302 won't stop pinging
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302 won't stop pinging
Hello, I have a 1994 F-150 that has been having a pinging problem for the summer. It only seems to ping under load going up a hill unloaded or any thing other than flat ground on the highway while towing my boat at 65 mph(have to sometimes slow down to 50 mph). Upper intake manifold gasket was replaced due to a small leak, distributor cap and rotor, MAF sensor has been cleaned and I swapped in a spare I had(no difference), spark plug wires are new and are routed correctly, timing is right on 10 degrees, the fuel pressure is within spec while at idle(hose isn't long enough to tape to the windshield), and the knock sensor was swapped with junkyard one(can't find a new one). It has a small exhaust leak, could this be causing it? Any other ideas of what could be causing it?
Cargo Master
Joined: Mar 2010
Posts: 3,330
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From: Laramie, WY
Hello, I have a 1994 F-150 that has been having a pinging problem for the summer. It only seems to ping under load going up a hill unloaded or any thing other than flat ground on the highway while towing my boat at 65 mph(have to sometimes slow down to 50 mph). Upper intake manifold gasket was replaced due to a small leak, distributor cap and rotor, MAF sensor has been cleaned and I swapped in a spare I had(no difference), spark plug wires are new and are routed correctly, timing is right on 10 degrees, the fuel pressure is within spec while at idle(hose isn't long enough to tape to the windshield), and the knock sensor was swapped with junkyard one(can't find a new one). It has a small exhaust leak, could this be causing it? Any other ideas of what could be causing it?
Does fuel pressure increase when you disconnect the vacuum feed to it? Would certainly be better to test pressure with a load on, a weak pump often won't come up obviously bad with idle tests.
How does the harmonic balancer look? Could it have slipped on you?
Are you sure the knock you hear isn't just the exhaust leak?
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A few thoughts: Any modifications to the truck?
Does fuel pressure increase when you disconnect the vacuum feed to it? Would certainly be better to test pressure with a load on, a weak pump often won't come up obviously bad with idle tests.
How does the harmonic balancer look? Could it have slipped on you?
Are you sure the knock you hear isn't just the exhaust leak?
Does fuel pressure increase when you disconnect the vacuum feed to it? Would certainly be better to test pressure with a load on, a weak pump often won't come up obviously bad with idle tests.
How does the harmonic balancer look? Could it have slipped on you?
Are you sure the knock you hear isn't just the exhaust leak?
Cargo Master
Joined: May 2001
Posts: 3,208
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Heat, lean, to much advance is what causes pinging. My guess is lean. You either still have a vacuum leak or the MAF is bad. Disconnect the MAF it will go into limp mode see if it pings then if it doesn't then I think that will be the culprit.
Cargo Master
Joined: Aug 2007
Posts: 2,560
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From: New Zealand
Traces of oil getting into the cylinder(s) will cause pinging; the oil effectively lowers the octane rating of the gas.
I had the same problem a couple of years ago. Changing to a colder plug helped........but a leaking intake valve stem seal that was allowing traces of oil into the cylinder, was the cause of the problem.
I had noticed one plug would sometimes look white, & sometimes match the other seven. The white ash was burnt oil coming past the stem seal; the ping slowly got worse.
I replaced it (& all the others while I was in there), & the problem was fixed.
Good luck
I had the same problem a couple of years ago. Changing to a colder plug helped........but a leaking intake valve stem seal that was allowing traces of oil into the cylinder, was the cause of the problem.
I had noticed one plug would sometimes look white, & sometimes match the other seven. The white ash was burnt oil coming past the stem seal; the ping slowly got worse.
I replaced it (& all the others while I was in there), & the problem was fixed.
Good luck
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Lead Driver
Joined: Feb 2002
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From: Greater Austin, Texas
I am not sure when Ford changed the 302 over to the 351W firing order. If your firing order ends in "7-8" you need to make sure the #7 and #8 wires are routed away from each other as much as possible. This was the problem on my 1990 F150 w/302 when it pinged all the time, even on premium fuel.
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It was a trusted mechanic that did the timing and manifold gasket but he did remove the spout. The timing was set around 12 or 13 degrees but he put back to 10. Condition of the plugs looked good this spring but I will check them again this weekend.
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I will check the vacuum that I am getting from it when I get the chance. It was 19.5 inches of mercury before the upper intake manifold was replaced. I will also try disconnecting the MAF sensor and see if that does anything.
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Senior User
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I am not sure when Ford changed the 302 over to the 351W firing order. If your firing order ends in "7-8" you need to make sure the #7 and #8 wires are routed away from each other as much as possible. This was the problem on my 1990 F150 w/302 when it pinged all the time, even on premium fuel.
Thread Starter
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Senior User
Joined: Sep 2016
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Traces of oil getting into the cylinder(s) will cause pinging; the oil effectively lowers the octane rating of the gas.
I had the same problem a couple of years ago. Changing to a colder plug helped........but a leaking intake valve stem seal that was allowing traces of oil into the cylinder, was the cause of the problem.
I had noticed one plug would sometimes look white, & sometimes match the other seven. The white ash was burnt oil coming past the stem seal; the ping slowly got worse.
I replaced it (& all the others while I was in there), & the problem was fixed.
Good luck
I had the same problem a couple of years ago. Changing to a colder plug helped........but a leaking intake valve stem seal that was allowing traces of oil into the cylinder, was the cause of the problem.
I had noticed one plug would sometimes look white, & sometimes match the other seven. The white ash was burnt oil coming past the stem seal; the ping slowly got worse.
I replaced it (& all the others while I was in there), & the problem was fixed.
Good luck
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Thanks for the info. I will just be keeping it stock for good measure. I will be checking the plugs on Saturday as I don't have much time to work with this week.
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