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Chasing a high idle issue - Anyone have a vacuum line diagram?

Discussion in 'Mondial' started by 2cam, Mar 6, 2020.

  1. 2cam

    2cam Formula Junior

    Aug 28, 2014
    527
    Austin, Texas
    Full Name:
    MikeS
    Team Mondial,

    Happy Friday! I'm chasing a high idle issue on my '88 3.2 (it idles around 1500/1600 rpm when warm) and am going through a process of elimination to ID and fix the issue. I'm going to start by checking all of the vacuum lines and go from there. However, I can't seem to locate a decent vacuum line or parts diagram online to guide my efforts. Does anyone on the board happen to have one or have a link to one?

    Also, any other suggestions of what to check that may be causing the high idle would be appreciated (I have checked the carpet position, throttle cable to ensure it wasn't sticking, and the throttle body plate to ensure that it was closing at idle).

    Thanks!

    2cam
     
  2. spicedriver

    spicedriver Formula 3

    Feb 1, 2011
    1,740
    Check for a stuck AAV. It should close all the way when warm. Shoot some WD-40 inside. Put a screwdriver through the opening and work the plate back and forth. You should feel the plate push against the spring.
     
  3. theunissenguido

    theunissenguido Formula 3
    Silver Subscribed Owner

    Jan 21, 2004
    1,492
    Argent/Brasil/Blgium
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    Guido
    gsfent likes this.
  4. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,749
    Texas
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    Steve Magnusson
    #4 Steve Magnusson, Mar 6, 2020
    Last edited: Mar 6, 2020
    Please give version also - a US version 3.2 is fairly different from a euro version 3.2.

    Also, are you saying that the warm idle was OK, and it has suddenly changed without anyone mucking with anything?

    Along spicedriver's thought about the AAV not closing properly when warm, you can just "pinch" one of the rubber air lines going to the AAV closed at warm idle (to simulate a fully closed warm AAV). If the warm idle drops = strong sign the AAV needs repair/replacement.

    If you have a US version 3.2, another simple test to do is just unplug the throttle microswitch at warm idle -- the warm idle RPM should increase. If it doesn't increase, that indicates that the idle switch contacts inside the throttle microswitch are not closed as they should be when the throttle plate is in the idle position. Could just need adjustment or replacement.
     
  5. 2cam

    2cam Formula Junior

    Aug 28, 2014
    527
    Austin, Texas
    Full Name:
    MikeS
    Thanks for the responses so far everyone. I appreciate the diagram and the suggestion of the AAV. I have that on the list as well to check. I'll add the microswitch to it.

    Steve, to answer your questions, it is a U.S. car. I purchased the car in the latter part of 2018 and the idle was slightly high when warm (about 1000 rpms) at that point. Interestingly, it was a bit low (about 800 rpms) when cold - just the opposite of what you would expect. I had the car serviced last year (new tbelts and cam seals that necessitated removal of the intake and a few other items). Immediately after receiving the car back (like as soon as I picked it up) the warm idle was sitting at about 1500/1600 rpms. The cold idle had increased slightly as well, but only by about 100 rpm. Fast forward to a year later and I'm just finding a bit of time to track down and address the issue(s). A couple of other interesting data points - the car is easy to start when cold (doesn't require any pedal), but when warm does require a bit more effort. The car also doesn't seem to rev as quickly or as hard to redline as it did prior to the service. Almost as if the ignition isn't advancing to the degree that it should. I'm not sure if these are related in any way to the high idle issue, but thought that I would mention them in case you guys feel that it might point out a more specific cause or other items to check. More than likely, there are several issues at play which is why I'm wanting to ensure that there are no vacuum leaks and then check items like the AAV and the microswitch to ensure that they're properly functioning.

    Thanks again for the input so far!

    2cam
     
  6. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Jan 11, 2001
    18,749
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    Steve Magnusson
    It sounds more like it was just improperly mucked about with (rather than some simple flaw happened that can be corrected easily). These CIS system are intentionally adjusted at warm idle to be 1000 RPM so your comment that "Immediately after receiving the car back (like as soon as I picked it up) the warm idle was sitting at about 1500 rpms" is just confirmation that it wasn't done correctly. You're probably in the situation where it all needs to be mucked with again ;). One other simple diagnostic thing you can do is confirm the frequency valve is correctly buzzing/vibrating whenever the engine is running, but you are really back to square one where the mechanical adjustments (throttle plate position, air bypass screw position, and mixture screw) would need to be checked/made at warm idle with the O2 sensor unplugged (after confirming the AAV is working, the throttle microswitch is working, and the FV is buzzing).
     
  7. Chris Mondi

    Chris Mondi Rookie

    Oct 30, 2018
    32
    Full Name:
    Chris Riedinger
    There’s a sensor on the coolant expansion tank. If it or the wiring is faulty, it will cause a high idle. I had the same problem, it’s fixed now


    Sent from my iPhone using FerrariChat.com mobile app
     
  8. mike32

    mike32 Formula 3

    May 13, 2016
    2,435
    Uk
    Before you start pulling things out, check the throttle cable has not been caught by the drivers floor carpet, then press the accelerator and once you take your foot off does the cable have slack in it at the top of the engine. It attached to the spring loaded lever, wd40 this and be sure it springs back fully. The cable or this can stick and give you a high idle
     
  9. 2cam

    2cam Formula Junior

    Aug 28, 2014
    527
    Austin, Texas
    Full Name:
    MikeS
    Chris and Mike. Thanks for the suggestions! I'll add the sensor to the list. I did check the carpet (all good there) and the throttle lever does seem to return adequately.

    Thanks!

    2cam
     
  10. moysiuan

    moysiuan Formula 3
    Silver Subscribed

    Nov 1, 2005
    1,742
    Toronto, Canada
    Full Name:
    Andy
    The AAV sounds like a culprit from the symptoms described, but should not have been affected by the intake off maintenance done which suggests something else. The throttle position sensor is a suspect, it needs to be adjusted such that you hear a click just as the throttle is opened. Put your ear close to it while the engine is off, and open the throttle with your hand, a tiny click should occur just as the throttle is moved from is rest position. If not, you loosen the mounting bolts and turn the item slightly (the bolts allow for such slight movement for adjustment), and retighten until you get the siwtch click sound just as the throttle is opened. It is possible the TPS has failed, but adjustment is a worthy first effort.

    A wild card might be a leak at the fuel injectors, there are rubber oring/donought type sleeves which the injectors are sitting in. Since the idel is changing based on whether the car is warm or cold, this suggests some expansion contraction is occurring which is causing some air leak. You can put a few drops of power steering stop leak fluid on the injector where it mounts in the intake, this will soften up a hardened rubber oring, but the oil will also seal the air leak at least temporarily. Won't do any harm, and rule out air leaks there.

    It could also be a dirty O2 sensor, giving incorrect signals to the car regarding mixtures and affecting the idle.

    You should also check and set the idle in the first instance, by adjusting the throttle idle screw and the air bypass bolt. Warm up the engine thoroughly, keep the engine running and close the air bypass screw. Adjust the throttle stop screw to give an idle speed of 450 RPM (ideally use tachometer), then set the air bypass to give the desired idle RPM.
     
  11. 2cam

    2cam Formula Junior

    Aug 28, 2014
    527
    Austin, Texas
    Full Name:
    MikeS
    Thanks Andy! I appreciate the thoughtful and descriptive response. I'll add these to the list as well.

    2cam
     
  12. blownfuse

    blownfuse Karting

    Jul 16, 2012
    92
    Campbell, California
    I'm chasing a similar high idle issue. US 88 3.2 w/ ABS.

    Adjusted my throttle position switch, hear the click, seems to be in working order.

    Have checked the thermo switch beneath the coolant reservoir and it seems to be fine as well.

    Did the "pinch the tube test" with my AAV and nothing happened, but I'm still going to take it off and WD-40 it for good measure.

    One odd observation: when I disconnect the wires from frequency valve, the idle speed seems to drop from 3000 rpm down to about 1500. Is this a red herring?
     
  13. Steve Magnusson

    Steve Magnusson F1 World Champ
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    #13 Steve Magnusson, Mar 28, 2020
    Last edited: Mar 28, 2020
    The audible click is a good sign, but, to really test the functionality, just unplug it at warm idle -- the idle speed should increase and then decrease when you plug it back in.

    Yes, the "average" duty cycle at warm idle supplied to the FV is 50% (so it's partially open). When you unplug it, this is 0% duty cycle (fully closed) which significantly leans out the A/F ratio.

    (Your result is a good sign showing that your FV is working -- when plugged in ;).)
     
  14. blownfuse

    blownfuse Karting

    Jul 16, 2012
    92
    Campbell, California
    Nothing seems to get the idle speed to decrease. I'll unplug the switch and then manually bridge the contacts to see what happens.

    Also, thanks for the FV lesson! :)
     
  15. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Steve Magnusson
  16. blownfuse

    blownfuse Karting

    Jul 16, 2012
    92
    Campbell, California
    As I disconnected the AAV, I found the internals were moving just fine, but I noticed the electrical connector going to the AAV only had a single terminal wired. The other terminal had fallen out of the connector. What is this connector for?
     
  17. blownfuse

    blownfuse Karting

    Jul 16, 2012
    92
    Campbell, California
    Steve, you brilliant, brilliant man! As I was jiggling the connector trying to loosen it from the switch, the idle dropped beautifully to 800 rpm. Looks like an intermittent contact there. Will put the AAV back together, clean and secure the contacts, and my idle problem is solved.

    I might even be able to get this puppy smogged now!

    Aaaaand now on to the half-dozen other projects (driver window not raising, fuel filler flap solenoid inop, radio won't turn on, brake reservoir float switches, yadda yadda)
     
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  18. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,749
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    Steve Magnusson
    Glad to hear that you are making progress -- welcome to the process of "sorting" a Ferrari ;) You are lucky that someone hasn't wrongly turned every mechanical adjustment in an effort to "fix" things without realizing that some component wasn't working correctly -- this happens quite often.

    The AAV connector is just a constant +12V signal and ground to run an internal electric resistance heater. The AAV will still heat up and close just by absorbing heat from the engine, but it will take longer than it should without the electric heater working. The voltage between the two AAV wires should be 12V whenever the fuel pump is running.
     
    theunissenguido likes this.
  19. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    141
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
    It's really easy to pull the AAV, clean it and inspect. I was having an intermittent idle change and I noticed it got a lot better after pulling. cleaning and reconnecting.

    While it's off it's easy to put 12v and watch it open.
     
  20. Subito Grigio

    Subito Grigio Karting

    Jun 2, 2009
    190
    Mike32, above mentions ensuring a driver’s-side carpet touching or covering the accelerator pedal. As I read through the comments that also sprang to mind.

    As I mentioned elsewhere - and it bears repeating and emphasizing - please don’t have a second carpet or mat on top of your driver’s side floor carpeting. (Toyota emphasizes this on every single dealer maintenance estimate and bill). It happened to me: INSTANT 7,000 rpm panic in a QV is not fun. For some strange reason I just happened to look at the pedal after looking at the throttle cable at engine. I was extremely lucky. Thank God. No second carpets on that side please!


    Sent from my iPhone using FerrariChat
     

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