Birty Dastards Jeep Club

Tech Forum => Workshop => Topic started by: matco on October 25, 2005, 05:55:40 PM

Title: engine running probs
Post by: matco on October 25, 2005, 05:55:40 PM: hi i'm having a few probs with the running on a 98 4.0 tj on startup can be a little rough and hard to start then once warmed up is ok runs smooth a little rough around 2000revs but otherwise ok, then after only a few moments rest ie switching ignition off and coming back restarting(engine still warm) runs ok to 2000rpm then really feels like its holding back on power and miss fires(running really rough!) realeases at 2500 virtually full power and is ok then runs rough for a few miles usually with little throttle feels like going to backfire and power is down, but clears and runs normal really odd! does anyone have any ideas.
the tj also runs on gas perfect!
any help wud be greatly appreciated
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Post by: isle of man on October 25, 2005, 06:14:14 PM: check the co sensor on the exhaust before the cat (the first one) from the down pipe.

peter henry
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Post by: matco on October 25, 2005, 08:39:24 PM: i used a lamda testing tool and it seems to work very well but only tested when engine was running good and not lumpy, will check again

ok have checked lambda again but cant see any problems does anyone else know anythin to try
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Post by: matco on October 31, 2005, 06:26:02 PM: im still having probs
although the lambda seems to test ok can it be an intermitent fault with this and what do you think my next course of action should be?
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Post by: greggmo on October 31, 2005, 06:36:07 PM: have you changed the throttle position sensor? it might be worth a try.
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Post by: isle of man on October 31, 2005, 06:39:27 PM: so you have checked all the obvious things i presume? the fact it's intermitent does point somewhat to the electrical side of the system......may be it is time to book the vehicle at the "stealaship" as you don't want to change anything unecessary......double check the map sensor and interchange if possible......sorry can not be more help.

good luck,
peter henry
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Post by: Anonymous on October 31, 2005, 06:47:34 PM: checked your plugs? Mine does it after idling for a long period, need to change my plugs as I they are fouling up
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Post by: matco on October 31, 2005, 07:25:53 PM: ok will give it a try i managed to pick up a later spec manifold last year which just happened to come with a throttle body and all sensors! all for £50! i knew it wud be worth keeping. will keep u all posted
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Post by: Tug Boat on October 31, 2005, 09:06:52 PM: Hi, here's 2 penath from a 'Newbie', You say it runs perfik on gas, maybe you have some crud or H2o in the tank. Try running some fuel system clean through, it emulsifies it, and also cleans up the injectors. Pick some up from H'fords. I had this trouble a couple of weeks ago, after a fill up in S'port by the way, did this, and also had it booked in, it ran fine most of the time, but when it didn't I could have chucked the keys over the hedge. It then suffered an unrelated flat battery, suppose the re-setting of the PCM must have done the trick cos nothing could be found to contribute to the cause of the trouble at C.andC. Now all is well goes like a good'n.