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328 Idle issue...

Discussion in 'Technical Q&A' started by spirot, Mar 3, 2007.

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  1. spirot

    spirot F1 World Champ

    Dec 12, 2005
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    Tom Spiro
    #1 spirot, Mar 3, 2007
    Hey Guys, I have a strange issue on my 328... I think it may be Aux air valve, but not sure.... when I start the car, it warms up normally ... 2k RPM then down to 1500 RPM and instead of dropping down to +/- 1000 RPM, it sticks around 1500RPM.... and when you drive off and put the clutch in it goes up to 2000 RPM sometimes, sometime to 1500RPM and sometime back to 1000 RPM... whats going on here? I just noticed this last week... I'm going to check the Aux air valve tomorrow... but anything else cause this... I thought it may be the throttle cable, but if the cable it would hang up at one speed, not move around ... so it seems like an air issue to me.... any ideas... I did a search and only saw about the aux air valve, and brake boost line??? any help is appreciated.

    Cheers!

    Tom
     
  2. htapaul

    htapaul Karting

    Aug 21, 2006
    95
    Morton Wa/Mtn Ctr CA
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    Paul
    #2 htapaul, Mar 3, 2007
    I just got back from a great drive to Palm Desert on the Palms to Pines Hwy 74 on my 328.....same problem...when I reached down to check my gas pedal for free play, I noticed that the carpet/mat had pushed forward and was jammed again the throttle....pull the carpet back....900rpm. Think I need to secure the rug/mat in some way to prevent the forward creep. Paul
     
  3. miketuason

    miketuason F1 World Champ
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    #3 miketuason, Mar 3, 2007
    OR the linkage on the throtle body sometimes sticks, mine did. When the RPM is high try to push the linkage close and see if the RPM drops, if it does the just lubricate the linkage and you're good to go, that's what I did with mine and problem never came back.
     
  4. spiderseeker

    spiderseeker Formula 3

    Jul 22, 2005
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    Steve
    #4 spiderseeker, Mar 4, 2007
    Last edited by a moderator: Sep 7, 2017
    Carpet creep is the most common probelm.(Birdman has a fix for that now).
    My throttle was sticking last year and a little grease fixed it- the arrow in the photo is where to put the grease.
    Image Unavailable, Please Login
     
  5. spirot

    spirot F1 World Champ

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    Tom Spiro
    #5 spirot, Mar 4, 2007
    I dont think its the carpet, cause It happens when the carpet is out of the car... also dont think its the cable... cause if it was, the idle would not go up, without me touching the throttle...I've lubed up the throttle area on both sides, and I know the cable slides smooth... all you have to do is take out the cotter pin, unscrew the cable stop, and you can pull it easy....

    its seems like it happens a lot now... even when its gotten fairly warm... once the fans come on I noticed it does not happen...???
     
  6. Sunracer

    Sunracer Formula Junior

    May 18, 2005
    661
    Makati City
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    Pierre Beniston
    #6 Sunracer, Mar 4, 2007
    If your car uses mechanical advance in the distributor to control the ignition timing make sure the weights are moving smoothly and freely. I had an erratic idle problem on a car, the weights were sticking slightly instead of returning to their normal position. When the timing got stuck advanced the idled would increase. PB
     
  7. carlrose

    carlrose Formula Junior

    Nov 25, 2003
    324
    #7 carlrose, Mar 4, 2007
    Hi Tom

    There is no mechanical advance in a 328. The Microplex electronically controls the ignition advance curves.

    Does the engine run properly otherwise? Once you've excluded the mechanical aspects as listed above, a few thoughts (not a comprehensive list):

    * Expansion tank temperature sensor failure, thus not signalling injection ECU to switch to "warm" duty-cycle.
    * If the oxygen sensor has failed, the K-lambda Jetronic ECU will default to a slightly "rich" setting. Similar if you have an exhaust leak allowing extra air into the exhaust (the O-2 sensor will interpret this as a "lean" condition and enrichen mixture; this can occur on the 328 if the air injection circuit valve -domed off-white plastic part on top left intake - doesn't close when signalled by vaccum switch under left top rear frame. Make certain this vaccum line hasn't fallen off).
    * Intermittent vaccum leak.
    * Idle bypass valve (located under expansion tank) incorrectly opening when warm, allowing extra air into plenum.
    * Incorrect "warm" fuel pressure reducing fuel distributor plunger lift, causing, essentially, a "rich" warm-run mixture (fault in WUR).

    I'm sure others will chime in.

    Best,

    Carl
     
  8. f355spider

    f355spider F1 World Champ
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    #8 f355spider, Mar 4, 2007
    The quick check of the aux air valve would be to pinch off the rubber hose to it when the engine is racing...if the idle drops back down, you found your source of the problem.
     
  9. spirot

    spirot F1 World Champ

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    #9 spirot, Mar 4, 2007
    Hey Guys... I think I found a hose that goes to the cold start injector that was making a sucking sound... it also looked collapsed...

    when the car has been running for 20 - 25 min... I pinched the hose runnig from the Aux air to plenum, and the idle dropped... same happend when I pinched it around the cold start...

    I'm assuming a pin hole or crack can affect idle? I took off the Aux air and tested it in the freezer and oven ... and it seemed to work ok... closed up all except for a small sliver when in the oven, and opend up when in the freezer...

    there is an electirical connection on the Aux air... where does that circuit go to? can that be a problem??

    I taped over the air hose going from the Cold Start injector with duct tape and the idle seems better, but its still running hi when you come to a stop sign... a couple of blips on the throttle and it goes back to 1000RPM.... its nutz! tracking all this down!
     
  10. f355spider

    f355spider F1 World Champ
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    #10 f355spider, Mar 4, 2007
    I would simply replace the hoses on each side. Could't cost you more than $40 or so. Cheapest fix you'll ever have... ;)
     
  11. spiderseeker

    spiderseeker Formula 3

    Jul 22, 2005
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    #11 spiderseeker, Mar 4, 2007
    you said "there is an electirical connection on the Aux air... where does that circuit go to? can that be a problem??"

    It applies voltage to a heater within the aux air valve that closes the valve as the car warms up and no longer needs fast idle. The contacts on the aux air valve should read about 23 ohms I think. (something other than open)
    Voltage from the cable should be 13.8 I think. (I think the cable connects to a similar heater in the WUR as well).
     
  12. GTHill

    GTHill F1 World Champ
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    #12 GTHill, Mar 4, 2007
    Also check the motor mounts. If the mounts are loose or broken, or the spacers are gone, it could cause the engine to shift and change the tension on the throttle cable.

    Gene
     
  13. f355spider

    f355spider F1 World Champ
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    #13 f355spider, Mar 5, 2007
    After 20 minutes the car should be on the warm idle (1,000 rpm) and if you pinch the hose and the idle drops, the air is getting into the system somewhere. Either ahead of the hose from a leak or a bad aux air valve.
     
  14. spirot

    spirot F1 World Champ

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    Tom Spiro
    #14 spirot, Mar 6, 2007
    Ok, after driving my self crazy ... I think I found the problem... at first I thought it was the hose going to the cold start... so just replaced it, and its better but still same thing happening... so starting to pinch hoses...and the one that goes to throttle bypass... when pinched makes a huge Idle difference... so disconnected it from the Aux air valve... and plugged the end... and it still is doing the same thing... so began to pinch the hose, and it the RPM drops... so then I put a clamp on it, and pinched it again and heard a whistle from the hose when I reved the car up... so I'm guessin its the freakin hoses... they seem like they are stock... so 20 plus years old... I have some hose, & will cut a piece to fit and see what happens... this is so pissing me off...
     
  15. f355spider

    f355spider F1 World Champ
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    #15 f355spider, Mar 6, 2007
    You're making progress...keep us posted! :)
     

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