Random Backfire when cranking.

[holyford86]

Get a random backfire when cranking, sometimes it will even stall the starter for a split second, sometimes it will backfire and then you need to crank it for about double the normal cranking time, mostly happens when engine is partially warm but will do it on cold start or when fully warmed also. Only codes present are a code for clutch pedal position switch because it's jumped. This is a 93 federal emissions 4.0 with a manual transmission, installed in a 86 ranger. No other codes KOER or KOEO, Wiggle test comes up ok, live data looks good, and a vacuum gauge shows nothing strange when its running. No random CEL flashes (I installed one) either. Only aftermarket modifications are a pair of pacesetter headers and an AEM Brute Force dryflow filter. Has me stumped

 

[John Solo]

how long has the problem been happening? and have you been using any particular type of fuel? I had a back firing problem and it was from some crappy fuel I got from the gas station down the street from me.

 

[holyford86]

Few months now, doesnt seem to be fuel related either, 95% of the time I buy gas from the same station, run fuel injector cleaner about every 5 tanks of gas, always use 87 octane too. No preignition when driving either.