tps or not?

lately my 89 has been idleing anywhere from 1500 up to sometimes 3000 rpm. some mornings when i start it it goes right up to 2500 and wont come down, if i shut it down and restart it sometimes it will be ok and other times its not. this sucks, im wasting gas and brakes. what is the problem?

The first two things I'd check are the IAC and then maybe plug off the 3/8" vacuum line on your intake manifold (hold your finger over it) and see if it gets better.
Cleaning the IAC piston off and the seat in the TB, may help and isn't likely to hurt. Don't push or pull on the piston, just let a few drops of oil kind of flow around the edge and behind the piston. Us a piece of plastic or a stick to scrape most of the junk off. Be careful about getting any spray cleaner on the TPS.
The large vacuum line coming off of the intake goes all the way around the engine bay under the battery and ends up at the vacuum canister behind the front bumper (passengers side). The line gets old and cracks or if battery acid has been leaking, rots under the battery tray. It also occasionally pops off of the canister and/or the canister breaks and leaks.

My 1990 (same Renix electronics as yours) has done exactly that twice, each time it was the Throttle Position Sensor. Its on its third TPS now. You can check the TPS with a meter, search for TPS, the procedure was posted not long ago. Cleaning the IAC as above is also a given, and easy to do.

4xBob said:

My 1990 (same Renix electronics as yours) has done exactly that twice, each time it was the Throttle Position Sensor. Its on its third TPS now. You can check the TPS with a meter, search for TPS, the procedure was posted not long ago. Cleaning the IAC as above is also a given, and easy to do.

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Guys, I've seen this problem posted a few times with the 87-90s. Try this: When it is idleing high, are you either 1) able to tap the throttle and it settles, or 2) able to grab the throtle lever at the throtle body and gun it lightly making the idle come back down? If so, let me know, I may have a solution. It took me two years to figure out my problem. I continuously thought it was the TPS or the IAC.

I've had the same problem with my '87 and it does help to tap the throttle a few times. Usually I just let it run for a minute till it comes down to normal idle which is a good idea to begin with. I'll check into the TPS and IAC since they sound like a good place to start

SkylineXJ said:

I've had the same problem with my '87 and it does help to tap the throttle a few times. Usually I just let it run for a minute till it comes down to normal idle which is a good idea to begin with. I'll check into the TPS and IAC since they sound like a good place to start

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Unplug your IAC, then start engine. It should just idle and not rev up like normal. Then shut down, plug it in again, and start. If it revs up then down, it should be working OK. Check TPS for setting. If close, send me a message. I bet it happens more so when warm and not when cold. I have a feeling it isn't the sensors.

Had the same problem for a number of years with my '89 I-6. Problem would come and go...I eventually changed the IAC which did not help. Recently... the racing idle would not go away after warm up or a few days. I decided without checking the TPS to replace it cause it was the original and wires looked a little deformed.

Anyway I had to take the throttle body off because both machine screws broke on the TPS and noticed the T-45 torx bolts holding on the throttle body were not that tight. So to make a long story longer...check your torx bolts holding on the throttle body as they could be touch loose and letting in air where it meets the intake manifold.

AJPULLEY,

Can you describe your potential solution in this thread?

Bender said:

AJPULLEY,

Can you describe your potential solution in this thread?

Click to expand...

My problem turned out to be a misaligned throttle plate. It was just off enough not to feel in the pedal. However, it was enough to let air by, but only when the throttlebody was hot and the metal expanded at different rates. After time, carbon would build up and the high idle would become less pronounced, until I used an aerosol intake cleaner and removed it all.

Air enters at idle, for the Renix throttlebodies, through the IAC port, and a small hole near the 3 o'clock position if you look down at it with the TPS and IAC in the 7 and 5 o'clock positions respectively. To the best of my knowledge, the backstop, adjusted with a tiny allen, is so the throttle plate doesn't rely on closing completely to stop thereby creating a groove in the bore of the opening. I have it set not to allow extra air past the plate, but so the plate doesn't slam against the inner wall of the bore when closing.

Mine now idles perfectly, all the time.

According to Chrylsers' Renix manual, TPSs with a manual transmission should be set so that the output voltage is 17% of the input voltage. TPSs with an automatic transmission should be set so the output voltage (at the four termianal connector) is 83% of the input voltage.

And, TPSs from autos work fine with manuals; I use one.

Hope this helps someone.

I used to have an '87 that the idle would go out of control high.
It turned out that the wires laying on top of the intake manifold were not making good contacts in the connectors.
I pulled the connectors appart, some WD40, connected and disconnected
each connector a few times to clean the contacts, she purred like a kitten.
It is cheap and easy to try nothing to loose.

Mine did the same as yours each time the TPS was out of adj. or bad and x2 Langer on the IAC.

This is good guys. This stuff might help someone out there.

thanks for all the help everyone. i took it to my friends shop yesterday and he took a look at the iac turned it down all the way, still idled too high. long story short, the flap in the tb wasnt closing all the way. bent one piece of metal on the linkage a little, now everything is fine..... no money spent, thats the best of the story!