I have a 93 F150 Flairside XLT, 5.0, A4OD, that I purchased a couple of months ago. It had what felt like a slight miss. The person I purchased it from had just had a complete tune-up done, new plugs, wires, cap, rotor and fuel filter. After I purchased it I started tinkering with it trying to figure out what was going on. I notice that it cranked a lot before starting so I put a gauge on it to check the fuel pressure. It had about 31-32 psi with the key on but would drop to zero when the key was turned off. I replaced the fuel pump and it now carries 34-35 psi with key on and holds the pressure when the key is turned off. While this corrected the starting issue it still stumbles, surges and dies at times when under slight throttle. The truck will run fine at times and not act up. When it does start acting up you can feel it starting to surge slightly, in other words lets say you are turning off a road into a gas station and you need to go around to get on the right side of the pump. When doing this you are on the gas slightly and it will start surging. If you let off it most likely will stall on you. It starts right back up without any problem or cranking. I have cleaned the throttle body which wasn't dirty, also cleaned the IAC not really dirty, replace the Air Temperature Sensor which was really carboned up. After doing all this it still has the same problems. Also as a side note when it shifts from 1st to 2nd it shifts hard sometime but other times nice and smooth. I don't know if this is all tied together or not. Any suggestions or help would be appreciated.

 

Possible problem area is the Throttle Position Sensor. It is a variable resistor which moves with the throttle plate(s). They occasionally develop bad spots with poor contact, creating a headache for the computer which is trying to figure out just how far the driver's foot is "into it". You can check the TPS output with a voltmeter, and maybe see the "dead" spot as the throttle is moved. Or, for a fairly reasonable price, just replace the damn thing.

That transmission is, I think E4OD, is it not? My '90 F-150 with 5.8L and E4OD does exactly what you describe, now and then shifts harsh 1 to 2, but not unacceptably so. I regard it as a fluke. imp

 

IMP, thanks for the info. I will try replacing the TPS. Sure be nice if that would fix the problem.

 

While you're under the hood check real close for a vacuum leak. And you didn't mention whether you have a new fuel filter or not - always a good investment. Some injector cleaner in the gas might help too but not 'till after you change the filter (don't want to loosen up all the crap in the filter and send it on through to mess up the injectors) And really, a $20.00 voltmeter would be a really good investment

 

Chris_1 I cleaned the tank out when I had it out to replace the fuel pump and replaced the filter but for $11 I'll replace it again.

 

If you changed it and the pump you should have good fuel delivery as far as the fuel rail. You don't know about the injectors but running some injector cleaner thru the system may help and wouldn't hurt.
As mentioned by imp the tps is a suspect but I would suggest testing it before throwing money at it. There are lots of posts about how and exact voltage but basically you backprobe the correct wires, test how much voltage is coming in and then test the other wires to see how much is coming out or more importantly how smoothly the voltage rises and falls as you move the throttle open and closed.
You can watch the numbers rise and fall and if there's a stumble in it, it's bad. If not leave it alone it's not the problem.
Actually you can test just about every sensor under the hood with a cheap voltmeter and save yourself a lot of aggravation not to mention time and money.
You will have to spend a little time looking things up online but it's all out there and a little research will save a lot.

 

Chris_1 "As mentioned by imp the tps is a suspect but I would suggest testing it before throwing money at it. There are lots of posts about how and exact voltage but basically you backprobe the correct wires, test how much voltage is coming in and then test the other wires to see how much is coming out or more importantly how smoothly the voltage rises and falls as you move the throttle open and closed.
You can watch the numbers rise and fall and if there's a stumble in it, it's bad. If not leave it alone it's not the problem."

I have the procedures for checking out the TPS but haven't quite figured out to get to it, not much room at the connector and really can't see the TPS itself. I was considering removing the throttle body and leaving the TPS connected and checking it that way, plus if it is bad it will be much easier to replace. According to the procedures as long and it is still connected you can test it.

Also when the previous owner had the engine tuned-up instead of putting the plug wire is separators the plastic tied them so I'm going to separate them and put them in plug wire separators.

I really feel that it is an electrical issue because it is intermittent.

 

Don't overlook Chris' comment on the vacuum.

 

I've been throwing parts at my 93 2wd 5.0 for 2 months at the advice of "mechanics" Here is what's new in the order they were replaced (chasing what started as a no spark problem [now fixed] leading to a rough running problem.)
Rotor, Ignition coil, Ignition module,TPS, (this is when I cleaned the throttle body and the IAC, plugs, wires (I'm on the third set of wires - #2 and #6 which fried at the bottom corners of the boots. - checked for cross fire - wires not touching, oil filter, air filter, (Then this is when I had the codes read - got one code - 332 [insufficient EGR flow]), EGR, vacuum lines/hoses (not all) cleaned the O2 sensor ( as per a mechanics suggestion) EVR, Techtron fuel treatment twice with 10 gallons each of high octane gas, and last but not least, a new purge valve. So... no CEL, but still runs rough, spits and sputters, hesitates, no great loss of power as far as I can tell.

I'm stumped. Only runs bad when at operating temp. Starts fine. Stalled a couple of times in reverse. CAT? O2 sensor? fuel injection problem-fuel pump? I'm not holding my mouth right when I install a new part? A faulty TPS? EGR solenoid? - wouldn't this trigger a CEL? I haven't kicked the tires yet either. Hmmm.

 

Thought I'd let you know that you are thread jacking. That is interrupting another persons thread with your own issue. Not a big deal but a little inconsiderate when you have a large problem. However as you both seem to be having similar issues I can give some advice to both. But we like to walk people through diagnostic step by step so for the beat help start up your own thread.
OK that aside make sure you recheck for codes every time you do work. Not all error codes illuminate the CEL. You can read codes without a reader by following the procedure on the sticky on this board. Also use a vacuum gauge and test the engine. There are several vacuum tests you can perform that will tell you a lot about the engine. Leaks, exhaust blockage, valve train issues and accessories like EGR can all be tested with a vacuum gauge and vacuum pump. Pull you spark plugs and "read" them for indications about what's happening in the cylinder. In low light spray a mist of water over the plug wires and look for a lightning show. This indicates shorted wires and bad insulation as well as crossfire and bad distributor cap.