I needed a ECU and the previous owner said it never did this problem but its done it since i got it running with a used ecu which was advertised with these compatiblies:

BRONCO 92-93 Elec Cont Unit (ECU); 8-302 (5.0L), AT, E4OD, Calif
FORD F150 PICKUP 92-93 Elec Cont Unit (ECU); 8-302 (5.0L), AT, E4OD, Calif
FORD F250 PICKUP 92-93 Elec Cont Unit (ECU); 8-302 (5.0L), AT, (E4OD), low emis

I have a 1992 bronco 302 auto EB


the problem is like this it will randomly pop like its firing an open cylinder or something as if the timing is off or something like that. it doesnt do it all the time is speratic. it seems to do it more when its really hott like if i drive down the highway and get off at the ramp it will pop a ton sitting at the stop sign on the off ramp. its hard to describe and i cant seem to find any correlations with the pop. i checked plugs and wires, its got a brand new coil, I checked the wiring order. i really dont know what it could be.

 

Two thoughts...easy one first.

How about cross firing? Someone please correct me if i am wrong. Separate wires 7-8 as much a possible on the 302. I know on my 351 is it 6-5.

Now, the ecu. I chased missing, bumping, etc. for years at a steady 1,600 rpm 35 mph. Repairing the PCM (ECU) fixed it. Now at that constant speed it shifts and drops to about 1,300 rpm . The repair specialists said the PCM numbers must match and a used one may have the same bad capacitor issues as you currently have.

 

It seems like a crossfire, then gas stays in the cilinder and is later combusted which causes the detonation, or the gas on another cilinder gets combusted when it shouldn't.

Your timing chain could have skipped a tooth, check the timing, are the plugs gapped properly?. Then you could start looking at the ECU.

Before anything i would advice checking for codes to see if the computer has anything to say.

 

I'll second what both these guys have already said and add this: If you replace the ECM (ECU... tomato/tomahto), don't rely on anything but actual part numbers. Replacement units that have been re-flashed are a scary thought unless you can verify the OEM part number associated with the software version (not a simple task). Furthermore, if the truck was not "Built for sale in the State of California" just avoid any ECM so labeled. because sensor calibration and electronic control devices (EGR, TAB, TAD, etc.) are different on "CA" vehicles as well as ECM tuning.

 

the truck deff wasnt built for California. you really think that could be it?