VERY high idle

[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]

Originally Posted by 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

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]

Originally Posted by 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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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]

Originally Posted by 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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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.