So, I've got my 1990 xj with 315k miles on it. Runs smooth, all plugs nice and tan in color, 125-140psi compression, fuel pressure 31psi with regulator/39psi without, refreshed all grounds and connectors, recent cps, o2 sensor, fuel filter, no cat (not required in WA state after 25 yr old), thrush turbo muffler, and recent tuneup. Only 31x10.50 tires. 3.55 gears. Problem is no power! Feels like I have a 4cyl under the hood! My sons 91 with 33" tires and 3.55 gears will run circles around mine! Ive read all of Cruisers tips and am working my way thru them as time allows, but which ones apply to power output? Until I did a compression test, I thought the engine was just old and worn. It really does run great, just really short of power! HELP!

 

Auto or stick?

 

Auto, 242tc.

 

Brakes dragging?

 

I'll double check, but I don't think so. I just finished putting an 8.8 with discs in the back and it was doing the same thing with the 8.25 and drums. Btw, went to 4.88's at the same time and still not to much spunk to it. I don't think it's brakes dragging cause I've put about 2,000 miles on it many on the freeway and not had a problem with hot brakes. I really didn't know how bad it was till I drove my sons and realized how much it was down on power. I know the 91's have the HO and a little more power, but this is like night and day difference. The tranny seems to shift great, fluid is clean, but could it be something in the Trans? Oh, I have updated the cooling system to the later open system also.

 

It's sure not that his is an HO!!

Of my Tips, which have you completed? Most important are 1,3,4, and 5 for you. I would also look at 13.

 

I've done 1, 3, & 4. I'll work on 5 & 13 next. Thanks. When I purchased this Jeep, it had been sitting over a year with water in it from the famous wing window leak. EVERYTHING had mold growing on it! Even the spark plug wires! I ended up having to replace the ecu & cleaning every electrical connection I could find inside the Jeep. I also removed the faulty bendix abs system and replaced with dual diaphragm booster & master cyl. There are still lots of wire connections open from the abs removal. Just to give you a little more background on Ol'Moldy:-)

 

Thanks for the update.

 

Ok, #5 checked out good. I will redo the connections anyway when I clean up/out the abs wiring. Did #13 and seems to help. Feels like 4.5 or 5 cyl now It runs smoother and seems to rev easier to. I didn't get much chance to drive it yet before work interfered Any other ides to try? Seems the timing is at least part of the culprit. I'm thinking of trying seafoam to clean out the cyl head. Any thoughts? I'll post another update when I get a chance to drive it some more.

 

Oh ya, I did check for dragging brakes and they spin freely.

 

You're on your way to success.

I'm impressed with your diligence.

No Seafoam. If you're gonna use anything, get a can of BG 44K and add it to a full tank of fuel. drive until it's at 1/2 tank. Fill to full with gas. Run that tank down to 1/8 tank.

Still got the original injectors in it?

 

Just curious, but does the transmission seem to be shifting correctly? Also +1 on the injectors - not only should you upgrade to Bosch type III 3 holes, they may be really dirty/clogged.

 

As far as I know the injectors are original or at least appear to be factory style. Don't like seafoam huh? I'll try the BG44K. I did use some Toyota fuel injector cleaner a couple of tanks ago. I've had good luck with it in the past but the Jeep didn't respond to it at all. I do want to go to the 4 hole injectors, just wanted to get any problems fixed before I tried upgrades. Which injectors do you reccomend? Also I noticed the down pipe off the manifold looks like it was bent by a angry gorilla with a crow bar! Again I wanna upgrade but only after I eliminate current problems. Does anyone make a mandrel bent replacement for the downpipe? Thanks so much for your help.

 

Actually, stabsthedrama, I've been very happy with the way the tranny shifts. I leave the "power" button on cause I like the firmer shifting. Serviced the Trans after I got it running last year and the fluid was super clean with very little debris on the magnets. Fluid is still very clean with no burnt smell at all. Could be the pervious owner had it rebuilt/replaced at some time. Or just a lot of highway miles.

 

Update;
Put 746 injectors in, thanks Programbo, and it's running a bit better. Starts easier, smoother, and is definitely up to 5cyl status! Lol! Still not where it should be tho. It has good power just at throttle tip in but then just goes flat until ya rev the hell out of it. Even then there isn't much power, just high rpm's. Anymore ideas on this? Think I'm going to replace the down pipe next. Can't be good to have all that restriction at that first, horrible "bend"!