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Pinging 4.0 OHV, tried most solutions.

nameiztaken

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1991 EXPLORER XL
Making a dedicated thread for this, hopefully someone here has some tips on possible causes or things to check.

Getting some mild to heavy pinging on 87 octane when putting the vehicle under load (merging on highway, grades, etc). Its a 1991 4.0 with the 5spd. Also getting a somewhat rough idle, but nothing serious.

I think the IAC may be broken - as unplugging it changes nothing. I cleaned it and had no improvement other than raising my idle rpm from ~800 to ~950. It does not appear to move when I turn they key on with the engine off. One fuel injector is ticking louder than others (checked with long socket extension)

Some of the stuff I’ve tried:
Replaced lower/upper intake manifold gaskets
Searched for vacuum leaks, couldn’t find any. Unplugged individual vac lines at tree and plugged the tree, no change
Replaced fuel filter & checked pressures, ~29-39psi
Replaced spark plugs and wires with autolite single platinums
Replaced coil pack
Replaced pcv valve
Cleaned maf (3x)
Cleaned throttle body and IAC
Cleaned intake air temp sensor (2x)
Used seafoam through brake booster line
Used techron in the gas (2x)

Not much difference after all of those repairs.
 


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Gadget X

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I have always had to run 93 in mine to prevent pinging under load. It also seems to have a lot more "get up and go" with the 93, so that's just what I always run!
 




nameiztaken

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I have always had to run 93 in mine to prevent pinging under load. It also seems to have a lot more "get up and go" with the 93, so that's just what I always run!
I’m thinking about doing this as well, its not that much more at costco.
The only reason I haven’t yet are the warnings that higher octane may cause more carbon buildup - making the original issue worse.

I also heard that 87 octane was better in the 90’s, when this car was built 🤷‍♂️
 




nameiztaken

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Just removed the octane shorting block near the firewall and have had excellent results - car has more power, and the pinging is entirely gone. I’m going to continue trying to remedy the issue the correct way but if I cant, this may have to be the fix.
 




Gary Crist

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I once had a client whose intake manifold on a Lincoln was defective.
So they replaced it with a manifold ( IIRC a Torker) with no EGR provisions. This car is where I
learned how important EGR was to stopping pinging! Nothing would stop
the ping, even timing. Lean part throttle was a killer!

I wonder if stopped-up or otherwise restricted passages result in reduced flow of EGR
and higher combustion pressures and temps as well as "glowing" combustion deposits etc.
 




nameiztaken

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I once had a client whose intake manifold on a Lincoln was defective.
So they replaced it with a manifold ( IIRC a Torker) with no EGR provisions. This car is where I
learned how important EGR was to stopping pinging! Nothing would stop
the ping, even timing. Lean part throttle was a killer!

I wonder if stopped-up or otherwise restricted passages result in reduced flow of EGR
and higher combustion pressures and temps as well as "glowing" combustion deposits etc.
My explorer is a non-EGR model, which could be contributing to this.
 




nameiztaken

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Just an update, over the past couple of days I have gotten a significant improvement. The month old non-oem PCV valve appears to have been sucking a large amount of oil out of my crankcase, so I replaced it with a new one of the same brand since I cant find a motorcraft one locally. I’m fairly certain I don’t have significant blowby issues, only 130k miles, so I’m not sure whats up with this.

I used about a cup of water into a vacuum line like shown in this video and got a significant improvement. This is surprising since Seafoam made no noticeable difference previously... The explorer idles far better and has more get up and go, but still pings occasionally or when really giving it the gas on the highway.
Still trying to find a complete solution.

New pcv is on the left
BC6AC325-7387-43E8-A41B-91905F85873D.jpeg
 




Gary Crist

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If your PCV valve was sucking oil, you would be smoking mosquitoes
out of the neighborhood! I had that on a Chrysler 2.2. It looked like
about a cup per burn. Oil return holes in the head were plugged up too.
This is another reason valve cover gaskets start to leak. Oil return holes fill
with deposits and the covers can fill with oil.

Ford 429s and 460s were notorious about pinging and running on after shut-off
during the coveted mid-70's. We would run about 1/2 to 1 gallon of ATF through
them and it would help some.
 




nameiztaken

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If your PCV valve was sucking oil, you would be smoking mosquitoes
out of the neighborhood! I had that on a Chrysler 2.2. It looked like
about a cup per burn. Oil return holes in the head were plugged up too.
This is another reason valve cover gaskets start to leak. Oil return holes fill
with deposits and the covers can fill with oil.

Ford 429s and 460s were notorious about pinging and running on after shut-off
during the coveted mid-70's. We would run about 1/2 to 1 gallon of ATF through
them and it would help some.
ATF through the intake? or in the gas/oil. I’ve heard of the atf in oil just before an oil change trick.
 




nameiztaken

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This oil buildup inside the intake is another reason I am suspicious of the pcv system. I am losing about 1/3 of a qt of oil per month. Thinking about adding an oil catch can
23923A96-0A1F-4A0B-AF8A-01781F021B0E.jpeg
 




Gary Crist

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That is normal reversion. What weight oil are you running? If it
is a 5W-X or a10W-X, try an oil change to straight 30 for 1 oil change,
see if it there is a difference. BTW, how much oil loss per 1K miles are you talking about?
 




nameiztaken

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That is normal reversion. What weight oil are you running? If it
is a 5W-X or a10W-X, try an oil change to straight 30 for 1 oil change,
see if it there is a difference. BTW, how much oil loss per 1K miles are you talking about?
I haven’t been able to figure out how much I’m losing per thousand miles yet but its slow enough to not be too concerning. (but definitely more than normal)

Have been running 10w30 Mobil 1 for all oil changes. Bought it in January, don't know what was in it before.
 




Gary Crist

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Next time you are low on oil add a quart of Valvoline VR1 say
straight 30W. It has high Zinc and will not hurt the cats. I use
4 quarts 10W-30 Mobil with 2 quarts of 20W-50 in my EDGE.
It quieted down the cam phasers so they don't click so bad.

Those V6 OHVs, are killer engines and you almost can not kill them!
 




gmanpaint

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Might be the fuel pump relay, has degraded due to heat and age. It won't feed the pump all the power it needs under load, and the engine starves for fuel.
A new Relay is cheap, and worth a try. Worked for mine when I faced this exact issue years ago.

Another thing to note:
The wires leading into the Power distro box, and the box itself do degrade with age, as engine bay heat will take it's toll on them. This is a harder fix, but doable with salvage parts.
 




nameiztaken

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Next time you are low on oil add a quart of Valvoline VR1 say
straight 30W. It has high Zinc and will not hurt the cats. I use
4 quarts 10W-30 Mobil with 2 quarts of 20W-50 in my EDGE.
It quieted down the cam phasers so they don't click so bad.

Those V6 OHVs, are killer engines and you almost can not kill them!

Yeah I really like the 4.0 ohv, even with the ping its still a reliable motor that I can depend on.
Might be the fuel pump relay, has degraded due to heat and age. It won't feed the pump all the power it needs under load, and the engine starves for fuel.
A new Relay is cheap, and worth a try. Worked for mine when I faced this exact issue years ago.

Another thing to note:
The wires leading into the Power distro box, and the box itself do degrade with age, as engine bay heat will take it's toll on them. This is a harder fix, but doable with salvage parts.
Going to replace that relay and see if it changes soon.

Today I followed the Ford TSB for removing carbon (except I used seafoam) - pinging condition has once again improved more. I may buy a borescope to have a look inside the cylinders, now I’m curious.
 




Exploder321

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Making a dedicated thread for this, hopefully someone here has some tips on possible causes or things to check.

Getting some mild to heavy pinging on 87 octane when putting the vehicle under load (merging on highway, grades, etc). Its a 1991 4.0 with the 5spd. Also getting a somewhat rough idle, but nothing serious.

I think the IAC may be broken - as unplugging it changes nothing. I cleaned it and had no improvement other than raising my idle rpm from ~800 to ~950. It does not appear to move when I turn they key on with the engine off. One fuel injector is ticking louder than others (checked with long socket extension)

Some of the stuff I’ve tried:
Replaced lower/upper intake manifold gaskets
Searched for vacuum leaks, couldn’t find any. Unplugged individual vac lines at tree and plugged the tree, no change
Replaced fuel filter & checked pressures, ~29-39psi
Replaced spark plugs and wires with autolite single platinums
Replaced coil pack
Replaced pcv valve
Cleaned maf (3x)
Cleaned throttle body and IAC
Cleaned intake air temp sensor (2x)
Used seafoam through brake booster line
Used techron in the gas (2x)

Not much difference after all of those repairs.
My '01 5.0 had the exact same problem, for the longest time I thought it was carbon build up on the piston heads. Turned out it was the EGR system. I had gotten the 'insufficient EGR flow' error intermittently, checked the valve operation, vacuum lines, even changed out the DPFE sensor, still it pinged. The last time I ran the codes at autozone, they called out the DPFE sensor as bad, which surprised me since I had changed it a while back; it must have been defective. With the new one in ( a BWD unit ) it hasn't pinged since. Be sure all your vacuum lines are good, the one to the EGR from the modulator became brittle and broke, spliced it with a small piece of vacuum line. Good article at the link:

Just saw your 'non-EGR' comment, this should help someone...
 




Exploder321

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similar situation on a 4.0 Ranger... he changed the intake manifold gaskets...

 




nameiztaken

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Did the math - in exactly 30 days and 1,490 miles I lost approximately one quart of synthetic 10w30.
 




~X~

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Just curious, how is your cooling system, have you done a flush? Ever take readings with an infrared thermometer & compare them to your gauge on the dash? You see where I'm going here.....
 


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nameiztaken

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Just curious, how is your cooling system, have you done a flush? Ever take readings with an infrared thermometer & compare them to your gauge on the dash? You see where I'm going here.....
haven’t really touched it aside from replacing the tstat (now has a 197f motorad).... but the pinging didnt happen when I tried a 180 stat for a couple days. I drained about a gallon of coolant out and replaced it.

My temps do creep up at idle in the California summer heat, and I also noticed the temps climb when it starts pinging.
Edit: the temp needle never passes the A on NORMAL.

You might be on to something lol...
 




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