[Fernando]

If the timing is computer controlled, then I find the pinging strange, I believe most vehicles with computer controlled timing use a knock sensor and retard timing as necessary... I don't see how the distributor works as a cam position sensor... I must admit I have not heard about this before.

[Fernando]

Well I did my homework. The OP is right, the fuel injected vehicles need no adjustment and the timing is computer controlled. May be that the compression ratio is too high or fuel delivery is poor. You may check this with a wideband O2 sensor, racing dudes use these for engine tuning and the sniffer test machines also measure this value. You can also do a compression test, but if I were you I would look for the wideband sensor and analyze the behavior and air fuel ratio during the pinging moments.

[Que89YJ]

X2 Fernando. It's either or as far as knock goes. Wide band O2 will give you a better look at the air fuel.

[Tuffy1]

Where do I find a wide band O2 sensor? How do I get one for my vehicle application? I am confused, never heard of this. Thanks for the help so far, keep it coming. I am bummed about this, I have a brand new motor, and I can hardly drive it because it pings, I do not want to damage the new motor. I am nearly broke after the rebuild, so money is at a premium.

[rejeep]

tuffy..
I have the same problem you do after a 258 rebuild..
after much time and money spent on distrib, 100 octane, etc.. it comes down to the fact that there is too much compression in the motor..

these motors ping sometimes from the factory.. that’s why there was a knock sensor installed...

between the head and the block find out how much was taken off.. I can’t run anything but 100 octane without it pinging..

I finally found a virgin head that I am swapping on without cutting it to lose some compression...

find out how much was taken off the block and the head and there might be your answer..

[Fernando]

Originally Posted by Tuffy1

Where do I find a wide band O2 sensor? How do I get one for my vehicle application? I am confused, never heard of this. Thanks for the help so far, keep it coming. I am bummed about this, I have a brand new motor, and I can hardly drive it because it pings, I do not want to damage the new motor. I am nearly broke after the rebuild, so money is at a premium.

The wideband 02 sensor is application independent, it's like the 02 sensor all vehicles have but much more responsive, this will let you know if you are running lean, it has a much more ample register not just close to stoich... this is all engine tuning theory, normal passenger cars with no modifications are programmed from the factory to work within certains specs, for fuel economy and engine life...however modified engines are a whole different story and wideband instruments allow for greater modifications since they work outside the parameters of the cheap stock sensors passenger cars come with.

Pinging may be caused by lean mixture, you need to find out your air fuel ratio accurately, for this, you need the wideband 02 sensor... if your air/fuel ratio is correct and you still have pinging, then you need better octane fuel.

I have a feeling they trimmed too much from the block and head, and now you have a high compression engine which requires special gas, 100 octane as mentioned before, the only way to get around this is to install a stock head. How much they removed from each part is crucial info and you should be looking for those values, however one must discard the cheap fixes first, if you have a shop around that tunes racing vehicles or one of those fast furious kind of shops, they should have a wideband 02 sensor and they may help, so you discard the cheap first.

Also I have heard about a thicker head gasket that you can buy and this may help you keep your modified head, since the thicker gasket will decrease compression ratio. It may be worth researching what's available.

[JST42LN]

Tuffy
I have a 89 motor which i stroked, borred 30 over comp cam and summit pistons. i do notice a ping if i use reg. fuel, only a slite ping with plus under heavy loading,
I havent tried 93 oct yet. but when I researched my project, there were a lot of guys who did strokers, that had this prob. with the boring , the cam, and the decking
of the head and block, you most likley raised the compresstion to much, summit does sell differant thickness head gaskets, Im about to start checking mine with the air/fuel
gauge to see whats going on. some of the strokers need and ajustable MAP sensor. searc h for stroked motors and do some reading . it helped me alot. good luck and I'll
let you know how I make out.

[Tuffy1]

Thanks so much for the info, keep it coming. I have no access to this wide-band O2 sensor, I live in a pretty rural area, so I am kind of on my own with this. Can I just add octane boost to the engine to see if the pinging goes away?

Also, I checked the spark plugs today, they are very white, I know this means it is running lean, now where do I go from here?

I will speak to the engine builder, as well as check the compression.

I spoke with Hesco, they told me my timing at idle is spot on, which is about 13 degrees. I am going to check the fuel pressure while driving and see what it is while it pings.

Keep the info coming as well as the ideas.

[Old4X]

Have you thought about swapping in a Howell system? The initial timing is adjustable on those.

Any feedback from the cam grinder on what you might could do to stop the ping? Different indexing or a different cam?

edit to add: If the computer controlled system can't be reflashed for your application, you can always put the carb and OEM distributor back on it. At least that way you could set it up so it doesn't hammer itself to death, and work on a solution for the FI in the mean time. At least you can be driving your Jeep.

[Tuffy1]

I am committed to get this motor to run well as is. I have put a great amount of work into it already. The motor ran great with the current MPFI before it was rebuilt. Just need to figure out this pinging. The wide band O2 sensor, can one make adjustments with that tool, or is it only to read values?

[Fernando]

The O2 sensor will only let you know what's going on in terms of air/fuel ratio... no adjustments.

At this point I feel you have all the info you need, however you do not have the tools for testing what's going on inside your engine. My advice is to find a way to test, numbers don't lie, there is no magic or easy fix for this, or maybe there is, but you need to reach a diagnosis first. Find how much they trimmed of the head and block, what kind of pistons you have, and measure your compression, examine your air/fuel ratio and you will find the problem.

Be prepared to accept that maybe you can not make this motor run well as it is with regular pump gas, the more you tell us about it, the more I feel the compression is too high for regular pump gas and that is what is causing your pinging... you said your plugs were white, which is a clear sign of detonation, this will damage your engine very quickly. Remember that if compression is too high, you may remove the head and install a thicker gasket and this will help, you will not need another head for example.

There are ways to fix this, just not easy ones, it may take time and you may have to exercise a bit of patience. I say this in the friendliest tone and with the best intentions. Without measurements and tools all we can do is guesswork.

[Fernando]

The O2 sensor will only let you know what's going on in terms of air/fuel ratio... no adjustments.

At this point I feel you have all the info you need, however you do not have the tools for testing what's going on inside your engine. My advice is to find a way to test, numbers don't lie, there is no magic or easy fix for this, or maybe there is, but you need to reach a diagnosis first. Find how much they trimmed of the head and block, what kind of pistons you have, and measure your compression, examine your air/fuel ratio and you will find the problem.

Be prepared to accept that maybe you can not make this motor run well as it is with regular pump gas, the more you tell us about it, the more I feel the compression is too high for regular pump gas and that is what is causing your pinging... you said your plugs were white, which is a clear sign of detonation, this will damage your engine very quickly. Remember that if compression is too high, you may remove the head and install a thicker gasket and this will help, you will not need another head for example.

There are ways to fix this, just not easy ones, it may take time and you may have to exercise a bit of patience. I say this in the friendliest tone and with the best intentions. Without measurements and tools all we can do is guesswork.

[Tuffy1]

Fernando,
Thanks for the info, keep it coming. I will find out what the compression is in the cylinders, as well as some of the other numbers. The engine builder built it to spec for 9.2:1 compression ratio, I was told that should still be able to run 91 octane pump grade super unleaded. I still question whether or not the timing is correct. Though the timing is correct at idle, just not sure what is going on when it pings. I was also told I may need to go to a larger fuel injector, what are your thoughts?

I may be able to gain access to hook up a chrysler OBD2 scanner to the motor to check timing while driving, I am going to start working that direction as well. I am also going to speak with the engine builder again. I know we used stock pistons, but the block did get shaved a slight bit, the head very slightly, all while staying with the 9.2:1 compression ratio. I think it may be right on the edge of not getting enough fuel, as well as a possible timing issue. The motor runs nice and smooth until the pinging starts at moderate throttle and on hills.

What if I raise the octane in the fuel and see if the pinging goes away? I can buy octane in a bottle to raise the octane in the gas, if the pinging goes away, then what? What do the white plugs signify, will octane make the plugs turn to a light brown? I am confused by the way the plugs look, is that an indication of timing, fuel octane too low, or not enough fuel?

[Old4X]

If you want real high octane, forget the magic bottle stuff. Drain your tank and fill with 100 octane Avgas. It is about $6/gal in your area. Be advised you can not run this stuff through a cat converter, it will ruin it.

Your problem is you are trying to run a computer controlled fuel system way outside the parameters of the programming for that computer. The only way to make it work without major hardware changes is to re-program the computer. There are folks that do this on GM and some import engines, but none that I have heard of on your specific computer.

If you are unwilling to do the needed hardware replacements, you can always do bandaid fixes like exotic gas, water injection, or hacked TPS and MAP sensors. Without setting up the ignition/fuel system properly, you are running a real risk of burning a hole in your pistons, burning valves, and generally making a mess of your engine.

[Tuffy1]

I do not think the motor is "way" outside the parameters of the factory computer if at all. It is NOT a stroker. Many people are running strokers with no issues. I just need to find out what the real problem is. It may be that my 17 year old junkyard obtained fuel injectors are too weak and not quite giving the amount of fuel they should be. Or it may be a timing issue.