Fingers

Hey guys... plz help... i've checked the error codes, got the O2 sensor... changed it... no more error codes... idle still bounces. checked for vacuum leaks with starter fluid... nothing... checked the vacuum pressure with a gauge and it was 9 (forgot the scale, but i know it's a good number to see)... replaced the catalytic converters with a bonez high flow (unrelated, but thought i'd let you guys know). Anyways, the idle bounces pretty terribly... like... one time i can stop at a red light, the idle will be 1000 and steady. 10 seconds later, it will bounce from 500 to 1200 ... and so forth... ANY IDEAS!?!?!? I've recently had an engine rebuild too. it was like that before and after rebuild.

HAILERS

Go to the factory manual online. Set the timing, Set the idle to 750 with the initial set coupler installed. Set the tps with the engine HOT.

gold87na

yesterday mine did the idle jump from 500-1100rpms for the first time. As it was doing it I poped the hood and ajusted the idle. When I lowered the idle (about 1/4 turn) it went away. I don't know for sure if this would help you but it worked for me.

Fingers

I tried adjusting the idle, but obviously, i did not do it correctly. Also tried setting the TPS
BAAAAHHHHH!!!!!
Could someone describe in detail on how to set the timing and the idle properly?! I believe the tps is set perfectly since i got exactly 1 volt at idle, and approx 4.7 at WOT

HAILERS

Try going here where I posted some jpg out of the manual: https://www.rx7club.com/forum/showth...threadid=74531 Sounds like the tps is just fine, IF it was set while the engine was HOT. Probably was, but just in case I thought I'd mention it.

Fingers

Great, thanks hailers... i'll try that tonight and see how it goes.

Fingers

Oh yes, i thought i'd mention this... 750 RPM on that idle adjust screw was the LOWEST it would go. I mean, that screw had to be tightened ALL The way in order for the RPM to be set at 750. Friggin weird. Could that be a result of the idle mixture screw too?

asherwood

By reading the posts about the ports I surmize that you have a '86-88'? I'm trying to cure the same problem on my '91...

You mentioned the transistor in the ECU, how'd you know it was bad and what did you replace it with?

I'd swear that although the BAC in my car seem to check out, there is no effect on the idle by disconnecting it or compensation when I add load to the engine when the barkes are applied, the result is that the idle drops and bounces betweem 600-800RPM

I'll be following this post for ideas on what to check on mine...

HAILERS

Fingers, the idle mixture screw could be part of the problem. Hard to say. It could also be the throttle stop screw on the front of the throttle body has been played with. Tiny screw with a jamnut of 8mm size on top of it. Its possible that screw is holding the secondary throttle plate open a touch. Could be ............a lot of things. Even the primary throttle plates could be cracked open a touch. When the fast idle and thermowax are set initially, the primary throttle plate is set at something like 17-20 thou with a relatively cold thermowax. When the engine heats up and the roller falls off the fast idle cam, that 17-20 isn't that anymore. More like nothing. 'Anyway, Asherwood, I had N332 ECU for a turbo . Well I noticed the bac was not doing anything for me when a load was put on the engine. In fact it was not doing anything at idle when I took the plug off the bac. I had read a site http://www.teamfc3s.org/info/articles/idle.html that detailed how to determine if the bac is any good and if the transistor in the ECU is burnt up. The article is for a turbo, but a bac is a bac is a bac, more or less. I did not do everything in the article because I had a spare ecu that I patched in to prove the problem was the first ecu. I went to Radio Shack to get the part for about a buck fifty and with minimal soldering skills, fixed the bad bac. Take a look at that article. Maybe it will help.

HAILERS

Fingers, since the extra high idle could be several things, you might get a can of starter fluid and spray aroung the inlet areas to see if you have a vac leak. If you spray and the idle picks up you have a leak at that spot. About the only slightly dangerous thing with starter fluid, is to make sure you don't pour a constant spray directly into the inlet. As in full blast. The engine will kinda ping and rattle if you go hog wild like that. But just spraying at joints and mating points of the intake won't harm squat. Don't spray directly into the altenator either.

HAILERS

Fingers, another thing that would cause that high idle would be if the timing was advanced more than the factory setting. You really need to get a timing lite and set the timing spot on. Don't try to set the timing if you can't get the idle below 1000 because the ecu starts advancing the timing around that rpm, give or take. I trust you have a normal car and are not going to write back sometime later telling us how you have some monster porting job on the engine that you forgot to tell us about, and still can't get the idle down.

asherwood

Thanks!

Fingers

Nope :P no porting job. Sorry i didnt get a chance to try it last night. It snowed like a ************ up here in ottawa. I have to get my shovel out.
Thanks guys
-Ross

Fingers

Hey guys, I think my problem is fixed. I tried that idle mixture screw, and set my idle properly. It was still bouncing... so i started playing around with various valves and whatnot. I found this one on the top of the throttle body. It looks like a small flathead screw, with a 8mm nut holding it in place. I adjusted that screw to the optimal setting and BINGO!!! IT FIXED IT!!!!!!!!!!!! so thanks for all your help guys. Much thanks to Hailers!!

Fingers

Also, my car seems to start up quite nicely now (doesnt go to 2.5K right away)
Could anyone explain what this screw does? (non turbo, i think you guys know what i'm talking about)

AKABILLY

How does porting affect idle? The reason I ask is my '91 has a Mild Street port. Should I be setting mine differently than you would on a stock?

Fingers

anyone know what this screw does?