I purchased my father's old 1993 Ford F-150 4x4 4.9L 5 speed back in March with about 204,000 miles on it. It was not driven much in the last few years; only around up at the cabin.
When I bought it, I did a few things to tune it up (air filter, spark plugs/wires). I also replaced the rear fuel tank because it was leaking. I have to get around to replacing the front tank because that has a slow leak as well.
The truck ran just fine up until July, about 4 months and 1,500 miles after I started driving it.
The truck started to hesitate and stutter while I am driving it; worse as the load increases such as up a hill or in a higher numbered gear. It started with only a couple of brief hesitations, but then within about 100 miles it is almost always hesitating. I can rev the truck in neutral and not get any hesitation/stutter.
Since the hesitation started, I have replaced the distributor cap/rotor, PCV valve, fuel filter, fuel pressure regulator, and the EGR valve (an engine code was coming up for insufficient EGR flow).
The check engine light has ceased to come on now, so the EGR valve took care of that, but the hesitation/stuttering still continues.
There are no other engine codes showing up. The hesitation/stuttering occurs with either fuel tank selected, so I do not believe that it is a fuel pump issue since there are two separate fuel pumps.
Another thing that I noticed when I purchased it is that fuel is being transferred between the two tanks because I will run one tank to empty but then when I go to fill it up, it will be about 1/4 full of gas. My dad said that the truck never transferred fuel between the tanks before. I know there was a recall on these trucks for faulty check valves to prevent fuel from being pumped between the tanks, but I am not sure if the recall was ever done to this truck.
Could the engine be starved for fuel because the fuel is being pumped to the other tank as well as the engine and this is what is causing the hesitation?
Has anybody else had these problems or does anybody have any other recommendations for what could be wrong?
i really wish i knew what to tell ya. i have a 92' f-150 supercab 4x4. i really love the truck, but its been giving the same trouble. i changed all the same stuff you have. i took it to 2 different machanics. all that they wanted to do was change the same stuff again. i have noticed that mine doesn't pull back or hesitate quite as bad if i have overdrive off. it may be because engine is running at higher rpm. not sure. i dont think it is in fuel system. i have dual tanks also. i havn't had any touble with fuel transfering between tanks. it feels like missfire of some kind, i just cant track it down. i have the 351, 5.8 with automatic e4od tranny. i thought maybe it was a vaccum leak, but if it is i can't find it. there seem to be a lot of knowlegable folks here, maybe some one can give us the answers we need. good luck, God bless.
Sounds like it's being starved for fuel for one reason or another.
I have a 1988 F250 and I can tell you when that partial fill up of one tank when using the second tank thing happened to me it was the fuel selector valve on the rail near the fuel filter. Your set up might be a bit different. I also had to replace both tanks because they leaked and I replaced both in tank low pressure pumps at the same time. My truck would buck/stutter intermittently especially with load or on hills when this was going on.
I got my selector valve from Silver State Ford in Nevada (online) for about $85.00. I think they are a sponsor of this forum.
Check your fuel pressure. Could be an electrical failure too. My pick-up coil caused my truck to stutter and shudder about 7months ago. I'm at school and didnt read all of your problem. Did you change the Ignition coil?
I just wanted to let everyone know that I have got the problem resolved. What ended up being the problem was the new Motorcraft spark plugs that I got and installed wiggled themselves loose. This was causing a misfire/loss of compression. I got a different brand of plugs to try instead and they have 3 more threads on the spark plug and stay tight in the cylinder head.
So, people may want to be leary of putting the Motocraft SP-435 spark plugs from Autozone in their 1993 300 inline 6 cylinder engines.
Perhaps you didn't tighten them enough. Motorcraft is always the way to go so no problems with using them just be sure to tighten them properly and that goes for all spark plugs. STAY AWAY FROM E3 SPARK PLUGS THOUGH!!!