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High Idle problem goes away w/o fuel pump Relay..

Rambopants

NAXJA Forum User
Location
VA
My Idle has been shooting to 2,500 on start up and hanging there. Some here posted a realy location for and 88 so i figured its the same as my 87 and began pulling them out. First figured it was the IAC relay but the jeep shuts off when i pull that one out. So i pull the Fuel pump relay and start the jeep and it Idles perfect, put it back in and goes back to 2,500 even with a new relay. Anyone know what this means?
 
I'm guessing the relay you're pulling actually IS the IAC relay. If you pulled the fuel pump relay, it wouldn't run at all.
 
Oh ok, I just read that the 87 and 88 wiring was different and that they are actually backwards in the 88 diagram i was going by, Still not sure what to do about this problem.
 
Try replacing the IAC relay with the one from the fuel pump. If same thing, take out and clean the IAC, but be gentle with it. Couple drops of oil goes a long way.
 
my 88 does it to once in a while disconnect the battery for a minute or 2 and try again usually fixes it, local shop owner and Jeep guru says its the TPS going bad
 
Something we all need to do more often is to carry a volt meter around with us, then when ever the renix decides to idle high, pop the hood and test the TPS idle voltage while the idle is high!!!!!!

Does no good to test a TPS and its ground when it's working! :laugh3:

The last comment about a TPS going bad, key word going, reminded me of this. I have been meaning to post that thought for some time.
 
It won't always be a bad TPS.

Mine did it with 3 different TPS's. One brand new. It's a ghost in the machine, happening at random times, and stopping with equal randomness.

Only one thing is constant - it only occurs on RENIX Jeeps.
 
In some cases it must be some bad (Bill Gates style) program code in the Renix ECU that ignors the CPS engine RPM data in favor of other data. They must have found a way around it because the later years don't have as much high idle trouble as the renix seems too. Or ours are just so old that everything is failing at once and makes it look worse.

Some of the time it is a large vac leak that is just too high for the ICM to control.

Other times it is a sticking ICM, or failure in its wiring and relays to get the message to drop the idle air flow and idle.

Still other times it is a floating ground signal confusing the ECU as to what the TPS voltage (idle) really is. To make matters worse it stores the last few TPS idle voltages in memory and if they were off it acts on that old bad table data right after a repair.

Of course other things like prior owners mods can add to the FUN of the high idle chase!!!:doh:

Perhaps we should start a Renix High Idle fix it as fast as you can contest event for the meets!!!! I have no doubt we could find plenty of volunteers with high idling renix Jeeps, YES?

:clap:

:party:
 
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