2000 jeep cherokee 4.0L

[aharrold]

Recently purchased 2000 Jeep Cherokee w/ 4.0L has rough idle. Spark plugs changed, diagnostic shows no problems...any suggestions?

[aharrold]

also, throttle body gas been cleaned, has coil pak instead of wires, rpm's do not seem to vary during rough idle, very noticable when standing by exhaust, runs strong but gas mileage is terrible

[tblack]

Originally Posted by aharrold

also, throttle body gas been cleaned, has coil pak instead of wires, rpm's do not seem to vary during rough idle, very noticable when standing by exhaust, runs strong but gas mileage is terrible

Could be clogged injectors or a bad tps. Try taking somewhere where they can clean the fuel system from the tank to the injectors. If it sucked a valve it could miss a lot, but the 4.0L seems late model. Does it have a lot of miles on it? I always say, assume it's not an internal engine problem first then go from there.

[rksnc]

Checking fuel trim with scanner could lead you as to finding out some problems. Your short term fuel trim should be close to -2 to 2 . Egr could be dirty.