1991 Testarossa idle / drivability issue | FerrariChat

1991 Testarossa idle / drivability issue

Discussion in 'Boxers/TR/M' started by VEXMoto, Nov 26, 2024.

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  1. VEXMoto

    VEXMoto Rookie

    May 1, 2023
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    Josh
    1991 Ferrari Testarosssa with an F113A040 engine.
    Complete fuel system was gone over from rust in the filler neck getting into the tanks / lines / fuel distributors.
    Distributors sent to CIS Flowtech for rework, along with the injectors (4 ended up being replace). New pumps, filters, diaphragms, and the fuel tanks removed and outsourced to be cleaned and repaired (a couple porous leaks in the casting).
    After reassembly the car ran wonderfully, drove like a brand new Testarossa! I mean this car was a dream to drive.
    After about 50 miles of road tests, the car developed a hard start and a low cold idle. It will dip down to 500 rpms and "hunt" its idle, then bounce up and idle around 2,000rpm. After the vehicle is at operating temp, it stays at the 2,000 rpm idle. The aux air valves were replaced after seeing one appeared to be stuck closed.
    I've kinda hit a wall with my diagnosis (and lack of familiarity with 90's Italian cars), and seeking any input I can get.
     
  2. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,236
    30°30'40" N 97°35'41" W (Texas)
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    Steve Magnusson
    #2 Steve Magnusson, Nov 26, 2024
    Last edited: Nov 26, 2024
    Interesting 1st post (for joining more than a year ago) -- and not a problem much reported (if ever) on TR. Who/what are you? Your FChat Profile is a little thin ;)

    Your post implies that it was tweaked up perfectly, warm idling at 1000 RPM with the O2 sensors unplugged with equal vacuum in both banks when the air bypass screws are opened a reasonable amount (say 1/2 ~ 1 turn) -- call this Condition 1, and warm idling at about 700 RPM with equal vacuum in both banks when the air bypass screws are fully closed from that condition. Was that true?

    You state that now the warm idle is 2000 RPM (call this Condition 2) = the only way that can happen is if more air entering the engine and/or it has more ignition advance at idle.

    So my third question would be:

    What was the (equal) intake vacuum during Condition 1 (please also give your elevation from sea level), and what is the intake vacuum in both banks now in Condition 2 (they might be different)?
     
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  3. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
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    southwest Germany, France ( Alsace ) and Thailand
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    romano schwabel
    great, a member here since about 1,5 years, not introducing himself a little so we would know about his technical knowledge to start to help but asking in first post :(

    never have this seen before in aluminum tanks. also the tanks are not casting, pure aluminum plates bended and welded
    you may pm steve magnussen here. he is the "guru" ;)

    oh, I just see he answered already
     
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  4. VEXMoto

    VEXMoto Rookie

    May 1, 2023
    3
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    Josh
    Sorry gentlemen... long time listener, first time caller.
    This is my first dip into a vintage Italian machine. My personal background is a 12 year JLR technician, and 20 years overall in automotive. I enjoy long walks on the beach, riding motorcycles, and learning new skills. :)
    (I swear I am not trying to come over arrogant, more comedic.)

    And yes I'm aware of the tanks being aluminum. There was a leak in the pass side tank in a weld at a corner.

    (Condition 1) this is a near accurate point, except o2's are plugged in. I have not taken a vacuum measurement of bank 1 and bank 2 yet. Prior to this issue the car was running wonderfully, with a smooth idle and no other hiccups. The drivability was smooth, and the car seemed much improved after fuel system repairs.

    "What was the (equal) intake vacuum during Condition 1 (please also give your elevation from sea level), and what is the intake vacuum in both banks now in Condition 2 (they might be different)?"
    I'll get a vacuum reading in the morning when I have some time to mess with it again. I am roughly 52-56' above sea level.

    I genuinely appreciate your time with this. I'll come back with some more info very soon.
     
    turbo-joe likes this.
  5. Veedub00

    Veedub00 F1 Veteran
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    Jun 30, 2006
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    Troy, Michigan
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    James
    Anytime I messed with anything in the fuel or air circuit I always go through and reset the idle according to the manual. I made a manometer using a long tube, board, and marvel mystery oil. I use a tachometer to get the rpm perfect as the gauge is off. The throttle plate setting and air bypass screws are very very sensitive and micro adjustments will make your vacuum different in the banks. That’s what works for me. I also bought a wide band O2 sensor to get very accurate readings on the A/f ratio to dial that in as well.
     
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  6. raysur

    raysur Formula Junior
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    Which wide band did you buy?
     
  7. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
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    #7 Rifledriver, Nov 27, 2024
    Last edited: Nov 27, 2024
    From personal experience I can tell you those fuel filters do not stop rust and CIS fuel injection is exceptionally sensitive to rust.

    I suspect with CIS fuel pressure levels rust just gets forced through. With low pressure systems we never had that problem. And besides, carbs eat rust reasonably well. CIS does not.
    In any event, I am with Steve, its more likely an air problem if all really was ok prior.

    Personally I do all diagnosis with O2s disconnected. Too many cases of them disrupting things and car runs perfectly without them. Reconnect only after there is certainty car is running perfect. O2s can make small, recognizable, easily diagnosed problems into a large engine wide problem, never mind the system can make its own problems.
     
  8. Veedub00

    Veedub00 F1 Veteran
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    Yeah. For sure. Get it running right with the tps sensor unplugged and jumped (18-2?) effectively eliminating the “e” part of the KE jetronic. Needs to be disconnected to set the idle according to the manual anyways.
     
  9. Rifledriver

    Rifledriver Three Time F1 World Champ

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    Manual says a lot of things.
     
  10. ago car nut

    ago car nut F1 Veteran
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    Aug 29, 2008
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    Inovate Motosports, is one of the better A/F ratio meters and recorders. Can be downloaded to a computer.
     
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  11. VEXMoto

    VEXMoto Rookie

    May 1, 2023
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    Josh
    Fixed.
    Connector latching failure on the passenger side relay box. Repaired 2 pins that came out and car starts / runs / drives exceptionally well again.
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