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.

 

I am thinking he means pull a vacuum line when the truck is warmed up and drop it into a bottle of water, rev engine, let the vacuum suck the water in. It is meant to clean carbon deposits that can cause pinging.

 

Right, roughly
I learned about "giving one a drink of water" on an old Cadillac with a 472 or 500 motor
They would carbon up like no tomorrow (nobody ever floored them)?
They would actually knock due to carbon buildup on the pistons
We would take a full Coke bottle of room temp water and feed it down the throat of the carb (hot engine) at about 3000 rpm
That would start killing the motor but also take the carbon off the pistons and the combustion chamber
Rev it up a few times and feed the H2O
That is the drink
So, it happens rarely these days, but does happen
You have one that pings or runs on, has spark knock, etc. It might be worth a try

 

Have you checked or replaced the intake air temperature sensor?

 

I have this problem on my 460 truck. It's been that way as long as I can remember. I can mask the problem with premium fuel, but that's gotten spendy. Over the years I have replaced all the EGR system (EGR valve, EVP sensor, EGR solenoid twice, and all the vacuum lines) thinking that had to be the root cause but to no avail.

Now having read this thread and others like it, I decided to dig back in and see what other causes there could be. I first checked fuel pressure and got this:

KOEO 42 psi
Idle 34 psi
WOT 42 psi
Unplug FPR 44 psi

These pressures are good, amiright? I don't have a lean condition based on the plugs I pulled so I think fuel delivery is OK:



So next I wanted to look at timing, specifically total timing, since I read some posts saying some were seeing 50 degrees BTC in come cases. Yikes. Well, that is not my case. With initial timing at 10 deg BTC, I am seeing about 45-46 deg BTC total. That is still too much, I think, so I backed off to 5 deg BTC initial and tried again. Now got about 41 deg BTC total. OK, if I a little is good, more must be better. So I checked it at 0 deg BTC initial and got about 36-38 deg BTC total. That is where I think it ought to be so I am leaving it there for now.

It's hard to tell but I ran down to the grocery store and did not hear any pinging. It's about 98F here, so should be hot enough. Perhaps the initial timing adjustment helps, but I cannot be sure yet. It's fooled me before. But I will say that it seems the initial timing only affects total because the truck drives totally normally otherwise, plenty of power like a 460 in an F150 should have.

Really just trying to document what I am trying and also see if anyone else has any other ideas.



I have not and my Ford Fuel Injection book does not give a test procedure for this, so I just ordered one since it was only about $20. Seems like a failure of this part would make the ECU think the air is cold and therefore would richen the mixture, which should stave off pinging. It can't think it's much hotter than it actually is, but hell I'll give it a try.

 

Don't replace anything without checking it first.
Your ECT and IAT can be checked with just a multimeter.
Check the ohms when the vehicle is cold, and then let the engine warm up and check it again at operating temperatures. It should fall pretty close to this chart. The ECT and IAT sensors are the same type of sensor and follow the chart below.

How did you check your WOT fuel pressure? Did you take it on the highway and floor it for 5 seconds while watching the gauge? Or did you blip the throttle in your drive way?

 

Blip the throttle at home. Thank you for the chart.