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SONNYG 02-21-2012 07:05 PM

Engine races even when hot
Hello everyone
good to be here
my 04 special edition races sometimes even when its all hot. It does not do it all the time. Over the weekend it would not change all of a sudden
then it started running good again
thanks for any info

Frango100 02-22-2012 07:39 AM

Re: Engine races even when hot
First of all, welcome to the garage.
Normally this could be 2 things: or the TPS sensor is the problem, or the throttle body idle air passage is dirty. The last one normally gives a hunting idle, but because its the cheapest of the 2, i would start with the cleaning. Remove the idle air stepper motor from the throttle body and clean it all very well. Be carefull not to twist the stepper motor plunjer.
But also, because of the irregularity of the problem, its more probably the TPS which is causing the problem. If you have a scanner which shows live data, you can monitor the TPS output and see if it is steady or not.

01grand 02-23-2012 08:50 PM

Tps is most likely the culprit, it was doing similar things to me plus it messed with how the transmission shifts because it thinks the throttle is where it isn't.

Forced Induction 04-10-2012 11:12 AM

Re: Engine races even when hot
What is a cost effective scan tool for the WJ that scans in real time? DO they have any that record data also?

I think I have a similar problem. When the truck is warm sometimes the idle hunts for a few minutes before it settles down, and also the trans is constantly hunting it seems anymore. Just driving with cruise on it will sometimes unlock the converter as if to accelerate, then re-lock a few seconds later. It also seems to downshift with very little throttle pressure sometimes. Very strange happenings but maybe it is all related?? Just wanted to get some ideas.

Recently had air intake off while changing spark plugs and the trottle body had a ton of carbon build up behing the butterfly. Didn't take it off to clean it as I didn't have a new gasket or anything, but I'm thinking I should probably clean her up or maybe change it out for a ported Ryan body!! :)

Thanks for the help guys.

Frango100 04-10-2012 04:29 PM

Re: Engine races even when hot
When the idle air passage is dirty, you get a hunting idle. Your problem seems to be more the TPS itself. However its a good idea to clean the throttle body and especially the idle air control stepper motor plunjer and air canal.

01grand 04-11-2012 06:18 AM

I have an actron 9580 scanner, it was 150 on amazon and it reads engine, tranny, and abs codes and it can data log and has a big listing of reported fixes for codes that pop up. Just got it recently so I havent used it much yet but it was one of the few that would tell me why the abs light was on.

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Forced Induction 04-11-2012 11:16 AM

Re: Engine races even when hot
Thanks for the info. I am really looking for real time data and it sounds like this will do the trick. Amazon has it for 160ish now which isn't too bad.

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