4.0 pinging

Kdub · Apr 5, 2004

Hello,

I did a search and could not find anything on the topic. I have a 98 XJ the pings under light load. Like when I drive up a slight grade at hwy speed or drive up on an on ramp. I can get it to stop pinging if I let off the gas or push on a little more power. It seems to be a light to mid load thing. It has done it for the 4 years I had owned the Jeep, but now that I am doing more hwy driving I'm afraid of beating the rod bearings out of it.

Would putting a cooler thermostat in help? Not one so cold it would put it into closed loop. I'm thinking of just stepping back from the 195 to a 180.

The Jeep runs like a champ other than the pinging.

High test and mid grade seem to be about the same as far as the pinging, and with regular unleaded it will beat it's guts out just pulling away from a stoplight.

Thank you

SimpleXJ · Apr 5, 2004

http://www.naxja.org/forum/showthread.php?t=14533&highlight=ping

RichP · Apr 5, 2004

If it has been living in heavy traffic and sedate driving for most of it's life you probably have some heavy carbon build up in the head, you could try taking it out in less traffic area and blowing it out for a few miles with alot of heavy acceleration. Sometimes that works or helps some.
First thing I would do on is a good top engine cleaning or decarbonizing with GM top engine cleaner or seafoam poured thru the throttle body and a good throttle body cleaning with the throttle body off the engine and on a work bench. One or two bottles of Chevron Techron additive thru the tank and see how that works.
Second would be a good tune up, wires, plugs, cap and rotor plus a new air filter. If that does not work you might want to go a bit deeper and have the injectors professionally cleaned or replaced and it might be time for a new set of O2 sensors. I also only use OEM for the plugs, wires, cap and rotor.

SimpleXJ · Apr 5, 2004

RichP said:
If it has been living in heavy traffic and sedate driving for most of it's life you probably have some heavy carbon build up in the head, you could try taking it out in less traffic area and blowing it out for a few miles with alot of heavy acceleration. Sometimes that works or helps some.
First thing I would do on is a good top engine cleaning or decarbonizing with GM top engine cleaner or seafoam poured thru the throttle body and a good throttle body cleaning with the throttle body off the engine and on a work bench. One or two bottles of Chevron Techron additive thru the tank and see how that works.
Second would be a good tune up, wires, plugs, cap and rotor plus a new air filter. If that does not work you might want to go a bit deeper and have the injectors professionally cleaned or replaced and it might be time for a new set of O2 sensors. I also only use OEM for the plugs, wires, cap and rotor.

Yeah, that GM cleaner is good stuff! Not sure about seafoam, but the GM should do it.

SimpleXJ

Matthew Currie · Apr 5, 2004

The GM top engine cleaner is great. Just two cautions. First of all, the directions call for you at one point to pour enough in to stall out the engine. I found that my 95 is essentially stall-proof, so I had to just pour in enough to bog it down, then shut down quickly.

Second, if you live in a neighborhood, you might do well to do this job at night, or when everyone else is away. The smoke screen you'll lay down after restarting is formidable.

Bender · Apr 5, 2004

I find it hard to believe that the 4.0L with a stock compression of 8.8 would ping unless something was very wrong.

I used to have a crackd exhaust manifold that would give a very audible "pinging" sort of noise when the engine was under load. It was most apparent on the highway where the engine would be under a constant load for extended perioeds...i.e. more than few seconds as in the city you'd be shifting by then.

You're injectors also get louder under throttle.

I

RichP · Apr 5, 2004

The idea of the stuff is to stall the motor but also to also soak the combustion chamber withoug burning it off which allows the stuff to soak in and expand in the carbon which will kind of shatters it. The combination of the cleaner and a hot chamber makes steam, as far as I know the top engine cleaner has a water content which is where the steam comes from. Old timers used to use just plain old tap water to do the same thing but I have seen head warpage [ I warped one head myself that way on a 66 6 cylinder mustang, my moms] result from this. Chrysler has a top engine cleaner that is mostly chemical, it's a spray in type that works pretty well also and those I know who have used it were satisfied with the results.

Atl XJ · Apr 5, 2004

I was experiencing pinging from my engine and I took it to the mechanic and had them flush it out with their machine and it stopped the pinging and it runs really really smoothly now. It always ran pretty good before since I keep it well maintained, but now you can't even tell if its turned on or not at idle. Also, I had it emmissions tested after that and my emmissions numbers were rediculously low (the numers that should be low).

Eagle · Apr 5, 2004

Kdub said:
Would putting a cooler thermostat in help?

No.

I concur that a top engine cleaner treatment is the best chance to correct this.

Kdub · Apr 6, 2004

Thanks for all the input. The Jeep does see a lot of short trips of less than a mile four or more times a day. I'll be making another 1000 plus trip in a few weeks. So I'll try running some cleaner through it before I go and maybe some techron in the first tank of gas once out on the hwy.

4.0 pinging

Kdub

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SimpleXJ

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RichP

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SimpleXJ

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Matthew Currie

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Bender

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RichP

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Atl XJ

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Eagle

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Kdub

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