Car stalls when shifting from N/P to D/R when hot?

[jangell]

This one is a little odd: when the car is cold, everything works fine. I can start it, back out of my space, shift into drive and I'm off.

But when the car is hot, shifting from P/N into D or R will often cause the car to stall.

I believe this is an idle issue of some sort. When hot, the idle will seek between ~600 RPM and ~1300 RPM. If I time it JUST right, (as the RPMs are increasing) I can shift into D or R without stalling. Otherwise, the RPMs drop down to ~500, and then the car dies.

I'm just not sure how to go about diagnosing and fixing this issue. The car is an automatic with Ed Uding's cams and DPI's SPEC I exhaust, and the top of the engine was recently reconditioned (heads skimmed, valves adjusted, etc).

I haven't driven the car too much since the engine overhaul. I thought I had it idling at ~800 RPM, but it doesn't seem to find a stable idle and keeps seeking, although to be honest I haven't just waited around with the car idling to see if it evens out or not.

Thanks!

-- Joe

[David T]

You probably need to bump up the idle a little bit more.
David Teitelbaum




This one is a little odd: when the car is cold, everything works fine. I can start it, back out of my space, shift into drive and I'm off.

But when the car is hot, shifting from P/N into D or R will often cause the car to stall.

I believe this is an idle issue of some sort. When hot, the idle will seek between ~600 RPM and ~1300 RPM. If I time it JUST right, (as the RPMs are increasing) I can shift into D or R without stalling. Otherwise, the RPMs drop down to ~500, and then the car dies.

I'm just not sure how to go about diagnosing and fixing this issue. The car is an automatic with Ed Uding's cams and DPI's SPEC I exhaust, and the top of the engine was recently reconditioned (heads skimmed, valves adjusted, etc).

I haven't driven the car too much since the engine overhaul. I thought I had it idling at ~800 RPM, but it doesn't seem to find a stable idle and keeps seeking, although to be honest I haven't just waited around with the car idling to see if it evens out or not.

Thanks!

-- Joe

[jangell]

You probably need to bump up the idle a little bit more.
David Teitelbaum

So, just turn the curb idle screw a little bit more?

Thanks!

-- Joe

[Bitsyncmaster]

So, just turn the curb idle screw a little bit more?

Thanks!

-- Joe

Do you have a carb or is it still K-jet?

[jangell]

Do you have a carb or is it still K-jet?

K-Jet. I would like to do EFI someday, but there are a few other non-engine things I have to fix up first.

-- Joe

[Elvis]

There are thounds of threads concerning seeking / hunting idle.
Get that fixed and the problem is gone.

most common - mixture is off due to vacuum leak or similar problem.

[David T]

This case is not so simple. He does not have the stock cams. If these custom cams have a lot of overlap you do not get a lot of vacuum at idle and you have a bad quality idle. The general fix is to raise the idle but unless you make modifications to the Idle ECU you can't do it by just turning a screw. The quickest, easiest way to increase the idle is to fool the ECU by messing with the thermistor and making the ECU think the motor is always cold. I would call Ed U and ask him what he recommends.
David Teitelbaum




There are thounds of threads concerning seeking / hunting idle.
Get that fixed and the problem is gone.

most common - mixture is off due to vacuum leak or similar problem.

[Bitsyncmaster]

My new idle ECU has user adjustable idle speed but if your engine is hunting as bad as you say, I don't think the idle speed is your major problem. Have you tried cleaning the idle motor yet?

[Elvis]

Simplest fix is to open the curb screws, at least then you can drive the car
and it's not annoying.

The original ECU can also be easily modified to push idle up, but these are
just band aids to cover the real problem.

My idle once behaved similar. The cover for the mixture screw had fallen off -> big
vacuum leak !

[jangell]

I completely forgot that everyone said to adjust the curb idle screw and adjusted the mixture screw instead, making it slightly richer than before. I've been running it this way for a couple of weeks now and the seeking and stalling problems seem to have completely disappeared. It does idle a little high, though, at around 900-1000 RPMs, but it's a smooth idle and feels fine. I'll have to go back and adjust the curb idle screw instead, and bring the mixture back down again.

Thanks!

-- Joe

[Bitsyncmaster]

Remember, never adjust the mixture to get best idle. Yes you can get great idle stability with a rich mixture but it will kill your MPG and CAT among other things.