HELP! I've scoured through as many posts as I could find and can't find a solution to my problem.

I was given a 1989 F250 with a 5.0 as a donor car for a 58 F100 project. 140,000 miles. I decided to go a different direction with the 58 so I decided to get the 89 running and sell it. The 89 was a nop start when I got it. Computer was fried. Once running it needed an IAC and a tuneup (cap, rotor, plugs, filters, oil.) I also had to pull the bed and replace the sending units/low pressure pumps and the alternator. It idled good (a little stumble) and accelerated great. Problem is it has a ping when at road speeds and barely accelerating. With a load it is worse. Give it gas or let off the gas and it stops. Timing is set at 10 degrees BTDC with spout off. Seafoamed it and tried backing off the timing. Still there. What confuses me is the pinging is worse when I retard the timing. After the seafoam the stumble is gone. Runs as smooth as any engine I ran. Has good oil and fuel pressure and is not overheating.

I did rap on the back of the engine while looking at the timing and nothing changed. I confirmed it is plugged in. I am assuming it is bad. Can a bad knock sensor cause it to ping? I ran it in pitch black at idle through about 4000 rpm. No arcing.

I have about $1000 into it (brakes, trans work) and dont want to spend extra money throwing parts at it without an informed guess at what it might be.

Anyone out there have any suggestions?

 

Pull the plugs and examine them for color, if one of the cylinders is running lean due to a dirty/partially clogged injector the computer won't be able to compensate for it. Could also be an EGR problem, you could try blocking the EGR valve at the intake to see if it makes any difference. I don't suspect the valve is sticking open as that would cause a rough idle. Also bring #1 piston up to TDC and verify the balancer outer ring hasn't slipped, this isn't uncommon with engines this old.

 

I chased pinging problems with my 302 for awhile. I would agree with looking at the plugs to see if it is a single cylinder. If I remember correctly the knock sensor is more of a back up to stop pinging in case it does ping. Is the coolant very rusty?

 

Start by pulling the codes and doing a KEOR test. The KEOR test should test the knock sensor if you have one.

 

Thanks all for the replies. Gonna dig into it this weekend. No codes but I did have to run the tests a second time due to a knock sensor code. Cleared the second time. With the timing light hooked up and hitting the block near the sensor, I get no change in timing.

Plugs are new (maybe 50 miles) so I don't know what they will tell. Engine does run very smooth from idle to high rpm. I flushed the coolant out when I got it and don't remember anything too dirty about it.

I'll check the balancer ring but when I retarded it, the pinging was worse. Anyone have any thoughts on that? Is the computer over compensating?

I haven't pulled the egr to look at it but it passed the vacuum on at idle/stumble test. Could be intermittent.

 

Are you sure you were turning the distributor in the right direction?

 

LOL, yes. I knew someone was gonna ask and I have been trying to think of a witty answer but I'm drawing a blank.

 

Well I dug into it today. Confirmed the timing marks are correct. Pulled the EGR and it functions fine and is really clean inside. But.... found out the egr tube on the exhaust side is broken. It must have been cracked because it came completely loose when I was putting it back on the EGR.

So 2 questions for those who have experienced this:

Would a leak in this tube cause the intermittent ping I described above?

Can I replace it without taking the intake off?

 

I'm betting the cracked tube was sucking air and causing a lean condition at cruise and light accel. Whereas it would normally be getting inert exhaust air it was getting fresh air. And when you would floor it the egr shuts therefore cutting off the vacuum leak.

 

That would make sense. I ordered a new tube and get it on Tuesday. Everything I've read says I need to take the plenum off. New question is would retarding the timing create more vacuum at cruise and light accel conditions?

 

That would make sense. I ordered a new tube and get it on Tuesday. Everything I've read says I need to take the plenum off. New question is would retarding the timing create more vacuum at cruise and light accel conditions?

 

No, but in a carburetion application less timing at cruise causes a less efficient burn that's why vacuum advance came along. I would say the same applies for fuel injection, fuel delivery method is different, but burn is the same.

 

hey what would the rusty coolant be a sign of.......

 

The 302 in my truck was pinging in one cylinder due to rust plugging up a water jacket and making that one cylinder run hot. It's an unlikely scenario. The coolant was brown sludge when I bought my truck though.

 

Poor maintenance.