cherokee runs rough, backfire, missfire, etc

[smokinu]

Well if you didnt pull all the plugs at once.

When we pulled just the number 2 cyl plug compression seemed fine... when we pulled two and three thats when compression dropped.

 

[89Cherokee95]

Interesting, what would cause that to happen?

 

[smokinu]

Well in my case the compression was jumping from cylinder to cylinder. So it came out normal.

Once i removed both plugs the compression was blowing out into the other cylinder.

Here is a pic of where my head gasket let go. And cause all my issues. It was also cracked in the number 1 cyl.

http://imgur.com/GDbY5Nh

 

[89Cherokee95]

I see, well if my head gasket is anything like my valve cover gasket I wouldn't be surprised, it was practically disintegrated into nothing, so its possible that something similar is happening with the head gasket. Is there a way to check if its blown - short of removing it?

 

[smokinu]

I see, well if my head gasket is anything like my valve cover gasket I wouldn't be surprised, it was practically disintegrated into nothing, so its possible that something similar is happening with the head gasket. Is there a way to check if its blown - short of removing it?

Have a shop do a leak down test.. it will tell you if its leaking and from where.

 

[89Cherokee95]

I have a friend who is a heavy duty mechanic coming in a week or so, he will be able to help me to a test (cant afford nor want to have a shop messing around in there XD)

 

[89Cherokee95]

I am beginning to think that there is alot more wrong with this engine then I originally thought, I am buying another cheap cherokee with the same engine as mine, rebuild the engine in that, replace everything I can, and then swap engines, this thing was never treated properly for most of its life, and I think its finally starting to show, so its best if I just swap engines.

Thanks for all your help

 

[89Cherokee95]

Whatever the problem is/was... it finally failed. I ended up buying another jeep for parts and to rebuild the engine then swap it in, but I still need this one to work for now as its my only vehicle. Once I got the parts jeep (it ran perfectly so I know that all electrical was good) I swapped over a bunch of sensors ( IAT, IAC, coil. Plug wires, distributor) I set the engine to TDC and set the new dist in, turns out that I messed up somewhere and ended up blowing the muffler to pieces from a backfire (the concussion was massive ) fixed the distributor to rest at 5 o'clock when engine is at TDC and it ran for a few hours, it was really smooth, but had about as much power as if it were a lawnmower engine, it got progressively worse until it stalled a couple times and refuses to start, I replaced the cps and made sure that it's getting spark, I also replaced the fuel sending unit and made sure its getting enough fuel, when it was running I checked it with a timing light and at idle it was about 15 degrees advanced - same as my friend running jeep, its also getting good compression about 150 on all cylinders (except #2 which gets 175) so its not spark, fuel or compression, the dist is set to what the manual says. I am stumped it SHOULD run but refuses to, if there is something else that could prevent it from running please let me know

Thanks for all the help, even if I can't get this engine running- I have deffinetly learned a lot about this system

 

[89Cherokee95]

I found the problem! turns out, the coolant temp sensor wire had a bare section and was grounding to the intake manifold, I guess the computer got a weird reading from it and decided to prevent the engine from starting.

However an old problem still exists.

on a COLD start, the engine will idle fine, but if you try and accelerate it will bog down and backfire, like its getting waaaay too much fuel and lasts until its warmed up. I swapped pretty much every sensor from a known good running 90 xj and the problem still happens, so its either something in the wiring harness or something mechanical. its not the MAP, as running it with unplugged is just about impossible, and its got a good vacuum line, what else could cause it to run really good at idle, but bog down and with enough gas to almost kill it if I accelerate?
something is causing the ECM to send so much fuel that it almost kills until its warmed up.

any ideas?

 

[89Cherokee95]

I swapped the fuel rail and all the injectors, and it fixed the problem with #2 cylinder. Also, when I bought a new ICM, they must have given me one for the wrong year it was ever so slightly different on the bottom, I swapped it out and it starts and runs perfectly now, the thing probably runs better then it has in a year and a half! anyway, thanks for the help.

I am really going to have to get used to have 80 more HP, I squeal my tires on just about every corner XD

 

[89Cherokee95]

it was the fact that the tach was jumping all over the place when it would bog down that made me think ICM, turns out, I was right.