94 F150 Cuts out above 2000 rpm

[JZiggy]

Hey guys,

I'm posting on behalf of my friend (and handyman) who owns a 94 F150 with the 5.0. He and I occasionally wrench on his truck and he calls me for troubleshooting ideas.

The truck starts readily, idles fine, and will drive with no issues until the engine speed hits 2000 rpm. Once it does, the engine cuts out immediately and dies. It will restart with no problem. Apparently this happens even if you rev it up past 2000 rpm in neutral.

I don't know much about Ford ignition or EFI systems, but it feels like an electronic problem.

I would appreciate any ideas of where to start.

The truck did have a tune-up last year (plugs, wires, cap, rotor, fuel and air filter).

 

[CT8]

You will have to start with the basics first then expand.

 

[Nick1994]

Check for vacuum leaks or possibly a bad crank sensor/ MAF sensor.

 

[Bud_One]

Plugged Cat converter ?

 

[qdeezie]

FYI - The '94 F150 doesn't have a crank sensor, but does have a MAF sensor.

However, you need to check for codes. If you don't have a code reader, you can go to F150forum and see how to check for codes with a paper clip.

That is the best place to start.

As for what might be wrong with it, sounds distributor related or possibly MAF related as mentioned above, but that's just a wild guess.

 

[4wheeldog]

The symptoms sound like a plugged fuel filter, to me.

 

[Olas]

My first thought was fuel filter but OP says he replaced it recently.. Any codes? Is the fuel pump noisy?
Bad cats can smell like eggs, do you get that smell?
Unplug the MAF and see if the problem goes away to eliminate the MAF - don't know the f150 specifically but it should revert to an inbuilt table if the MAF goes bad.

 

[eljefino]

Is there a neutral interlock that keeps it below 2k "because you're in neutral"? Does it make good power below 2k?

Could be the Thin Film Transistor ignition if they still used that in 94. They conked out all the time.

 

[thunderfog]

I would also suggest crank sensor.

edit: D'oh. Never mind.

 

[meep]

how does it stall? does it fight to run or just act like "key off?"

is it driveable? will it move under its own power (up to 2000 rpm)?

does it matter if it's warm or cold?

i keep thinking fuel starvation too. fuel pressure regulator getting tired?

 

[JZiggy]

Great thoughts and questions!

- According to him, when it stalls it just cuts out abruptly, like key-off.

- It is driveable, so long as the tach does not touch 2000 rpm. If he toodles around keeping it around 1800 it drives perfectly normally.

- Warm or cold does not matter

Good idea about the MAF sensor.

The other tricky thing for me is that I have moved cross-country so I can't go see the truck myself.

 

[JZiggy]

Rock Auto shows a MAP sensor but not a MAF sensor.

 

[Merkava_4]

You can do an exhaust back pressure test by removing the upstream oxygen sensor and installing a back pressure gauge in its place. Anything over 2-PSI (at any RPM) is a plugged up catalytic converter.

 

[Lubener]

Originally Posted By: 4wheeldog
The symptoms sound like a plugged fuel filter, to me.


I agree. Possibly cannot get enough fuel when demand is at highest.

 

[95busa]

Ignition module

 

[JZiggy]

Ignition control module sounds like a good one to try.

 

[AdRock]

The 94 will have a MAF if its an automatic, MAP if its manual. I had this exact problem on my 95 f150. The coil would go dead as soon as a certain rpm was hit. So check the coil. Since it happens at the exact same rpm no matter what the conditions are Im betting its in the ignition system somewhere.

First check the codes. But my guess is either the coil or the ignition module.

 

[simple_gifts]

Originally Posted By: Lubener
Originally Posted By: 4wheeldog
The symptoms sound like a plugged fuel filter, to me.


I agree. Possibly cannot get enough fuel when demand is at highest.


I can understand not going past 2000rpm, but totally dying? IDK. I would think the engine would just run poorly or not be able to accelerate; this was the symptoms on my Caprice that had a clogged FF.

 

[JZiggy]

It's an auto.

Looks like we're starting with the coil and the MAF sensor. Where would these be located under the hood?

 

[punisher]

Originally Posted By: eljefino
Is there a neutral interlock that keeps it below 2k "because you're in neutral"? Does it make good power below 2k?



A bad MLP sensor was my first thought to, but that usually doesn't kill the engine, it just cuts out/shudders. Get a scan tool, pull codes, go into DCL and select "MLP"(manual lever position sensor)PID and verify it isn't in P/N when in other drive gears. MLP sensors don't set codes usually.