High Idle

[grn93]

Hello there...........just joined the forum, hope you can help me with my problem. I have a 93 Explorer with the 4.0 litre engine, auto tranny. I took the engine down to the block, had the heads hot tanked and a whole new valve train installed after a valve job. Put the truck back together and it fired right up however it idles around 1200 rpm now. When you put it into gear, it revs high for a second then it drops down to about 850 which is about where it should be idleing when in park or neutral. I have tried adjusting the screw on the throttle linkage near the throttle body, checked all my vacuum lines and everything seems fine. Any idea as to why it is idleing so high and how I can set it lower. Thanks.

Ian

 

[Billy177]

i would suspect a vaccum leak but try this first.

Idle Re-learn Procedures


1) Turn off all accessories & disconnect the battery for 5 minutes.

2) Reconnect battery. Disconnect the Idle Speed Control (ISC) solenoid located just behind the throttle body on the drivers side of the upper intake plenum.

3) With the truck in NEUTRAL, run the engine at 2500 rpm for 30 seconds.

4) Let the engine idle for 2 minutes.

5) Put the truck in PARK (or NEUTRAL if manual trans.) and adjust the idle speed stop screw until the idle is at 700rpm.

6) Turn engine off and let sit for 2 minutes then repeat steps 1-5 once.

7) Disconnect battery for 5 minutes then reconnect.

8) Reconnect the Idle Speed Control (ISC) solenoid.

9) Run the engine at idle for 2 minutes.

10) Quickly depress the accelerator pedal to the floor and release it immediately, allowing the engine to return to idle.

11) Lightly depress and release the accelerator allowing the engine to return to idle.

After carefully following the above steps, the engine should now have reset its base idle to factory specifications. The idle should now be smooth and at approximately 700rpm at operating temperature. If this procedure does not correct the fast idle condition, carefully check for vacuum leaks at the throttle body flange gasket and at the intake snorkel to throttle body interface. If no vacuum leaks are detected and the condition still exists, a condition that is unrelated to the mechanical throttle body assembly exists and must be diagnosed and repaired.

 

[grn93]

I'll give it a try and let you know.

Ian

 

[grn93]

Well i tried the procedure and the truck still idles at approx. 1200 rpm. Turning that idle screw on the throttle linkage at the throttle body didn't help either. How would you know if the idle speed control (ISC) solenoid is not working. If I disconnect it while the engine is running..............nothing happens. It was working fine before the motor job so I can't see it now not working. Would a faulty one cause the high idle ? I can't find a vacuum leak anywhere so I'm stumped. Put nearly a thousand dollars into the motor job and now the darn thing's idle is messed up. The truck is uninsured right now so I haven't driven it (other than letting it idle) so could that have something to do with the problem. Perhaps the idle will settle down after a few hours of driving so the computer will "learn" and fix it ? Any help would be appreciated !

Rick

 

[aldive]

A bad thermostat will cause a high idle also.

Good luck .....

 

[grn93]

Put a new thermostat in it when it was apart. After replacing the head gaskets and intake gaskets, putting in new rockers and pushrods, would the TPS setting be altered or need checking. Could that be my problem ?

Ian

 

[grn93]

Anyone ???