Ok, so I am having some issues on my 1991 F250 460EFI Truck. Bought this 76k original mile truck recently after it has sat for almost 15 years and it had a ton of issues. Rough running, Pinging, Vacuum leaks and some tires produced in 1989 . The big problem I am having now is after all I have replaced I'm getting an intermittent pinging/rough running problem on the truck. Sometimes Ill drive the truck and Ill have no issues especially when the truck is still cold'ish and in open loop. And then other times I start to have really bad pinging at any load 2k rpms or more. It also gains a rougher idle like it would have with a vacuum leak. The timing (set to 10btc with spout unplugged) is advancing all the way up to 46 degrees when the spout is in. Obviously this would be causing all the pinging. My question is what is telling the truck to do this? Current list of stuff replaced on the truck is ECM,FPR,EGR/EGR Position Sender, MAP Sensor, O2 Sensor, Fuel Pump, Fuel Filter, SparkPlugs, Wires, and Cap/Rotor.

Ran fine for a single drive after replacing the fuel pump. After restart it started to ping again.
Ran fine after disconnecting the EGR/thermacktor vacuum line and caping those. Next restart it pinged again (Noted not as bad though but still there... This also threw an engine light obv)
Ive done a smoke test for vacuum leaks in multiple places and found nothing.
No Codes on KOER/KOEO
Temps are fine on the dash

What kind of things happen after the car has warmed up? Like what valves open that would cause a really bad vacuum leak or to cause the ECM to think it needs more timing?
What things effect the amount of advance the ECM throws at the car?
Any ideas? Im kinda stumped at this point and am going to take it to a real mechanic if I cant figure it out. Just trying to not spend much more money if I can help it.

 

You had fault codes for all those parts and they tested as being bad? New parts don’t mean they are good. No codes from the computer at all? Not even the system pass code? Fuel pressure is within specs?

 

Fuel Pressure within spec. Thats how I found out the FPR was bad and then the Fuel Pump was bad. Most of those parts were honestly me throwing money at the problem. After I figured out the fuel problem I jumped to EGR because the car got an EGR code during KOER Test. Changed the valve and the position sender. Plugs/wires/cap/rotor was all preventive stuff. I did the MAP/O2 Sensors because I throught that maybe it could be throwing my fuel maps off because I was getting a 41 Code for system lean. I had triple and quad confirmed fuel was good at this point so it had to be something else. Then I found as I was playing with timing that with the spout pluged in I was advancing a TON. Idle was fine at about 20-25btc but when i revved to 3k it was at 45-50btc. The 41 code went away after I capped off the Thermaktor and EGR for testing purpose but im still getting pinging. My timing is still jumping a ton

 

Have you confirmed the replacement PCM is correct for this engine? 40 smething degrees of timing sounds like what a Mustang computer would do not a truck computer.

 

As far as I can tell it is. It was happening before I switched out the ECU anyway. I doubt that the ECM was replaced before this because it was an original ford one. I matched my ecu to that one and ordered it. IT was listed under a F250 460 auto trans on rock auto.

 

They will all run timing approaching 50 degrees at times
The timing is verified correct at 10 before with the spout out?
I'd give it a drink of water and go from there
You know what that means right?

 

Yes, I have seen timing that far advanced. Usually on deceleration, but if the sensors are reading incorrectly, then anything is possible. Make certain the EGR is working.

 

​​​​​ Verified it's at 10° at least according to the timing marks. I'll check that for sure that the balancer hasn't slipped or something today.

And no what is giving it a drink of water???


​​​ is there an easy way to test the EGR valve? It's brand new with the position sensor. As listed above I did get a code for it and did replace it and it helped an idle stumble I had. I unplugged it just to trouble shoot vacuum leaks now and on the first drive it worked fine and then the next it was pinging again. What sensors effect the timing. I'm down with just getting a couple new sensors if need be. MAP/O2 are already replaced. Does the EGR solenoid cause something like this to happen?

 

Unplug the vac line with truck idling, and apply vacuum to the EGR valve manually, if the truck stumbles and dies, EGR valve is good.