Rolling Idle

[JakeM]

hey guys!

about 6 months ago I started having a bit of a rough idle and sometimes when I push in the clutch my RPM's would either spike about 500 or they would stick and not go down.

well finally finished poking around and found 1 vacuum line with a small hole, fixed that. small tear in TB gasket, fixed that. replaced both IAC and TPS. EGR was fualty so I did an EGR delete.

now whilesitting still my car idles perfectly at 1000 RPM's cold, 900 at normal temp. but I still have a rough idle if the clutch is disengaged and im moving(doesn't happen every time though, just most the time). if I just pushed in the clutch either the RPM's jump 500 or they stick at whatever rpm it was at when I pushed it in (just for a few seconds) and then it works its way down to 1500 and usually stays there until I come to a complete stop.

im stumped because wouldn't I still have an idle problem sitting still too?

 

[tmoney20g]

What year car ? If 1g, could be a closed loop problem with the idle stop switch, also your base idle set screw can be adjusted and warm idle should be ~750rpm.

FYI, when you push the clutch in, there's LESS of a load on the motor, it's like double-super neutral. That's why your rpm's jump up 500.

Just sounds like your idle is set too high in the first place, or something is making it higher, like more of the same problems you have already fixed.

 

[JakeM]

What year car ? If 1g, could be a closed loop problem with the idle stop switch, also your base idle set screw can be adjusted and warm idle should be ~750rpm.

FYI, when you push the clutch in, there's LESS of a load on the motor, it's like double-super neutral. That's why your rpm's jump up 500.

Just sounds like your idle is set too high in the first place, or something is making it higher, like more of the same problems you have already fixed.

sorry, its a 1995 eclipse GS, so a 2G

but the thing is im running out of options to check,
checked vacuum lines
used the carb cleaner trick around injectors to check seals
got rid of EGR
replaced IAC and TPS

one thing I did realize was that before I did the EGR delete and when I was messing with the TPS and IAC was that my throttle body was really dirty so I cleaned it (didn't have time to clean intake manifold) and less than a week later I also replaced the TB gasket and it was already really dirty again. is it possible that it is too dirty causing a clog somewhere?

 

[tmoney20g]

It was dirty as in oily? Or physically dirty?

You could also do a boost leak test by pressuring the system to find leaks. I know you don't boost per se, but pressurized leaks are louder than vacuum testing for leaks. It makes it easier to find and diagnose.

 

[JakeM]

It was dirty as in oily? Or physically dirty?

You could also do a boost leak test by pressuring the system to find leaks. I know you don't boost per se, but pressurized leaks are louder than vacuum testing for leaks. It makes it easier to find and diagnose.

like ALOT of carbon buildup

and I will try that when I have time going out of town for thanksgiving.

thanks for the tips

 

[tmoney20g]

Not sure how you'd have carbon on the throttle body, the EGR recircs to the intake manifold, so that'd be past the throttle body, same with the PCV valve. At least that's how the 1g's are.

 

[JakeM]

Not sure how you'd have carbon on the throttle body, the EGR recircs to the intake manifold, so that'd be past the throttle body, same with the PCV valve. At least that's how the 1g's are.

Maybe I have too much back pressure then? On 2g s the pipe that brings it back to the IM is right next to throttle body, but now that I think about it, it shouldn't expanf really it should be sucked back down the engine, I could see how if there was too much back pressure that it would sit around in the IM for a bit

 

[JakeM]

I have a cold air intake and I was wondering if i put the stock air box on if it would fix it, also I don't know if I mentioned this before but I have IAC code but both the IAC and the power connector to it works and now just recently I've been having random lights Pop up on dash, like parking brake light randomly lights up on and off, oil pressure light comes and goes randomly too, is it possible my computer is going bad?