84 GTB QV not running correctly, please help | FerrariChat
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84 GTB QV not running correctly, please help

Discussion in 'Technical Q&A' started by NSXER, May 29, 2006.

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  1. NSXER

    NSXER Formula 3

    Jan 4, 2004
    1,307
    Kansas
    #1 NSXER, May 29, 2006
    Just purchased this car last week and love it, my first Ferrari (US model).
    First, the car would not start after driving it awhile (Hot start problem) and it would not run smoothly, a definate lope in the idle. When driving the car it will hesitate under load, it is most noteable at lower rpms 1K-4K but still occurs at higher rpm. After reading through this great site I determined that it was one of four things and replaced them all this weekend. Replaced plugs, replaced plug wires, replaced fuel accumulator, replaced fuel pump valve. Cleaned points and looked very carefully at the spark plug extenders to make sure they were not burned through, no holes found. Looked at the vaccum lines for cracks and they look great. Also the fuel pump runs great.
    I am now at a loss because all the above did not make a difference. I was sure that the accumulator was the hot start problem but it would not start tonight after a 30 minute drive but fired right up after letting it sit for 30 minutes. Could it be the coils? can the crankshaft position sensor or flywheel sensor cause this? After the car sits for awhile it fires up great but still hesitates. It hesitates more when it is cold though and gets better when it warms up. I had never driven a 308 before so I am not sure what to compare it to but it does seem down on power. The car does not smoke and still has the cat. converter on it. Any information or advice would be great!
     
  2. matteo

    matteo F1 World Champ

    Aug 1, 2002
    13,748
    On a plane somewhere
    Full Name:
    Heir Butt
    #2 matteo, May 29, 2006
    A coil error would be a consistant issue and not more of a warm running condition.
    This would be consistant as well.

    Where are you located? Some of what you describe about the warm up sounds right. The warm running issue sounds fuel related to me.
     
  3. NSXER

    NSXER Formula 3

    Jan 4, 2004
    1,307
    Kansas
    #3 NSXER, May 29, 2006
    I am located in Winfield Kansas, about 35 miles southeast of Wichita.
    What do you think is the next step? Is it not getting consistant fuel? Could it be the injectors clogging? If I unplug the wire from the back coil, should the car still run on the front cylinders and vice versus? Would this tell me if a coil is bad and it causing the drop in power? Thanks

    Brian
     
  4. jwise

    jwise Formula Junior

    Apr 2, 2003
    781
    Portland Maine
    #4 jwise, May 29, 2006
    Sorry to hear about problems so early in the relationship. These cars are a little picky....

    Anyway- I would get a full cold/warm/hot fuel pressure test to try and pinpoint any fuel problems. If there is no ferrari mechanic in your area, a decent mercedes/vw/porsche place should have the equipment to test the bosch system on your car. At least with this, you can rule out many potential problems. Should take a mechanic about an hour, or more to do this.
     
  5. matteo

    matteo F1 World Champ

    Aug 1, 2002
    13,748
    On a plane somewhere
    Full Name:
    Heir Butt
    #5 matteo, May 29, 2006
    Brian,

    Are you having a warm start condition or a missing/down on power condition?

    Matt
     
  6. hardtop

    hardtop F1 World Champ

    Jan 31, 2002
    11,298
    Colorado
    Full Name:
    Dave
    #6 hardtop, May 29, 2006
    Sometimes fuel injectors go bad and don't close causing the system to loose pressure and usually this results in tough warm starting even though cold starting is fine. You may want to call around to Mercedes, BMW or VW dealers to see if someone can check them and/or get new ones which will be much cheaper than getting them from Ferrari.

    Dave
     
  7. dakharris

    dakharris Two Time F1 World Champ

    Jun 7, 2001
    29,441
    Sleepy Hollow
    Full Name:
    Cavaliere Senzatesta
    #7 dakharris, May 29, 2006
    After you try easier (cheaper) fixes, you may want to look into the catalytic converter and/or the oxygen sensor. If it still has both and they are original, it is possibly in need of replacement of one or both. Does Kansas require smog certification? If you didn't have to pass smog, this is an area that you wouldn't think about.
     
  8. hardtop

    hardtop F1 World Champ

    Jan 31, 2002
    11,298
    Colorado
    Full Name:
    Dave
    #8 hardtop, May 29, 2006
    PS: If you want to switch coils, you must change all the wires on them, otherwise the ignition timing will be off one bank.

    Dave
     
  9. NSXER

    NSXER Formula 3

    Jan 4, 2004
    1,307
    Kansas
    #9 NSXER, May 29, 2006
    You guys are the best, thanks for all the advice!
    I am in the garage right now trying different things, here is what I have just tried.
    1) Opened airbox and started car. Increased throttle to make sure that vaccum was pulling the "round circle plate"? down that is under the airfilter. This checks out well and the car revs fine.
    2) Started and shut off car several times. Seams like about every other start the car revs better and then after some starts it does not rev as well.
    3) Tried to start the car on just the front coil (front cylinders)...starts fine. Tried to start on just the rear cylinders...does not start. Bad rear coil?
    4) Pulled one of the injectors, to my eyes it looks fine. How do you check them?
     
  10. NSXER

    NSXER Formula 3

    Jan 4, 2004
    1,307
    Kansas
    #10 NSXER, May 29, 2006
    I just took it out for a 45 minute drive and it is starting to run much better. At above 2500 it does not hesitate nearly as bad or in 4 or 5th gear. When I came home though and shut it off, let it sit for 20-30 minutes it did not start. I turned the ignition key part way and unplugged the blue plug from the Bosch fuel and the pump runs great. Anymore thoughts? Thanks again
     
  11. hardtop

    hardtop F1 World Champ

    Jan 31, 2002
    11,298
    Colorado
    Full Name:
    Dave
    #11 hardtop, May 29, 2006
    I had a QV that did this and it turned out to be the injectors.

    Dave
     
  12. Doc

    Doc Formula Junior

    Sep 13, 2001
    886
    Latham, New York
    Full Name:
    Bill Van Dyne
    #12 Doc, May 29, 2006
    If the car wouldn't start with one of the coils dc'd, then at least it seems that you've narrowed it down to one bank. Check the coil wire, coil, and all of the wiring going back to that bank's Digiplex.

    Also, there is a bulkhead connector which connects the Digiplex's wiring to the engine wire harness located roughly under the expansion tank and near the oil cooler. Disconnect it and clean the connectors with electrical contact cleaner--sometimes that can help.I had an '85 308 which malfunctioned in this way and the coil wire was bad--as well as a flywheel sensor.

    PS-do you still have your NSX? I bought a '92.
     
  13. NSXER

    NSXER Formula 3

    Jan 4, 2004
    1,307
    Kansas
    #13 NSXER, May 31, 2006
    Thank you to everyone that chimed in. The car is running much, much better now. The injectors were part of the problem. I also replaced the cat with a test pipe yesterday. It does not hesitate at all now.
    Yes, I still have the NSX. I have owned it since 1993. Glad to hear that you purchased one, you will love it. The best thing you can do is put on Taitec exhaust and headers, makes the car so much more fun to drive. Hope that you enjoy it.
     

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