Intermittent 4AGE stalling/ bad idle problem

[Chrisso]

For the stalling problem when the throttle snaps shut, do you have the throttle stop and dashpot underneath it adjusted properly, and is the dashpot spring working, and the restrictor valve on it?

Page 3 or 4 here: http://autoshop101.com/forms/h21.pdf

[RobertoX]

Yeah, I checked this also, pretty sure it is ok as it cushions the throttle when it snaps shut.
The adjustment on it is still in the same position as it was before there was a problem (has a paint mark)
Also I don't think it explains the sudden rough idle when the car has been idling for a while.

I get the car back on the weekend from having a shaken (Jap equivalent of a roadworthy/MOT)... bloody expensive! but anyway, I'll try to see if I learn a bit more then.

By the way, good article there Chrisso

[Chrisso]

No worries. I had similar problems with the intermittent rough idle. I ended up taking of the intake and TB and cleaning all the mating surfaces and resealing with gasket goo. I also readjusted my TPS, throttle stop, and dashpot and it seems to have cured my problems.

On the downside, I wasn't thinking when I put the gasket goo between the plenum and TVIS plate and suspect I've blocked the vacuum line. Have to put my gauge on it and check.

One other thing I noticed is that I appear to have a FWD TB on a RWD intake. The problem is that the PCV port is on the other side of the TB. This presents two problems. First, the PCV isn't venting into the intake, and second, this TB doesn't align with the contours of the plenum and the TB can suck in additional air if this isn't blocked.

However, given you're in Japan, I'm guessing you've got the right TB on the right plenum.

[RobertoX]

Yeah, the PCV is definitely working correctly, as can be seen by the large plumes of smoke after a heavy left hander...
The car is a japan ae86 so manifold /TB etc are all original.

I should confirm the TPS and throttle stop next I guess....

[Dr. Twinky]

Could just be the ECU playing up.

As you are aware, these motors have issues with idle. Fast idle, stalling etc.

You just need to find a medium where the idle is adjusted correctly so it doesn't stall when warm.
That how i fixed mine.

Wait for the car to get to operating temp (Radiator fan turns on) then adjust idle to be around 900-1000rpm. This should fix the issue.
Only thing is fast idle will be around 2000rpm - but hey, all my 4age's have been like this.

Good luck!

[LeeRoy]

You know 'fast idle' is actually their cold start mode, and they're meant to idle that high. 2000 was probably the lowest mine used to idle at when cold, normally closer to 2400.

[Dr. Twinky]

^ I agree.

Very normal.