I just purchased a 1991 F150 XLT Super Cab with a 5.0 V8. It ran like brand new a few days ago. Yesterday, it started bogging down, and running rough, almost like a miss. It clears up for a second, but then runs rough again. I added some sea foam to the gas, changed the fuel filter, still running rough. Any suggestions on how to get it back to running right would be much appreciated.

 

Oka any particular RPM or time (cold or warm) when this happens?

 

It happens usually when I first start it in the morning, then on and off all day.

 

So it was fine then started doing this... hmm. Plugs, wires, cap, rotor been changed? Try to tell me if it is a fuel or electrical problem? How about your check engine light?

 

The check engine light comes on when it boggs, then, goes off when it runs right. It feels like a miss, but no smoke, or knocking, other than that deep bogging sound like its running out of fuel when it boggs down.

 

Have you tried testing your fuel pressure. It could also be an electrical problem. Would you do me a favor and check if the electrode part in your spark plugs look kind of burnt.

 

What is the best way to check your fuel pressure? I will check the plugs this evening and let you know.

 

Well testing fuel pressure requires a gauge and you connect it to your fuel injector rail. It's easy to spot. It has a little black screw on cap. But wait why don't you disconnect the green vacuum line that goes to your fuel pressure regulator first. Tell me if the problem changes. Don't drive around with it disconnected though. Just rev your engine a bit and see if the problem persists. Also if fuel drips out of the vacuum line or it smells alot like gas when you disconnect you could be looking at a faulty fuel pressure regulator.

 

Thanks, I will try that first and let you know how that goes.

 

Oka. I know how it feels when it is your DD and you can't afford it having issues.

 

texasyakfisher71: I might be busy today so I don't know if i'll be able to get on. I'll try but if I don't I hope someone chips in. Anyways tell us how it went after what I told you to do.

 

Can you tell me where the FPR is located and where the vac. hose will be located on the FPR. I just want to be sure I'm unhooking the correct hose.

thanks again.

 

Ok, I pulled the vac line off the FPR. It changed and idle went up to close to 1000 rpm, and smooth. I did not smell the gas, or see any dripping but I could hear an instant change in the idle. Could running this truck close to empty, caused this? What else do I need to check? Even though it is running better, still not like new when I first bought it a few days ago. Maybe new plugs? Any other sensors could have been damaged? One more thing, the engine light never came back on while I had the vac line off the FPR.

 

One more question, what is the best code scanner to get? I want to run a scan and see what codes have come up.

 

Did you check the plugs? Where they black? An Actron code reader at your local AutoZone works well. Make sure it's for OBD I.