1. Home
  2. Jeep and Willys (new and old)
  3. 86 Cherokee appears to have one dead cylinder

86 Cherokee appears to have one dead cylinder

Replaced in chronological order: Plugs Ujoints Clutch Master Cylinder Cap Rotor Wires Muffler Catalytic Converter Tailpipe

Prior to doing all of these things, this 4 cylinder 2.5 liter Jeep all of a sudden started running really rough. It obviously needed ujoints, muffler etc., and clutch master in order to drive it at all, and the rest of the stuff I did in an attempt to cure the rough running.

Today after the muffler job, I stopped by a shop and asked for an opinion.

One of the mechs took the time to pull the plug wires off each plug one by one...

Here's what happened:

Forward cylinder: Engine slowed down when wire pulled off plug.

Second cylinder from front: Engine slowed down when wire pulled off plug.

Third cylinder from front: Engine did not slow down at all when wire pulled off plug.

Rear cylinder near firewall: Engine slowed down when wire pulled off plug.

So it looks as though the third cylinder from front is basically doing nothing.

Any ideas on what's up? Mech mentioned valves, piston, and rings.

Reply to
<Skip>
Loading thread data ...

Reply to
L.W.(ßill)

Skip did pass the time by typing:

Correct

Newer and I'd say stuck injector or bad harness, but an

86 is gonna be good ol Mr. Carburetor.

If your piston was holed you would be getting exhaust out the dipstick tube.

Collapsed lifter on the intake side of #3 would do that. If the valve isn't opening fuel isn't goin in.

First up is a compression check across all cylinders. If the compression is low, squirt in some oil and run the test again. If compression picks up it's rings, if not it's valves. I doubt it's the rings, that usually results in a rough condition with lots of blowby and real dirty oil.

Your probably going to have to pull the valve cover and watch as the engine turns. With luck it's just a collapsed lifter. Or maby a broken return spring on the exhaust valve..

Reply to
DougW

Reply to
Steve G

Got the throttle body fuel injection here... Lifter or busted spring sounds plausible... Can I pull the valve cover and not blow oil all over?

Reply to
<Skip>

Is a compression test something I can do or should I just get the shop to do that? And is it ok to drive it in this condition? Bucking a headwind, it struggles to break 60mph, but it's not running hot as far as I can tell. Could hold hand on radiator for about 5 seconds no problem. I drove it about 50 miles roundtrip today for the muffler... May be burning a bit of oil today but not sure since new muffler. (maybe smoking from new muff) Dipstick showed full a few days ago and it hasn't used any oil since last change sometime back It was garaged for about 9 months after the last oil change.

Reply to
<Skip>

Bill you rock, bro... ;o)

Reply to
<Skip>

Reply to
Steve G

No. You'll kill your new cat converter.

Reply to
bllsht

Reply to
Steve G

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.