I've had the car for two days now, and it seems to be dying when I put the clutch in on decellaration. I can watch the tachometer and see the RPM's drop way down, hit bottom, and not come back up. This only happens occasionally, but sometimes it happens two or three times in a row after starting it back up again. Most of the time though, the RPM's drop to about 750 or 500 when I put the clutch in and bounce between that and 1000 until I put it back in gear. Any suggestions?

 

there are a boatload of things that it could be. the easiest thing to check is see if your throttle body is gunked up, then start looking at all the idle contol systems..iac, bacv and such. also is the car turbo? aftermarket flywheel? and are you throwing any codes?

 

Lightweight flywheel, 1989 N/A with a (supposedly) street ported engine.

 

Any comments/suggestions?

Happened tonight on my way home from work as I was pulling onto a cloverleaf offramp, I've decided that it could be fatal if it catches me offguard.

 

dashpot?

 

That was happening to me all the time before my engine blew..... I wouldn't be worried about your engine blowing because of it, just relating! What's your voltmeter looking like? 12 or lower during idle? Check the Alternator, TPS may just be outta calibration / out of spec as well.

 

With my old alternator, it would do this. At night particularly, If I had my headlights, heater and other items on and depressed the clutch it would sputter. If I put on the brakes also, the lights would dim and i would sometimes die.

 

Actually that makes sense, the battery is from mid 2002.

I'll be checking out the alt output and battery output today in my auto class.

 

Well my voltmeter reads just above 12v constantly, I haven't had a chance to check my amp output yet though. FcZero, why did you ask about a lightweight flywheel? How would that be the cause of the problem? (Not being sarcastic, I have a lightweight flywheel and I want to know.)

 

vac leak?

just throwing stuff out there.

 

12v is too low, minimum is around 13 for the alternator to charge the battery, change that alternator out and I am confident that your problem will be solved.

 

yeah is this installed and working properly? its entire purpose is to prevent this kind of thing from happening...

 

a lighter flywheel spins more easily, the heavier stock flywheel is in place to provide rotational momentum. so in your case upon putting in the clutch the engine decelerates and loses momentum too quick for it to recover to "idle rpm" and the engine stops. unless of course the engine dies even when you get back on the throttle, thats a bigger problem.

i think it just might be that flywheel causing your engine to die. Assuming you don't correctly downshift and just let the car idle with clutch in while on the brakes coming to a redlight.

 

I've got a lightened flywheel with no problems though....

 

its incorrect to say its flywheel, it should not die bc of the flywheel, if it does than there was something wrong with your car before and the heavier flywheel just masked it.

 

When coming to a red light I usually just drop into neutral and let the clutch back up, sometimes the car dies even then though. Only did it once tonight, I watched the RPM's drop like a sinking rock as soon as I put the clutch in. Dropped all the way to about 100 then tried to bounce back up to 750 but couldn't do it and fell again, pretty much exactly like Magessty said. Doesn't really bother me in regular downshifts though because I blip the engine up to match the speed of the gear I'm dropping to so it keeps RPM's up, only bothers me when I'm coming to a stop or slowing way down.


Wtheck is a dashpot?

 

The dashpot is part of the throttlebody and its purpose is to slow down the closing of the throttle plates. It's like when you go into some public buildings and the big heavy doors always seem to close themselves gently (closes fast, then slows down before shutting completely) because of the little arm thing at the top of the door.

This is typically removed when you do the throttlebody mod. Do you have a stock throttlebody? Check the fuel and emissions section of the FSM.

 

I'll look into this tomorrow if the weather's good, magessty pretty much described exactly what was happening though w/ his flywheel theory.

 

the point is this--even with a lightweight flywheel, i'm pretty sure a functioning dashpot should keep that from happening.

But also make sure that your AFM is tightly secured to the intake. I had a loose clamp and that made my n/a randomly stall.

 

Will do, thanks for the input!

 

go to a napa or another auto parts store, and they will do a quick diagnostic procedure and be able to determine if it's a problem with the battery, alternator or neither. i just did this last saturday. if nothing else, it will help you rule out possibilities. i found this thread because of you WTB ad, so def. check this before you buy an alt.

btw, i have a LWFW (9.5lbs, about as light as they commonly come), and even with my bad batt, the rpm would never fall much below idle when the clutch was depressed regardless of how high they were to begin. so, based on arghx's description of the dashpot's function, i would check that for sure if your electrical comes back clean.

arghx- is there any way to observe the dashpot's operation from outside the tb? i'm going to check this out on my other car...

 

I had my intake gasket changed about a week ago, trying to fix an extremely high idle and super high emissions, and this problem is pretty much gone.

 

im pertty sure its ur throttle body cuz im having the same problem