code 76 on my '94.

[winterbeater]

you're right. i don't have the tools to check compression, the jeep has normal power when i mash down on the gas, i've drove plenty of xj's and this 4.0 has the same power as any other renix or H.O. also the throttle is very responsive, if it was a compression problem i would expect to notice it being sluggish or smoking.

should i check compression in spite of the motor running like a top?

i had a 2.8v6 xj 4 years ago so i do know how a motor drives when compression is less than great, that jeep was a "check the gas and add some oil" kind of jeep.

I would. Running rich and burning oil are pretty hard to distinguish between. It's not like compression testers are hard to borrow or expensive. And if you're pulling plugs to clean them anyway, you're doing most of the work. I am not sure that I would agree that your motor is running like a top.

 

[joe_peters]

Hey joe, i read somewhere that i bad pcv valve could cause carbon build up. you know anything about that??

hope everyone had a good safe 4th of july...

i blew up 2 5 gallon buckets, each one into atleast 15 pieces!

Well, I would expect oil in the air filter, valve cover and possibly front and rear main seals to leak oil from a clogged CCV system (I don't think any XJs came from the factory with the PCV type system). That said, easy enough to check--filtered air intake from air box to front of valve cover, should be open, clean, dry. Rear of valve cover should be going to the intake manifold through a vacuum port, just make sure it is all clear and flowing.

I would expect the plugs to be wet rather than dry fluffy (what a word!) carbon from a too rich condition.

 

[$700later]

hmm. thats a lot of food for thought. well for starters i guess i'll sea foam it and pick up a iac. i only know one friend with a compression tester, he's in the netherlands right now, so i'll wait for him to get back.

also, when i took the iac out, it was extended, when i check prices online the pictures show them closed up. not sure if that means anything or not, just thought i'd share! :variety:

 

[winterbeater]

IAC won't cause carbon build up. You can probably buy a compression tester for the price of seafoam. Harbor Freight has one online (get the threaded on, not the rubber bushing for the spark plug hole). Don't you have an auto parts chain where you can borrow one or rent it cheap?

 

[$700later]

i'm not worried about the iac causing carbon build up, i'm worried about it not letting any air in.

and if i rented the compression tester today and it gave me some bad news, well i wouldn't be able to afford to do anything about it for another week or 2. my buddy will be back by then, we usually team up on each others cars and work on them together so i really don't mind waiting for him, his family is nothing but mechanics anyway so its a good excuse to go shoot the bull with them.

 

[$700later]

sea foamed it today, i didn't really notice a difference in how it drove after doing that but i'm sure it helped. cruised around, went to pizza hut, and some mild trail riding, all of that adds up to 48 miles!

still idling pretty low and still hits the rev limiter at 3900.

it drives well so i'm pretty happy. i'll continue to tinker with it.

thanks for the help.

 

[$700later]

oh and i haven't checked the mpg but i only put 5 gallons in her and it still isn't on empty so it isn't guzzling the gas too bad. it was on "E" when i put the 5 gal. in.

 

[$700later]

FIXED

i had a short toward the back of the fuel rail, (one green wire that splits into 2 green wires) one wire goes into the mapp, one wire went into the fuel rail, (didn't trace it) and the 3rd wire went into the sea of wires in the harness. all 3 wires were green with a white stripe. instant fix, engine light turned itself off as soon as the motor fired up. runs like a 4.0 should.

thanks for all the help.