Before I open the can of worms.... (1 Viewer)

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Dec 1, 2016
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Utah Valley
Cruiser has 294k miles on it. Hardly drove it this year :( Planning a big trip for next year through the San Juan mtns but might have a bit of a chore for the winter months.

Recently I have noticed more of a vibration while driving. Initially thought it might have been something in the driveline but then it seemed like the beginnings of a misfire (never driven a car with a misfire, just what I suspected). Shop ran a compression test and found 148-150 on all but cylinder #1 which had 110. Before I pull it in the garage and tear the motor out and rebuild the damn thing.... here are the symptoms. Please let me know if you would recommend running any other tests or have ideas as to what else it might be.

The roughness or vibration is only present when accelerating, and gets stronger with speed.
When I let off the gas, it coasts just fine without any roughness.
In neutral, the engine revs smooth.


Please let me know what you think, thanks!
 
Plan to do some more troubleshooting first - rebuild is likely not necessary just yet. Check engine light on? Any codes?

Vibration and roughness - elaborate - does it feel like its drivetrain related or engine related?
 
No check engine light, would the paperclip method show any codes even though the light isnt on?

Initially the roughness felt driveline but is very much engine. I think its been getting slightly worse as time goes on. That being said Ive been wrong before thinking it was one thing and it turned out to be the other... so the only way to truly know is to run more tests I guess.
 
Seems somewhat torque related...so something like a U-joint, axle, or other driveline related thing IMO.

I had similar symptoms in my wifes Mini Countryman of all things....and it was bone dry CV axles.
 
just thinking the same, get it on a lift and start shaking things and tapping joints. You might find your problem.
 
I would inspect your U-joints carefully, I had the same issue at 223,000 miles. Found a small hairline crack in the rear U-joint on the front drive shaft. Replaced all problem solved.
 
No check engine light, would the paperclip method show any codes even though the light isnt on?

Initially the roughness felt driveline but is very much engine. I think its been getting slightly worse as time goes on. That being said Ive been wrong before thinking it was one thing and it turned out to be the other... so the only way to truly know is to run more tests I guess.

Yes, you can have codes and the light not be on. My 93 did anyways. I had no light, used the paper clip and ended up with 2 codes. It was the transmission communication code, apparently common on the early trucks and there computers. It does not cause a rough running engine, for me anyways.

So yes, paper clip it to get your codes...
 
If it revs fine at idle, but you notice a hesitation under load while driving it sounds like a fuel issue to me. Or it could be putting the engine in some kind of limp mode (which is odd there’s no CEL).
 
what condition are the tires?
tires are pretty new, lots of tread. Thought about maybe getting the wheels balanced again and doing an alignment for kicks
I would inspect your U-joints carefully, I had the same issue at 223,000 miles. Found a small hairline crack in the rear U-joint on the front drive shaft. Replaced all problem solved.
I had them re-done last year I think, will check them though good idea.

Yes, you can have codes and the light not be on. My 93 did anyways. I had no light, used the paper clip and ended up with 2 codes. It was the transmission communication code, apparently common on the early trucks and there computers. It does not cause a rough running engine, for me anyways.

So yes, paper clip it to get your codes...
sweet thanks!
If it revs fine at idle, but you notice a hesitation under load while driving it sounds like a fuel issue to me. Or it could be putting the engine in some kind of limp mode (which is odd there’s no CEL).
fuel would make more sense if it ran rough under neutral as well but when in neutral it's smooth as butter
 
Noticed the same with my 80 today on its first extended highway trip haha. It kind of feels "lumpier" the faster I go for me, not sure if it's the same for you.

Good suggestions in this thread, saved me from making one of my own! Interested to see what solves it for you in the end, it'll be at least another week before I can look into mine.
 
If you had a gopro or something you could mount that underneath and try to find any noises, visible movement, etc. while driving.

DM me if you want me to look at it and tell you I'm not sure, in person.

I'm happy to lend a hand if I'm of use.
 
Pulling driveshafts one at a time and then engaging the CDL and driving around can be a good way to help isolate sources of driveline vibrations. My truck exhibited the same symptoms you're describing here before I corrected the rear axle pinion angle after a lift. In your case, since it doesn't sound like you changed anything before encountering these symptoms, that makes me think it might be a bad u-joint, as others have postulated.
 
I had the exact same symptoms with my LX450. One of the front U joints was bad. Replaced and now fine.
Pulling driveshafts one at a time and then engaging the CDL and driving around can be a good way to help isolate sources of driveline vibrations. My truck exhibited the same symptoms you're describing here before I corrected the rear axle pinion angle after a lift. In your case, since it doesn't sound like you changed anything before encountering these symptoms, that makes me think it might be a bad u-joint, as others have postulated.

sounds like im pulling off my front DS tonight. thanks!

What should I do about the low compression on cylinder 1? Just leave it be?
 
What should I do about the low compression on cylinder 1? Just leave it be?

Redo the compression test to confirm valves vs. rings. Add a bit of motor oil to seal the rings better.

Were this a 3FE, I'd say to check the rocker adjustment, make sure you're not leaving the valve open a tad and letting pressure out.

A borescope down the spark plug hole might tell you more about the condition of that cylinder.
 
Low compression can be caused by more than one thing.
It could be rings.
It could be a valve out of clearance.

Proper trouble shooting is the way to find out.
 
A cylinder leak down test can aid in determining where the compression leak at the #1 cylinder is. It’s most likely a bad valve. The low compression in #1 coupled with it being well outside the limit for variance from the other five holes is a problem.

Does it use oil? Do you ever, at any time, see smoke from the tail pipe? Have you compared spark plugs?
 
Uses some oil yeah. Not really any smoke from the tailpipe but it does stink a little. Compared plugs when I pulled the stock ones out (well what was in there when I bought it a few years ago) but they were all pretty trashed. I will pull plugs again and post a pic.
 

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