dadsxj96

Is there anything that can make my XJ stop pinging even running on low octane gas ( RON 88 ). I live in a country where good gas cost twice regular gas. My XJ start pinging on low rpm's in the 3rd gear. My XJ actually already came with no catback and any oxygen sensor on the exhaust system. Any idea ? Somebody told me to use performance chips.

Gee oh Dee

Chips are garbage. If you have a 4.0 XJ than regular octane should be fine.

Get an o2 sensor to start with. Move from there.

lookin2wheel

Make sure your timing is correct first. Look at plugs, wires and cap. Keep engine RPMs in line with vehicle speed, inother words, if you are in 3rd and doing 20MPH, you will generally get valve chatter. If you are in 3rd and going up a hill, downshift. The 4.0L is designed and tuned to run on regular unleaded....85-87 octane; as are 90% of cars on the road. Do a good tune up man. That should be enough.

dadsxj96

I thought that timing is not adjustable on a Xj'96, since its running on a timing chain. I am driving on AT. So when i hit a flat road on the 3rd gear engine starts pinging and it gets worse if i accelerate. I just changed a new cap, spark plug wire, spark plug, coil and changed all the oils inside the car. It still happens. By the way, it more often happens if the car is in hot condition.

dadsxj96

Yeah, and expensive too. But my xj came with no o2 sensor. I mean like originally from the manufacturer. I think the gas here was still leaded at that time.

Gee oh Dee

What year is this XJ?

I mean...I know this is in Indonesia...but....

5-90

Just pour it in - if the engine is in good shape, it's not a problem.

Pinging in low-compression engines can usually be narrowed down to a few causes - and they're generally easy to remedy:

- Spark plugs retain too much heat at the tip. Go one step "colder" (a good counterman can help you.)

- Carbon deposits in the chambers, which get to glowing red-hot and cause preignition. I've covered how to blow them out using plain 'ol water, you can also use Seafoam or similar engine cleaner (follow instructions on the bottle.)

- Intake manifold leak, leading to a "lean" condition. Locate and correct.

The cause that is not so easy to correct would be your timing being off - it can be verified using a common timing light, but the system is usually a pain to reset timing. Fortunately, this isn't a common problem.

If you have a RENIX (1987-1990 w/AMC engine,) make sure your knock sensor is working properly, replace it if not. It's there for a reason - to help protect your engine from the effects of preignition/detonation.

To test the knock sensor, have someone watch the timing marks with a timing strobe while you tap the engine block near the sensor (if present) with a mallet - the timing should jump to an earlier fire for the next few engine revolutions to compensate. If the timing does not jump, replace the sensor. The knock sensor (if present) is screwed into a boss on the driver's side of the engine, near the oil sump rail, approximately under the #2 cylinder.

dadsxj96

Its a 96er. I downloaded mopar part catalog. And there are two versions of exhaust system. One with and w/o cat-back.

dadsxj96

Thanks , this is what I'm looking for. I just wonder how to check this knock sensor thing because its not cheap to get one over here. About spark plugs, unfortunately there is only one type for XJ in Indonesia. Or maybe i have to look on other suppliers. First i will get seafoam !

00SportXJ

Sounds like a intake leak or carbon buildup to me too.

The quick way to find the intake leak is to spray starting fluid around the intake manifold. If there is a bad gasket, bad vacuum line, bad injector seal, etc. it will rev up a little bit when it sucks in the starting fluid.

And for the carbon, I use water too. I go for a good drive to get everything up to temp, take off the intake boot and start slowly pouring water down the throttle. You just have to work the throttle with the other hand to keep it from stalling. It works great and is cheaper than Seafoam.

Good luck!

5-90

Just don't drown the engine!

I usually tell people to use a trigger spray bottle, it keeps you from putting in too much water at once. I also suggest disconnecting the catalytic converter at the forward flange - if you do have a lot of carbon out there, you don't want to blow it into your cat.

As far as the vacuum leak check - you can use starting fluid or carburettor cleaner (or other flammable aerosol - I've even used flammable hairspray a couple of times!) with the same results. Start with the engine cold, spray a fog around suspect areas (paying particular attention to the base of the throttle body and the rear of the combination manifold gasket,) and the engine will race when it sucks the stuff up - and you can usually see the fog get drawn in as well. Correct any leaks thus revealed.

FL Denmark

x 2 on it all
very good answer

dadsxj96

Thanks for all the nice feedbacks , today i just changed my TPS and all my problems are solved. I think there was some miss readings caused by the old TPS. I was wondering because the computer doesn't send any error reports.

Once again thanks