Any and all throttle body/IAC/TPS gurus....Please Help!!! Car won't idle..

[Maltman]

Hear is the story:

I think there has been some adjustments made to the throttle position set screw. I FINALLY found out why I couldn't pull anywhere near the ideal 4.8 volts at wot. It seems the set screw was way out and I wasn't able to take full advantage of the butterfly's range of motion.

So......I backed off the screw and readjusted the tps to .42-.44....then I was able to get 4.7 volts at wot. I couldn't back it off anymore since I could feel the plate "rubbing" the tb housing when it closed. So I set it to the point where I couldn't feel anything hitting.

Now, I figured this would put the IAC back in control of idle....but guess what....thing won't idle without my foot attached.

I have a snap-on diagnostic computer hooked up and it says IAC position is at 150 with key on, engine off.....I think I reset the IAC properly (jump A+B, key on, wait, unplug IAC, key off, remove jump, plug in IAC, done)??

Anyway, IAC would not go below 150 when running...if you call this running!

What can I do....or what should I do?

Oh yeah, fuel pressure is around 36-38 psi....rest of setup is in sig.

Thanks,

Mark

sorry about the length, but I thought I better add this:

Car idles if I open the butterfly more with the set screw and adjust tps...however, I lose wot voltage and most likely regain last years problems of lean conditions during wot!

 

[blackbuick87]

When you adjust the IAC screw do the IAC numbers change? You have that thing way out of whack to be at 150. It should be around 10-20. Are you setting it with the engine at operating temperature and in closed loop? You need to get the IAC less then 40 and THEN set the TPS, not vice versa

Dont worry about the WOT tps for now. Mine only goes to 4.4. As long as the throttle blade is all the way open at WOT that is what matters

 

[Maltman]

????

 

[striker_29]

Seems to be a lot of this going around man. I'm trying to figure it out to its a nightmare. Hell, my idle changes when I turn the screw, which seems logical, but they say is not suppose to happen. Go figure.

 

[BoostMasterK]

Bob's right, the idea is to get the IAC's in the right range, then get the TPS set.

Use the IAC setting procedure from Chad's tech menu http://www.geocities.com/rad87gn/tech/tech.html I prefer to warm the car up to operating temperature before trying to set anything- it helps with consistency and burn blisters on your hands are manly.

If you get the IAC and idle TPS right, but still can't get the TPS voltage you want at WOT, you can carefully widen the screw channels of the TPS sensor with a dremel or drill. By getting a little more wiggle room, you can position the TPS at just the right angle to get everything right. I think GMHTP magazine described this trick in the current issue, or you may find it on gnttype.org tech pages.

Hope that helps.

Mike [

 

[Maltman]

I worked on it today and got the iac values between 13-20 when warm....but concerning the wot tps values:

I understand opening up the screw holes to get the voltage, but this won't help if I'm already at the full range of the tb. Now, I can only get about 4.40 mv at wot with iac set right.

How are people getting min. values of 4.60????????

If I set it for that, iac values are high again!

mark

 

[Hawaiian Turbo]

4.40 is good. I'd leave it like that.

 

[Steve Wood]

You have more than enuf wot tps. Waste your time on something that will actually change the performance. Ask your chipmaker how much it needs.

 

[ALBERTAN]

If you must get into the elusive 4.55v-4.85v range, take one half moon retainer off at a time and file down the front curvature that prevents you front pulling the sensor towards the rad support when installed. Use any combination of a vise, dremel, hand file, or my personal favorite a leatherman's tool...its not hard metal. Anyways, knock yourself out and you will soon be able to get the values you are looking for. Or you could walk around the car and pull out the floor mat. Decisions decisions.

 

[Nick Micale]

Originally posted by Maltman
I think there has been some adjustments made to the throttle position set screw. I FINALLY found out why I couldn't pull anywhere near the ideal 4.8 volts at wot. It seems the set screw was way out and I wasn't able to take full advantage of the butterfly's range of motion.

So......I backed off the screw and readjusted the tps to .42-.44....then I was able to get 4.7 volts at wot [/B]

I have tuned and worked on MANY turbo Buicks and have been too lazy [or dumb!] to mess with the IAC!

Most idle problems when I get them are due to someone messing with the base idle screw on the TB. The factory put a cap on it to keep mechanics, and others, from turning it.

First set it to the factory position. That is with one thread showing on the outside. Set TPS. Idle not good, check vacuum or change chip. IAC will set itself.

 

[Scott Atk]

Another possibility that Ive seen before is the Trans. TV cable is so tight that it prevents WOT. Something you might want to check

 

[turbo buicks]

my IAC ALWAYS goes to 150 when i turn the car off and when i get it running that is where the real numbers start coming up. i think its supposed to do that. www.gnttype.org says that it will "lock on" the whatever the highest value was before reching Power Enrichment (PE) mode (i believe). i say set the TPS and the computer will fix the idle like its supposed to. if not it could be your chip or maybe an ECM going out. i try to set my TPS and if i get one end right it will screw up the other end and vice versa. i just set it right for idle and left it b/c you spend more time @ idle than you do @ WOT. if you cant set it by the #'s @ idle try setting it by ear until you think it idles right. always check for vacuum leaks. my EGR hose is in 2 pieces and my car always wants to die.

 

[timothydog]

I'm doing the idle thing now too.
When I switched to my z93 chip it kicked my idle up to about 850-875. Which is a little too high for my taste.

So I went in and tried to set the idle lower but it didn't do anything and now my IAC in road mode/park/idle are 60-70 at least.

Eventually I am going to get a new chip programmed for my car. But this one at least matches my injectors.

 

[BoostMasterK]

Originally posted by timothydog
When I switched to my z93 chip it kicked my idle up to about 850-875. Which is a little too high for my taste.
So I went in and tried to set the idle lower but it didn't do anything and now my IAC in road mode/park/idle are 60-70 at least.

If you have the idle screw even close to right, the chip is controlling the RPM so don't try to adjust it. If you don't like 850rpms, go back to the chip you were using earlier. Get the IAC setup to where you had it with the 13-20 counts warm and the 4.4V WOT. Reset the ECM, learn it and you're 90% fixed. I agree with Nick that once you get this right, you shouldn't need to mess with it again.

Now it sounds like you need to address the "travel" of the throttle blade. Get the up pipe off and watch the throttle blade as someone pegs the gas pedal. If it's not traveling to horizontal, then you have a bind, either (as someone said) the trans cable, floor mats...something. Figure out what's binding it. If it's the trans cable, don't release it more than a click or two at a time and check your shifts between adjustments. 0.2 volts is not much distance of travel.

If the blade is traveling properly, you just need to carefully work the TPS channels as mentioned above.

We've all been there, just take your time and use common sense so you don't create other problems fixing this one.

Good luck.

Mike [

 

[Maltman]

Wellllllll.....I think I got the bugs out!!!

I forgot to clear the ECM after reseting the IAC

After setting the idle screw with the iac in a "fixed" postion (unplugged), I was able to get the car to idle perfect, no stalls, and perfect starts!!!

....thank you all for the help and input!! I appreciate it a ton....sorta like therapy sessions when I feel the need to throw something after working on the car too long with no progress

Mark

....oh....mkazigian...I wasn't having problems with wot obstruction, just when the blade was closed...seems the tolerances are very tight and do not allow you to turn the screw out (closing the blade) past a certain point that I'm willing to bet is different on everyone's car......but thanks for the tip

 

[BoostMasterK]

Eureka

Originally posted by Maltman


Wellllllll.....I think I got the bugs out!!!...After setting the idle screw with the iac in a "fixed" postion (unplugged), I was able to get the car to idle perfect, no stalls, and perfect starts!!!

See now that wasn't so bad, was it?


Mike [

 

[turbo buicks]

well now that you got your problem fixed 2 new ones should pop up right about....NOW. J/K glad to see you go it fixed, i hate when things dont work like they should.