VERY high idle

[orthodoct]

Gentlemen:
New injectors, clutch, chip from Marc, plenum rebuild, headers, Corsa exhaust 18 months ago. Driving on country road today, passed a "turtle". Idle wouldn't drop below 4000. Had a heck of a time getting to destination! Checked everything roadside that I could, no change idle. Parked car for 1 1/2 hours, restarted, idle 2000 (normally 1100). Drove home, slow to return to idle with clutch in. Had similar problem when rebuilt and was IAC problem. Have a spare from Jerry. Before I tackle it, any other ideas of where to look? Cables are not stuck.
Thanks, my friends!
Ty
Crossville, TN

[secondchance]

I would look for vacuum leak.

[orthodoct]

Thanks, nothing obvious, but will check further.

[XfireZ51]

Is the car stock? NORMAL idle is 1100????

[orthodoct]

Marc Haibeck chip, new injectors from Jerry, Stainless Works ceramic coated headers with cats, Corsa stainless exhaust; everything else stock. 1992; have owned since new, stock idle has always been 1000 or so.
Thanks!

[XfireZ51]

Marc Haibeck chip, new injectors from Jerry, Stainless Works ceramic coated headers with cats, Corsa stainless exhaust; everything else stock. 1992; have owned since new, stock idle has always been 1000 or so.
Thanks!

Stock idle is set to 650.

[secondchance]

Stock motor with exhaust headers should idle between 650 to 700. I think you have a leak somewhere or IAC is hanging up. Or, could be TB binding somehow.

[orthodoct]

Will swap IAC tomorrow AM. Just looked for vacuum leaks and no obvious suspects. TB operating smoothly throughout range. Replaced all hoses and meticulously rebuilt just about everything when I had the plenum off. Had it so clean that you could eat under there. IAC swap should drop idle. Will advise. IAC was problem previously. Got new replacement from Jerry and it fixed problem. Swapped old one back in and it worked so I left it in. Hindsight 20/20. Should have left replacement from Jerry in! Was a helluva ride today! Had to drive 20 miles in second gear with 4000 rpm idle to keep it below 70 and got behind every stinking log truck in Cumberland County! Go figure. Sitting in town traffic at red lights idling at 4000 rpm with that exhaust system was an experience. One of the red lights was 50 feet from the county courthouse! Good thing that I have operated on half the cops in the county! Was 30 miles from home, so had no choice. Thanks for your help!
Ty

[Blue Flame Restorations]

Sounds like you got it fixed. My in-laws are in Clinton County, KY. Byrdstown TN.

[orthodoct]

Thanks, Brett. Very frustrating, thanks for your help. I have several patients from Byrdstown. I think that I will leave the password where we left it!
You are THE MAN!
Ty

[LGAFF]

tps sensor correct?

[Blue Flame Restorations]

Thanks, Brett. Very frustrating, thanks for your help. I have several patients from Byrdstown. I think that I will leave the password where we left it!
You are THE MAN!
Ty

Woohooo!!! I knew if we stayed at it, we'd get you up and going on the forum again.

Drive that Z like you stole it now!!!! Always here to help.

Brett!
Forum Administrator

[orthodoct]

Yes. Checked it first. Thanks!


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[orthodoct]

Thanks again, Brett. Here for you, too.
Ty


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[XfireZ51]

If this is a 92, has throttle cable ever been disconnected?

[orthodoct]

Yes, from throttle body when I pulled plenum. Has mechanical ASR.


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[XfireZ51]

Yes, from throttle body when I pulled plenum. Has mechanical ASR.


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Have u ever reset the cable length?

[Paul Workman]

I wonder if on a 92+ (w/ASR) if it is also possible to leave that throttle cable connected when pulling the plenum, and just flip the plenum over to lie on the edge of the wheel well (driver's side) like you can with the 90/91s? That would save the chance of messing anything up, PLUS facilitation the removal and installation by a few minutes - especially if it has to be readjusted afterwards...

[XfireZ51]

I wonder if on a 92+ (w/ASR) if it is also possible to leave that throttle cable connected when pulling the plenum, and just flip the plenum over to lie on the edge of the wheel well (driver's side) like you can with the 90/91s? That would save the chance of messing anything up, PLUS facilitation the removal and installation by a few minutes - especially if it has to be readjusted afterwards...

Paul,

That's nearly exactly what I do. Put a towel on the front tire, then flip plenum over w cable attached. Once back together, I do recheck the TPS voltage

[orthodoct]

If I have to pull plenum again, I will do so but realize that when I pulled plenum, it was first time since new so sort of did a " frame off" restoration of everything. Besides, it ran great for 18 months until yesterday, sat 1 1/2 hours then ok for 40 mile trip home on two lane mountain road. Only residual problem is 2000 rpm idle where it was 1100 or so previously but that is by the tach in the car. I think that it is IAC, but could have a bit of leak past plenum secondary intake butterflies. Probably did too good a job cleaning them. Held up to a bright light with them closed and didn't see any air leakage, but didn't realize until reading on the forum that the grease that I cleaned off was SUPPOSED to be there. Was disappointed to read that. As well as that engine was built, the secondary butterflies on the plenum should be air tight. I can live with an idle of a thousand or so. Runs like a bat out of Hades! Thanks, guys. Will advise once I swap IAC. Got hit with "honey do's" this morning! Great bunch of folks on this forum; glad to be a part of you!
Ty


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[orthodoct]

Hi LGAFF. TPS was first thing that I checked. Sorry about delay getting back to you.
Ty

[orthodoct]

Paul, how do you check TPS voltage? I have good multimeter and can build test cables. I also have the service manual for this car. I've had a ham license since I was 15!
Thanks!
Ty

[Paul Workman]

Paul, how do you check TPS voltage? I have good multimeter and can build test cables. I also have the service manual for this car. I've had a ham license since I was 15!
Thanks!
Ty

A HAM, no less! Welllllll...... Good to know.

My scanner is kaput, or I'd send you a picture of the schematic. But, assuming the wiring is the same on a 90, the TPS gets +5 volts on the gray wire (from the ECM), and the Black wire is GROUND, through the ECM.

The dark blue is connected to the wiper of the rheostat (of the TPS) which should be at 0.4 to 0.45 volts closed (idle).

I don't have a 91 FSM, but in my 90 version the schematic is on page 8A-22-1.


Note: Lee Gaffgan (sp?) or -=Jeff=- or Marc Haibeck can advise you on what to use in case you cleaned the DAC sealant from your TB. (I had it written down somewhere, but can't seem to locate the info, just now...)

____________________________

Now, as for the seal on the secondary throttle plates, they have NO control over the idle. In fact, many of us have removed the secondaries "SPTs" completely. The IDLE is controlled by the THROTTLE BODY; the Idle Air Control, (IAC) module, specifically, AS LONG AS the sealant around the main throttle plates is intact (read: not removed) and the throttle plates are not binding/sicking or there isn't air leaking in from a gasket seal. (Did you check the torque on the plenum? Also, the torque on the IHs need to be checked - but the plenum has to come off to check that. And, is the TB seal in good condition?)

[orthodoct]

Thanks Paul. Yep, afraid so, KC4NWF. Will try to send you a picture of my station. I guess private message is best way.I collect tube type Collins equipment. Have a 105 foot tower in my back yard. Some of it is magnificent equipment. Also restored a 1957 Collins kilowatt AM broadcast transmitter that is 7 feet tall and weighs 1200 pounds that was featured in two national journals. I am an orthopaedic surgeon and my electronics background is all self taught. You know, it's all just having a knack for mechanical stuff, especially orthopaedic surgery!! Yes, I am aware that the secondary butterflies in the injector housings have no effect on idle. I had all of that linkage apart when I cleaned the top end. I know that some of you folks removed the whole system. Mine is still functional. Unfortunately, the sealant around the main throttle plates is what I removed most of and had an oh sh-t moment when I discovered that I wasn't supposed to. There was oil in the plenum from leaky PCV cover and I thought that gunk was from that. That's what I meant when I stated that I was disappointed that the machining tolerances were so poor that they used that gunk. Maybe they had to because the manifold vacuum
is so high. My having removed it probably explains why my resting idle is 1100. If someone can instruct me in what to reapply and how to do it, I would be most grateful. I rebuilt that throttle body but knew better than to remove those staked plates. Rebuilt a couple of Quadrajets in my time and a Holley or two. No light leakage around them with them closed, but probably enough air leakage with the throttle closed with the tremendous vacuum to boost resting idle level from 650 to 1100. Is the resting idle of 1100 detrimental and is it worth the hassle of reapplying the "goop"? Thank you for your help! Look forward to hearing from you!
"73"! ("Best wishes" in ham speak!)
Ty


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[orthodoct]

BTW, yes, all torques were meticulously checked and every fastener that was to receive Loctite did so and I used the correct Loctite per the service manual. I should be able to find the schematic that you mentioned. Thanks again, Paul!


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[orthodoct]

All seals/gaskets replaced at time of rebuild with new ones from Jerry. I was VERY meticulous putting everything back together. Was quite a project. Had everything off including injector housings. Cleaned and repainted everything (including that DAC sealant, unfortunately).PCV cover was leaking, E10 gas had killed my injectors and the valley was a greasy mess. Replaced all injector housing and plenum bolts with new stainless ones from Jerry. Replaced clutch, both clutch hydraulic cylinders, new transmission seals. Installed beam plates. Got to know Bill Boudreau real well and sent him some syringes and other stuff to make his life in the shop easier. Managed to get all but one header bolt in. Took me close to six months in my rare spare time!


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[orthodoct]

Finally got to replace IAC. Dropped idle to 750. Road tested and appears fixed. Would still be interested in DAC fix if you folks don't mind. Thanks!


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[XfireZ51]

Finally got to replace IAC. Dropped idle to 750. Road tested and appears fixed. Would still be interested in DAC fix if you folks don't mind. Thanks!


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I'd put back old One just to verify.

[orthodoct]

I did, idle jumped back up. So far, so good. Short trips for awhile just to make sure!
Thanks!
Ty

[secondchance]

Finally got to replace IAC. Dropped idle to 750. Road tested and appears fixed. Would still be interested in DAC fix if you folks don't mind. Thanks!


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I see no problem with 750 idle. Factory tach is not that accurate anyway. Just as long as idle is around 750 with or without AC, I would be satisfied. I had my idle programmed to 850 to offset lumpy idle due to higher compression and high lift intake cams - My tach says 900.

[orthodoct]

Thanks.

[lfalzarano]

Had the same problem, even after replacing the IAC. I sent the the throttle body to Marc Haibeck for a rebuild. He found some gunk on the engine side of the plates that caused them not to close. It now runs faster and idles like new.


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