High idle

[Nick88TC]

Helllllllllo! Welcome to another chapter of fun with an out dated tbird! Heres whats up guys...and gals. Car runs. Has a high idle. When its cold it idles at about 1000RPMS. When its hot, it idles at about 1600RPMS. Now, when its idling high, i can kick it down, literally by tapping the throttle and it will drop down to about 11 or 1200 RPMS. Does that sound like a spring on the throttle body, or a vacuum leak, or what?

[SchoolBoy]

Do you know what your base tps voltage is? And have you checked the tps voltage sweap for dead spots? Have you cleaned your iac? Also there is a water temp sensor in the top of the intake manifold that feeds the ecu info if it goes bad it will cause this as well.

As for vacume leaks, look at the tps, iac and t-body gaskets.

[Nick88TC]

Ah ok. I havent checked any of those things yet, although i did clean the entire TB including the IAC, but i will check. I do know this car had cooling problems, and i still need to replace the heater core. As of right now, it is by passed. The temp sensor doesnt seem to be reliable as of now. It goes up almost immediately to running temperatures when you start it, then it kinda bobs up and down unpredictably as you drive. Might be time for some gauges. I need a boost gauge too. So! Ill probably get to that as soon as possible. My multimeter is junk, so before i get baseline voltage, ill need to buy one. There goes another paycheck! Thanks for the help schoolboy!

[Nick88TC]

Also, is there a particular kind of vacuum tubing recommended if i decided to replumb the vacuum system?

[Haystack]

Any vacuum leak will screw with the idle. Fix those first, then buy a $3 Harbor freight volt meter. Tps voltage isn't critical as long as it is within .6-1.27 volts at idle and 2.5 volts higher then idle to hit wot.

Buy a cheap 12v test light and run codes. The computer will tell you what wrong. For $20 or so you should be able to get it licked.

[SchoolBoy]

There are 3 coolant sensors on the 2.3t motor. The one on the top of the manifold is for the ecu. The one on the bottom of the manifold controls the radiator fan. The last one is just behind the the intake in the block, this one is for your dash gauge.

As for vacume tubing I'd be tempted to run a high quality silicone tube. But I have no idea where to point ya on that.

I'll second the harbor freight volt meter they work fine for simple stuff. Tps voltage is tested with key on, engine off! The range should be .92 with the throttle closed, to less than 5.0 at WOT. Now in rare cases the closed voltage can be set as low as .88 if its being finicky.

As for a boost gauge I like having my autometer on the A-pillar. But if you don't have a boost controller look into the GFB electronic boost controller as it also doubles as a boost gauge and has over boost protection. There is a link in my signature to my install along with the pros and cons.....

[fast4cylNJ]

Any vacuum leak will screw with the idle. Fix those first, then buy a $3 Harbor freight volt meter. Tps voltage isn't critical as long as it is within .6-1.27 volts at idle and 2.5 volts higher then idle to hit wot.

Buy a cheap 12v test light and run codes. The computer will tell you what wrong. For $20 or so you should be able to get it licked.

The TPS voltage on a is critical on a 2.3T. 1.27 volts will cause a high idle condition guaranteed as the computer will read that the throttle is in part throttle operation as soon as it sees voltage of 1v or higher. I've had great results setting the TPS between .93 and .97. I do this with the car running to account for any voltage fluctuations. Prior to final setting the TPS I would do as the others have recommended in addition to setting your base timing with the spout plug removed. You should be golden after this barring any vacuum leaks.

Tommy

[dznj]

If TPS is ok (anything lower than .97 closed), and no dead spots, there are a couple things to check. One is the wiring on the 3 and 4 wire connectors that run from the TPS and IAC across to the passenger side. There are 2 connectors there that can get flakey because they are so close to the turbo (heat cycling). The other is to simply turn down the idle screw with the IAC connected until the idle is 900 RPM or lower. See if that makes any difference. Furthermore, check timing. If you timing is off, it can cause all sorts of idle issues as well.

I just finished chasing a hanging idle in an SVO for quite a while.

Let us know how you make out.

D

[Nick88TC]

Thanks for all the advise guys, havent touched it yet, but as soon as i do, ill post results!

[Haystack]

There are slight varriences in acceptable ranges for tps voltage, but if you don't have a code, but the eec resets tps voltages everything the key is off. Each time a higher value is recorded, that is set as the new "idle" setting and wot is engaged at 2.5 volts or so over idle.

My 86 was sitting as high as 1.25 volts before it threw a code. The new sensor put it at .88 volts and I couldn't tell a difference. No idle adjustment was needed, I swapped it out in the auto zone parking lot.

[Nick88TC]

Well.... the tps gave me a smooth reading all the way thru the range. I replaced it anyway, just for s and g. Didnt help. I cleaned the idle air control valve out real good. Didnt help. I tried to get a reading off the IAC sensor, and i didnt get any reading at all. It says to measure the resistance, and i should be getting something between 7 and 12 ohms. I get nothing at all. Am i doing something wrong, or could my IAC be the problem? Its an 80 dollar part, id rather not throw more parts and money at the car if i dont have to.