My '94 300-6 is having a serious bucking problem. It idles fine, but whenever you are moving, but putting no load on the engine (ie. maintaining constant speed in the low range of any gear) the engine seems to either miss, or just loose power. I've replaced the fuel filter, distributer cap and roter, sparkplugs, I've plugged the EGR valve, taking it out of the system in theory and the problem still exists, so I don't think that's the problem, but the engine codes do point to the EGR. So all I can think of is the igniion module, which I know goes out on these. The problem is I have no idea where it is on this engine. Any clues?

 

the igniton module is probably on the inner fender i think it is the drivers side its a small gray-silver box

 

I've been having the same problem with my truck. I've replaced almost everything under the hood and still no results. So today I tool it to a shop. They unpluged my throttle sensor that is on the carb, and it stopped. It runs much better. let me know how you make out.

 

I think you mean the throttle body, get a new TPS. If you have a manual you will be fine. An auto will not shift correctly with the TPS unplugged. There are testing tequniques, all you need is a testor, search tps testing in the search thing, hope this helps. Take a fuel pressure test also. Check vacume lines and the map sensor.

 

well, it could be the TPS -- throttle positon sensor, or something else, I do not think that it would be the IM. If that goes, the truck just dies.... FYI.. the IM is located on the base of the distributor, light gray in color and you need a 5.5 mm socket or 5.5mm torx to get it off... any good parts store will have it, just ask for the Ford IM socket or wrench....
also.... my truck was losing power and bucking alot, then just died while I was driving... traced the problem to a corroded wire on a relay wiring harness...
just as a way to check, start the truck then shake all of the electrical connections that you can reach in the engine compartment... you might luck out...
also, pull the TPS and clean the sensor and clean out the trottle body with ether.... that should also make a difference....
And for the cost of the IM, I would change it anyway... it is only about $20-30

 

Mine was doing the same thing when the pickup coil went bad... Check to see if you're losing the tach signal (does the tachometer needle bounce quick when the engine misses?) If so you have a bad pickup coil. It's inside the distributor under the rotor. To change it you will need to remove and completely disassemble the distributor, including removing the shaft. It's not a hard job if you have the tools, but if you don't, I'd suggest taking it somewhere.

 

I found the IM, but I'm not convinced that's the problem either, It's a manual EFI. Where do I find the TPS to unplug it to test that? There is a sensor on top of the throttle body, maybe the TPS? I tightened the bolts on that at least 1/4 of a turn last night, and it's running better, but still not right.
I don't have a tach, which is starting to bug me trying to figure this out, because I can't see what the engine is doing when it starts to buck. But if I push on the gas just a little bit when I'm not moving, to get it just above an idle, I loose all power and if I don't floor it or let completely off the gas, the engine will die. Anymore ideas? thanks for the help!

 

The TPS is on the side of the throttle body opposite the throttle linkage (as it turns it spins a sensor in the TPS). The sensor on top of the Throttle Body is the Idle Air Control or Idle Air Bypass solenoid. Get yourself a Haynes manual and perform the electrical tests for these components. They are pretty simple, all you need is a multimeter and the procedure for testing. Good Luck.

 

ok, that valve and sensor on top of your throttle body ( the one you tightend the bolts a 1/4 turn), that is your idle air control valve, remove and clean with throttle body cleaner, make sure the carbon is gone and the sensor and acctuator move freely. be sure not to get the sensor wet with the ceaner or its done for, that carbon and dirt comes from the egr vave and gasket leaks. make sure the base gasket on the throttle body is not sucked in, use that throttle cleaner to spray the throttle intake mating surface while running youll know if theres a leak. also remove the sensor on the egr valve push the rod in slowly and let it out slowly any drag in or out means its more than likely sticking, also check for vaccum leaks around it to, athough bypassed the egr will still opperate when told so. valve, & sensor, problems and vaccum leaks around sensor will have a greater affect when the valve is bypassed if the valve is opening or closing to extremes the o2 sensor is going to eventualy no that theres no recirc gas there, and the o2 then compounds the problem by trying to compensate with injector timing , and air bypass protocall. new valve and sensor bypassed is a good idea, it solved some driveabillity issues on my 94.

sorry this is so long.

94 f-150. k&n, msd, jet, 3" flowmaster, all that money wasted on bolt-on's when all i really need to do match a nice cam to a ported head !!!!! and let it breath