Fast Idle

[kev62]

I have a 92 Sonoma 2.5L 5 speed standard, and even when i go on a long drive the engine will race when i engage the clutch to slow down at an intersection. It will continue to race even when i pull off on the shoulder and stop. Checked throttle linkage,Vacuum hoses, replaced the air filter, and pvc filter. I also used my code reader which gives me a code 12 only to indicate that everythings ok. Any idea as to what might cause this?

Thanks in advance, Kev

[dtl379]

check tps, idle air valve, and for small vacume leaks

[kev62]

Thanks dtl379, i'll check the items you mentioned, including the possibility that there still could be a vacuum leak.

Kev

[Schrade]

Is the high idle constant, or does it 'lope', like a yo-yo? If it yo-yo's, you've got a vac. leak...

[kev62]

It's a constant fast idle. I bought a GM code reader, but only code 12 flashes in the dash. Could it be in the computer?

[jzimms]

I have the same problem with my pick up. I have not got around to checking the tps but that is what many have told me it is. Mine only does it when I first start it. The fast idle disappears when I engage the clutch and am going down the road. I get this fixed and I should increas my fuel mileage as well.

Joe

[kev62]

Hello jzimms. Mine has the same problem. When i let the clutch out the strain goes on the engine and drive train,but just idling will go forward even on a slight uphill grade. When i push in on the clutch the engine will still race even after warming up. I'm going to blame it on the TPS also.
Regards, Kev

[dtl379]

If you try the TPS, and there is no help, there may be a vacuum leak. We have replaced our TPS, IACV, and more. Our idle prob started after we had the plenum off to check the injection unit. We have found multipule leaks, so this weekend we will tear down the intake again, and replace gaskets. If you think it may be a leak, have it AVAP (or EVAP, im not sure how you spell it) tested. If what we do this weekend doesn't help we are gonna have to.

[kev62]

Thanks dtl379, i'll check those gaskets also for a leak(s).
Much appreciated.

[jzimms]

kev62:
I cleaned my IACV and put it back on the pu and it runs much better. The valve was all carboned up so I used some carb cleaner and doused the thing bout 3 or 4 times. Runs much better now.

[kev62]

Hello, jzimms. Where is it located if you don't mind me asking?
Thanks, Kev Myles

[jzimms]

Originally Posted by jzimms

kev62:
I cleaned my IACV and put it back on the pu and it runs much better. The valve was all carboned up so I used some carb cleaner and doused the thing bout 3 or 4 times. Runs much better now.

Hey, Kev. Sorry for the long delay in responding. I have been out of town and did not get to a computer. It is on the drivers side of the Throttle body. You will need to take off the air cleaner and such. It is like a 32 or 34 mm and it looks as if it will not come out but it does come. There is an electrical terminal hooked directly into it of which you will need to disconnect, sorry I put that in there just for the obvious.

I soaked mine in carb cleaner and sprayed it up really good. It worked for about 1 or 2 days in cutting down the fast idle but it is back to its old ways. I am going to replace the TPS here shortly and let you know what happens.

Sorry again for the delayed response. I am back now and able to help out. I purchased a chiltons manual and it really has helped out. If you need any further help do not hesitate to holler.
Joe Z

[kev62]

Hello again jzimms, thanks for the reply. I'll try and remove it within the next few days to clean it up. I priced the TPS switch here and it costs $55.20 Canadian with taxes at Canadian Tire. Gonna call a few other places to compare prices a little later. They usually don't allow returns on electrical parts around here. Im fortunate in that i found some work and am able to gather up some cash, so i'll probably buy the TPS eventually within the next 2, or 3 weeks. I bought a Haynes Manual on mine when i first bought my truck back in 99. It has saved me a lot of money in repairs, because i maintain it myself anyhow. Please do inform me as to what the results are when you change your TPS sensor.

Best regards, Kev Myles