Noel Caraballo

iTrader: (2)

well i checked everything for vac leaks found nothing. Is it possible it can be the tps. Its a 90 jspec turbo engine. Is there a way to check it and or adjust it. It keeps bouning from 1500 to 2000. Thanks guys

cmanns

is your O2 sensor working right? I have a computer that checks it but I think theres a ghetto way to do it...

Also is your idle set right? Theres a screw on the top of the throttle body that you can adjust for me it adjusted the throttle, I got it 700 on the dot.

1rotaryrocket

Check the cruise control cable going to the throttle body. I just has an s5 that had a faulty unit and it was holding the throttle open and causing a rough up and down idle. I removed the cruise control cable and solved the problem.

Noel Caraballo

iTrader: (2)

o2 is working because i have an air/ fuel gauge installed and it moves from stoich to rich. I removed the cruise, all emissions. I just rebuilt it so i keep the idle at 1200 for right now. If i slowly rev up 1500 and 2000 it bounces between that. Its driving me crazy.

cmanns

prolly your tps then, try adjusting it. Vaccum leak only affects idle as far as I know.

even though its a fresh rebuild it should still idle low, when its fresh you dont want to stress it but let everything seat correctly

Noel Caraballo

iTrader: (2)

ive been trying to search on how to adjust it but i cant find anything but on the s4 style tps. I have the double style one. I saw mazdatrix has a new one for three hundred, YIKES

cmanns

I also herd when they go bad, you need to just replace it..

Go48

iTrader: (7)

Think twice about buying a new TPS to cure your hunting idle problem. I'm troubleshooting the same problem and a new TPS from Mazdatrix ($$$) did not correct the problem. The common belief that if the idle smooths out when you disconnect the TPS the problem is a bad TPS, does not always apply. Good luck with your problem. I will be redoing some of the intake/fuel/MOP work I did that apparently resulted in this problem.

90rx7newbie

i have a 90 fc and it does this idle problem when it hits a cetain point of warming up when i start it in the mornings.then it goes away,its embarasing.people think that i'm doing this myself. yeah right.
when i first got the car,the tps was no good,making the car run bad but it didn't affect the only the driving(throttle response).
i think its a coolant problem going into your throttlebody,maybe an air lock.
i'm trying to figure out this problem myself.
replacing the tps won't fix your problem.
on a honda when this happens(common) its the idle air cintrol valve(iac)not functioning, up around the throttle body,during the warmup period.
saveyour money don't buy the tps,do a little more research,might save you some money.

tarmac_terror

I also have a stock '89 J-Spec engine. I found that I was also having the same problem where the idle would start to bounce between 1.5- 2K, sometimes even up to 3K (and believe me, I can relate to the embarrasment of sitting at the traffic lights and having the car doing that!). Coincidentally, that was about the time that the coolant seal condition took a sharp turn for the worse... At the time though I was playing around a lot with the TPS, but didn't make the situation any better. Maybe try the "bubble test" to see if you're getting combustion products into the coolant...

Having said that though, once I pulled the engine, I did find that the rubber hose that connects to the turbo air exit (vertical pipe) had turned solid over the years and was no longer clamping properly over the turbo, so would have been leaking a fair bit... It's also pretty hard to get access to when the engine is in the car.

Not sure which one was the root of the idle problem for me, but these two things have been known to play with idle in the past... hope it helps.

- TT