Ping..lower octane?
might need some suggestions.
Lately I have noticed that sometimes the 4.0L pings/knocks as it shifts into OverDrive under very light throttle. Almost like the engine is running a low rating of octane. Been putting 87oct of Exxon on the last few tanks. Last tank was shell..same result. Could it be due a worn water pump bearing? Or failing or loose timing belt tensioner? Any help will be appreciated. 2000 XJ with 122K |
Been tuned up lately? The 4.0L is somewhat of a noisy motor (most in-lines are) but at only 8.8:1 compression, ignition ping is not likely under normal operating/driving conditions, I wouldn't think. No timing belt/tensioner, it's a chain.
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A way to find out is to top off the tank with Shell V Power. Even if it's not a full tank it will raise the average octane of your gas. If your ping goes away (I mean, like almost immediately, in my experience) then you know it's not a chain. I have pinging in my rig now when I use regular octane gas (so now I use 93). I think the cylinders are probably coated in carbon, making the compression too high and exploding the regular gas too soon. Sea foam through the gas tank is a way to clean the carbon out a bit. (Never used the vac line method with Seafoam but some folks on here have had good results). Cheers, and good luck!
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Pinging (pre-detonation) can definitely be carbon related.
As mentioned, a good experiment is to fill up with premium. If the pinging goes away, the problem is carbon. You can live with it or you can try a top end treatment (Mopar/Seafoam, etc) as that can be helpful in removing top end carbon. |
actually I just did a seafoam ..hardly any smoke came out..I was expecting tons of it..since the previous owner was an old lady..lol
It's just weird to me that it only happens as soon as I go into over drive at very light throttle. I'm just puzzled by it. I guess it won't hurt to put some higher oct gas in there..and see what happens. I also just did an oil change to 10w30 Syntec, new air filer, spark plugs. |
Originally Posted by puredrive
(Post 763578)
I guess it won't hurt to put some higher oct gas in there..and see what happens.
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