I have a 94 f150 with a 351(5.8)
my problem is that it has no pick & go on acceleration, but it pick speed once it gets going? What could be the problem & what i need to do to fix it? I was thinking it might be in the exhaust system. Any suggestions?

 

Check fuel pressure. Whens the last tuneup? How many miles? Did it just start doing this? Background information is helpful.

 

Agree with previous post, need more background info including axle ratio.

Unsure what is expected and don't know the specific Gen 9 ratings ('92-'96), but IIRC the Gen 8 ('87-'91) 5.8L was rated in the 225 hp range, long ways from today's offerings.

 

That could be a lot of things.
I need to ask some questions.

Does it just have poor acceleration?
Does the RPM go up but the truck not respond?
Or when you hit the accelerator does the RPM of the engine not increase it's fast as it should?

Do you have any dash lights on?
Do you have any way of pulling codes?

When you press the accelerator with the headlights on or the interior lights do they dim or flicker?

When you press the accelerator does the engine run rougher?
Do you have any smoke from the exhaust?
Do you have a misfire?




If you don't have a code reader and you have that old of a truck I would suggest buy a code reader. That should be OBD2. You can get a decent one on Amazon from anywhere from 70 to 180 bucks I wouldn't go cheaper than that. I have used the blue driver for some time and it seems to do pretty well it's not going to give you very in depth information but it can pull codes.

 

I have no codes. The lights does not flicker & i when press on the accelerator the engine does not reve up, transmission is not slipping. I did a tune up on it, new plugs, wires, cap & rotor, new distributor because the pin came out of the gear shaft. It's timed properly, I checked the timing numerous times. New ignition coil. Cleaned the throttle body, new pressure regulator. Did a fuel pressure test, has good pressure, even did a engine compression test, that's good. So, the only other thing I haven't tested yet is the exhaust cats. It does seems to have some exhaust coming out. Puzzled 🤔🤷🏿

 

How's the MAP sensor? Mine (on my 5.8L 1995 Bronco) sits right where water can drip on it when I go through a car wash. I've made a bit of a shield out of some plastic, and now I'm not replacing it annually anymore. When it's not working right, performance gets really weird.

How is the vacuum system? A significant enough vacuum leak will impact performance. That said, I get good performance out of my 5.8 despite there being enough of a leak that low-RPM moderate throttle (such as pulling a trailer up a very slight grade) can cause the vents to fade out. But if you're losing a lot of vacuum, that could be a big problem for performance. And it's hard to track down on those engines; the vacuum diagram is intimidating. And on mine I've never been able to smoke out the leak.

A clogged cat (you might even have two cats inline) will have an impact, of course.