Bad Shake at Idle

SBFJ60FIG · 03-17-07, 11:54 AM

Hey all...I just picked up a '97 ZJ with that was left at a repair shop since cost to fix was too high. Very nice guys at the shop and they filled me in on the customer's complaint and what they found.

99K miles, so not too high-

Issue was that at idle the truck shook like crazy-I guess it was really really bad. They took the mini oil pan down and found what looked like some sort of damage to that baffle in the pan.

Had to pull the motor out to access that pan fully (so they said but I bet a pan gasket could be changed in-chassis) and once out they found the baffle wrapped up in the crankshaft. Have any of you ever heard of such a thing?

I'm probably going to freshen up the motor anyway since it is out but am also toying with the possibility of giving it a thorough once-over, replacing leaky gaskets/seals and putting er back in-that is provided I find nothing else to give me reason to think it needs a complete tear-down and rebuild.

Any help would be great and I'll update you all on the progress/what I find.

Thanks!

cam75w/ls1 · 03-17-07, 05:15 PM

Had a motor eat the windage tray but it was from a broken rod(Not a Toyota!)that had pulled it up into the crank...

SBFJ60FIG · 03-17-07, 10:25 PM

All the con rods look good, only problem is that a few of them show signs of wear on the studs from where the baffle got wrapped up in the rotating assembly. Pieces of the baffle are still in the pan and for sure it's chewed up. I'm planning on going ahead and doing a bench rebuild since it's out and looks like it was leaking oil from quite a few places. Should be interesting to see what I find in there.

That motor sure feels scary on the engine stand!

SBFJ60FIG · 03-17-07, 10:28 PM

Also they said it ran fine off-idle. It was just bad at low RPM/idle.

Weird!

cam75w/ls1 · 03-18-07, 07:10 AM

If it ran fine off idle then it could've been a vacuum leak making it misfire, to a cylinder w/ low compression. Once the engine got up to speed then it had enough compression to start running right? I'm just guessing here. I've seen a fuel injector that had a bad spray pattern cause idle issues. Had a Ford F150 w/ a six that came in one time for a motor. I quoted the motor job over the phone and it came in the next week. Two other shops had worked on this truck and both said it needed a motor. I always do a preliminary check on anything that has been diagnosed by someone else. The problem was the truck ran bad and shook like crazy at idle and had zero power. I unhooked the coil wire to keep it from starting and listened to the motor while it cranked. Hmmh, sounded good. Started checking the firing order because I was hearing a little popping in the exhaust and found the problem. Two of the spark plug wires were crossed. Switched them around and it ran great. Called the customer and told him the engine swap was ready and the bill was $85.

SBFJ60FIG · 03-18-07, 08:56 AM

That's great that you checked and saved the dude a ton o $$$$$$. I've spent the earlier part of my life as a service manager for Ford, Toyota and Jeep dealers and not very many guys are too conscientious about their work. That's a good thought though...these guys seemed pretty sharp, but they also pulled the motor to get the oil pan off when the didn't have to (confirmed that last night with the ole Haynes manual) so I suspect no cylinder balance testing would have been done. I think at this point though (motor out) that I'm best off to tear it down. I cannot though fathom why the oil pan baffle would have been sucked up into the crank. I mean I guess the bolts all could have fallen out? It would be pretty amazing if there's no other damage internally. Thanks for the help!