Stuttering/Bad Idle

[CA93Fastback]

I have a 93 Fastback SE 5spd KA24DE. The car has just under 74,000 original miles at the moment.

I am having some idle problems. Until the engine warms up, it idles perfectly - at rest and in motion. I've never noticed a problem. After warmup though, the engine will sputter when decelerating (or while starting, on occasion), but it doesn't do it all the time. When it sputters, the tach goes haywire. About 2/3 of the time, the car will idle between 1150 and 1400 RPM immediately after decelerating (and tach is slow to drop to idle from whatever RPM it was at in gear). Other times, it will be just about right. Then there are the times when it will drop to 500 RPM and just stay there until I'm stopped. It seems to get back to 1K though pretty much always if I let it settle for long enough (w/ A/C on). With the A/C off, it idles in the 700+- 50 normal range (except for the engine sputtering times).

I've had the throttle body cleaned and the fuel system cleaned by a mechanic w/ super concentrated chemicals. He hooked it up to the computer, and NO codes were read.

When it sputters at the start, the RPM's will go up like normal then DROP down to around 500ish (that's when it sputters) before rising to 1200 or 1300, where it seems to be content. When it sputters in motion, the tach will jump from 1K-ish (after depressing clutch at cruising speed) to 1300ish after sputtering.

Basically, it's annoying the heck out of me, so I really want to get this fixed. Any advice would be greatly appreciated. Thank you.

[CA93Fastback]

I'm not sure what that "driving mom's car" business is about, haha, but it's actually my car - I just can't figure out how to edit my profile.

[U12 2NR]

You should hook up a fuel pressure gauge and see whats going on with the fuel pressure when the situation occurs.

Check for vacuum leaks. it sounds as though the idle components are doing something wrong. Check your throttle position sensor, AAC valve. Coolant temperature sensor. Basically with any problem where the answer isn't obvious, you have to go about checking everything and hope you find the problem in the process.

[SingleCamSam]

oops wrong thread.....:pface

[CA93Fastback]

Thanks. I'll letcha know what happens (within next few days).