so ive had this problem since ive had the car back from getting a rebuild.

whenever im driving (warmed up or not) and come to a stop the idle would bounce in the 1300rpm-1700 rpm range. sometimes a steady 1500rpm.

now, when i put the car into gear and slip on the clutch to where the rpms drop below 1000rpm will the idle stabilize at that area.

im thinking that my TPS could be out of spec because i think its causing my other problem. my gas mileage is terrible. ive been monitoring it and every tank i average it out from 10mpg to 12mpg and that it is from light driving.

a few other symptoms ive noticed while driving

- accelerating with partial throttle will reward me with hesitations. happens in the higher rpm range.

- on hot starts the car struggles to fire up. never had a time where it hasn't though.

car is a 89 TII with a JDM rebuild with LARGE streetport (approx 3,000mi on the rebuild.)
stock turbo, stock ECU, aftermarket FCD. 750 secondaries, new vacuum hoses.

 

Having the EXACT same issue here my friend. Have adjusted the TPS several times to no avail, I was hoping it was a vacuum issue, I've got silicone hose here I'm gonna replace the whole lot with.

It's strange however that when you engage the clutch it steadies out too, I was unsure as to wtf was causing that with me and finally someone has the same issue so I know it's not just my car. I'm getting my injectors cleaned since I've got leaking injectors but I'm thinking I might need to take a look at the throttle cable since maybe that's causing the problem?

I'm completely stock except for an FCD, exact same issue. Same terrible gas mileage too. If you figure it out, please please PLEASE let me know how you managed to fix it, I've tried everything I can think of and at this stage have resorted to just putting up with it.

Hot starts however are fine. Could it be the FCD causing the problem? Since both of us have FCD and both are having the same issue? What brand is your FCD?

 

I'm gonna guess a stock ECU & LARGE streetport could cause this problem.

 

I don't have a large streetport and I have the exact same issue. I do however have a very large exhaust, hence the need for the FCD. Bad fuel mileage can come from the streetport but the bouncing idle and everything? And considering I have the exact same issues including bad mileage without the large portjob?

I'm thinking it might be an issue with the FCD. OP - What brand is your FCD?

 

im not sure what brand it is at the moment ( my FCD) but ill check it out when i can. i also have a 3" exhaust, forgot to mention that. i know the streetport kills gas mileage but that much?

 

My n/a bridge seems to do that poorly on the highway but I haven't finished a tank on it yet, 1/8ish to go.

 

Get it tuned with some kind of fuel control.

Sounds like a real nice setup.

 

Well, the large port could definately reduce your idle quality and low speed operation. I would look into some engine management. How are you running larger secondaries without it?

 

arrrrghhh!!!

almost exact same problem...no problem starting other than having to give a little gas on a cold start or it will turn over slow down and die...warm start no prob.

the rpms will stay around 1500 until putting the car into gear and then letting it out again. after putting it into neutral it will be back around 800 to 900.

no porting, just a 91 jdm tII swap into the 87 na.

running a freedom ecu tuned (however it could be just needing to be re-tuned)
bigger turbo setup. 3" exhaust straight.

checked the tps. perfect and on target with what its supposed to be.

no vac leaks from what i can tell/hear

one of the only things i can think of was a buddy of mine who said he was having a similar prob with his 86 corolla was the intake was clogged. he said once he cleaned the filter and cleaned the ports up it went back to normal.

 

Exact same problem...kinda. The car will start up idle fine but when it starts to get warm it just idle surges like a MOTHER F. fom 1000- 2200. ITS BAD. i idk whats wrong cannot figure it out. cars all stock oem besides rx7 store down pipe

 

MTRfc: No dice for me there, I just replaced a dead HKS panel filter with an Apex'i panel filter, same problem, although my acceleration has improved now I don't have a crap filter in there. I don't think it's a clogged intake.

I wonder if it could be AFM? Though slipping on the clutch would not stabilize the RPMs out. It's not a slipping clutch since if you drop to neutral it continues to drop and surge back same as it does when in gear, only steadies out and becomes dead on when you engage clutch.

 

same problem i have a all stock 89 n/a, but it only seems to do this when its chilly out, i had posted a thread on a while back and no1 replied.

 

i got the idle prob you are describing, posted about it. i cleaned the TB, and that is it so far, but is was not really dirty. i was surprised at how clean it was...

still need to check hoses.

 

arrrrg! i hope someone is able to figure this thing out...

we all seem to have very similar problems...

the only thing i can really think of would maybe be bad afm? or its going bad? ur guys' ecu are stock? if so than that is one of the only things i can think of that would be left other than a vac leak...but im pretty dang sure that there aren't any on my car.

you guys remove the bac? i put the block off plates on mine and it seems a lot better but that problem we are talking about remains.

 

No I still have BAC here. And pulsation damper, but that's another story.

AFM could be bad but why would slipping on the clutch help that at all? Unless slipping on the clutch forces it open a bit more or something? I have a spare here I should replace it and try it. Also thinking it might be a bad TPS but I don't have a spare one of those around here. Might try to get hold of one since I'm thinking TPS is a definite possibility along with a vac leak. Long weekend coming up next week so will be trying to get the new silicone lines installed I have sitting here, once those are in there aint no way I have a vacuum leak then.

 

what happens if your coolant is low your bac wont register it ...make sure it is toped of

 

I am having the same issue described like everyone else.

Slipping the clutch does decrease my idle back down to an acceptable range (it did, but now it seems to be hit and miss)

I am going to verify TPS adjustment and Fast Idle Cam adjustment later today and see if that can be anything.

 

I have the same problem with the rpms bouncing around between 1,200- 1,600. I replaced my TPS since mine was completely shot and the car runs a lot better but the idle problem still remains. I think maybe cleaning the intake ports and replacing all the vacuum lines should fix it but I'm not sure. I guess I'll have to just wait until I do everything and see. Once I do I'll be sure to post the results on here.

 

If any of you's have the hose off the air pump try plugging it up/covering it with some type of cap. I did this today and my idle stopped bouncing immediately and after driving around for a little while the idle also went back to normal. It's only about 1 or 2 rpms off from where it should be, which for anyone who doesn't know it's supposed to idle at 750 for an N/A.

 

any pics fcsl0ve? im curious on what you're talking about.

 

i have no pics but the air pump has a hose that runs off it and connects to the factory air box. i took the hose off because the air pump is an emissions related part for the cat that i don't need since i'm replacing my entire exhaust system and i have an aftermarket air intake. i had a friend who's also a mechanic take a quick look at the car and he told me to cap the area where the air pump house ran off because it's considered a vacuum leak. so far since then it idles pratically fine.