Pinging noise?

[94Sport5]

Just noticed the other day a rather prominent (I believe) pinging noise. It's definitely noticeable in the upper rpm range, but especially if I have the AC on and have to accelerate with traffic. I changed the plugs and wires a few months ago, but had to use a digital caliper to make sure all plugs were gapped the same and not different as I didn't have a gapper at the time, but did the best I could with it to make sure they were all at spec. Could a weak coil cause this? It's original afaik and I have been having pretty sluggish acceleration when having to get on it lately accompanied by the clacking noise. I have noticed though, or it may be placebo, but higher octane gas seems to minimize it, which makes me believe it's pinging. Would checking the spark plugs with a gapper to be sure they are all at spec be step 1? Or would diagnosing the coil be a good place to start? Any help is appreciated, thanks!

 

[Roadrunner777]

Mild knocking in this engine is normal, it's even mentioned in the owner's manual. Three options, so far as I can tell:
1) Run premium gas, as you know
2) Connect the octane jumper, it's a plug just behind the fuse/relay box under the hood. This will reduce the knock, but also reduce gas mileage and might reduce performance
3) Live with it - It is not detrimental to the engine

Clacking noise is often valvetrain wear. You can replace the valvetrain components, or... LOL, live with it. Low oil pressure can do this too, but that's a whole nother can of worms about the oil pressure gauge.

Sluggish acceleration is also, sadly, normal. It's horsepower/weight ratio and gearing.

All of these are symptoms of a typical 25-year-old first generation explorer. There isn't a lot of cost/benefit in trying to minimize the symptoms.

Unless something is not normal. Did the old plugs look even and normally worn? I assume you are not getting a check-engine light? Yeah, I think if you surveyed this forum, most people have these symptoms and are just going with it. A failing coil would show up in the old plugs.

 

[94Sport5]

I have the old plugs at home that I will observe closely when off work. FYI I recently got 20 mpg highway on a 250 mile trip, just a bit under the best I have seen from it (22mpg). Reason I think it's abnormal is because I have had the vehicle for 3 years and this problem popped up several months ago, but has never gotten this severe. I have heard if it's spark knock or pinging it can be detrimental to the engine as the piston is being forced down by the pre detonation before reaching tdc, but people hear different things.
As for the acceleration and sluggishness, when I first got it and pretty much up until this problem arose, it felt much better seat of the pants wise if I had to get on it, and also the clocked acceleration time was much quicker @ 10 seconds n change, vs 12 or so seconds now. Not that it's a race car, but to show the difference in performance and how it seems to struggle when needing to accelerate after noticing something quite new, I thought it to be abnormal. Thanks for the reply!

 

[Roadrunner777]

Those are impressive mileage numbers, makes me wonder if you have a less common differential ratio that benefits mileage but reduces acceleration.

About the knock/ping, yes... you're right about that, but for some reason, it doesn't seem to be a problem with this particular engine. A lot of this reminds me of carbon buildup. There are some remedies out there for carbon buildup, none of which worked noticeably for me.

This is a tough one in a way because there are so many possible problems, or even several in parallel. And at this vintage, you really cannot rule anything out. It's almost unfortunate you don't have a check-engine light to point in a direction.

 

[94Sport5]

Yes you are correct about the diff ratio, it's a 94 3.27 geared with 5 speed manual. I have made attempts to cleaning carbon using the Ford tsb procedure with what seemed like minimal results, quite a lot of smoke though. I agree this is a tough one to nail down..I do have a live data reader/code scanner, the scantool III, but I don't quite know if there's a way to pinpoint the problem with that, besides reading the data of course. Have done it a couple times but everything seemed to be normal unless I'm overlooking something there. I forgot to look at the old plugs too, will be sure to check those out today!

 

[94Sport5]

Also I too, would agree with the gear ratio/acceleration/mileage argument, if it wasn't for the fact that I used to get good mileage AND decent acceleration..granted 12 seconds isn't forever to get to 60 but it sucks considering it used to be way smoother and feel a bit more powerful. That's why I'm intent on believing the sluggishness and pinging is not normal, because they came up seems around the same time. I have held it to the floor before and noticed it get up to like 3750rpms and the acceleration/torque stops dead, rpms struggling to keep going up accompanied by bucking as it tries but that could be a different problem. By the way I'm having trouble with the typing box on here, it's like an insert button is stuck on intermittently and it erases and goes over my words all the time, or if I type too fast or erase a couple letters it goes crazy lol..is that a common problem when using a phone or something? Jw.

 

[Roadrunner777]

Well, that sounds like fuel starvation to me... If I had that, I would go straight for a new fuel filter.

Although... in a weird circular logic kind of way, it could be, as you first said, a weak coil.

With what I see right now, I'd probably still do the fuel filter first. It's a lot cheaper and if it wasn't the issue, I wouldn't feel too bad about spending the time and money on a new fuel filter anyway. It would purely suck to drop $100 on a coil and have it not be the problem.

 

[gmanpaint]

I agree with fuel starvation here.

Change the filter, and do a pressure test at idle and wot.

One thing to note that can also make this happen is a failing pump relay. Happened to mine, after going thru exactly what you are. Ignition and fuel pings can be hard to differentiate on that engine.

Heat and time takes its toll on the wires leading to and from the power distribution box under the hood. This can and will burn up a relay. Pull the relay, look at the bottom of it. If it has the white underside, and looks like its turning brown, bingo. Also make sure the wires leading into that relay, are in good condition. Might just be loose, and a good push into the box might be all it needs.

Just something else to consider here.

 

[MrQ]

Fuel starvation is probably the culprit here as said before. Pressure for a first gen return system should be between 30-35 PSI. Anything below that is not good. Also check your fuel pressure regulator. It is the round thing on the left side of the intake behind the upper coolant hose on the fuel rail. It may be bad. To check it remove the two 8mm bolts and the vacuum hose on the side. If there is fuel coming out of the vac line then its a bad regulator. If that is good and the fuel filter has been replaced and your pressure still sucks, it's time for a fuel pump replacement.

Running premium gas or removing the octane jumper is a short term solution (octane jumper is supposed to be for diagnostic purposes only and not normal operation). Pinging is NOT normal on older OHV engines. It happens because fuel/air ratio is wrong and the system can't compensate enough with advancing or retarding the timing.You need to find the culprit. High carbon deposits are the most common reason, this increases the compression ratio and its why higher octane gas helps. Running fuel system cleaner can help.

Also phone posting has always been quirky for me as well on this forum, so don't feel bad.

 

[94Sport5]

Great responses from everyone I appreciate it! I have tested fuel pressure I believe it was in March or April, replaced the fuel filter July last year to my surprise the old one was completely clear and probably still okay. I documented my last fuel pressure test which I will paste in the next post. I have not looked at the fpr at all I don't think, so I'll start there before checking any other ignition components, then the fuel pump. My phone service went out till tomorrow so any findings will likely be posted tomorrow. Determined to get this problem solved! Starting to lean toward fuel issues as I remember complaining about fuel smell a couple months back. Plus once I took the gas cap off while it was running to fill up fast and it made the vehicle sputter and die! I heard the egr system somewhere or other can cause this symptom. Thanks everybody.

 

[MrQ]

That would be the EVAP system. There is a vac line going to the tank running along the fuel lines near the quick disconnects in the engine bay. That hose may have come off or off the vac tree on the intake. Also, the system keeps a negative pressure in the tank and by opening the gas cap while it was running created a vac leak.

 

[94Sport5]

First test- Cycle key once, goes up to 30 psi, cycle again stays about the same maybe 31ish psi. With key off for a min or so it loses pressure kinda fast, 2 psi every 10-15 seconds about 12 psi lost in 2 mins so down to 18 psi. Then it falls really slowly. Second test- From being started to shut off fuel stays at 32 psi, holds it for one minute then drops to 29-30psi. Cycling key to on raises to 37-38 then drops down to 30 pretty quickly with key still on. Cycling key on again, it raises to 38 then continuously drops again slightly fast to 30. Started car when cycled key again, (@38 psi when cranked) and pressure holds steady at idle @ 28 psi. Quick revs in neutral bring it up to 32 psi while running. Driving it hangs around 28 psi. In 2nd gear accelerating sort of heavily up to 3500 rpm brings it up to about 34-35 psi. WOT goes up to about 34-35 psi maximum. Fuel pressure seems sort of low at idle, and gradually drops with key off. These were my findings a lil less than a year ago.

 

[MrQ]

Yes you have a leak down somewhere. FPR first, but if that's not it you have a fuel pump replacement in your future. If you have a 2wd it's a fairly simple process to drop the tank with quick disconnects, a jack, socket wrenches, screwdriver, and patience. 4wd's have the skid plate you have to remove first (which the engineer who designed them deserves to burn in the deepest pit of hell for his over-complicated and horrible design )

 

[94Sport5]

Lmao it's 4x4 and really hoping it's the fpr, at least that's right up front. Ugh I seen the tank dropped beginning of 2018 should have just replaced it then since it was off but didn't notice any running problems at that time except the rear axle noise which got fixed (rear pinion bearings were so toast the pinion would move 1/4 inch in all directions YIKES lol). See I was suspicious on why the pressure dropped so quickly. I remember my old mechanic saying that there's a check valve in the pump that can fail buy he also said most times the fpr diaphragm fails first or something like that. Funny how I have spaced about the fpr this whole time. Least I got a step 1 now!

 

[Roadrunner777]

When I did pressure tests... my tester has a bleed-off feature, and I was amazed how the standing pressure dropped by bleeding just a tiny bit. The fuel system is very rigid, so a tiny amount makes a big pressure difference. My pressure held after shutting down at about 32 PSI, and it stayed that way for 4 hours before I disconnected it.

The gas smell/stalling with the gas cap off thing is notable. I think I might try to address that before buying parts and spending time on the FPR. Ah... a failed FPR diaphragm will end up sucking gas into the vacuum tree, and you might want to look at that vacuum line and see if evidence of gas is present. This will also make the driver's side rear spark plug darker because it gets that gas and that cylinder ends up running rich. It could be a different part of the FPR, again, a full set of pressure readings would speak volumes.

I would still do the fuel filter... I had a time where I added seafoam to a full tank of gas and it absolutely killed the fuel filter. It's a shame the fuel filter connections are such a PITA.

Honestly, I'm just sitting here and more potential causes keep coming into my mind. I have seen a clogged CAT converter do this. I have seen a muffler do this because a part got loose inside and caused a serious exhaust restriction. To me, the coil pack is still on the table.

Fuel pump relay... yeah, that's a good one too. On that, really, it's a good practice to have a brand new relay in your glove box. All the relays are the same, so this WILL eventually come in handy, and it's like $12 vs a tow truck. I might get a new relay and just swap it out for diagnostic purposes.

I think, if I were approaching this and being the thrifty old fart that I am, I might do this:
1) Check vacuum lines and try to resolve the gas cap/stalling thing. That's very quick and free.
2) Check the FPR vacuum line for evidence of gas, and if found, replace the FPR. That's a given.
3) Swap out the fuel pump relay with another one in the box, the blower one for example. Test.
4) Do a full set of pressure testing, maybe I would replace the fuel filter first if I didn't have a pressure tester handy.

The more I think about this, the more I might try to address the stalling gas cap thing first. You could maybe just pull that vacuum line off the tree and cap off the open port. You will probably get a check engine light when you do this, but it might be the easiest way to root cause. It would completely suck to replace the FPR only to have the same problem and find the cause to be a loose vacuum line.

There's 2¢ and then some. Good luck!