1996 Jeep Grand Cherokee 4.0L

Hi. I am having engine problems. I get the check engine light after driving a short distance. The codes are: P0300 (Random/multiple cylinder misfire detected) and P0301 (Cylinder 1 misfire detected). It runs fine in park or neutral. It shakes and runs rough in drive with the brake on. I describe it as chugging. It smells like a snowmobile. About a month ago, I did the distrib, distrib cap & rotor, plugs, wires, fuel filter, and set the timing. It ran great during that time until Sunday. I picked up a snowmobile and it overheated. The radiator blew near the bottom. I did the radiator, water pump, and thermostat yesterday. I did the plugs again yesterday. The insulators were red/orange. I also did the wires today. The plugs helped about 87%, wires made no difference. Not sure what is next. Thanks in advance for any help!

Compression test? You might have a bad head gasket or head from the overheat.


1996 Jeep Grand Cherokee 4.0L

Hi. I am having engine problems. I get the check engine light after driving a short distance. The codes are: P0300 (Random/multiple cylinder misfire detected) and P0301 (Cylinder 1 misfire detected). It runs fine in park or neutral. It shakes and runs rough in drive with the brake on. I describe it as chugging. It smells like a snowmobile. About a month ago, I did the distrib, distrib cap & rotor, plugs, wires, fuel filter, and set the timing. It ran great during that time until Sunday. I picked up a snowmobile and it overheated. The radiator blew near the bottom. I did the radiator, water pump, and thermostat yesterday. I did the plugs again yesterday. The insulators were red/orange. I also did the wires today. The plugs helped about 87%, wires made no difference. Not sure what is next. Thanks in advance for any help!

Just borrowed my brother's compression gauge today. I'm going to test it tomorrow after work. Head gasket was my thought. I'll post the findings. Thanks.


Compression test? You might have a bad head gasket or head from the overheat.

I did the compression test. Cylinders 2-6 read between 120 and 150 psi. Cylinder 1 read 70 psi. So it needs a head gasket. When I bought the Jeep, I couldn't tell if the valve cover is leaking, or the head. I guess it is the head.