F150 5.0 acceleration problem
 

Hi, I hope someone might have dealt with this problem before, but I have a 1994 F150 with the 5.0/302 engine. The problem is that at times, when I go to accelerate (step on the gas) the engine sort of just won't go or you could say it boggs down, misses and a few times popped a little.

It seems to happen most often after the truck is warmed up and I have shut it off for a few minutes like to run into a store for a little bit. You start the truck and try to get it moving and the engine won't respond for a few seconds, the engine boggs and seems to try to accelerate, but it takes a few seconds and then it will finally go. Oh and sometimes when you first start it up when the engine is cold, the idle races up to about 1,500-1,600 rpm until you shift it into gear, then the idle seems normal. All if this stuff doesn't happen every time, maybe once out of every 10-15 times I start it up, so it comes and goes.

The engine doesn't stall, it's sort of feelslike something is holding the throttle body closed, but that's not the case. So far I swapped out the mass air flow sensor for another one that seems tobe OK. I replaced the oxygen sensor (it was dead according to my scanner) and today I ended up putting a new EGR valve andEGR position sensor. The Throttle position sensor is also new and the idle air control valve is about 2 years old.

So does anyone have an idea where to start looking now to fix this problem. By the way, according to my scanner, there are no trouble codes set in the computer.

Thanks in advance, Ron

RE: F150 5.0 acceleration problem
 

Sounds like the IAC (Idle Air Controller)is hanging open. Check the IAC to ensure it's clean and fuctioning properly. This can cause a high idle problem. It can also cause hesitaion as the MAF cannot initially compensate for the IAC being open when it should be closed.

RE: F150 5.0 acceleration problem
 

Thanks for the reply to my posting! I was starting to wonder about the IAC, but I replaced it with a unit from NAPA less than two years ago. So I don't think it would go bad so quick, but with the quality of some of the parts today, you never can be sure. Anyway, I'm going to borrow another IAC off a friend's spare motor from a 94 F150. I'll see if it helps, if not, the search continues.
Ron