No cold start high idle (1 Viewer)

[MikeL15]

Hi Mud,

Recently I cleaned my throttle body and associated components on my ‘94 LC after my idle was all over the place. I also did the plugs/wires/etc. as they had not been done in sometime. After putting it all together, my high idle on a cold start (currently 15-20 degrees F in the morning here) no longer exists. RPMs go to about 1600, then immediately fall to around 1000 where as before it would idle at around 1600 and over a few minutes work toward 1000 as it warmed up and eventually settle somewhere around 800 in park. It seems like it is now running very rich at startup, as I can even smell a little gas. Once warmed up, it idles perfectly now. I have driven it a few hundred miles since performing this maintenance, giving time for the computer to recalibrate.

Just wondering if anyone else has experienced this or has any suggestions on what to troubleshoot from here. Thanks!
Mike

 

[Tanner H]

Are your vacuum lines original in that area? Even if you peeled them off carefully, they can cause hairline cracks giving you tiny tiny leaks. The ''larger'' vacuum line going into the top of the throttle body was leaking slightly on mine, giving me the same symptoms you had. while it was idling i could place my ear right up to those cluster of lines and could hear the hiss.

I replaced the line and idle was back to normal after a day or so.


And just in case....did you disconnect your battery for some reason? if so, that will reset the ecu and give you low idle cold starts for a few days.

 

[Vasiliy]

I have the same problem, 2 y past, haven't fixed yet I doubt tiny leak can give this symptoms. Try to found OBD1 scanner and check which command ECU giving for IAC valve

 

[MikeL15]

Thanks for the replies, I will be messing around with it in the next couple of days, I will replace the hose and see if I can get an OBD1 scanner. Ill let you know what I find!

Thanks!

 

[IoN6]

Could also be the Engine Coolant Temp sensor (different from the sensor for the gauge).

 

[MikeL15]

I have replaced the coolant temp sensor and the IAC with a spare, it did not resolve the issue. I have been unable to locate a vacuum leak (if there is one) and replaced a few hoses as a precaution. I pulled the VAF and tested it per the service manual. Everything tested surprisingly perfect. I am kind of at a loss on where to go.

It holds at 1600RPM for approx 1 second, then drops to 1000RPM for another second, before falling to 850RPM and running poorly until warmed up. It is as if the ECU is telling it to do this, but I don’t believe this to be the issue as it started almost immediately after cleaning the throttle body.

Regardless, I’ll post what I find, thanks for any help!

 

[Broski]

I have this exact issue on my 94 obd1. It started out of no ware, Went to start it one day and there was no cold start Hi idle. I have had my mechanic Troubleshoot this to no avail. He's a well respected Toyota Mechanic / Cruiser Head and DD a 80. I well be watching the thread to see what you come up with.
Thanks for posting