97/98 2.5 petrol Sport - lumpy running

[Rocket_88]

My 2.5 petrol Cherokee Sport has done a little over 30,000 miles. It always starts without a problem, hot or cold; it stops cleanly and accelerates well. To all intents and purposes, there's nothing wrong with it... except that while accelerating, cruising or on the over-run there's a slight lumpiness to the running that is best described as an intermittent misfire.

It's been the same in all the time I've owned it (approx 3 years/5000 miles) and never got any better or worse. It had a full service shortly after I bought it but that made no difference. It occurs to me that this might just be the way this engine runs but if anybody's had a similar experience and managed to resolve it, I'd be grateful for some advice.

Regards
John

[LittleHoov]

What all was done in the full service? My first thought would be to replace the distributor cap and rotor, as well as plugs and wires.

It sounds like you have a miss condition under heavy load/low rpms, such as chugging up a hill. Which is usually an ignition issue.

[Rocket_88]

Thanks for taking the trouble to reply.

My first thought was the ignition system but foolishly, perhaps, assumed that the garage who had been asked to investigate the condition when servicing would have checked those components and replaced as necessary.

Before parting with any cash, I posted just in case somebody would leap in to say that it's some known condition peculiar to the 2.5 Sport. As it is, I'll take your advice and replace the ignition consumables.

Thanks again

John

[LittleHoov]

I don't know of any condition like that, but I'm not overly familiar with Jeeps in general. I just so happen to have one.

All Im saying is, that unless you know for a fact the shop replaced those things, that would be where Id start.

[fredjacksonsan]

My thinking is the same; these engines are recommended to have spark plug changes every 30000 miles, regardless of apparent condition. Cap and rotor should be on the same schedule. I know when I had my 97 Wrangler with the 2.5 it ran much more smoothly after changing those parts.

Post back once you get them done and let us know how it's running.