So I finally got around to replacing cooling system stuff, like...radiator, water pump, thermostat, radiator and heater hoses, clamps, fan clutch, electric fan, temp sensor, coolant, and radiator cap. Hope I didn't over look anything.

I also replaced the starter, alternator and battery, since everything was exposed and easier to get to with the radiator out. The valve cover gasket and oil pan gasket was done last month. Spark plugs and air filter replaced, oil and filter changed, and tranny/toruque converter had a complete flush service too.

Everything runs great...except I still have this ruff idle thing going on, when I'm in gear and stopped. It seems to run at about 600 rpm and gets a bit ruff. If I gently apply a tad bit of acceleration and bring the idle up to around 700 the idle actually raises up to about 850-900 and it runs really smooth. Even at ruff idle, it accelerates and drives great.

Any suggestions as to what needs replacing? I figure this Jeep has had very minimal service from the previous owner. It's 15 years old and I prefer to just replace what needs to be replaced, without a bunch of guessing. I ust want to get it right.

Thanks!

 

So as far as you know the throttle body and IAC have never been cleaned?

 

You may have disturbed the Engine Coolant Temperature sensor connector or wiring when you replaced the temp sensor.


Do you get a CHECK ENGINE light? Does the CEL bulb work?

 

As far as I know it has not been done. It's an '01

 

No check engine light. I checked the sensor. The idle problem was present before I changed everything I mentioned.

 

Do you think there may be a dead spot in the TPS in the idle range....

 

It feels like it, but I'm not any kind of expert, just don't have enough experience with TPS'. I do know that it idles low and when it does, it idles ruff. Once I increase the idle slightly, maybe 100-200 rpms, then it smooths out right away.

 

Should I just replace the TPS and go from there?

 

Yes, I would say so. Get one from NAPA.

 

I would replace the cam sensor if you haven't already.

 

Whoa...cheap stuff first...

 

Why the cam sensor?

 

They are cheap.

 

Son number four who drives a 2001 xj had a rough idle that became worse and worse and turned into long starts with the rough idle. Finally it just stopped running one day after school and gave a cam sensor code.


Pulled the sensor and sure enough the magnet had come loose and stuck to the shaft. So the hall affects switch was not getting any activation. Put a new one on ($28 at orileys) and it runs like a champ with no more rough idle.


My thoughts are that the magnet had fallen facing down in the sensor but still affected the hall affects switch but was misaligned for awhile making it run rough and then dropped and stack to the shaft causing it to stop running completely. When you take it off you will see what I am talking about.


Also a side note, it cleaned up a lower end noise that we thought for the longest time was lifter noise common with the 4.0. After the new cam sensor, no more noise. My hypothesis is that the hall affect switch must have been worn and giving a slightly erroneous signal to the computer causing some timing variance that caused the lower end noise. My personal xj is a 97 and son two has a 99 and doesn't have this type of ignition or any lifter noise so I feel it was directly related to the signal from the cam sensor since it went away right after changing it. But that's just a guess as I never really put it on a oscilloscope or anything.

 

Veeeery interesting experience for sure. Okay, I'll investigate this. I did manage to get the IAC and throttle body cleaned up nice. I don't have a ruff idle all the time, just after it warms up and I'm sitting at a light. It idles low, around 500-600. When I ease on the accelerator a tad bit and increase the idle about 100-200 rpm's, the idle smooths out perfectly. The thing runs really well otherwise. I wonder if it's not some kind of idle adjustment or ????