Truck is a 92 with a 302. I have a misfire at Idle and under heavy load. It only happens when the engine is warm.
This is what i've done to remedy the problem. I replaced spark plugs, Spark plug wires, coil, and Ignition Control module. I have also checked the distributor cap and rotor and the both apear to be in good shape.

The only thing I can think of is a problem in the distributor. Pick ups maybe?

Anyone Have any Ideas?

Thanks,
Mike

 

It sounds like you have replaced almost all your secondary ignition, so it probably is not with the fire. If I were you I would check for vacuum leaks, and if you find none, try to get access to a compression guage. If your compression is fine its in fuel clogged injector or bad injector. How many miles do you have on it? Hope this helps.

 

It has a 129k on it. I Starting to think it's fuel myself but It runs very well when its cold. I would think if it was fuel related that it would run the same hot or cold.

Thanks for the response. I Will work on the fuel system this week end and see if I can find anything


Thanks,
Mike

 

you have the nortorios crossfire problem . #7 and #8 plugs fire one after the other on the 302 . this leads to crossfire in those two cylinders . but can happen on others also . you need to seperate your plug wires so as no one wire touches another one at all the full length from the cap to the plugs . buy some wire seperators to add to what is there already to prevent "crossfire".

Make: FORD TRUCK Model: F150 Year: 1990

Service Bulletin Number: 90-4-14 Bulletin Sequence Number: 009 Date of Bulletin: 02/90

NHTSA Item Number: SB011916
Component: ELECTRICAL SYSTEM:IGNITION:OTHER PART
Summary:
SPARK KNOCK OR ENGINE MISS CAUSED BY INDUCTION CROSS FIRE-THIS OCCURS BECAUSE OF MISROUTED SPARK PLUG WIRES-FIRING ORDER OF 5.0L ENGINE THAT 8 SPARK PLUG FOLLOWS #7 SPARK PLUG-PLACING WIRES #8 AND #7 NEXT TO EACH OTHER AT SEPARATING BRACKET M AY INDUCE CROSS FIRE-CHECK POSITIONS OF #7 AND #8 SPARK PLUG (ASF-42-C) WIRES AN D REROUTE CORRECTLY IF REQUIRED-ALL 1987-90 FORD BRONCO/E150,250/F150,250 TRUCKS TLH

this TSB doesn't include your year . but if you look at the date of it ,it was wrote in 1990 . your 302 is subject to the same problem .

 

Great info! Thanks.

Mike

 

Good job Ray! I never even thought about there being a TSB about it, I just thought it was something we greasemonkeys knew about. Go figure.

FWIW, the same thing applies to the spark plug wires for cylinders #5 & #6 in 5.0 HO engines and 351's. Actually, anytime you find two sequentially fired cylinders that are next to each other on the same bank, this problem is likely. Also, plug wire resistance tends to increase with heat, which is why this problem sometimes is more present after the engine warms up.

Take care,
-Chris

 

I would like to thank those of you that have come up with the fix for this problem. I too have the same problem with not running well when hot. I so far have replaced the distributor, cap, rotor, coil, TFI module, egr valve, installed a manifold 3/8" heat block off spacer from BBK, re-ran all fuel lines, replaced EFI fuel pump, checked all ground connections, checked ignition wires and spark plug wires for resistance with no luck. This is on a brand new FMS SEFI 5.0 crate motor that I have installed in a 1970 F-100 short bed that has been in the family since new. When cold this motor runs really good, but when I shut it off for about 15 to 20 minutes then try to drive it it stumbles, misses and virtually won't run.
I am going outside right now and try the fix and hopefully this is all that is wrong. I am keeping my fingers crossed......
Norm

 

Well that didn"t work either. I seperated the plug wires (# 5, #6 & #7) [HO 5.0] and insulated all the rest from touching anything metal or other wires and no change when hot. I have a Mercedes Mechanic in the family and he drove it with the problem and said that it is running lean and that it could be the O2 sensors. The only thing left is to change the spark plugs, wires, and o2 sensors. Which to do first??? Does anyone know what the spec. voltages should be for the O2 sensors test??

 

I have a 1993 F150 XL 302 5-spd with the same problem. It doesn't knock when cold, only warm and under heavy acceleration or at 65mph+. I have replaced the plugs, wires, distributor cap, rotor button, ignition module, magnetic pickup, egr valve, o2 sensor, map sensor. I put glass cloth tape around the spark plug wires just for a test to prevent short to ground but that didn't work either. Took it to Ford and wasted 1hr service charge for them to tell me they couldn't find anything wrong. Took it to a trusted mechanic and he couldn't figure it out either. Tried higher octane and even mixed some higher still no luck. I have checked the vacuum lines, fuel lines, and fuel injectors still no luck. I suspect the throttle position sensor next. Does anyone have other ideas?

 

EGR valve.

tom

 

I have a 92 Ford Econoline E150 van with a 351 Windsor everything was running fine and perfect change spark plug wires now runs rough and sputters when I try to push on the gas any suggestions that I should check that may be wrong was running fine and perfect like I said don't understand why is running so rough and sputters now

 

Check to make sure you put the wires back on in the correct order.