Misfire and Hesitation.....1994 X

[backfrmcolorado]

Just drove my 94 X from Michigan to Iowa and back. 600 miles each way. Almost the whole trip i was running about 70-80mph on the freeway. Now in town or going slow after i start the truck in the morning it has a misfire at idle and in reverse, hesitation on acceleration from a dead stop and it seems to have a misfire up to 2300 RPM after a dead stop accelerationvthen runs strong.
What could this be? Runs great at high speed and after its been ran about 50miles??? Kinda stumped on what could cause this.

Thanks to anyone who can help,
Adam

 

[Roadrunner777]

My first thought was ignition... I'd go through the plug wires make sure they are ok.

 

[backfrmcolorado]

Thats what i thought...i just replaced all plugs and wires just before i went on the trip. I checked and retightened all plugs and pulled off completly and reinstalled the wires firmly. The coil pack and crank pos. sensor were replaced only a few months ago as well. I do know i have a CEL light but bulb is burnt out and needs one O2 sesor but its been that way for almost a year now.

Its wierd how after runnung awhile or above 2300RPM it runs fine... however the whole time on e-way the rpms were 2500 and higher. You can feel the power pick up as soon as you hit that RPM range and shifts.
Could this be computer related as it learned to run that way for so long? Possibly pull battery wires and reset computer?

 

[Roadrunner777]

I think my next step would be to read codes, just for reference, then reset the computer, run it for 5-10 minutes (if it runs that long) and read codes again.

If I had a fuel pressure gauge, I'd check pressure, just so I could positively rule out fuel issues.

 

[That-Guy]

Check for spark first then test the coils. If both work it sound identical to my 94 explorer and a lot of others. I tested it and found a misfire in cylinder 5. Replaced the fuel injector and it works perfect again.