Hi everyone,

I have just recently purchased a 2002 tj magna and it's idling around 450-500 and feels like absolute crap after its warmed up and sitting on idle speed. It just feels like its going to stall it's dropping that much.
People have been talking about the base idle screw adjustment but I can't find anything about it online and can't see it for the life of me.
From what I have read it's a last resort measure, but what else can I do to fix it up temporarily. It's booked for a service next Wednesday and it's 10k overdue on the last service, but we need to take it to the beach tomorrow as it's the only reliable car we have.

After any advice possible.

TIA Pat

I had a TS that did that, had to learn left foot braking while keeping the RPM up with the right foot. No fun having the engine stall and loosing power steering while slowing down to turn a corner. lol

Replacing the ISC fixed the problem.

Base idle screw is found on a carby engine, not an EFI engine. The idle is controlled by the ECU via the ISC. ISC dies, you get crap idle.

Replacing the ISC fixed the problem.

Base idle screw is found on a carby engine, not an EFI engine. The idle is controlled by the ECU via the ISC. ISC dies, you get crap idle.

Actually the throttle body on a TJ does have an idle control screw, but as pathamilton1501 was saying it is a last ditch solution to start "screwing" with it. It is set when the vehicle roles off the production line and ideally should only be adjusted by the service department.

My 2002 TJII Sports does the same thing. Replacing the ISC didn't do anything to help.

Adjusting the TPS helped a little (although it still isn't adjusted 100%). I still need to do it properly with a feeler gauge and multi-meter.

The thing that helped my idle the most was installing a new Coolant Temperature Sensor. A guy on eBay is selling genuine ones for $19 delivered as apposed to Mitsubishi's $127. I thought, why not...

It is not called an idle control screw though . . . . it's the "engine speed adjusting screw" and should only be adjusted with everything else operating correctly and in conjunction with the MUT-II tool. (from manual section 13A)

Winding the screw out to increase airflow and thus increase idle works, but you are just creating a second problem to cover up the original problem.

HINT: if you turn this screw, count the turns you move it so that you can put it back where it was later.
And before you ask, yes, I did do this before replacing the ISC on my TS to temporarily increase idle.

Actually the throttle body on a TJ does have an idle control screw, but as pathamilton1501 was saying it is a last ditch solution to start "screwing" with it. It is set when the vehicle roles off the production line and ideally should only be adjusted by the service department.

My 2002 TJII Sports does the same thing. Replacing the ISC didn't do anything to help.

Adjusting the TPS helped a little (although it still isn't adjusted 100%). I still need to do it properly with a feeler gauge and multi-meter.

The thing that helped my idle the most was installing a new Coolant Temperature Sensor. A guy on eBay is selling genuine ones for $19 delivered as apposed to Mitsubishi's $127. I thought, why not...

Thanks both for your input. Is it worth adjusting the idle manually at least until the service next week? Just for comforts sake? Is it going to hurt the car any?

Shouldn't hurt.
Don't expect a "service" to fix it though, unless you specifically mention the problem and ask them to fix it.

It is not called an idle control screw though . . . . it's the "engine speed adjusting screw"...


Tomato...tomato :woot:

Shouldn't hurt.
Don't expect a "service" to fix it though, unless you specifically mention the problem and ask them to fix it.

Yeah I'm not too much, happy to cover it up for a bit until I have the cash to fix the underlying problem as long as its not going to hurt the car any. Going to give it all a good clean out and make sure that's the issue before I start putting cash into it, just need it to behave for tomorrow.