I have a 92 f150 with the 300 and a 5sp. After the truck warms up, and I am driving around at low rpm's the truck will buck, but not all of the time. I can get it to stop bucking by mashing the gas. But it will do it again when I return to low rpm.

I have recently replaced, sparkplugs, wires, cap, and rotor, map sensor, throttle position sensor, and the fuel pressure seems to be in spec.
thanks

 

Think simple like a fuel filter or a fuel pump. I have changed either one in similar cases.

 

My 93 F150 has that same bucking problem. I changed the spark plugs, the wires, the cap, and the rotor button. This seemed to take care of the problem for a little while, but after I bought some cheap gas, the problem started all over again. I also had replaced the fuel filter earlier, and this did nothing to solve the problem. As for the fuel pump, I have dual tanks, and the problem seems to be the same for both tanks. I assumed each tank had its own fuel pump, but I haven't researched it yet. Any help would be greatly appreciated.

 

I get an occasional bucking situation, usually only in first gear. I attributed it to my first being quite low (3.90) compared to my last F150 (3.01). It seems to happen when I let the clutch out in a certain way and I think is just a kind of tug of war between the engine and the road due to a certain sensitive point in the engine's rotation cycle. I doubt it is the running quality of the engine as it was just tuned and the throttle body cleaned out. Is my hypothesis all wet or am I on to something?

 

Hey Charles I hear ther is a new Product out Especially for fords. It supposedly cures fuel problems that can be associated with bucking.The product is called anti- buck and can be purchased at your local sporting goods store. It is fairly cheap. Just look for the can with the big dear on it. Be sure to Check your local game laws before antibucking to make sure the season is in. Because fines are expenzsive these days

 

Just to add some more since I've seen the replies. I don't know if Charles is having the same problem I am, but my bucking started out happening in second gear only (weird, but true). Eventually it spread to all gears (not just pulling out), and it will occasionally happen even at highway speeds in 5th gear. In addition to the changes I named above, I've put enought fuel injector cleaner through it to clean a whale. Good quality stuff. Another question. Since I have dual tanks, do I have two fuel pumps, or does one fuel pump feed from both tanks? Any help (serious help) would be appreciated. Thanks.

 

To answer your question, each tank has its own fuel pump. Don't use to much injector cleaner you will eventually do more harm than good.

 

I have an 87 300-six that does the same thing in any gear. I too have done everything but change the ICM to correct the problem. Any thoughts if this will do it?

 

I ran a key on engine off, test and got memory codes of 179 and 327. The 179 code is somthing to do with the O2 sensor, that I have already replaced, and the 327 code is sopossed to be a fault code from the EGR valve sensor. I tested the signal voltage, it was fine, and tested the sensor, It seemed ok but I bought a new one and replaced it, didn't help. Now I am lost, I haven't a clue what the problem is. I have checked for vacuum leaks and all the simple stuff, no luck.
Thanks for any help.

 

Do you have dual tanks and if so is the problem localized to one tank. If it is I would change the fuel pump. If that doesn't cure the problem try the fuel selector valve.

 

Got the same problem. It's the EGR valve. '86 to '94 Fords have a problem with the EGR valve stem getting gummed up with exhaust crud, which causes the valve to stick open when EGR is not needed.

A simple test: On a cold engine, disconnect & plug the EGR vacuum line and go for a drive. The check engine light will come on as the engine warms up- just ignore it. If the engine runs smoothly, it's time to replace the EGR valve. Ford gets $145.00 for the valve without the feedback sensor. Add $40.00 for one of those little gems if you want to spend the money.

 

I've had the same problem in the past. I've done a complete ignition tune-up, new 02 sensor, the works. Mine seems to do it at a very specific temperature range. It will start up fine, but after driving for about 2 or 3 minutes, it will buck very badly for a minute or so, it's all I can do to keep it running. Once it's warmed up past this point, it will run just fine all day. I figured "temperature problem, I'll replace the coolant temperature sensor." Well, it worked fine like that for about 9 months then the problem came back. The resistance of the sensor is fine, as is the reference voltage coming out of the computer. I read somewhere that the computers in ford trucks can "learn" from an engine and its sensors as they wear. So I unhooked the battery for about 15 minutes. Sure enough it's running fine now but it's almost certainly a temp fix. I haven't had any luck reading computer codes. Does this help anyone?

 

I've had the same problem in the past. I've done a complete ignition tune-up, new 02 sensor, the works. Mine seems to do it at a very specific temperature range. It will start up fine, but after driving for about 2 or 3 minutes, it will buck very badly for a minute or so, it's all I can do to keep it running. Once it's warmed up past this point, it will run just fine all day. I figured "temperature problem, I'll replace the coolant temperature sensor." Well, it worked fine like that for about 9 months then the problem came back. The resistance of the sensor is fine, as is the reference voltage coming out of the computer. I read somewhere that the computers in ford trucks can "learn" from an engine and its sensors as they wear. So I unhooked the battery for about 15 minutes. Sure enough it's running fine now but it's almost certainly a temp fix. I haven't had any luck reading computer codes. Does this help anyone?