horsepuller
12-11-2002, 03:03 AM
question: can poor compression cause engine stumble at 50 and 60 mph? Have an '88 grand wagoneer with 102K miles, all stock, no upgrades. Ran great until last week. On hwy, while accelerating at around 50 and 60 mph or while going up long hills, engine started to stumble badly. No problem at lower hwy speeds or flat roads or at idle. Started reading this web site and haynes manual and realized there could be many causes, so took to mechanic at local Jeep dealer. He found a bad EGR valve and replaced it, still stumbled at 50 and 60. Fuel and ignition systems checked out good, and he spent some time on the carb. Same with vacuum test. Ran compression test with following results:
cyl/psi
1/150
2/150
3/115
4/150
5/120
6/150
7/135
8/150
Did wet comp. test on #'s 3,5, and 7. #'s 5 and 7 did not increase pressure, #3 did come up. They say it looks like bad rings on #3 and valves on #5 and #7. Roger all that, but does it make sense that the poor compression would be cause of stumble? That's what they think.
cyl/psi
1/150
2/150
3/115
4/150
5/120
6/150
7/135
8/150
Did wet comp. test on #'s 3,5, and 7. #'s 5 and 7 did not increase pressure, #3 did come up. They say it looks like bad rings on #3 and valves on #5 and #7. Roger all that, but does it make sense that the poor compression would be cause of stumble? That's what they think.