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Hot Idle Issues.

Iggy

Well-known member
Joined
May 7, 2015
Messages
50
Location
Ashland. Wi
My car is having issues Idling when warmed up.
When the car is cold it idles from 2000-2500RPM, but from what I understand that's somewhat normal for our cars. Once it's warmed up however Idle makes a drastic change to 5-700RPM and it's usually a rough idle at that. Here's the kicker tho, if it's warm and you rev it up, or you driving along and you put the clutch in, it dies. When I try to re start it while it's still hot it won't start. It will however start if you give it a little gas.then it goes back to rough idle until the next time you rev the engine up. It's also running hotter than it should.
Also, and this may not be related, but it's also a problem. The car will occasionally "chug" or "stammer" at about 4500RPM, it's almost like a rev limiter.
Also I just did a Timing belt job, and replaced the battery. before the T belt job the idle was rough, and low, but it never died. The 4500rpm chug was also present before the T belt job.
 
Last edited:

EfiniX

Well-known member
Joined
Oct 18, 2012
Messages
647
Location
portland, or
That idle is WAY too high for warming up. There's a cold-start bump to the fuel that richens up the mixture, but that's only for cranking and a second or so of initial idle. After that, it should settle down somewhere under 1500 rpm's.

Are you running a key-diver chip? Are you 100% sure you are at 5* base-timing? What sort of ECM control (if any) do you currently have?

Potential causes:
(bad could refer to a bad sensor, or bad wiring)
bad timing
bad ISC
bad CAS
bad ECU (check it for burned up ISC drivers or blow caps. see ECM Tuning for photos of what to look for)
bad engine temp sensor (I've got a youtube video on how crazy the idle can be when this happens)
bad MAF (malfunctions due to heat-soak)
bad clutch wire (if you have a key-diver w/ launch control enabled, a bad clutch wire can ruin your day)
 

EfiniX

Well-known member
Joined
Oct 18, 2012
Messages
647
Location
portland, or
For my $0.02, check the ISC first. And if you haven't before, check your ECU!

click

The ISC driver burning up is common on an ECU that's never been serviced. In fact, a failing ISC can burn up your ECU driver as well, so start here FIRST.
 
Last edited:
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