No More High Idle on Cold Start (1 Viewer)

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Have you tested the VAF? That could certainly be causing problems. Its easy enough to verify the resistance of the coolant temp sensor, might be worth doing if its not OEM.

Tested the VAF awhile ago and it appeared to be okay although I would like to find a borrowed unit locally to swap with to rule it out. OEM and aftermarket ECT sensors both tested within 1/10th of an ohm of each other and were within the specified FSM range.
 
Quick update here. I picked up a throttle body off of a '94 complete with IAC and TPS, slapped in an OEM engine coolant temp sensor and made a block off plate for the EGR valve while I was in there. Net result? NO CHANGE. The only component in the startup equation that has not been swapped is the VAF. I suppose I may try that next. I'm reselling any parts I swap on so I'm never out much money during this crusade. That's the one positive. :)
 
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Well, swapped in a VAF. No change. I'm guessing it's wiring at this point. Has to be something easy since no mechanical parts have made a dent in it. If anyone comes across a similar new thread at some point, slide me a PM if you don't mind. I'm not on here that much and would hate to miss it.
 
Damn man, that sucks! You definitely get an A for effort. Make sure to update us when you get it. Gonna start warming up soon though.
 
Ha. Thanks. Warm weather or cold, it still behaves the same. We've had some warm mornings lately and it starts and idles just like it does if it's below zero. Revs up at drops immediately to 650 rpm. Only difference is that it will stumble for a second when it's really cold. I've just learned to accept it but every once in a while I'll still pop the hood and start looking around.
 
Wanted to throw this out there. I've read numerous posts of people unplugging their IAC on a warm engine for testing purposes and their idle remains steady. I unplugged mine the other day and the idle varied wildly, between 2,000 rpm and 600 rpm continually back and forth. Any ideas on this?
 
mine jumped around also don't remember if it was cold or hot engine, Yota master tech told me that's normal and indicated iac is working when plugged back in super smooth. I can go unplug it again and see
 
mine jumped around also don't remember if it was cold or hot engine, Yota master tech told me that's normal and indicated iac is working when plugged back in super smooth. I can go unplug it again and see
 
Dropped it off Friday at a new mechanic I found that is well-versed in OBD1. He's going to have it for a week while we're skiing in Winter Park, CO. Fingers crossed.
 
Ha! The guy didn't even get around to looking at it. Oh, well.
 
I have an idea on this that I've been thinking about....see if you ALWAYS have 12 volts on the BATT terminal on the ecu. Maybe you don't have 12 volts there and the ecu continues to reset. You won't have high idle after reseting the ecu
 
Sorry for the late reply. Not a bad idea. Can you help me out with where that is on the ECU pins? My FSM is currently unavailable. Boo.
 
Well, shoot. Disregard. Looks like I already tested pin2 back on page 4. 12 volts dropping to 10.5 during cranking.
 
Hey. No, I did not, unfortunately. I've gotten used to it as it doesn't affect drivability. In fact, just made a 2,000-mile round-trip to Colorado. Runs perfectly, just no cold start high idle.
 
Definitely share your experience if you'd like.
 
I've had this issue as well and i noticed it right before summer of last year.

It used to start up at around 1300-1400rpm and now it starts up to 1000rpm then it goes down to 650-700 normal operating range.

My number 1 suspect was the coolant temp sensor. I didn't bother going through it as I don't see any negative draw back to its performance as I always warm her up for about 10mins anytime I leave anyways. Not my DD by the way.

What could be the worst case scenario if you let it run that way?
 
This thread looks like it may be useful to me, as I have experienced a high idle now as well in cold weather. Only happened twice so far, but high idle as usual at startup, then it idles down to 600 or so, but then after driving it a little ways the idle jumps back up to almost 2k. Hasn't happened every time, but it has happened. Going to start by checking throttle cable for proper free play and grease them up good, hoping its just sticking.

I may need to review this thread later though!

Hope you solve this issue @harrydunn
 
I've had this issue as well and i noticed it right before summer of last year.

It used to start up at around 1300-1400rpm and now it starts up to 1000rpm then it goes down to 650-700 normal operating range.

My number 1 suspect was the coolant temp sensor. I didn't bother going through it as I don't see any negative draw back to its performance as I always warm her up for about 10mins anytime I leave anyways. Not my DD by the way.

What could be the worst case scenario if you let it run that way?

Yah, the coolant temp sensor made logical sense to me but that was not the problem. I wonder if I have a small intake leak that seals up as the engine warms. I would think that would cause a higher idle though on cold startup.
 

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