-Cleaned EGR out and freed it up.
-Changed the TPS and adjusted it.
-Changed the ground to the engine block.
-Timing was adjusted.

The truck stillr runs rough. It backfires, and sounds like a dead cylinder. I had performed a compression check and the readings were 150-145. w/ Cyl #1 at a low of 140. Truck has all new plugs (gapped), wires, cap, rotor, TFI.

I pulled the codes and it spit out 31 again.

What now? I am utterly confused.

 

Disconnect the vacuum line from the EGR, and plug it. Does this make any difference?

If no, then try this:
Attach a hand vacuum pump to the EGR valve, and while the engine is idling, bring the vacuum at the EGR slowly up to 15-20".

Did the engine stumble, or stall while doing this?

 

All the engine does is stumble. It runs like it has a dead cylinder. I have checked the spark on all 8 cyls and they check out. New plugs in each cyl. too.

I removed the EGR and cleaned it up. Tested it by putting a vacuum pump to it and it rose and returned fine. Resistance on the sensor checked out and the Vref was good.

This thing has me stumped. I just want to junk the POS.

 

I'm trying to help you, but you didn't answer my questions.

I need to know if running it with the egr vacuum hose plugged makes any difference. If it doesn't, then I need to know if the engine stumbles (worse), or stalls, when you apply vacuum to the egr with a hand vacuum pump, at idle. If there is no noticeable difference, let me know.

 

Alrighty. Sorry about that. Ran out there and tested it out. The truck runs ok with NO vacuum applied to the EGR. When Vacuum is applied it dies out if idling and runs horrible when above idle.

I have no problem leaving the EGR unhooked, but it still doesn't fix the problem.

However, without the vacuum the truck still shudders and shakes when put into any gear. Like it is loading up with fuel. I know before I drove it in the garage the damn cats where glowing. Cut the pipe after the first cat and it still ran like it is now.

Thanks again, PKRWUD I would have completely lost it by now if not from the help on here.



Also someone told me the FPR may be bad. How do I check this. Just sniff the vacuum line for it?

 

To check the fpr, check the vac line for fuel. If you dig the smell, sniffing it works, but looking for liquid is better.

You should check the running fuel pressure, and see how fast it bleeds down after you turn off the ignition.

As far as your code 31, do this:
unplug the electrical connector at the EVP sensor, and insert a jumper between the brown/white wire and the brown/light green wire in the connector at the harness. Run KOEO codes again, and look for a code 35. Ignore all other codes. If you get a code 35, the sensor is bad, and must be replaced.

 

How can you adjust your TPS? I just changed mine (91 F150 4.9L) didn't know I could adjust it.

 

You have to enlarge the holes for the screws. So that it spns. I installed a new one and it brought the voltage down to were it was suppose to be.

 

You've lost me. Mine has two screws for mounting. Am I missing something? I've got a '91 model 4.9L. I hope I'm not just being stupid.

 

I dont know how much help this could be, but my 93 F150 was doing the same thing. I ended up have to change the Fuel Pressure Regulator. I know the trucks are different, and I even have a different engine (5.0). I dont even know if your engine has a regulator, but if it does, that could definately be the problem. I was told by the dealer that my particular engine had to have a required 17#s of fuel pressure to run.

 

Clyde. I meant the two holes on the actual TPS sensor. Stock [at least on mine] they allow for no adjustment. If you take a drill and lengthen them you will then be able to spin the TPS sensor until you have the correct voltage.

Jumped the sensor and still got code 31. Looked in the vacuum line for the FPR and it was wet. Changed the FPR and all is good now. Finally.

Thanks for all your help guys.