strange idle when first started

when i start my xj it some times will idle at 3k for a few mins then it might idle down or i will have to shut it off
to get it to calm down now the strange part is it only dose this once in a wile most of the time it starts up and idles fine its an 89 4.0 auto if that helps

oh and the reson it is a problem now more then ever is it did this weird idle wile i was sitting on the trail waiting to back down a trail in 4 low
i hit a tree sence the motor over powers the breaks and i couldnt turn the key off fast enough

Does this idle only happen on restart? First part to clean and test would be the IAC. THere are also some posts for the RENIX like yours that talk about a bad vacuum line (I think near the throttle body). If you have an EGR, that could be sticking open too letting too much air in.

I have the same issue but I know what is doing it on mine. In the engine bay on the pass side there is a group of 4 relays, all in a row. There is one that is called "+b latch" relay. This one controls part of the IAC motor. When it does it again open the hood and move the relays around in there spots. Its one of the two middle ones. I am just to lazy to buy a new one to replace mine, so I just hit it abit and it works good for a week or so then I gotta do it again. It may not fix yours but it works on mine.

um no it has happend a few diferent times never on the first start of the day but any other time it has

can i just make a plate to block off the egr or will that make it run rough
im going to replace that relay since it looks like its 20 years old and i have one in the garage already freebie
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thanks for the help ill keep you posted john