About a week or so ago I noticed an odd rattling coming from the engine area while under hard acceleration on the freeway. It didn't sound like what I typically think of as knocking or pinging. But this is the first large V8 engined car I've ever owned.

Today I heard it again under hard acceleration. This is with definitely at least 1 or 2 tanks of gas since the last time.

What are the conditions that might cause pinging in my ZJ, and do you have any suggestions on how to remedy the problem?

Thanks

Mine used to do the same. I started to run mid grade or premium gas and it stopped. It doesn't like the cheap gas.

Exactly what he said. If you want to you can go and buy an octane boost and put it in your tank now if you have low octane in it and if it goes away you know it is because of the low Octane. Mine also requires the good octane or it rattles and jumps and just doesn't want to go.

Try running fuel injector cleaner through the system.

How do your spark plugs look? how do the wires look?

How do the rotor and cap contacts look?

Is your air filter clean or dirty?

I am having a similar issue with my 96 zj. (4.0) when under hard acceleration, it will ping. I have replaced all plugs, wires, filter, cap, rotor. Next I am going top replace the fuel filter.

it pings alot on 89 octane gas, and the pinging is lessened with 93 octane

Mine does this also. I replaced spark plugs, distributor cap, rotor, wires, and added redline fuel injector cleaner but none of that worked. I filled the tank with premium fuel (i think it was 93) and pinging went away.
I still use the cheap gas but I wonder why it started doing this in the first place.
Could it be the K&N filter?

Still pinging at 93 octane? Something is very wrong. You haven't upped the timing on it have you? I use 87 in my XJ 4.0 with no problems whatsoever. But pinging and 93 octane....MY GOD!

Still pinging at 93 octane? Something is very wrong. You haven't upped the timing on it have you? I use 87 in my XJ 4.0 with no problems whatsoever. But pinging and 93 octane....MY GOD!

I agree there is a problem, but most 4.0 will not ping, in colorado, our low octane is 85 and premium is 89-91 depending on which station you are at, and i used 85 everyday since new for my 4.0 and it ran great with no pinging or anything. Then i got a used v8 filled with that colorado crap gas and it was not pretty, went to the mid grade (87 here) and the pinging stopped. Just trying to say it is hard to compare 4.0 to 5.2 when it comes to the fuel they prefer...

Mine does this also. I replaced spark plugs, distributor cap, rotor, wires, and added redline fuel injector cleaner but none of that worked. I filled the tank with premium fuel (i think it was 93) and pinging went away.
I still use the cheap gas but I wonder why it started doing this in the first place.
Could it be the K&N filter? 93 ZJ Laredo 4.0

Wasn't comparing, was answering that guys problem. :roll:

Mine does this also. I replaced spark plugs, distributor cap, rotor, wires, and added redline fuel injector cleaner but none of that worked. I filled the tank with premium fuel (i think it was 93) and pinging went away.
I still use the cheap gas but I wonder why it started doing this in the first place.
Could it be the K&N filter? 93 ZJ Laredo 4.0

Wasn't comparing, was answering that guys problem. :roll:

What?

..
Gentlemen one cause of Pre-detonation is carbon buildup in
the combustion areas of the engine that will raise the compression
ratio and act like a glow plug.

Here is a link to the gentle and successful way I have been removing
Carbon in my FSJ for 18 years.
link> CARBON & FUEL ADDITIVES (http://groups.msn.com/JEEPTECH101/jeeptech.msnw)
..And read the thread below.
http://www.nagca.com/forum/viewtopic.php?p=50266#50266

http://65.166.200.170/ubbthreads/images/graemlins/tree%20twinkle.gif
http://65.166.200.170/ubbthreads/images/graemlins/santa2.gif

Have a good onehttp://www.michiganjeepers.com/forums/images/graemlins/popcorn.gif and CUL.. Don S..

You guys ever heard of CHEVRON?? You can use 87 octane all you want and it won't ping. Plus, you actually get more milage out of the gas than any other. A lot more worth getting this gas than using the cheapest you can find.

I think the reason it's good is because the gas has something they call TECHRON which they say cleans up gas deposits (like on your valves). Some think it's STP.

Gentlemen one cause of Pre-detonation is carbon buildup in
the combustion areas of the engine that will raise the compression
ratio and act like a glow plug.
Agreed 100%, and surprised nobody mentioned TSB 09-05-00, which among other things, instructs on de-carboning the combustion chamber with Mopar CCC, p/n 04318001AB.

I read what wax, mazur, and stocker wrote and went out today and sported for a 12 oz bottle of Techron. Dumped it in and drove home. Later I had an errand to do so I chose to go via a stretch of road I ALWAYS ping on.

What is in that bottle?

I have dumped my share of chemicals down various openings in my lifetime but I gotta say this is the first time I have ever seen such a noticeable difference.

You guys ever heard of CHEVRON?? You can use 87 octane all you want and it won't ping. Plus, you actually get more milage out of the gas than any other. A lot more worth getting this gas than using the cheapest you can find.

I think the reason it's good is because the gas has something they call TECHRON which they say cleans up gas deposits (like on your valves). Some think it's STP.


Chevron isn't available everywhere.
87 octane is 87 octane.
Most of the Jeep engines require higher octane fuels if anyone cracked open the owners manual.
If you have rattling on 93, there's a problem. Not knowing the 96 design, does it have an EGR valve? Is it connected? functional?

Chevron isn't available everywhere.
87 octane is 87 octane.
Most of the Jeep engines require higher octane fuels if anyone cracked open the owners manual.
If you have rattling on 93, there's a problem. Not knowing the 96 design, does it have an EGR valve? Is it connected? functional?

My manual says to use 87 octane.

I had to look around for Techron. Found it in a mom and pop type auto parts store not one of the big chains. Of course I'm sure I could order it online if I look around, just one of those things where I wanted it in my hand to have a look.