Jeep Grand Cherokee V8 trouble

[900ssduke]

I have a 2001 Grand Cherokee V8 at 85,000 miles. On start up, the revs climb to 2000 before taking a good 30 secs to drop down to 1000. It is very erratic at tick over, sometimes dropping to 750 rpm. Its not much better when hot. Intermittantly, at 65 - 70 mph it judders a bit, as if it was transmission snatch but 4 or 5 times in a 10 second period. I had a 4 litre Jeep before this, it did the same thing and was traced to a dickie exhaust probe (oxygen I think). Anybody else had similar problems. Its now in local dealer and they are scratching their heads and seem unprepared to listen to my take on the situation at the moment.
Andy

[chevy-stu]

900ssduke said:

I have a 2001 Grand Cherokee V8 at 85,000 miles. On start up, the revs climb to 2000 before taking a good 30 secs to drop down to 1000. It is very erratic at tick over, sometimes dropping to 750 rpm. Its not much better when hot. Intermittantly, at 65 - 70 mph it judders a bit, as if it was transmission snatch but 4 or 5 times in a 10 second period. I had a 4 litre Jeep before this, it did the same thing and was traced to a dickie exhaust probe (oxygen I think). Anybody else had similar problems. Its now in local dealer and they are scratching their heads and seem unprepared to listen to my take on the situation at the moment.
Andy

I'm not a mechanic, and don't know Jeeps, but it like a sensor issue, my old chevy used to run bad when the lambda sensor and throttle position sensor went awol....

[Trooper2]

Does it run rich when you first start it, can you smell un-burnt fuel at the tailpipe? Has there been a drop in fuel mileage with the other issues? If so then it's most likely one or both of the front O2 sensors have packed it in. It's in the range of mileage for when they go.

[900ssduke]

Thanks for the replies. They are going to try a throttle position sensor, the wee computer is throwing out a fault signal on this. I'm not sure if the fuel economy has dropped, it seems to be a pretty steady 2 buckets per mile. It does not smell of too much petrol out the tailpipe. Hopefully get a new sensor tried out tomorrow, I'll keep you updated. Thanks, regards,Andy

[900ssduke]

New throttle position sensor fitted and alls well. £120 lighter plus the £115 taken off me last week to "reprogram the computer" and give it a wash.