The Good Ol' Ping, but not a question, a discussion

[jtb1689]

So, I've been up and down this forum learning about the ping and common causes and such (some of you may have seen my other threads). I've done the basics so if you have more advice for curing my ping click here

As far as my discussion I'm looking for, bear with me here, I'm no technician but I have a thought I figured I would pitch to the more experienced. The story goes, I have a KKM, I also have a ping. My roommate with a '93 recently installed an IFab with modified TB and 5.0 MAF, a couple months later, he has a ping. Now, when you supercharge an engine, you typically have to tune and run 92+ octane in order to keep up with the massive volume of air and many times change up compression ratios otherwise even the slightest ping could cause you serious issues (I know that was a really short and dumbed down explanation, like I said, bear with me here). Now I have noticed the 1 or 2 times I've tried it, running 92 as opposed to my typical 87 eliminated my ping. Is it maybe possible that the intakes which allow a higher volume and maybe even slightly more dense (i know its not a big difference in volume but there is a difference) air into the engine cause a ping without a higher octane fuel? Essentially a smaller version or my supercharger example. At the same time though I would think this is what the o2 sensors would be for which is why sure, maybe those are bad. Let me know your thoughts, and like I said, i'm trying to look more into the theory and discuss this rather than have people just come up and say "Clean your MAF, that will fix your ping." Thanks again guys.

P.S. I am trying to learn these things clearly so any input or enlightenment on how our engine works, why things happen and don't, anything like that is also welcome.

 

[Michiganbear]

well, several things will lead to ping..

1. boosting (turbo or supercharging), without proper tune and fuel.
2. advanced ign timing (not much we backyard guys can do with a DIS on this one)
3. poor quality fuel (as noticed when higher octane is ran, ping goes away)
4. increased compression ratio due to carbon buildup in cylinders.. increasing the octane manytimes will cure this, but its a bandaid fix for the problem.


a cold air intake or other intake modification other than forced induction really shouldn't cause a pinging problem. however, it may cause the computer to advance timing too far (see #2), or it may cause additional carbon buildup in cylinders (think its causing the computer to run the engine richer than needed, which is the opposite of what they advertise milage wise). they may be able to allow the engine to breath easier, and therefore getting more air in the cylinders, raising the effective compression ratio. does the ping happen only at WOT?? or does it happen at lesser throttle settings? if it only happens at WOT, I would be willing to believe there is enough additional air getting thru the throttle body to raise the effective compression ratio. if its pinging at lesser throttle plate angles, well, your NOT allowing the cylinders to fill fully with air, so your ping is likely caused by something else. remember, even at WOT, I doubt many engines will acheive absolute 0 manifold vacuum, meaning the cylinders are filling fully on each intake stroke (unless boosted, which is another thing alltogether), so they are not filling the cylinders to max volume either.

 

[jtb1689]

Now that's the kind of response I'm looking for, thank you michiganbear. Yea it doesn't happen at WOT, it typically only happens like everyone else's, under load until I give it some more gas and push the auto-tranny to shift down, then it goes away. Or when trying to moderately accelerate at higher speeds like 75 or 80 (which I guess is the same as being underload). So then basically, unless it pings at WOT, there isn't really a logical way to put a better intake path (filter, tube, maf, tb, whatever mods) at fault?

Any other opinoins are still welcome too guys, I'm trying to get a wide array of thoughts here

 

[Michiganbear]

if the maf and tb were not matched (ie, a 4.0 maf, with a 5.0 tb) you can cause some major computer confusion.

one of the main inputs to the computer for controlling spark and fuel (timing and amount in fuel's case) is the maf. they are CALIBRATED to the tb thats expected on the vehicle (not a particular one by s/n, but by the size used). so in theory, an incorrect match of the 2 can cause all sorts of issues.

but, again, as long as the throttle plate is not WOT, your still running with a fair amount of vacuum in the manifold.

remember, we call it 'ping', when in reality, its detonation, or uncontrolled ignition. what happens is the computer (or dizzy in an old school system) sends a spark to a cylinder.. now, that piston is NOT at TDC, but a few degrees before it (from around 10 at idle, to as much as 40 when running). if the effective compression ratio (what the air/fuel mix sees, not the static which is calculated by measurements), is too high, the sparks ignites the mix too quickly. causing an uncontrolled flame front inside the cylinder.

higher octane fuel actually burns SLOWER than lower octane fuel, under the same condition (same cylinder volume and same cylinder pressure (compression ratio)). the reason people need higher octane in boosted engines, is the cylinder pressures are higher, due to forced induction. also, an engine can be built for higher compression ratio, and needing higher octane as a result. Now, the amount of additional power provided by a higher compression ratio (we wont go into boosted for this discussion), is a pretty considerable increase, for a small increase in ratio. also, with higher octane, and a slightly reduced timing advance, you can get even more compression, and more power out of the same displacement.

since the pinging your getting is under load (passing accelleration, or other), I am willing to bet the computer is just sending too much advance into the system for the revs your at, as evidenced by once the tranny drops a gear (engine revs increase), the ping goes away. you can run more advance the faster the engine spins (to a limit of course). the air/fuel mix does NOT know how fast the engine is running, and will always burn at approx the same speed (there are some variances due to the difference in the density of the air/fuel charge, caused by different manifold vacuum levels).

you see, our EEC-IV (as primitive as it is), is one HELL of a number cruncher when it comes down to controlling everything (timing, fuel injector pulse, which cylinder gets spark, and in the case of the autotrans cars, it controls them somewhat as well). it does all this, while monitoring all the sensors, several hundered times a second.

 

[Blacksheep Josh]

 

[jtb1689]

A few things I have then.

1) So a 5.0 MAF housing (still running OEM 4.0 electronics) with the OEM throttle body could cause an issue. Yet, many many people have made the switch to the 5.0 MAF and had no issues and stated noticing gains. Also, if you were to modify the throttle body to mimic the BBK after market throttle body (such as spdracer34 did) would that help in solving the ping if it was caused by a mismatch?

2) I unfortunately (or fortunately depending how this goes from here on out) found out today that my "ping-band" (like torque band) has widened into the WOT region. Though it started at just under load like everyone else, for some reason when testing it out this evening after what you said, it no longer disappears when a downshift occurs and continues getting faster as the rpms get faster when I have it floored (and yes, my TB is wide open when pedal is all the way down, I recently checked. no cable mod needed ). Fun stuff, any change in ideas then?

3) Should this lovely ping be caused by the computer telling the plugs to ignite too soon, I'm SOL?

4) An old thought I forgot to mention earlier. I was told by a friend that had a yota years back that his ping was caused by too little back pressure due to leaks in his exhaust. When he heard mine he was quick to say that was my cause. Well, my exhaust is fairly new with no holes. But just to be sure I welded the places where tubes met, didn't fix anything as I suspected. However, one morning I started the engine and popped the hood to do the usual checks, just to be sure no new noises arose. I noticed some white smoke, like the exhaust, coming up from the engine (since it was cold and the engine hadn't warmed up yet)...wierd. After careful inspection it appeared to be coming up from where the exhaust manifold is. Could a leak in the exhaust manifold cause a lack of backpressure great enough to cause a ping?

4) I just love problems that are SO difficult to diagnose, let alone fix when you finally figure it out . If only my ping could have just been caused by a bad MAF, I would have no complaints.

Thanks again, and your welcome for some good reading Josh.

 

[corkey]

just a thought,,

just a thought , ,

quite a few things can contribute to the ping situation, air fuel mixture, fuel pressure, and timing of spark,, one of the things i have not seen you talk about yet is the timing of the cam position sensor,, it has to be in there right and in the best shape,, maybe it is getting bad like slop in it, or, maybe the sensor in it is going bad,, causing the spark to happen at the wrong time,, and resulting in the ping situation, ,

the fact it is getting worse could even be a sign of the timing chain getting a bit sloppy too , it will get stretched over time,, and hard driving or bad oil will do the same thing to it,,

one thing i have wrong with mine, ohv 4.0 is that i have bad pushrods or rockers, i can hear it at idle, , and it affects the way my engine sounds as soon as the rpms, come up, almost like a bad ping, or sort resembling a knock, but not from the bottom end,,but if it was that you would know the difference , but don't rule it out , maybe,,

don't get tunnel vision looking at only 1 thing , it will make the frustration factor way too high, just eliminate 1 thing at a time till you find it ,, it might be getting worse a bit, but it is not killing your engine to the point it isn't driveable, there are some on here with a few noises, and lots of miles on them,

 

[Michiganbear]

Corkey, I was gonna add just about word for word what you just said.. even the part of the bad rockers.. on MY truck too!!

The cam sensor issues are a possibility.. but there is also a crank position sensor on these too.. thats much more exposed to the elements also. Cam position sensor or worn timing set are definatly on the list of things to look at, as well as the crank sensor (which is more involved in setting the ign timing than the cam sensor). the cam sensor is more for determining what cylinder is needing fuel/spark, not the more precise measurement of when it needs it.


These can be a very very frustating thing to try to diagnose, due to the many things that affect it.

 

[jtb1689]

I will add those to my list of things to check. Thanks for the advice too which I have been following. That's been the annoying part, every time I have something new that I can check/replace that COULD solve my issue, but every time it doesn't . But, oh well, it's all just part of owning a car I guess. I did consider rockers, pushrods, and lifters but ruled those out, or at least moved them to the bottom of my list of things to check for solving the ping, when I didn't hear any problems at idle. What do you guys think about the exhaust manifold idea though? Before I go down there and spend my afternoon working to loosen (after soaking in liquid wrench, pb blaster, wd-40 or whatever I have around) bolts and tighten things back up on the exhaust manifold I figured I'd see if anyone thinks it would be worth my time in solving the ping.