Basket case

[Poppasmurff]

Ok so here goes, I bought this 1983 CJ7 in UTAH used, its in pretty rough shape, was told it recently had an over-haul on the AMC 258 i6 / 4.2l I6. This thing has almost no wiring under the hood, the oil pressure guage, temp guage and elec. choke is hooked up along with the charging and start system. The HEI distributor is kinda wired in but seams to work. The computer and diagnostic wiring cables are hacked out. Now the problem, the engine ran smooth when i brought it home but seemed to be lacking power and burning alot of fuel. I found 2 vacume ports un-capped so....I capped them. Now the engine surges almost 500 RPM at an idle. I rebuilt the MC2150 carb (has #46 jets), no affect still surges, pulled the plugs, all of them heavily sooted and 3 & 4 broken (huh?!) so replaced them. No change, Removed distributor cap....Rotor FELL OUT!!!!! how?!?!.... Replaced rotor with new and torqued both hold down screws to 7 in lbs. re-installed distributor. Still no change. Surges 500 RPM at idle. Checked all intake and manifold gaskets for leaks. Non found. I'm at a loss here and help would be appreciated!

 

[Torxhead]

Since you state that the plugs are heavily sooted, I would suggest going to smaller jets to lean it out. Since the computer is gone, you could get a wiring schematic to r&r the electrical system.

 

[mtnwhlr]

Hook a vac gauge up and see if you have a steady vac and post how much vac it is running.

 

[Poppasmurff]

Hook a vac gauge up and see if you have a steady vac and post how much vac it is running.

I'm running a MC2150 and there are exactly 3 vac ports and NON of them have any vacuum.

 

[Poppasmurff]

Since you state that the plugs are heavily sooted, I would suggest going to smaller jets to lean it out. Since the computer is gone, you could get a wiring schematic to r&r the electrical system.

Have dropped it down to #46's now. still same affect. have repaired the wiring even factory tach works now!!!!

 

[mtnwhlr]

There is ported vac and nonported vac the ported vac is off the carb above the throttle plates and will show zero at idle. nonported vac is manifold our at the base of the carb that is what you are looking for.

 

[Poppasmurff]

There is ported vac and nonported vac the ported vac is off the carb above the throttle plates and will show zero at idle. nonported vac is manifold our at the base of the carb that is what you are looking for.

Hmmm..... time to pull it off I guess, no vacuum at either unless I revealed it up then the ported line produces 4Hg @ 1400 RPM. I'll check all my passages. Will take a few days it I'll post back and see what I find. Thanks.

 

[Poppasmurff]

Well its been a painfull process but Im stumped. I still have no vacume at either port on my carb unless I rev it over 1200 RPM, and my engine still surges wildly at an idle. Almost stalling then reving to 1000 RPM then back down to 4 or 500 RPM then after a bit it will smooth out idle high 900 RPM (thats where i have it set to run beacause of this ). I've rebuilt this carb 3 times now, traced all my ignition wiring changed plugs cap, rotor, rebuilt the carb, any body got any ideas? Thanks.

 

[007]

As you know, vacuum can leak in more places than ports. I'd replace the vac lines and then test again, then I would try to capture vac pressure at both the carb as well as at the manifold if possible. You can also spray around possible leak areas to help locate them. If there's no leak anywhere, I'd look at fuel supply issues next, followed by some electrical issue in the ignition (voltage drop) causing the issue.

Just some thoughts...

 

[Hedgehog]

While you are at it replace the PCV valve. The bottom needs to breath properly.

 

[mtnwhlr]

I think you need to take a good look at the head for a blown head gasket or valves, rockers,pushrods. Have you done a comp. test or pulled the valve cover for inspection?

 

[Poppasmurff]

I had to pull the valve cover and do the gasket, I checked for bent or overly loose push-rods and rockers, all very sludge crusted but operating correctly, Havn't done a compression check yet (head smack) Ill do that tomorrow afternoon and get back to ya with some numbers. Thanks!!!!

 

[Poppasmurff]

ok so, after being called away to work I finally got home for a few days and did a Compression check, I have 100, 99, 105, 105, 110, 108 from #1 through #6. Its abit out but still shouldn't make it lope like I have a full race cam out of a top fuel car.

 

[Poppasmurff]

Ok so I got it all figured out. Thank you for all your in-put and help. It turnrd out to be a bad 2 stage power valve. The re-build kit doesn't come with one and as they are $28.00 just for the valve I didn't swap it out. I broke down today and got it. Man what a difference. Jeep idles perfectly and runs great. I just need to tune it for the 6800 ft altitude I live at.