High idle....

[elwesso]

I know this has sort of been beat to death recently... But i think mine is a little weird...

When I first the car, the idle was about 650 (notch in between 500 and 1000).. the idle was a little rougher than I wanted, so I ran seafoam through the intake, cleaned the TB, MAF, and cleaned contacts on CAS, TPS, and MAF... I even swapped in a different maf...

Now, my idle is around 800-900 (just below 1000).. its pretty smooth and calm, but I dont know why it went up like that... I was reading that the TPS could be bad, or maladjusted.... I dont know why it would just start like that...

Also the coolant temp sensor, but it seems like that makes the car idle around 1200 or so.....

Plenum is VERY clean.....

[Q451990]

It's possible that your cleaning openend the passages enough to increase the idle. Can you back it off with the IAC?

Heath

[DAEDALUS]

An engine's speed is tied primarily to the amount of air it gets. Increase the air (decrease restrictions) and the idle will go up. Cleaning things up was the intent of using the seafoam, so maybe that's a good sign. Not sure if that explains that big a jump, but the other things can be ckecked out easily enough. Have you tried playing with the IAC adjustment?You can back-probe the TPS and coolant sensors. Measure their voltages and compare to the values listed in the FSM. A bad coolant sensor could make the car think it's not warm enough. A bad TPS, not sure if that would affect idle.

[elwesso]

I dont really like playing with the IAC... My old Q had a plastic screw, tihs one has a metal screw and its kinda hard to adjust... I may take off the IAC so I can clean/adjust it... I would assume that it was adjusted properly at T3, when all the work was done.. Could be wrong, Fred took it to some non specialized (but qualified to the job at hand)..... Ill try it... 2.5 turns.....

There is a vacuum line on the intake tube, and just for kicks when i removed it the idle went to where its supposed to be..... So it seems to me like maybe there was a minor air leak before and now theres not? like I connected osmething thats supposed to be hooked up...

I may just put on the coolant temp sensor from my old Q and see if it changes... The resistance values arent too accurate, but i suppose in this case an "ish" is OK....

When the engine cools down, i may take off the IAC...

[DAEDALUS]

If anything, there's a leak now that wasn't there before. More air = more RPM. But if it runs smooth maybe a leak isn't the problem. Can be checked with brake cleaner mist or propane gas, from what I've read recently. Haven't tried that one yet, but if it works, then much better than getting chemicals all over the place. The adjustment made by T3 would have been correct for the engine's condition then to meet the idle speed spec. If you blew off a bunch of crap from your intake valves and the engine's getting more air, then it needs to be adjusted again. You're thinking that if you unhook the temp sensor and the idle doesn't change then that's the problem?

[elwesso]

Well I could try that but i wasnt thinking along those lines... It could just be goofy and give a weird reading

weird thing is the car runs very strong..... Wouldnt seem like its different than usual.....

[elwesso]

I went out and took off the IAC valve... The screw is stuck.. I can throw on hte IAC from my old Q and see what happens.. That way the idle will at least be adjustable.....

[Q45tech]

IAC must be removed and cleaned at least every 60,000 miles as 85% of idle air [whenever throttle is closed or almost so] enters the engine thru IAC........that's a lot of air and dirt and some PCV oil vapor in 4-5 years of idles -----decelerations!!!!!!!Hope this is clear............43,300 grams [95 pounds] of air per hour of idle flows into engine and 90% at idle flows thru IAC.

Luckily after oem filter air is clean to better than 1 part in a million.......dream on no air filter available for a car is 99.999% efficient.

Think how dirty the throttle valve and chamber gets, the IAC gets just as bad but few clean it regularly.

Newer drive by wire have no IAC as the the throttle plate control motor accomplishes the task. and simplifies the mechanical control aspects of TCS at the same time..........with the foot throttle dissassociated from the actual throttle via electronics.

Most - many IAC problems are associated with oil air filters and cones and not changing oem air filters frequently..............worse as the motor ages as more PCV vapors from blowby from rings as the oil vapor kicks back backs up into large hose where IAC gets its air from as PCV flutters and opens and closes!

[elwesso]

I cleaned the IAC last night when I took it off... It was fairly dirty.. But I still cant adjust the screw.....

Id like to get a hold of a 96 IAC, that is non-adjustable... That way in order to achieve a perfect idle Id have to work and fight for it, and not just turn a screw .....

So I guess ill just assume that the IAC is misadjusted (no way other than hooking it up to a consult that would show duty cycle)(or having a scope)... ANd since I cant adjust it, ill get the other IAC and at least make it right.....

I also replaced with a new OEM air filter right after I got the car (I had it ready for my old Q)

[qship96]

Wes,not sure the IAC is any different on the 96q-mine is still factory sealed with a wax plug coating,but the 96 fsm still shows that there is a screw adjustment under this coating that is adjusted if need be by removing this wax-maybe all 90-96 came from the factory sealed by wax,and those who have had idle-speed adjustments and are missing the wax,never knew it was originally factory sealed?

[elwesso]

I read somewhere that the IAC was made non adjustable..... But I guess it wouldnt matter... maybe when they said non adjustable they made it like that.....

[elwesso]

im going to el bump o this thread...

I swapped in my old FPCU, and it doesnt hunt at a hot startup like it used to... That may have helped some..

But what happens is when its so so warm (like when the temp gauge is on its decent up) it idles perfect..... Then you drive it and get it fully hot and it idles at 1000...

What do you think this could be?? im kinda stumped.. I feel like a cheater putting my old IAC on and being able to adjust it... maybe the TPS needs reset??

[Q45tech]

I adjust my IAC at least 3 times per year usually less than 1/2 turn around the 2.5 turns out point as the film builds up under throttle plate. Summer AC and heat vs cold winter no AC. Then before summer I clean the TB [usually only a tiny amount of dirt/PCV/egr back flow when throttle is suddenly closed.

With my high mileage the dirt builds faster but that would be true of 100k also depends on driving style.

You can't use the inside tach as the rpms need to be set within 25 rpms.

[DAEDALUS]

maybe the TPS needs reset??

Measure the voltage at idle. If it matches the range in the manual it's fine. I don't think it'll affect idle much, but while you're poking around in there make sure the idle switch shows closed when the throttle is closed.

[elwesso]

Yesterday I swapped on my IAC. I cleaned it, and adjusted it to 2 turns out. It idled at 1250 RPM

Right now its backed in all the way, and it idles at 1000... I guess that means i have an air leak somewhere. BUt everything looks fine, i cant find anything, and no appreciable air leaks can be found... You would think youd hear a hissing sound

There is a hose near the throttle bodyon the intake, and when i remove it, the idle goes down to where its supposed to be... This is kind of strange...

This is kind of frustrating because I dont know whats causing it to idle high.,..

[elwesso]

el bump O?

Anyone have any ideas?

[rsiwicki]

Wes....

Try this as it dropped the idle on my Q for some reason that still to this day I can't figure it out. My car use to run at 750rpm all the time and then when I tried checking the codes in the ECU for the first time ever in my life by adjusting the screw back and forth the idle all of a sudden dropped down to 600rpms exactly and has remained at 600rpms ever since...even after I switched out the ECU for the JWT ECU it still idles down at this level and it has never idled below 700rpms. The 600rpms is fine with me and it idles smoothly so no problems there....but I still can't figure out why the idle is now at 600rpms. It did this after I did the check and clear all codes procedure. You asked for an idea so here is a wild shot for ya......

btw...going to the 1/4 track tonight for some new ET's :-) but it is so damn warm down here in Miami...high of 79 and low of 70 last couple of days. I was really hoping for low 60's at very least but at least I will be cooler than running last July in the mid 80's and high humidity....will post results late tonight when I return...hoping for 14.45 or so...but not to sure being that it is so damn warm still out.

[elwesso]

Rob

I do konw about that, i think ill give that a try... I mean i got nothing else to do!!

I sent out your package...

Also, i swapped ECUs and it didnt do anything...... One from my old Q...

[squeefoo]

ECU Temp sensor bad? MAF voltage? Check ground straps?I had a Ford truck do all kinds of weird stuff 'cuz the engine ground straps were corroded.(shrugs shoulders)

[squeefoo]

Quote from Elwesso:... Someone helped me out, and with some TLC i was able to fix the idle.....

So of course now you can't leave this thread hanging; as so often happens.

[elwesso]

ACtually I was getting ready to repost but as it turn out I didnt fix it...

So let me get Q45tech-ish on everyone.....

Im fairly sure this has to do with the timing.....

ok so yesterday I called JWT to figure out what was going on... Like they said, I have to jump (the TPS) the center pin and the 5v... which I believe is the right 2 pins..

So I jumped it and adjusted the timing.. When I jumped it, it showed the timing was WAY advanced... so I backed off the timing...

Then when I plugged the TPS conector, it showed the timing was way retarted... BUT the idle was perfect.. The timing was at like 5* or something...

Now the timing is back to 15-17* (where it should be) and its still idling high...

Im thinking ill just live with it.....

[DAEDALUS]

You may indeed have an issue with timing, but if it's where it should be at idle, then it isn't the cause for the high idle.

[elwesso]

I dont understand this...

The car runs great, its ultra fast.. Right now, the mileage doesnt seem to be good... its at half tank and has 97 miles... I did fill the car up while it was running.....

Youd think that if it had a vacuum leak performance would suffer...

[rsiwicki]

Wes....are you trying to blow yourself up??? It is dangerous to fill up a car with gas while it is running.....then again so are my make shift drag strips on the freeway

I think gas mileage is worse always during cold months but damn...97 miles on a half a tank is not going to buy your prom date too much popcorn at the movies.... j/k with ya. Who knows...if I get rid of my car I can sell you my car that may not look the best but sure runs like a hell on fire with a very low idle and no leaks.....

[elwesso]

Fred always did that... I usually dont do that but I have been because its more convenient..... Since the shift lock doesnt work.....

thats about 9MPG, but maybe i didnt fill it up completely... but that was from a highway drive so either way im getting bad mileage... oh well!

I tihnk ive got a decent handle on the leak, i took the plugs out and cleaned them, and made sure they were in there really good... Seems to be better now.....

[DAEDALUS]

The spark plugs?

[elwesso]

PLugs have about 30k on them

The car does idle a little rougher than i like.. All injectors are about 12ohms...

[Q451990]

I assume you've checked to make sure there's the proper amount of slack in the throttle cables? Have the paint marks on those little screws on the throttle body been broken? Hopefully they haven't been adjusted.

Heath

[elwesso]

Yes the throttle cable has plenty of slack... And yes, none of the screws have been tampered with.....

Edit: I think what im gonna do is take it to an independent I know and they can hook it up to the smoke machine to see if there is any vacuum leaks......

[DAEDALUS]

How about an independent with a smoke machine and a Consult?

What's the MAF sensed voltage at idle? If it's higher than it should be then it may not be a vacuum leak...the engine is asking for the extra air in some way. If it's right where it should be then a vacuum leak makes more sense.