1990 4.0 4x4 - Ranger-Forums - The Ultimate Ford Ranger Resource

4.0L OHV & SOHC V6 Tech General discussion of 4.0L OHV and SOHC V6 Ford Ranger engines.

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Old 11-13-2015
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Join Date: Apr 2011
Location: Athol Id.
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1990 4.0 4x4

Lots of miles and runs well. However when it reaches operating temps the idle is very rough to the point that I shift to neutral at lights/stop signs. Tell me what to replace Thanks Old Jim
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Old 11-13-2015
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Probably nothing needs to be replaced.

I would clean the MAF sensor and IAC Valve, either can cause poor engine running after warm up.

Is there a CEL(check engine light) when you first turn on the key?
There should be, and it should go off after a few seconds or when engine starts.
If no CEL then bulb could be bad or system is bad.

If no CEL at all then I would check if there are any trouble codes
You can check the codes yourself have a read here: Ford Ranger - Testing EEC-IV Equipped Engines

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