intermittent misfire

[brett64]

I have a 1996 V8 AWD that intermittently skips or misfires mainly after driving at highway speeds. It seems to run ok at WOT but skips at low load or idle. The odd part is if I stop and restart the engine it smooth's out for a while. I have replaced the plugs, wires and even the fuel pump and filters. No codes stored. Any ideas or other similar links that you can refer?

 

[Flash]

Are you getting a crank sensor code.

 

[brett64]

No codes at all. No flashing CEL either.

 

[1997XLTRollover]

Failing coil pack?

 

[brett64]

That is what I'm thinking or bad fuel injector/s. However the tank was clean as new when I replaced the fuel pump and I have been running fuel inj. cleaners with no success. I hate throwing money at problems such as this. But I also hate a skipping engine!

 

[1997XLTRollover]

Hows your fuel pressure?

 

[98splorer]

Look under the hood in the dark and see if there is any arcing at the coil packs. You can also hear the cracking sounds. That was causing similar issues in my 98 AWD. It resolved with replacing the coil packs.

 

[brett64]

I have not checked the fuel pressure. Good idea about looking in the dark at the coil packs. I had a code about the evap sys. over a year ago. I cleaned the unit above the spare tire and the code never came back. I have not studied how that system works but I guess it could have something to do with the skipping. I remember when this was my primary vehicle when on vacation and filling the tank while the engine was running as I would top off the tank the engine would start skipping. Therefore now I stop when it clicks off.

 

[brett64]

I checked the fuel pressure it is 30 psi with vacuum and 40 psi with out vacuum hose attached. The coil packs are not making any crackling sounds or arcing in the dark. All (4) outer (-) to center (+) terminals on the coil packs read .6 ohms. I replaced the spark plugs and wires 7-8 months ago and the random skip never went away. I also disconnected the EVAP tube and plugged the intake side to eliminate a malfunction there. The outside temp or rain does not seem to have any effect. Some days it runs smooth as silk and others will skip a lot or very little. I am totally whipped with this. I was thinking about replacing one coil pack at a time and maybe the crank sensor. Any ideas?