96 4.0 idle issue...
 

Evening all...

Ok so... my 96 4.0 XJ has recently developed an idle issue.

Some times it will idle very rough, the rpm drops, feels like it’s going to stall but doesn’t. There a strong fuel smell via the exhaust.

So far I’ve never noticed it when started from cold. Usually after been driving for a short period, sitting at traffic lights. Then when I take off and feed in the gas pedal it hesitates, sometimes a little pop and then takes off normally.

Some times it’s fine. Whilst driving she’s fine, it only occurs at lights or stationary while idling.

Some times it’s be idling rough at lights then with out me doing something it’s like the rpm kicks up and then idles smooth...

So yes it’s full of fuel.
I’ve sprayed the throttle body with cleaner
I’ve sprayed the MAP with airflow cleaner (vac hose & elec plug)
Checked, cleaned the K&N air filter (have the original BIG plastic plenum thingy still, looks good but I’m sure it’s just a big heat soak)
Replaced spark plugs and made sure their gapped correctly.
Oil was replaced recently
And she always has run smooth and cool for me.

It’s my third XJ, so I’m not a newbie, just never had one do this...

So any ideas anyone ?

Any codes coming up?
Have you cleaned your IAC.
Have you checked your O2 sensor.

Cheers,

Honestly no, slipped my mind to check the codes... I’ll check tomorrow...

check for slop in the dizzy shaft.

Ok morning everyone...

Checked the codes...

21**: Oxygen sensor detection neither rich or lean -or-

21**: Oxygen sensor input voltage stayed above normal operating range.

Worth throwing in a new O2 sensor. NTK from Rockauto Is a good option. Sounds like it might be playing up and bouncing around open/closed loop.
Also, as suggested, do check distributor shaft wobble, and always good idea to put a fresh cap and button on. A few years back, mine was hesitating at idle, and that’s all it was..

Hopefully your on the right track...
Cheers,

Thanks Alex, will look into the cap and rotor also.