tmaxx411 Posted February 7, 2014 Share Posted February 7, 2014 i have an 89 comanche 2.5l with throttle body injection. it has idled high, and rough since i purchased it, and i am at the point i would like to fix why. so i start trying to diagnose it, simple stuff first, spark plug order, and the such. i come to find out that i can pull the spark plugs off both rear plugs, with no change to the motor. so i determined that the spark is getting to the plugs (pulled the leads off while its running and watched it) and there was spark getting to the plugs. i went, and got 4 new plugs, thinking that would fix it, and there was no change. i'm at a loss where to go next. fuel injector? wouldnt that affect all 4 cylinders though? i recently replaced a bunch of the vacuum lines as well, to eliminate some small leaks that were present. compression is 145 across the board, and it drives well enough, just backfires on decel, and has a high, rough idle. Link to comment Share on other sites More sharing options...
tmaxx411 Posted February 7, 2014 Author Share Posted February 7, 2014 also, when fully warmed up, the truck is below the first line on the temp gauge. not sure if its the gauge or the engine itself Link to comment Share on other sites More sharing options...
yxmj Posted February 7, 2014 Share Posted February 7, 2014 I have the same motor and I noticed that compared to my 4 Liters it is grumpy when it is cold......revs high....runs rough......but once warm purrs like a kitten........the rule of thumb that I have taught my wife and kids (all jeep drivers) is that jeeps are happy when all gauges are more or less at 12 o'clock.... ...I think part of the problem might be you are running cold Link to comment Share on other sites More sharing options...
djdr1988 Posted February 7, 2014 Share Posted February 7, 2014 Your thermostat might be stuck open allowing coolant to constantly flow and not heat up the engine to normal operating temp. Try replacing this and see of your temp runs hotter. This may help with the problems. Link to comment Share on other sites More sharing options...
tmaxx411 Posted February 7, 2014 Author Share Posted February 7, 2014 I'm thinking thermostat as well for the coolant issues. its behind the housing for the upper hose correct? also i figured out the crappy running issue.. intake bolts werent tight enough. Link to comment Share on other sites More sharing options...
yxmj Posted February 7, 2014 Share Posted February 7, 2014 I'm thinking thermostat as well for the coolant issues. its behind the housing for the upper hose correct? also i figured out the crappy running issue.. intake bolts werent tight enough. Yes 2 bolts and it is out....put in a 195 Link to comment Share on other sites More sharing options...
cruiser54 Posted February 7, 2014 Share Posted February 7, 2014 As for the poor running, check the intake manifold bolts to be sure they're snug and you're not pulling unmetered air into the engine between the manifold and head. There are also a few hoses below the throttle body that end to crack and leak vacuum badly. Link to comment Share on other sites More sharing options...
tmaxx411 Posted February 7, 2014 Author Share Posted February 7, 2014 thanks. yeah, it was those stupid intake bolts. they were tight, but not tight enough. i'll do a thermostat soon and see if that fixes the cold running problem Link to comment Share on other sites More sharing options...
cruiser54 Posted February 7, 2014 Share Posted February 7, 2014 With it idling, spray throttle body cleaner around the intake to head area and those vacuum lines to see if the vac leaks are gone for sure. Link to comment Share on other sites More sharing options...
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