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Wolfie_85

Well-Known Member
Joined
April 20, 2014
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City, State
Iowa
Year, Model & Trim Level
1994 Ford Explorer XLT
I recently had a head gasket failure. Don't worry! It's been fixed. But, what puzzles me is that I STILL have that damn ping. After what was pretty much the disassembly and cleaning of everything from the heads up, along with the replacement of all the gaskets therein and any other parts that needed replaced, it still pings under certain load conditions on the highway (accelerating between 2-3,000 rpm).

Now, it surprised me a touch. I know all the causes. I know some of the cures. I thought my silver lining here would have been a cure. :p Anyway, pretty convinced it's the MAF. Any other ideas?
 



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Pinging is detonation before the spark occurs, it's an uncontrolled burn. This happens for a few reasons; lean mixture, high compression or low quality/low octane fuel.

Let's break that down. Lean mixture can be a real turd. Anything from a vacuum leak to malfunctioning sensor could cause it. High compression would occur for 2 reasons, either you modified the engine for it specifically or you have severe carbon build-up. In your case, neither of those is right so you can wipe that off. The Explorer is rated to run on today's fuel as long as it's 87 octane or higher. I don't think you can find lower than 87 octane so that's a non-issue as well.

So, pretty much either a vacuum leak or malfunctioning sensor. Vacuum can be straight forward and testable with a gauge. Malfunctioning sensors are trickier. You can test them but it's not always easy. There also could be corrosion in wiring or just a bad connection.

I saw a video by a guy on YouTube called Scanner Danner where he worked on an EEC-IV Ford, I think it was a 1988 F150 or something. Anyway, it wouldn't spark, it wasn't getting pulses for spark. He went through and tested things and said it HAD to be the ICM. Bought a new one and still the same problem. Turned out that if he unplugged the SPOUT timing connector, it ran perfectly. That's because that connector turns on the computer timing advance and with it removed, it was defaulting back to unoptimized but running settings. What went wrong was the wiring to the ECM relay was bad, causing the computer to get low power/voltage and not work properly. Jumped the relay before the faulty wiring and it ran beautifully with the SPOUT back in place. These vehicles are old enough that things as basic as wiring can really screw with a system that otherwise works.
 






Honestly, with all I've tinkered with on this truck, the wiring is the one thing (short of the interior stuff I've replaced) that I haven't checked out. I will have to dig around.
 






If the rocker arms are worn down on the pushrod end and have never been replaced, it could be that the the "ping" you're getting is from valve clatter.

When they are only starting to wear, it's more like light pinging, if you keep driving it until they are badly worn, it gets to be real obvious and loud valve clatter under load.

No other way to fix it other than new rocker arms.

http://www.explorer4x4.com/lifters/lifters.htm


Sometimes easy fixes like new spark plug wires or even a new coil pack can fix ping issues that aren't from a vacuum leak or sensor.

If cheap parts were ever used, sometimes they can cause issues and replacing them with either OE or a known good brand can be the fix. This goes for plugs, wires, sensors, etc. Cheap plugs and wires in particular have been the source of a lot of issues, and people have spent a lot of time and money looking for issues that turned out to be nothing more than the cheap plugs and wires giving poor performance.

The 4.0L OHV seems to work best with Motorcraft platinum plugs, so using other plugs, even Autolites, and especially any gimmicky multi-electrode plugs, can cause weirdness, anything from rough idle to poor combustion -and then pinging from carbon build-up.

I'd say clean the MAF real good, check the intake tube for cracks and leaks, and the vacuum fittings and lines going to the intake. The hard plastic lines get brittle with age from the engine heat and eventually have to be replaced with vacuum tubing.
 






Guys, I'm going to show my ignorance big time and ask how you troubleshoot a vacuum leak. Specifically, how much vacuum is a normal reading, where, and under what conditions? (I've done electrical, electronic, pneumatic, and hydraulic troubleshooting, but never vacuum.) If this is a new thread, please feel free to move it, but thought it was an appropriate question for this one.
 






One way to troubleshoot would be to get a stock vacuum reading (remove a cap on the vacuum tree, attach gauge there) and then to remove all the hoses from the vacuum tree, cap them off and get another reading. This will tell you if you have vacuum line issues. What it won't tell you is if your intake gasket, fuel rail gasket, upper intake gasket, throttle body gasket or charcoal vapor canister hose is leaking.
 






I just replaced the charcoal canister hoses. All the gaskets from the head up were also replaced. So, I am leaning toward the MAF, the wiring to the MAF, or a vacuum leak somewhere. I haven't had a chance to look, and the weather isn't going to be cooperative for the next couple days. :p I can't wait to figure it out. I have a ton of outside stuff to do!
 






I don't often say much about one product or another, but Gumout Multi-System Tune-Up is great. Got rid of the ping (for now)! It is packaged the same way Seafoam is, in the same type of container. It just works better with ethanol fuels (all there is around here) to clean up carbon deposits. I apparently had some carbon on a cylinder wall or two.

But, since I've had the truck, I've tried every other product and fuel available to me, with limited or non-existant results. This worked on the first tank. Highly recommend if you have ping, but ruled out the MAF, vacuum lines, intake gaskets, or just plain crappy gas. :)
 






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