Engine Hesitation ?
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Northstar Engines and System Technical Discussion Discussion, Engine Hesitation ? in Cadillac Engine Technical Discussion; I own a 1997 Deville with a 32 valvue Northstar 135,000km/h The last week or so while stopped at a ...
  1. #1
    Steve-o is offline Cadillac Owners Member
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    Engine Hesitation ?

    I own a 1997 Deville with a 32 valvue Northstar 135,000km/h

    The last week or so while stopped at a light the engine sounded like it was missing and had a slight hesitation when accelerating. Once at higher speeds it seems to go away.

    I took it in and had the spark plugs changed (AC Delo platinums) but that didn't solve the problem.

    When I run the cars diagnostic's I get a display of ( PCM P0603 HISTORY) which I beleive is the Control Module Long Term memory Reset.

    Any idea, and would it be costly?

    Thanks in advance.

    Steve-o

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  3. #2
    OlManRivah's Avatar
    OlManRivah is offline Cadillac Owners Fanatic
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    Re: Engine Hesitation ?

    Do you blow it out occassionally to clear the carbon build up out?

    Stomp on it while looking in the rear mirror for the tell-tale, short burst of smoke. Search the Forum on Carbon buildup.

  4. #3
    Geno Castellano is offline Cadillac Owners Fanatic
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    Re: Engine Hesitation ?

    Quote Originally Posted by Steve-o
    I own a 1997 Deville with a 32 valvue Northstar 135,000km/h

    The last week or so while stopped at a light the engine sounded like it was missing and had a slight hesitation when accelerating. Once at higher speeds it seems to go away.

    I took it in and had the spark plugs changed (AC Delo platinums) but that didn't solve the problem.

    When I run the cars diagnostic's I get a display of ( PCM P0603 HISTORY) which I beleive is the Control Module Long Term memory Reset.

    Any idea, and would it be costly?

    Thanks in advance.

    Steve-o

    The 97 you have has an onboard diagnostics system that includes a very sophisticated engine misfire diagnostic code. If the engine was missing or misfiring it would set the diagnostic code. So, I am not sure what you are feeling or describing but it would be hard to figure it was a misfire as the diagnostic code should set. Even if an injector or something was causing a problem with a cylinder it should set the misfire diagnostic.

    It might be worth while to check the fuel pressure regulator. Pull the vacuum hose off the fuel pressure regulator with the engine idling and watch the vacuum nipple on the FPR for any sign of fuel leakage for several minutes.

    Otherwise, there may be an engine mount failing or one of the torque strut isolators that is failing that is causing a ground out that feels like a miss.

  5. #4
    kevinK is offline Cadillac Owners Member
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    Re: Engine Hesitation ?

    I had the same problem in the past week or so. I have a 98 Deville with 111K. It has been reliable with no major repair except a new alternator, new coolant and new brakes. I have been experiencing acceleration hesitation and stumbling, mostly noticeable at about 1300RPM to higher RPM. Once it got 70 to 80 mile/hr, it runs smooth. I just canít pass any car. Even a KIA passes me by.

    There is no code detected except an IPC B2511 history. The FPR does not dripping.

    Geno, since you mentioned failing of engine mount or one of the torque strut isolators, may I ask you how to check them?

    I put the gear on drive and give some gas with the brake on, and noticed the front end of the engine raised close to an inch. Does that mean the engine mount is bad?

    Thank you for your time.

  6. #5
    Geno Castellano is offline Cadillac Owners Fanatic
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    Re: Engine Hesitation ?

    Quote Originally Posted by kevinK
    I had the same problem in the past week or so. I have a 98 Deville with 111K. It has been reliable with no major repair except a new alternator, new coolant and new brakes. I have been experiencing acceleration hesitation and stumbling, mostly noticeable at about 1300RPM to higher RPM. Once it got 70 to 80 mile/hr, it runs smooth. I just canít pass any car. Even a KIA passes me by.

    There is no code detected except an IPC B2511 history. The FPR does not dripping.

    Geno, since you mentioned failing of engine mount or one of the torque strut isolators, may I ask you how to check them?

    I put the gear on drive and give some gas with the brake on, and noticed the front end of the engine raised close to an inch. Does that mean the engine mount is bad?

    Thank you for your time.
    Check them like you described by loading the engine against the torque converter while holding the brake and watching the engine and listening for any groundouts. The engine/transmission will normally move about an inch doing this so that doesn't indicate any sort of problem. The main thing is to watch for sudden, jerky movements and grounding noises. The mounts don't "fail" per se but the elastomeric isolators will degrade with time and heat and sometimes shear competely through - but the mounts will still support and contain the engine/tranny - you just lose the isolation.

    An engine mount wont cause poor performance or driveablility. I'm not sure what your performance issue is. The first thing that I'd check is the fuel pressure, though. Get a fuel pressure gauge on it and check it out. A failing fuel pump, restricted fuel filter or inlet sock on the pump could certainly cause that problem.

  7. #6
    kevinK is offline Cadillac Owners Member
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    Re: Engine Hesitation ?

    Quote Originally Posted by Geno Castellano
    Check them like you described by loading the engine against the torque converter while holding the brake and watching the engine and listening for any groundouts. The engine/transmission will normally move about an inch doing this so that doesn't indicate any sort of problem. The main thing is to watch for sudden, jerky movements and grounding noises. The mounts don't "fail" per se but the elastomeric isolators will degrade with time and heat and sometimes shear competely through - but the mounts will still support and contain the engine/tranny - you just lose the isolation.

    An engine mount wont cause poor performance or driveablility. I'm not sure what your performance issue is. The first thing that I'd check is the fuel pressure, though. Get a fuel pressure gauge on it and check it out. A failing fuel pump, restricted fuel filter or inlet sock on the pump could certainly cause that problem.

    That is it. I did feel the same jerky movement. The isolation must be gone. When I feel the jerk I would releive the gas pedal and that caused poor performence. Thank you very much.

    I will also change the fuel filter and check the fuel pressure. Can I use any fuel pressure gauge? Or do I have to use the one mentioned in service manual:J-34730 1a?

    After checking the fuel pressure, I may have to go to the dealer to change the mount.

    Will report back.

    Thanks again.

  8. #7
    Geno Castellano is offline Cadillac Owners Fanatic
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    Re: Engine Hesitation ?

    Quote Originally Posted by kevinK
    That is it. I did feel the same jerky movement. The isolation must be gone. When I feel the jerk I would releive the gas pedal and that caused poor performence. Thank you very much.

    I will also change the fuel filter and check the fuel pressure. Can I use any fuel pressure gauge? Or do I have to use the one mentioned in service manual:J-34730 1a?

    After checking the fuel pressure, I may have to go to the dealer to change the mount.

    Will report back.

    Thanks again.
    If you are feeling a jerk in the drivetrain with a certain degree of throttle opening then I'd suspect that a mount is a good place to start. Get the car in the air on a hoist and do the power brake test so that someone can watch the mounts under the car. It should be very easy to determine which one is bad. Usually if a mount isolator fails it can put more load on adjacent mounts causing them to weaken as well. So don't be surprised if anther one fails later.

    You can use any sort of handy gauge that is good for at least 60psi. Find an old R12 AC charging hose - the female shraeder valve fitting on the end is exactly the same as the male schraeder valve fitting on the fuel rail. Use the hose and an old gauge of some sort and you're in business.

  9. #8
    kevinK is offline Cadillac Owners Member
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    Re: Engine Hesitation ?

    Hi,

    Checked to fuel pressure today. It is normal: about 50PSI. I have not got chance to change the fuel filter yet.

    When I loaded the engine against the torque converter while holding the brake, at gear 1, 2, 3, D and Reverse, I could feel the jerky movements and see the engine vibrates at about 1400-1700RPM, same feeling at acceleration. I think you are right that the engine mount probably worn out. I will bring it to the dealer on the coming Tue. However, why the car runs smooth at highway around 60-80m/h with about 2000rpm. No jerking at all. My question is that could a transmission problem cause the same symptoms? Iíd like to know before I go to the dealer. Transmission is an expensive repair. I donít want to be ribbed off by the dealer.

    Thanks for your time

  10. #9
    kevinK is offline Cadillac Owners Member
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    Angry Re: Engine Hesitation ?

    Took the car to the local Cadillac dealer. The tech checked the engine mount and said they are OK. He ran a scanner and told me that there are misfires at two cylinders. I asked that why I did not see any code. The tech said that the code was cleared by someone. (?)

    The dealer asked $430.0 to change plugs and wires. I asked them changed the fuel filter ($46.00) and said I will change the plugs and wires myself. I paid the diagnostic charge of about $80.00.

    Got ACDELCO plugs (#41950) and wire set from Rockauto today. It took me about two hours to change them according to instructions from previous post here (thanks very much). The car runs exact the same as before. Nothing changed.

    Basically, the car runs very weak at about 1300 to 1800RPM. The engine jerks a lot at this RPM on any gear. At neutral, it is smooth. Once it reached about 2000 rpm at about 60-70 mph, it runs smooth. There is no code. So, please help me. This is killing me: my Cad got no power, canít even pass a KIA.

  11. #10
    Geno Castellano is offline Cadillac Owners Fanatic
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    Re: Engine Hesitation ?

    Did you check the fuel pressure while the engine is under load (when it is causing the problem)? Checking the fuel pressure at idle doesn't mean a whole lot in this situation as it only shows that the pump is providing sufficient flow when there is little load or demand on the engine. You may need to get the fuel pressure guage on the engine and drive the car and watch the fuel pressure when the problem occurs to see if it falls off or drops. Just tape the fuel pressure gauge to the windshield with duct tape for a temporary look at the pressure while driving.

  12. #11
    kevinK is offline Cadillac Owners Member
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    Smile Re: Engine Hesitation ?

    Quote Originally Posted by Geno Castellano
    Did you check the fuel pressure while the engine is under load (when it is causing the problem)? Checking the fuel pressure at idle doesn't mean a whole lot in this situation as it only shows that the pump is providing sufficient flow when there is little load or demand on the engine. You may need to get the fuel pressure guage on the engine and drive the car and watch the fuel pressure when the problem occurs to see if it falls off or drops. Just tape the fuel pressure gauge to the windshield with duct tape for a temporary look at the pressure while driving.
    I have not had chance to check the fuel pressure again. Last time I took the car to a gas station shop and they checked the pressure with engine off and ignition on. I did re-check the wires that I installed. ONE WIRE WAS LOOSE FROM THE COIL! I pushed it in and THE CAR IS RUNING FINE and I passed a lot of cars on highway. No more jerking on accelaration, but I do feel it is slightly less powerful than before. When I loaded the engine against the torque converter while holding the brake, I could still feel the jerky movements and see the engine vibrates at about 1300-1700RPM, same as before, but no jerking at acceleration on the road. I don't understand this. I am also puzzled by lacking code in the dashboard, despite of two misfires.

    I greatly apreciate all your help and thanks.

  13. #12
    gorky is offline Cadillac Owners Member
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    Re: Engine Hesitation ?

    I've got same problem on a 94 with a 97 engine.

    ran fine before the engine swap. now there is a dead zone about 1500-2100 RPM.

    And at a stoplight the engine will begin bucking, and it will hunt idle RPM's between 600- 1000RPM.

    Sometimes it will idle fine in park, then without any external input, the idle will start to stumble and it will sound like mild backfires.

    i thought it might be the loose coil connections but that wasnt it.

    also thought it might be a vaccuum leak tricking the MAP sensor, because when i first noticed this i saw a large crack in the PCV hose from the rear bank of 4 cylinders to the manifold (next to MAP sensor). but i've since fixxed that too, and the problem persists.

    spark plugs are new.

    no codes.

    ??????????????????????????????

  14. #13
    kevinK is offline Cadillac Owners Member
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    Re: Engine Hesitation ?

    I would try new wire set. Good luck.

  15. #14
    gorky is offline Cadillac Owners Member
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    Re: Engine Hesitation ?

    its not the wires.

    and i pulled out the vacuum line on the fuel regulator too, no leaks that i could tell. but i haven't checked the fuel pressure under load yet

  16. #15
    gorky is offline Cadillac Owners Member
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    Re: Engine Hesitation ?

    hey kevin,

    thanks alot for the suggestion.

    i was premature in ruling out the wireset. turns out when i had my engine swapped, i thought a new wireset was installed, along with all new spark plugs, belts and hoses. my mechanic just told me that the set that came with the '87 engine looked so new that he did not change it out. they did look brand new.

    but since the wireset was only $55 from Autozone, I decided to give it a try prior to giving up and taking it to the dealer.

    best $55 i've spent in a while.

    just like in your case, the engine still didnt feel as strong as it did before, but the hesitation and the stumbling in idle are gone, and the acceleration is much more even throughout that 1500-2100 rpm range.

    Does anyone know if failed spark plug wires can lead to a secondary failure in the coil modules, is there a way to check out the coil modules? The power in the engine still is not back to its original glory.

    thanks again,
    gorky

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