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How to detect pinging - are there different types that sound different?

I was wondering if there are different styles of pinging and associated sound from each. I recently purchased a 1994 Geo Metro and have been fixing and tuning it up. The mileage is phenomenal.

I have never heard the “ting” or “pling” style of ping from my Metro but have heard it in other cars and a video illustrating ping in a G10 Metro. Larger displacement V8 and V8 engines have more of a metallic popcorn type rattle noise. I am pretty sure I had some light pinging today.

This sounded like a rapid light rattle under medium throttle and would go away at full throttle which seems like ping. It was very rapid like a machine gun but not nearly that loud of course. I don’t think I would have heard it had I had the fan blow on full. There was a slight loss of power when I heard this sound. I backed the timing off a bit when I pulled into the gas station and continued on without nearly this much of the sound or loss of power. I have a pretty good percentage of E85 in my tank and the rest is E10. My dist is now rotated slightly over halfway towards the bumper so more of the slot is visible towards the front bumper and not as much so towards the firewall.

I had been running the engine on run of the mill synthetic oil and switched to Euro synthetic oil once I figured the engine was going to hold together. It had been sitting a while and the rings were likely a little sticky and I think my compression has been coming up, causing me to have to back off my timing a bit. I need to check the timing on this with a light but does it sound normal to have the timing backed off this far? I thought factory was right in the middle of the slot and I am slightly more than halfway to the front bumper.

I seem to hear this sound for an instant and then it goes away. Are there different types of ping? I hear the terms knock, detonation, and ping used interchangeably but know they are different. I assume each makes a different sound. What would a rapid light rattle signify? I was wondering if it was normal to this engine but the fact it nearly went away when I reduced the timing tells me it is some type of pinging.

Conor

You’re using E85? Can’t imagine your Metro is set up for that, which means you’re running way lean.

Spark knock and detonation have different causes but they end in the same result: a very sudden combustion and resulting shock wave, so I think in general they sound about the same.

What may make a difference is where in the combustion chamber the sudden burn occurs.
With spark knock it generally happens in the last bit of unburned fuel/air mix far from the spark plug.
But with a hot carbon deposit or hot spot on on an exhaust valve etc. it could happen elsewhere.
Think of tapping a cymbal in different places with a drum stick.

Regarding different engines the size and shape of the pistons and other parts will give different resonant frequencies.

Regarding E85, just say no.
With just the right (wrong) amount of lean-ness combustion temps soar and hot spots can promote ping.
You can also burn out exhaust valves.

And it can also result in a hole in your piston, if it’s bad enough.

I have about 30% E85 in my tank but may have accidentally gone over that amount which could be an issue. The forums for these cars all suggest it from time to time. It does boost octane and seems to clean the fuel system without damaging it.

This was designed to be a world car and many countries like Brazil have lots of alcohol in their gas like E85. It will not eat the fuel system but do know that running a lot of E85 in a U.S. spec Metro can cause running issues without more major modifications. I think the injector, heads, etc. may be different on these other cars.

I got ahold of a timing light and my timing is now reasonable but was obviously advanced before that time. I backed it off another degree and will fill up with only 87 octane E10 next time to see what happens.

I will post back next time I fill up which is a good long time in a Metro!

Conor

What circuitsmith said.
Like all noises, the specifics vary depending on individual design characteristics, but pinging can range anywhere from the sound of marbles in a tin can to a light rattle.

Pinging can actually be specifically diagnosed with a sensor that measures vibration and converts it to electrical signals (called an “accelerometer”) and a screen that can display these signals. Any good shop should have this. But it sounds from your description like you already know you’re pinging and why.

It was NOT designed for E30, that’s for sure. You simply are not putting enough BTUs into the combustion chamber, regardless of octane. Big mistake, regardless of what ‘they’ say.

Start using 87 octane or whatever the owner’s manual calls for.
Don’t ever use that E85 again. Cars designed for E85 (there’s no way your car was EVER designed for E85 back in 1994) have vastly upgraded fuel injection systems, from front to back.
Have a professional put the timing back to where it was supposed to be.
You’ll probably fail the smog inspection if your timing’s off too far. In my state they DO check the timing.
Cars designed for E85 may have a distinctive fuel filler cap and they’ll definitely state they’re E85 compatible somewhere in the owner’s manual. Sometimes they’re marketed as “flexible fuel”

Gotcha! It looks like I will be running normal E10 gasoline from now on. This would explain why this seemed to start right after my last fill with part E85.

The weak link in these engines is the exhaust valves which they are known for burning. They do tend to run a little rich by nature so that helps with this and allows for some margin. Most valve burning comes from dirty or the incorrect oil not allowing proper lifter/lash adjuster operation and oil burning.

Thanks - no more E85 blending for me,

Conor

My Wife’s Car Is Flex Fuel Capable. It Is Supposed To Be Able To Run E-85.

I was going to try it. However, even on her E-85 vehicle, after reading all the admonitions in the Owner’s Manual, I’d never put it in unless it was the only thing available.

E-85 cars are sold just so the manufacturers can get “extra credit” from the Feds in their average MPG or some darn thing. It’s for corn farmers and folks who profit from it.

CSA

I put the timing back to normal with a timing light so that is done. They don’t check timing here but I am more worried about damaging something from detonation, etc. and want to avoid that.

I will be running out the E85 blend and adding regular gas.

Conor

I’d recommend draining the E85. Or, if you don;t have much left anyway, filling it immediately with hightest to dilute the E85.

The longer you run with E85 is the greater your risk. Once damage is doen, it cannot be undone, but it CAN often be prevented.

Do A Little Research On E-15 Fuel. The Feds Want To Start Selling It For Only 2001 And Newer Cars. It’s Been All Over The News, Lately.

I haven’t seen any manufacturers onboard with this. Some of them are saying that it will void even a new car warranty if it’s used in an E-10 car.

CSA

Thanks for the update.
Please let us know when things are back to normal.
FYI: you can get burned valves when they were out of adjustment (tight) for too long.

Yeah, I filled the car with regular gas to dilute some of the 85. It was about half a tank. Either way, I will keep doing this every half tank for the next few. It is definitely better with the timing back a little bit. I had it too far back at first and moved it up a tad. Odds are the timing will need to be adjusted again as I get back to a more normal amount of regular gas.

The valves on this engine have hydraulic lifters/lash adjusters so they don’t need adjustment. They can get messed up by the wrong weight or oil and not having clean oil in the engine. Retarded timing and bad rings/burning oil is also a no-no for burning valves in this engine.

Either way, things seem better and I am sure it will improve more as I run the alcohol out of the gas.

I will let everyone know how it goes after another fill up or two.

Conor

I am also going to replace my O2 sensor today. Many people have told me not to replace this until a check engine light comes on but I understand they don’t go out all at once. This sensor has like 160-170k on it and the engine I had before this one burned lots of oil and smoked like a coal burning steam train. I think it is due no matter what and I have been told it could be contributing to several quirky things the car is doing, this being one.

I will let everyone know how this goes.

Conor

Ok, the O2 sensor made a HUGE difference in how the car runs. I think this was a large part of my problem.

Wherever I put my timing back to seems really like it might be the sweet spot after this.

Conor

Glad to hear you’re almost in the end zone.