I have a lumpy idle on my 97 4.0. Feels like a miss. Off idle it runs great. I checked fuel pressure to be 43 psi at idle. Any ideas on a fix?

Thanks,

Flash

 

Idle air control. You need to clean it and the throttle body. Takes fifteen minutes, two cans of throttle body cleaner, and a toothbrush.

 

the aic and throttle body is definitely where i'd start. i used seafoam when cleaning mine (after removing the throttle body). 43 psi seems a little low to me but if it's just the idle then don't worry. throttle position sensor is another part that is notorious for going bad and causing idle problems in chryslers. how long have you had yer ride? how many miles? cheers!!

 

I didnt know it had a TPS (Throttle position sensor). Where is it located?

Thanks for the responses...going to clean the IAC and TB today.

Flash

 

Lumpy idle.......was this guy possibly the previous owner? LOL

 

The TPS is the sensor on the throttle body closest to the motor, it's round. And x2 on using seafoam. Run it through the TB while the motor is running. That alone may fix the issue.

Sent from my iPhone using CherokeeFM

 

Er...scratch that TPS is the sensor in the middle, and it's not round

Sent from my iPhone using CherokeeFM

 

haha I was thinking the same thing

 

Most likely a bad wire. I had the same thing going on in my last cherokee and replacing the bad wire fixed the lumpy idling problem.

 

Has new Bosch plug wires installed...

Flash

 

Look for vacuum leaks, check the plastic line that goes to the MAP sensor if it is firewall mounted, do a compression test and see if any of the cylinders are low on compression. Low compression could mean a burnt valve or worn rings.

 

Before you start getting crazy on valves and vacuums and looking for broken wires...have you given it a tune up lately? Like plugs cap wires filters, etc.? There's literally like 50 things that can cause a rough idle. Start with the simple stuff that you should be doing yearly anyway, then start looking for the odd things.

Sent from my iPhone using CherokeeFM

 

Agreed with Cattyxj, start cheap and work deeper into yer pocketbook from there. The first ? is how mechanically adept are you? Are you able to do the work yourself? Again start cheap...

 

Checking vac lines doesn't cost anything. Full tune-up: $30 minimum. Just sayin'!

 

What could be more simple and cheaper than checking for vacuum leaks? And what is so odd about doing a simple compression test?