Fast idle/ throttle position switch adjustment | FerrariChat

Fast idle/ throttle position switch adjustment

Discussion in 'Boxers/TR/M' started by c4b4the04, Oct 4, 2020.

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  1. c4b4the04

    c4b4the04 Formula Junior
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    Jun 9, 2017
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    Northern Virginia
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    Cassidy
    Hi all,

    88 F113B. I may have knocked the brass air valve adjusters when I resealed the motor back in spring. With the AC on this summer, it kept idle far enough down I didn't worry about it. Now that I've got the AC off, it's idle is very high, like 1800.

    As I recall, unplugging the three wire throttle position switch can raise idle roughly 500 rpm? That sounded like what I was dealing with. I drove the car for 45 minutes, stopped and disconnected the throttle switch, no change at all.

    So I see there are replacement generic company switches for 50 bucks as the Bosch part is no longer produced. Is this a 'try and adjust' part or just replace? 27k on the car, switch and harness show no signs of damage or wear.

    I'm guessing it could be tested if I take it off, like the center Pole of the three is common and the outer two terminals are idle and wide open, or something like that? It's not a potentiometer if I recall.

    Thanks for the advice all, want to do this one right so I can get back to enjoying. I've got 800 miles since my big overhaul and otherwise doing well. Well, that and I'm not sure how to turn just the heat on....with the recirc button it turns the AC on too. Only a year and a half into ownership and mostly warm weather driving!


    Sent from my iPad using FerrariChat
     
  2. Veedub00

    Veedub00 F1 Rookie
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    Jun 30, 2006
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    You can measure the throttle position switch at the ecus.

    You can also put a jumper on the 1 and 2 of the tps connection and that will make it default to always closed. You do this for the idle adjustment process.

    also check your carpet to make sure it’s not pushing on the accelerator.
    Check your throttle linkage for binding too.
     
  3. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
    25,040
    30°30'40" N 97°35'41" W (Texas)
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    Steve Magnusson
    #3 Steve Magnusson, Oct 4, 2020
    Last edited: Oct 4, 2020
    That's clear evidence that the idle portion of the throttle microswitch is not working correctly (either bad switch or misadjusted).

    This jpeg shows how to test the switch at its own terminals (but you have to manually rotate and hold the "D" shaped shaft thingy in the correct location for the two conditions):
    Image Unavailable, Please Login

    And this jpeg shows how to check the idle switch operation at an unplugged injection ECU connector:

    Image Unavailable, Please Login

    PS I've had to replace mine twice for the idle switch not working -- and the second new one had the Bosch "green dot" on it (which I believe Bosch uses to indicate/track something has been improved/changed on a component).

    PPS Is the Bosch PN on your existing throttle microswitch 0280120310 or 0280120312?
     
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  4. c4b4the04

    c4b4the04 Formula Junior
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    This is fantastic, and part of the reason I felt confident jumping into a TR. Thank you so much for the info, the pics inside and an alternative way to measure the reading. I will jump in both feet later this week and figure it out. I have a feeling it is out of adjustment but seeing it inside really helps me understand the system. If the switch is bad it will be obvious pretty quickly and I can't really make matters much worse by moving it. I see there just isn't much to it inside there.

    Thank you again, great info. Will report back and see what part number I find. I was going off of a Rockauto search that had the P/N for the car. I will pull my actual number and see.

    Cassidy
     
  5. c4b4the04

    c4b4the04 Formula Junior
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    Ok,

    So the switch was way out of adjustment, I verified with a voltmeter and my switch works 100%. It was simply not near contacting at idle. A few clues this was altered during the previous owner's time, as one of the screws was replaced with a flat head and I found the original when I overhauled the trans and repainted back in the spring. I think they adjusted it off of idle to bring the idle up, seeing how the car needed service and this was a fast trick to make it idle faster. Never had a fast idle with the car until after my refresh. New injectors, new wires, new plugs, new fuel pumps, new pump relays, new filters and clean throttle plates will do that...

    So now I just need to sync the banks. I have a slack tube manometer that I used in the past to balance cross-fire injection throttle bodies on GM cars. Would that work? It is a very long loop of clear hose with dye (not mercury like some older ones) that would show me vacuum relative to each other. In theory, that should get my banks perfect.

    Oh, and I wanted to ask....those Diagnosis sheets, where can I purchase those? I have the factory WSM, are they inside and I am not looking in the right place? They seem super useful for real services like these.

    Thank you all, so nice to have a smoother and reasonable idle again.

    Cassidy
     
  6. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    No, the Diagnosis Sheets (No. 1 thru No.6) is a separate publication (like the later wiring diagrams), and not part of the WSM. This link:

    https://www.dropbox.com/s/b92n145onqihpb5/TR Diagnosis Sheet N 1 US MicroPlex Ignition.pdf?dl=0

    will get you a pdf of Diagnosis Sheet No. 1 (covering the Microplex MED120B ignition), and this link:

    https://www.dropbox.com/s/gm81j3cq3048qe1/TR Diagnosis Sheet N 6 US KE-Jet Injection.pdf?dl=0

    will get you a pdf copy of Diagnosis Sheet No. 6 (covering the KE-Jet with Lambda injection - where I've added some notes/corrections that I thought were necessary),

    but they aren't easy to use without the 25-pin breakout connector test box (and the results given assume that you are making each test in the exact order shown).
     
  7. c4b4the04

    c4b4the04 Formula Junior
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    Excellent knowledge, thank you. Is the breakout box as simple as making one up, pin for pin to the harness? It probably isn't so simple but I'd be more than willing to take a stab at making something like that for the community. 3D printed connectors are a marvelous thing...
     
  8. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
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    steve, how can I download from the dropbox those sheets?

    when you not have the adapter 95970020, are the numbers in the sheet the same as on the microplex ignition box? or are the numbers different on the adapter and the ignition box?
     
  9. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
    25,040
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    Just click on the link, the file should open, then on the right hand side of the screen above the title there should be three buttons: "Sign in", "Sign up", and a download arrow symbol -- click on the download arrow symbol.

    The terminal numbers on the test box are the same as the 25-pin terminal numbers on any ECU where it is used (ignition, injection, ABS). On a euro KE-Jet without Lambda TR, you would want Diagnosis Sheet No. 5, but many (if not all) tests would just be a subset of what's shown on Diagnosis Sheet No. 6.
     
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  10. turbo-joe

    turbo-joe F1 Veteran

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    :) :) :)
    thank you very much steve. I think because of my age I not see right anamyore ;) have not seen the download arrow, only have read "logg in" and "register"

    also great that the numbers on the testbox are the same as on the ECU. so it is no magic then to test without this box
    where can I find the sheet no.5? may be you have a link also?
     
  11. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
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    30°30'40" N 97°35'41" W (Texas)
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    Steve Magnusson
    Don't have No. 5, and I don't have any specific source in mind, but you should check with Maranello Concessionaires (www.ferrariparts.co.uk) IMO. I had purchased individual copies of No.1 and No.6 from www.ferrariliterature.com (IIRC) many, many moons ago; however, I believe the complete official publication would include all six sheets.
     
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  12. c4b4the04

    c4b4the04 Formula Junior
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    Jun 9, 2017
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    I haven't had a chance to test this out, but I noticed when I was setting the idle switch to contact that the wide open throttle (WOT) contact seemed to be making contact much sooner than a true wide open throttle position.

    The idle is doing great now and the car pulls fine under 3000 rpm, recovers to a little bit of a fast idle at a stoplight but not bad enough to worry with at the moment.

    What I DO feel is that there seems to be less power up top, say, above 3000 rpm. It isn't awful but it feels less 'snappy' than it used to, almost maybe like it is too rich? Which, according to what I've read about K Jet (non Lambda), would be rich at WOT state. Is there a chance my TPS is just not adjusted correctly? I can't clearly see the number but would some Bosch sensors maybe have WOT at a smaller rotational range than another?

    My current idea to test is to pull the connector on the TPS and go for a drive. It would then be a fast idle of course BUT I could tell seat-of-the-pants if it feels more normal again.

    Thoughts?
     
  13. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
    25,040
    30°30'40" N 97°35'41" W (Texas)
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    Steve Magnusson
    The name is a little misleading. The WOT switch should close when the throttle opening is in excess of 60 deg (not just at true WOT) - see page D80 in the TR WSM. It should really be called "the throttle is at a fairly large opening, or more, switch" ;).

    One easy thing you might do about the "there seems to be less power up top, say, above 3000 rpm" is to check that intake manifold vacuum is reaching the Microplex ignition
    ECU -- if this line is blocked or unplugged or cracked or kinked, the ignition timing is significantly retarded.
     

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