Idle problems when cold

[i8yourfwd]

I've run into yet another issue with my s13. When the motor is cold, the rpm will bounce between 1000 and 1500 rpm, occasionally it'll bounce below 1k and sometimes actually die out. I've had it die out on me at a stop once or twice, and it's died out on a roll, when I shift to neutral, a couple of times. It sounds like the engine is trying to catch the bouncing rpm but it fails to when cold. When the engine is warm and has been running for a while however, it runs just fine, stable idle and everything.

Any ideas on what the issue could be?

[!Zar!]

Psch, I got chu.

[ThunderbaySr20]

bov vented?

[SidewayZ-s14]

Bad TPS maybe?

[hassanbakar123]

whats the tps have to do with the cold.

[reinvent]

I've run into yet another issue with my s13. When the motor is cold, the rpm will bounce between 1000 and 1500 rpm, occasionally it'll bounce below 1k and sometimes actually die out. I've had it die out on me at a stop once or twice, and it's died out on a roll, when I shift to neutral, a couple of times. It sounds like the engine is trying to catch the bouncing rpm but it fails to when cold. When the engine is warm and has been running for a while however, it runs just fine, stable idle and everything.

Any ideas on what the issue could be?

Air Regulator , at least in theory. The air regulator opens when the engine is cold and supplies enough air to boost idle about 500 rpm. What is your normal idle rpm? I guess you could unplug the air regulator to see what that does.

have to reach your hand around back to unplug it. i think you have to remove a staple in the plug. 89/90 is different

[i8yourfwd]

Air Regulator , at least in theory. The air regulator opens when the engine is cold and supplies enough air to boost idle about 500 rpm. What is your normal idle rpm? I guess you could unplug the air regulator to see what that does.

have to reach your hand around back to unplug it. i think you have to remove a staple in the plug. 89/90 is different

http://img178.imageshack.us/img178/2762/rearsideuh0.jpg (http://imageshack.us)
Normal idle rpm when warm is about 700 or so.

I'll check that out, I have a DE so the picture helps. A while ago, my ecu was throwing a CEL that came up as an EGR problem. Could that be causing the idle problems? I guess it could be a possibility, since the egr recirculates the exhaust gas.

[reinvent]

scratch the air regulator idea. Try to trouble shoot the egr issue.

[FaLKoN240]

Have you tried cleaning the AIV?

I do that on all my cars when I buy them usually helps with rough idle problems.

It could also be your coolant temperature sensor, this sounds a lot like the problem I've been having...

[i8yourfwd]

Have you tried cleaning the AIV?

I do that on all my cars when I buy them usually helps with rough idle problems.

It could also be your coolant temperature sensor, this sounds a lot like the problem I've been having...
The CTS is new, how do I clean the AIV?

The CTS was giving me cold start problems, so I replaced it a couple of months ago.

[reinvent]

The CTS is new, how do I clean the AIV?

The CTS was giving me cold start problems, so I replaced it a couple of months ago.

the aiv can send exhaust into the air intake box if the reed valves are warped. you can fix this by simply disconnecting the rubber hose that goes to the air box. allow the aiv to get air from atmosphere.

you can unplug power to solenoid if you think aiv is doing something weird.

the aiv only helps with pollution control during idle. cleaning is easy. just open up . no complicated parts or anything inside.

you can also disconnect the o2 sensor for diagnostics.

[rob_g]

Air Regulator , at least in theory. The air regulator opens when the engine is cold and supplies enough air to boost idle about 500 rpm. What is your normal idle rpm? I guess you could unplug the air regulator to see what that does.



if the air regulator were to be faulty and stuck open, would there be any problems with removing it and blocking off the hose for it and hole on the manifold?

[KiLLeR2001]

When is the last time you changed the water temp sensor?

[NeedCAforS13]

When is the last time you changed the water temp sensor?

The CTS is new.

The CTS was giving me cold start problems, so I replaced it a couple of months ago.

cts = coolant (water) temp sensor. and its new apparently.

[FaLKoN240]

Sounds like I should change the CTS on my daily car if that helped your cold start issues. LOL.

[i8yourfwd]

Sounds like I should change the CTS on my daily car if that helped your cold start issues. LOL.
Yup! Totally fixed my cold start problem. I fix your cold start, you fix my cold idle, okay? :D