Hey guys. I'm new to the forum and this is my first post. I dont have time to read past posts to find my answer as I am getting desperate to get this fixed. So...I have a 1994 Grand Cherokee Laredo with 193,000 miles. It has a few issues...
1) will not go into 4wd.
2) engine is hard to restart after driving.
3) engine idles VERY rough in park and under load. also backfires/pops after starting but stops after the engine warms up.
Please help me out. This is my only vehicle and I cant afford thousand dollar dealer repairs.

 

is the check engine light on? if so cycle the key on-off-on-off-on and either count the flashes or look on the digital odometer for trouble codes. that will give you a place to start.

 

ooops. should have mentioned that. check engine light is not on.

 

you can still try cycling the key and see what comes up, not all faults will throw a CEL. ignore 55 and 12. 12 is battery has been disconnected with in the last 50 starts, 55 is end of codes.

 

Well...12 and 55 were the only codes I got.

 

I was having this issue with my dearly departed Cadillac, drove me nuts figuring it out.

The heating element on the upstream O2 sensor had fried. The sensor was fine, so never threw a code other than the misfires it was causing. A friend who works as a mechanic at a Chevy dealer finally figured it out.

The heating element was part of the O2 sensor on that car. I must have thrown $300 at this before replacing a $20 something sensor.

On your 4wd: Will the transfer case lever move, or is it stuck?

 

Check the fuel pressure for the poor running problems, I think the spec is around 45psi. Inspect the transfercase linkage for you 4x4 issues.

 

The shifter moves into position but the 4wd will not engage.