Okay guys and gals-you have gotten me this far -now I hope you can get me to the finish line. My wife's 97 AWD 4.0 Aero is running very well now except I get a P300 code at low speeds-below 30 MPH. I have the code reader hooked up and can drive all day long up to 90MPH and never get the code,slow to a stop then start up again and boom check engine light. I have cleared the code several times and it keeps coming back-sometimes right away and sometimes I think its gone for good only to return. With the P0300 sometimes I get the P0304,P0302,P0306 and once P0301.But sometimes just the P0300.The truck has new wires,plugs,IAC,TPS and MAF.Any ideas on where to start or should I just give up and get hosed by the local Ford dealership?

 

My son replaced the plugs and wires about 8,000 miles ago on our 1999 Ford Explorer with the 6 cyl engine, with no problems at all during that time. Then about 1,000 miles ago, the "check engine" light came on and stayed on. I rechecked the wires and checked for vacuum leaks, and found nothing wrong. AutoZone ran the codes and we first got a code P300, which is a "random multiple misfire". Not much to go on. They reset the computer and a couple weeks later the "check engine" light came on again. A code P303, "plug 3 misfire" popped out of the computer. I checked plug 3 and found nothing wrong. The weird thing is that this afternoon the "check engine" light went out, and has not come on again after about 50 miles of driving.

My son-in-law, a Ford mechanic, had previously told me to run some injector cleaner through the engine because he thought the number 3 injector was clogged. Turned out he was right. I ran Lucas injector cleaner through three tanks of gas and the "check engine" light mysteriously went out this afternoon. This may be of help to you if your "check engine" light comes on again, and you get a code P303.

Tom Norman