned gas to be exhausted. Are you sure you don't have any codes?

    Make sure your battery is charged fully. I have noticed that when the battery is well on a Catera, it starts almost instantaneously, even faster than many newer cars which seem to spin for a few seconds before starting.

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    Pee_beds is offline Cadillac Owners Member
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    Re: Heavy overfueling on cold start - seeking advice

    Hi, thanks for the reply, the exhaust is rich with unburnt fuel and fills my garage immediately. If I give it throttle it stumbles and spews smoke for a second until the revs pick up. No codes at all, even on the scanner. I just got back from the wreckers where there used to be a 1997 Catera but they crushed it. Buggers.

  5. #4
    MoistCabbage's Avatar
    MoistCabbage is online now Cadillac Owners 10000+ Posts
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    Bad FPR?

  6. #5
    Pee_beds is offline Cadillac Owners Member
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    Re: Heavy overfueling on cold start - seeking advice

    Good suggestion, would explain the no code situation. Why does everything seem to require the removal of the damn intake plenum?

    Love hate relationship with these cars isn't it? I've only put on 400 kms since buying it and am really starting to not like this car, I bought it as a secondary vehicle thinking it would be great for a road trip but I think I'll be too afraid of it acting up along the way.

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    hgqguy is offline Cadillac Owners Fanatic
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    Re: Heavy overfueling on cold start - seeking advice

    Check your fuel purge valve. its possible that it is stuck. and I belive its in the same area of everything else on the motor.

  8. #7
    Pee_beds is offline Cadillac Owners Member
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    Re: Heavy overfueling on cold start - seeking advice

    I'll be damned it was the fuel. I put premium in shortly before this problem occurred (the previous owner put 100,000kms on it and ran low octane fuel the whole time) and thought the car would appreciate it. Since the overfueling was barely noticeable at operating temperature I didn't notice the difference until I parked the car and pulled the plug wire when it was cold (at least not hot).
    Today I filled up with regular and the car runs great, what the hell? Does the ECM need to be calibrated or has it lost it's ability to 'learn'?

    On a side note I picked up an engine for $60 and pulled the fuel rail/regulator/injector assembly and swapped it over on Friday. Quite easy to do, I had no idea the intake plenum was so easy to remove, I didn't even have to remove the coolant lines or replace the o-rings.

    Thanks to everyone who took the time to read or reply here.

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    MoistCabbage's Avatar
    MoistCabbage is online now Cadillac Owners 10000+ Posts
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    In no way would different octane fuel cause the engine to run rich. Octane has absolutely ZERO effect on air/fuel ratio, and the ECM/PCM has no way of telling what octane fuel is in the tank.

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