I've done as much searching as possible on this and I think I need some help. It seems that pressing in the clutch pedal causes the revs to drop slightly while the car is idling. However in some instances while driving when I take the car out of gear and keep the clutch depressed the RPM's will drop straight down to zero. This can happen while coming to a stop or while rolling. It occurs most often when the AC is on but has done the same thing once or twice without the AC.

I have been testing this by coasting while in gear (2nd or 3rd) at about 25 mph with AC on and I clutch in and keep the pedal depressed (doesn't matter if I take the trans out of gear or not) and maybe 2 out of 10 times the RPM's will drop pass the idle point and stall the engine. It is random but is consistent. It's as if the engine isn't able to catch it at the idle point (850-1100 rpm) like it should.

I have checked the following:
1) Clutch switch spring. Spring is intact. I cleaned up and scuffed all metal contact surfaces.
2) TPS. Adjusted TPS to within spec. Also made adjustments to Throttle and AAS to correct idle down to about 850 rpm (was at about 1500 with same symptoms).
3) I bumped the idle from 850 to 1100 and it had no effect on the stalling issue.
4) Tested IAC with 12 volts and there was an audilble click of the solenoid engaging.
5) Similarly while idling with the AC on, turning on the headlights can also stall the engine out.
6) There is a hot start issue. Which is what makes this issue worse. Stalling out is not so bad. Stalling out and not being able to restart while in traffic is something else.
7)Car runs and drives fine otherwise. It is a fresh rebuild (stock with Atkins seals) with about 500 miles on it. The OMP lines are full and I'm sure they should be feeding the injectors by now. I am premixing with Marvel (4oz per tank). There is almost exactly 20 inhg of vacuum while idling and it drops down to about 13/14 with AC engaged (is this normal?).

 

Total shot in the dark but do you hear anything out of the ordinary when you press the clutch in?

My thought was that if the throwout bearing is bad it could put extra load on the engine.

 

No throwout issues. There's no weird noises and it seemed fine when I had it out.

I think it might be the dashpot damper. Mine is too short and doesn't stick out all the way. For a temp fix I drilled a hole and inserted a screw to extend the length that gets me a little bit of damping. It seems when I have it as tight as possible the car only has the issue 1 out of 10 times. To double check I fully disengaged it and it does it 7 out of 10 times.

Interestingly I noticed that the car cuts out only if I rev beyond 4k and allow the revs to drop with the clutch depressed. Anything below that and the idle catches fine. I'm assuming there's more momentum at those higher revs to slam the throttle close.

 

Have you checked the dashpot? A bad dashpot will cause all sorts of problems with stalling, common problem.

Dale

 

Dale - see previous post. Adjusting the dashpot decreases the frequency of this occuring. However now I have a roaming idle. The roaming idle does go away when either the lights or the AC is turned out. There is also a strong fuel smell when it is roaming.

 

@teebeekay did you ever pin point the issue or did you sell the car 😂

 

hrmm...I don't remember what I did but I no longer have this problem. I think I may have gotten a new dashpot and then readjusted my idle.

 

ok groovy thank you very much.