I have an issue I have been challenged with for some time & have replaced a lot of parts & searched many forums - found similar issues, but none where the idle returns to normal. Any input is appreciated.
2004, 4.0, 5 speed, 4.5" rubicon super flex, 4.56 gears, 31" tires, Airaid intake, 62mm throttle body, banks header, no muffler (only the 3 cats), only 79,000 miles (see also - www.DuneToyz.com
Here's the deal -
- start the Jeep in the morning & drive it in town - just fine.
- but at any time, if I get on the freeway for a period of time driving at a set speed, lets say 65, when I stop, my idle is high - 1200rpm - if I get in stop and go traffic, this can be a bit annoying
- but if I get stopped for long enough or at a stop light, the computer auto-corrects & brings the idle back down to normal.
Here is what has been replaced in the last 6 months
- catalytic converters are all new
- I tried another 62mm throttle body
- new TPS and IAC
- new intake/exhaust manifod gasket
- both pre and post o2 sensors
- have not found any vacuum leaks & return to normal idle wouldnt appear typical of a vacuum leak
- I even replaced the crank sensor the other day
The last thing I can think of that I have had issues with before, but it always exhibited power problems, is the fuel pump - I have actually already gone through 3 or 4 fuel pumps in this beast (but while it looks like a baby and I take extremely good care of it, I do run high RPM and use the rev limiter when thrashing around in the dunes) - or maybe a leaking injector?
But in this year Jeep - there is no schrader valve on the fuel rail.... so I am going to have to fab up a loop with a tee with a valve in it - so I can connect an electronic sending unit - I have fuel pressure gague kit so I can monitor real time - just need to get it hooked up.
I have a decent Actron scan tool that can record and chart and stuff - but there doesnt seem anything odd - TPS is at normal position - even when idle is high, of course the MAP changes because of the idle speed, but at normal idle it seems fine, intake temp sensor seems to be reading correctly. o2 sensors seem to have normal readings.
Any suggestions for this phenomenon will be appreciated.