my engine is pinging, need some tips...

[yj30]

I just noticed it in the last week or so, my engine seems to be pinging or a rattling sound when I get roughly over 1/2 throttle under load. It doesn't do it with no load revving of the engine and the funny thing is it doesn't do it when the engine is cold (when it sits all day during work etc.) only after it gets up to temp.

Any help would be appreciated.

[subculturenm]

Little more info - what grade of gas do you use? Is your timing advanced? (Can you do that on a YJ?) How's your idle? Do you have oxygenated fuel in your area?

Pinging is detonation, as you know, and is caused by too much timing advance, poor fuel quality, too low of an octane, or other things that probably aren't worth considering in your case. Since Jeeps engine don't have very high compression, you should be able to run regular unleaded - in other words, a simple fix would be to run higher octane fuel, but that would just be a bandaid, and not a very good idea considering gas prices.

[yj30]

I just run 87 octane which is the lowest available here. I never heard of oxygenated fuel... My idle is fine when initial start up or when engine is not up to temp as well but gets rough after the motor is up to temp, kinda sounds like its missing or something. I run a Weber 32/36, roughly 900rpm at idle.

I have no idea what my timing is set at but the pinging just started roughly a week ago, can the timing change on it's own?

I was also thinking about the fuel, I will try running higher octane and see what happens.

do you know what my timing should be set at?

[jules]

Mine pings under load if I use regular gas (4.2L, BBD). Putting premium makes it run like it has a turbocharger:D . No pinging and big difference in performance. I usually get a tankful if I plan on wheeling. I just blame age and mileage.

[subculturenm]

-=- originally posted by jules -=-
Mine pings under load if I use regular gas (4.2L, BBD). Putting premium makes it run like it has a turbocharger:D . No pinging and big difference in performance. I usually get a tankful if I plan on wheeling. I just blame age and mileage.

That's a common misconception when it comes to gas- higher octane does not improve performance. If your engine isn't at 10:1 compression ratio or better, you're throwing money away by using high-octane fuel. Age and mileage only make higer-octane fuels even less necessary. You're probably only feeling the difference of better QUALITY fuel, not the difference in octane.

yj30 - if it only started recently, then it's probably nothing more than bad gas. I'd get a can of decent fuel treatment (like Seafoam), add it to your tank the next time you fill-up, and see what happens.

[yj30]

I'll look out for the seafoam, I have however put in about a half tank of 92 octane today (my tank was almost empty) I usually run 87 octane, anywyay, the pinging has quited down probably over 70% so yea, either bad gas or my timing is off...