2001 Jeep Cherokee poor gas milage - rough idle

Tiny
JEEPER01
  • MEMBER
  • 2001 JEEP CHEROKEE
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 54,000 MILES
My 4.0 starts fine but after it warms up it idles so rough that the exhaust rattles, also gas milage has gone way down. Engine lt. Says cyl. 3 missfire. I have changed the spark rail. Plugs, and checked injectors. Replaced fuel pump. I have not changed O2 sensors. The drive rod for the oil pump and camshaft position sensor was recently replaced by a shop, so I assume the timing is ok. I took the cat. Converter out and it is ok.
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Saturday, March 7th, 2009 AT 9:13 AM

3 Replies

Tiny
OBXAUTOMEDIC
  • EXPERT
Hello,

Well, to make it easier and so we don't have to spend time searching for the problem the jeeper2001 has could you please post the problem you are having.

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Saturday, March 7th, 2009 AT 9:28 AM
Tiny
BUICKRODGUY88
  • MEMBER
I used to have kinda the same problem it would idle really rough and hitch really bad going down the road had to change the TPS (throttle position Sensor) and the upstream oxygen sensor (the one up before your cat. Converter. Hope I was of some help here.
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Thursday, March 12th, 2009 AT 12:01 AM
Tiny
OBXAUTOMEDIC
  • EXPERT
Ok,

Check for good spark it should be Bluish/White. Check IAC (Idle Air Control Valve), check compression fuel pressure and fuel regulater.
Check for vacuum leaks.

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Saturday, March 14th, 2009 AT 9:49 AM

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