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1992 Explorer XLT Pinging Problem. Tried EVERYTHING. HELP

turboki

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Hey guys,

long time lurker first time poster here. I've got a 92 XLT that I built into an overlanding truck and started my Pan-America Highway trip. Well, pretty soon into the trip I started getting pinging going uphill. 91 gas helped, but it was there the whole time. By the time I got to Northern Canada, a weird thing started happening. The truck would throw a CEL but the pinging would completely stop. As soon as I would turn the truck off the CEL would clear itself and the pinging would start. Well I was in the middle of nowhere and had no reader at hand so I couldn't see what was happening, but I kept it full of 91 and drove it back to San Diego without too many issues.

Since I've been back I've tried everything I found on these forums. SeaFoam treatment, cleaned MAF, replaced Manifold Temp and O2 sensors, checked for vacuum leaks, replaced the PCV valve and replaced the head gaskets (had some unrelated oil/coolant leakage, so I know the lower intake is tight to spec. I also replaced the coil pack, the wires and plugs as well as the fuel pump. I checked out the injectors and they looked clean, but just as a precaution I ran some cleaner through the system for a few days. I also got my hands on a SnapOn diagnostic tool which shows everything in the truck to be honky dory. Yet the damn thing wont stop pinging when I'm going uphill. Now I even removed the Octane Short Bar that prevents the timing from advancing allowing you to run shit gas without pinging, but it's still pinging on big hills. The rest of the time it drives strong, idles perfect, has no issues. The noise it makes when going up hills is like 2 spoons clicking against each other, but not consistently. Its more like change in the dryer.

I really don't know what else it could be. The only thing I can think of doing is a full rebuild on the whole block, but I really really don't wanna invest that kind of money into it at this point.

Can you guys think of anything else it could be?

Also, the 92 does not have EGR or a BARO sensor so these are not the cause.
 


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Ramblinwilly

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1. Timing and Timing belt or chain.
2. Compression Check & Leak down test(how long does the cylinder hold compression). If compression is low, determine if it is valve(s) or ring(s).
 




malohnes

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Sounds like loose Lower Intake Manifold bolts. Could also be upper manifold bolts as well. Worn rocker arms and pushrods are common for our rigs and could also be contributing to your condition. It took me a long time to fix my pinging, which resulted in a blown head gasket from a cracked head. A top-end rebuild ultimately cured the issue.

All these things: cracked heads, blown gasket, loose intake bolts, etc can cause your pinging. There are other things too, such as your engine running hot and heavy carbon build up. You seem to understand in your posting above, and took care of some other obvious basics but I'd also do some more searching in the forum for others who have tried curing there pinging issues. It is quite common.
 




Anime

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Probably the worn rocker arm issue. The factory rocker arms were made from metal that was a little too soft and they get indentations from the valves, leaving a lot of space that the lifters eventually can't compensate for and you get valve clatter under load.

The only fix is new rocker arms. Not super expensive, not hard to do, but you do have to pull the rocker arm covers. It's a good chance to replace the upper and lower intake gaskets while you're at it, and of course the valve cover gaskets as well.


lifters9-01.jpg



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




turboki

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It's not the heads or intake bolts. I've already rebuilt the top end twice since the pinging started, including replacing some of the worn in rocker arms. Everything has been torqued to spec. It's not carbon buildup either, as the heads only have about 10000 miles on them since full rebuild and the bottom end looks clean as a whistle.

Correct me if I'm wrong, but if there was anything wrong with the timing chain it would cause all sorts of issues, not just pinging under load. Besides, in my experience, the chain is the last thing to go on a motor.

The only thing that's a little wonky with it is the compression. The lowest compression is 140, the highest is 180. That's a big difference, but according to the manual up to 25% difference is allowed. Now, would low(er) compression cause ping?
 




FR-425

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I'm getting the exhaust leak feeling here.

Hard pulls get the exhaust manifolds hot enough to open small crack that at lower temps doesn't leak. Freaky I know. High temps can also temperately warp them creating a leak at the gasket surface.

Neither condition requires immediate attention.

Give them a close look for discoloration that looks like carbon "spider webs" this would be from a tiny crack.

Clean looking spots on the visible gasket edges = leak.

Small exhaust leaks will cause random "pinging" sounds when there is a monetary negative pressure. i.e. cylinder down stream from the leak fires and draws fresh air into the exhaust at the leak causing un-burned fuel to ignite.
 




Ramblinwilly

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I'm getting the exhaust leak feeling here.

Ditto here. But since you are chasing an unknown cause of an issue, I'd still recommend checking the timing. Chased a similar issue down awhile ago and it wound up being that the timing was off just a hair.
 




turboki

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I'm getting the exhaust leak feeling here.

Ditto here. But since you are chasing an unknown cause of an issue, I'd still recommend checking the timing. Chased a similar issue down awhile ago and it wound up being that the timing was off just a hair.

I was under the impression that the 1st gen explorers have fully electronic timing, so there is no way for me to adjust it. Is this correct or is there a way to muck with the timing?
 




turboki

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The exhaust leak is not only possible but probable. I'll check it out.
 




malohnes

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When you rebuilt the top end, did this include the timing chain, because that is also a probable place to look? As I understand other than base timing, there are no timing adjustments to play with other than the shorting plug.

Your compression doesn't sound very even, but it may not reflect head or gasket issues. Pinging could very well come from one cylinder. I would investigate that area too. I have a 15 point difference between the best and worse cylinder and I understand from those with more knowledge and experience that 10% is fine, anything greater is suspect.
 




FR-425

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Turboki,

Yes the first gen 4.0's are fixed timing. The only adjustment is in the initial set-up "Cam Swap" for example. Other than that the Octane Shorting Bar is the only user manipulation of timing.

Yes you could send the PCM to a tuner for a flash but I seriously doubt there would be enough improvement over stock tune on a stock engine to justify the cost.

Here's a thought though, You may be getting a sloppy signal from the crank position sensor causing the timing to jump around. Speed sensor may add to the problem if it is also generating a noisy signal. Your PCM seems good or you would be getting random unrelated codes.

Not to mention the Knock Sensor! uh if 92's have them?

93 and 94 do have a knock sensor which retards the timing up to 3 degrees on trigger.

THE OWNERS MANUAL SAYS THAT "LIGHT" PINGING UNDER HEAVY LOAD IS EXPECTED AND NORMAL AND WILL NOT HARM YOUR ENGINE.

I get a little "light" random pinging when I try to maintain 60+ on a 6% grade but it is "light" and I am not really concerned.

I have had severe pinging it the past but it was EGR related. I have also removed the Shorting Bar. Runs much better without it. With it in, full throttle on 87oct was not an option. Remember in '95 Premium was 93oct @ $1.45 and regular was 89oct. and no ethanol! So they designed this engine to run on 89oct minimum. Even 91oct is not high enough to run wide open with the shorting bar in.

When I tow or take a mountainous highway drive I run 91 with the bar out and only get a slight, very slight ping.

Reduced compression is not responsible and cannot be.

Octane rating is based on how much heat is required to ignite the fuel.
pinging is caused by ignition before spark. "red hot carbon acting like a glow plug for example" or crappy fuel that ignites just by heat produced by compression alone. That's how diesels work "compression is so high - 22:1- that it ignites the fuel without spark assistance.
 




Ramblinwilly

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Please correct if I'm wrong but I thought timing could be changed by disconnecting the spout connector.

Right near the ignition module you will see a connector that is a simple jumper. The wires are usually yellow and the connector goes nowhere. Should be within 4 inches of the module. The module will be on the distributor on some models and on the fender of others. Have the engine warmed up then disconnect this jumper. The purpose of this jumper is to tell the computer not to adjust the timing while you perform your base timing check or adjustment. Otherwise as you adjust it, the computer would keep trying to set it back. When you get the correct jumper unplugged, you will see the timing has changed to base timing.
 




turboki

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Turboki,

Yes the first gen 4.0's are fixed timing. The only adjustment is in the initial set-up "Cam Swap" for example. Other than that the Octane Shorting Bar is the only user manipulation of timing.

Yes you could send the PCM to a tuner for a flash but I seriously doubt there would be enough improvement over stock tune on a stock engine to justify the cost.

Here's a thought though, You may be getting a sloppy signal from the crank position sensor causing the timing to jump around. Speed sensor may add to the problem if it is also generating a noisy signal. Your PCM seems good or you would be getting random unrelated codes.

Not to mention the Knock Sensor! uh if 92's have them?

93 and 94 do have a knock sensor which retards the timing up to 3 degrees on trigger.

THE OWNERS MANUAL SAYS THAT "LIGHT" PINGING UNDER HEAVY LOAD IS EXPECTED AND NORMAL AND WILL NOT HARM YOUR ENGINE.

I get a little "light" random pinging when I try to maintain 60+ on a 6% grade but it is "light" and I am not really concerned.

I have had severe pinging it the past but it was EGR related. I have also removed the Shorting Bar. Runs much better without it. With it in, full throttle on 87oct was not an option. Remember in '95 Premium was 93oct @ $1.45 and regular was 89oct. and no ethanol! So they designed this engine to run on 89oct minimum. Even 91oct is not high enough to run wide open with the shorting bar in.

When I tow or take a mountainous highway drive I run 91 with the bar out and only get a slight, very slight ping.

Reduced compression is not responsible and cannot be.

Octane rating is based on how much heat is required to ignite the fuel.
pinging is caused by ignition before spark. "red hot carbon acting like a glow plug for example" or crappy fuel that ignites just by heat produced by compression alone. That's how diesels work "compression is so high - 22:1- that it ignites the fuel without spark assistance.


Ok, so my pinging is very light, only under load uphill, so it could be "normal", but if possible I would love to get it to go away completely. My truck is loaded down with all my gear so it's pretty heavy and running without the octane block makes the pinging barely noticeable, but I am running 87 gas.

I still need to check the exhaust, and I might just pick up another PCM from the junk yard and see if it makes a difference.

I also have a very intermittent issue where my voltage gauge starts freaking out for a few minutes and then settles down. No noticeable change in lights, audio or performance, just the gauge starts freaking out. Usually when it does settle it stops at a lower position then normal. I know these gauges are crap and don't actually tell you anything too useful, but could this possibly be interfering with the PCM? Just to note tho, the pinging and the voltage gauge freaking are never in sync... so I don't think one causes the other, but maybe there is some relation.
 




FR-425

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Negative on the gauge causing any probs it's not in the feed back loop.

Cluster is prob get'n dusty. Computer cleaner canned air and some electronics cleaner will bring your cluster back to like new. Get the stuff that is "Acrylic friendly" and it won't hurt the gauge face or the acrylic lens. Brings the White back too, improved back lighting.

Run 91 on road trips. Whenever I hit the highway or go wheel'n it's 91 and that does the trick. Commuting to work and it's the cheap stuff and less skinny pedal.

When hauling a trailer I just have to give in and take it easy on the old gal.

On 6% grade with my 3500lb trailer You just have to slow down to 35 get it in 2nd gear and it'll pull 35mph at 2550rpm Half throttle. Nice and gentle on the motor.

With no trailer but loaded I just slow to 45 disengage the TCC then drop to 3rd gear which is the 1:1 grear. This is what is recommended in the owners manual " NO towing in OD" Transmission must be in "D" drive. " for steep grades the same is true"
This is not only about engine performance you will kill the transmission hard pulling and towing in OD. THIS WARNING IS IN ALL CAPITOL LETTERS IN THE MANUAL. Maybe some people have killed an a4ld or two doing this?

You will be able to pull 55mph on the speed-o @ 3100rpm or so depending on tire size.

stock tires will run 55 mph @ 3350 according to the manual.
The manual says this is the preferred rpm for these conditions.

This is why the "55" on your gauge is still "red" Not like the old days when they did the red letters because the nation-wide speed limit was 55. It's because the vehicles towing duty max speed is 55.

You can only get so much out of 4.0l

P.S. If the gear selector is in OD and you mash it to the floor it will down shift into what you think is 3rd gear but it is in fact 3rd and 4th (OD) at the same time.

Same for city driving when selector is in OD, the OD drum is engaged at all times. It ads the 0.7:1 ratio to all the gears. Gives a smoother (slower) shift and under moderate acceleration will improve gas mileage.

I don't like it!
With 33's on 3:73's I manually shift to OD only after I get up to speed.

Also putting it in "D" changes the power valve position in the trans to high pressure position providing faster shifts and higher pressure on the clutch packs.

So even though the a4ld is known as AOD (Automatic Overdrive) transmission The manual clearly states that it is a "Manual" OD trans. Meaning it is up to the driver to control OD function.

On second gens they made it a little easier buy adding a push button on the shifter.

Why all the transmission talk on a PINGING question. Well I think many of us are "lugging" the engine-- full throttle at to low an rpm.
 




FR-425

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One last note on pinging:

Air intake temp. Hot air coming in will make pinging problems worse.

Modified or after market air cleaners are a BAD idea for these trucks.

The factory fresh air inlet is on the bottom of the air box pointed inward toward and just above the frame. Getting air from the wheel well, well away from engine heat.

The only air inlet mod that I have seen that works is moving the inlet up through the hood to get it out from under the hood.

The wheel well location is not so good in deep water!

So if you have a "super-D-duper" after market air cleaner, Ditch it!
 




FR-425

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:DI love my owner's manual sooo much I'm going to read it cover to cover again!:D

Lots-o-nice bits in there.:salute:

The "Exploria Biblica"
 




turboki

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Hey FR-425.

Thanks for all the info! I actually have a manual, so I try to keep the truck around 3000rpm max and light load on my own, but my tack is stuck on 4500 so I just go by engine noise. The intake is fully stock. Learned a long time ago that for the most part aftermarket intakes are a bad idea. I only have one more day before I leave for central america so I'll try and check out as many things as I can, but I think I'll just have to live with the ping and just treat it gingerly.
 




jd4242

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Hey FR-425.

Thanks for all the info! I actually have a manual, so I try to keep the truck around 3000rpm max and light load on my own, but my tack is stuck on 4500 so I just go by engine noise. The intake is fully stock. Learned a long time ago that for the most part aftermarket intakes are a bad idea. I only have one more day before I leave for central america so I'll try and check out as many things as I can, but I think I'll just have to live with the ping and just treat it gingerly.

Not going over 3, 000 can cause build up which will cause pinging, not saying its your problem now but sure doesn't help
 




malohnes

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Your voltage gauge bouncing could be your cables to your battery, be it a loose connection or corrosion. This happens a lot when corrosion migrates up the positive cable and prevents smooth current flow. I ended up replacing all my cables with custom cables and connectors to the battery and haven't had troubles since.

This could also affect your engine and promote pinging under load.

+2 om what JD said regarding lugging your engine.
 


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R&T Babich

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Voltage jumping around can also be a bad voltage regulator. Try hooking up a VOM for awhile to rule out the gauge being bad. If the regulator is acting up the voltage could jump up to 17v and the battery should keep it from going under 12.5v. Corroded cables/poor connections will add resistance and cause system voltage to drop below 12.5v. Either of these conditions can result in the computer doing strange things. What exactly is the gauge reading?
Did you ever change the timing chain and how many miles on it? Even though the timing can't be changed the chain stretches and the tensioners can only take out so much slack. I've had 2 engines where the first problem was a timing chain. Excessive slop in the timing chain can be checked by setting the crank to TDC and watching a rocker arm to see how far the crank can be rotated before it moves.
 




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