2001 Jimny rough idle when warm (suspect misfire)

Hi everyone,

I've owned a 2001 Jimny (soft top, G13BB engine) for a while now (barely had time to use it though due to the COVID pandemic) and I've been struggling with an issue for a while now: once the engine gets warm, it begins to have a rough idle, where the car shudders for a split second, the rpm drops a bit and then drops back to normal. The issue is completely absent when the engine is cold at idle or when the engine is running at higher rpm.

The car didn't have this issue when I bought it, then I had it serviced (oil change, timing belt change, general maintenance etc.) including replacing the spark plugs with some the previous owner had bought but never got the chance to install (Febi Bistein, my mechanic warned me he didn't like the brand) and the issue started to occur shortly afterward.

I first tried to have a look at the sensor at the top back of the engine (replaced it with one from a friend's car) and it didn't help.

Then I had the spark plugs changed again with some NGKs and the issue appeared to be gone. Drove the car for about 300 km (including refueling once) without the issue, Then suddenly, just after I refueled it a 2nd time, the issue was back.

What I plan to try next:

- borrow the spark plug cables from my friend and see if that helps in any way
- try cleaning the throttle

Any other ideas what I could be looking at?


Thanks a lot in advance.

Edit: Bad gasoline on the 2nd refueling seems unlikely, as another Jimny refueled in the same place at the same time and had no issues with it.

Try the idle air control valve in the throttle body, a good clean might help. Chris

Hi,
Yep swap the coil packs as they can be the cause of many running issues then it's clean the IAC valve as Chris states. The IAC stepper valve only comes into play when the engine is warm and can stick.
Good luck
Mike

Took longer than anticipated, but finally got to the bottom of it: it was the coil packs.