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Unread 03-20-2002, 12:13 PM   #1
Intrepidjeep
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Pinging 4.0L

Why the heck does my 4.0L ping on 89oct fuel? If I put half a tank of premium in the Jeep he'll be happy and won't ping, but I don't care to put premium in a pushrod truck engine!

I had the dealer take a look and he said that I need a PCM update. While I'm sure a PCM update would be nice to have, they want $160 for the procedure and I have very little confidence that it will actually cure the pinging.

Also I'm (just for the past week or so) getting the check-engine light turning on occasionally, with fault code 21 (O2 sensor). It's only come on twice in the past two weeks -- it stays on for a day or two and then goes out.

Do you suppose if the O2 sensor is bad that it could contribute to pinging? (It's covered under extended warranty, I just have to wait for it to come on again so I can take it to the dealer with the light still on.)

Thanks for any comments or suggestions . . ..

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Unread 03-20-2002, 01:46 PM   #2
4wheeler4CJ
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Yes, the O2 sensor can contribute to the pinging. I'd change that first, easy and cheap (relatively, LOL). It shouldn't even ping on 87 octane.

I personally run super in all my cars, only because it does help with longevity and I keep all my cars till they are over 200,000 miles at least. I've never even had to do fuel injectors or anything, which I partly attribute to running super (a little cleaner). But, again, that is only preference.

Excuse the ignorance, but what the heck is a PCM Update unless I'm just having a brain fart!
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Unread 03-20-2002, 08:33 PM   #3
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The PCM is the Powertrain Control Module. Basically for $160 they want to "flash the bios" so to speak, like on a computer. I'm sure it would be a nice thing to do, but for $160 I need to know more about what changes it will provide. I'll talk to them more when I take it in for the O2 sensor since the vehicle is still under a WarrantyGold bumper-to-bumper 100,000 mile warranty.

Man that warranty is starting to save me a lot of cash. It only cost me about $1250. Just having gradually made the dealer replace the four door speakers was $150 per speaker, parts and labor. They're replacing the last one at the same time they do the O2 sensor. (If I'd known all four speakers were going to start buzzing I'd have taken the vehicle elsewhere where they could put in better quality speakers -- Xplod's or something.)
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Unread 03-20-2002, 08:55 PM   #4
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Forgot to mention -- I usually run 89oct in my vehicles, mainly since in Florida's hot summers you can get a little heat-related pinging on most any engine sometimes.

Premium fuel has a little slower, more controlled burn rate which is good for higher-compression, higher performance engines. On an engine that doesn't take advantage of the octane boost, such as stock Jeep engines, you end up with fuel still burning as it leaves the combustion chamber and heads out past the exhaust valves and into the manifold. As a result premium fuel can cause deposit buildup and burned valves over time on an engine designed just for 87 octane fuel. This is just based on what I've read in car mags, etc.

Of course if you put in an aftermarket computer with a more aggressive timing profile, or raise the compression ratio, etc., then you will need to raise the octane or suffer problems with predetonation/pinging. Especially on turbo/supercharged vehicles, higher octane is *very* important at least as *insurance* for your boosted engine. Even a few moments of predetonation/pinging at full throttle can have damaging effects, or lead to detonation, which will cause a holed piston!

According to Consumer Reports' reviews of different brands of gasoline, as long as you stick with a good brand such as Chevron (with its Techron detergent additive), Texaco, Amoco, etc., you'll have the same amount of detergents in 87oct as you have in 93oct. Cheapie gas stations often don't have much detergents in their fuel, so I avoid them.
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Unread 03-21-2002, 04:58 PM   #5
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Just an update -- the Jeep's in the dealer today getting the O2 sensor replaced and the right-rear door speaker replaced. We'll see tomorrow if the pinging is reduced -- crossing my fingers here. WarrantyGold took care of all of it I'm glad to say . . .
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Unread 03-28-2002, 12:00 PM   #6
Rzrseg
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</font><blockquote><font size="1" face="Verdana, Arial">quote:</font><hr /><font size="2" face="Verdana, Arial">I personally run super in all my cars, only because it does help with longevity and I keep all my cars till they are over 200,000 miles at least. </font><hr /></blockquote><font size="2" face="Verdana, Arial">Hi there. Just thought I'd throw this in. Running anything above what is required to keep your car from pinging is simply blowing money out the tail pipe. A higher octane does absolutely, positively nothing but change when the gas ignites.
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Unread 03-28-2002, 01:02 PM   #7
4wheeler4CJ
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I hate to say it, but higher octane fuel will absolutely, directly affect pinging. Take any car that pings, use a higher octane, and it will ping less or be eliminated. It's a proven fact.

You can also help pinging with timing in some cases, simply by retarding your ditributor a bit. Unless timing is automatically adjusted through your computer, of course.
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Unread 03-28-2002, 01:14 PM   #8
Rzrseg
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</font><blockquote><font size="1" face="Verdana, Arial">quote:</font><hr /><font size="2" face="Verdana, Arial">Originally posted by 4wheeler4CJ:
[QB]I hate to say it, but higher octane fuel will absolutely, directly affect pinging. Take any car that pings, use a higher octane, and it will ping less or be eliminated. It's a proven fact.</font><hr /></blockquote><font size="2" face="Verdana, Arial">Yep, you're right. This is also what I said.

However, I was replying to a post that said he put super in his cars for longevity. I was commenting that once you have a high enough octane to keep your car from pinging, any additional rating is just wasted money.
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Unread 03-28-2002, 01:43 PM   #9
4wheeler4CJ
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That was me that uses Super for longevity, LOL

I disagree that it is wasted money to use a higher octane than "theoretically necessary". It is a personal preference, in a way. However, higher octane fuels ARE cleaner than lower octanes, and will sometimes offer a slight increase in mileage, depending on your motor and ignition system.

In my opinion, one reason I have never changed injectors or had any problems with fuel, even on vehicles that have logged over 200,000 miles, is because I use Super. Many people I know have had to do injectors as early as 100,000, and they use 87. I can't prove or disprove my theory, but it seems to have worked for me over the years. Knock on wood, I have yet to ever change a fuel injector. And I keep all my vehicles to over 200,000. Some FI, some Carbureted (usually my CJ's, LOL).

Who really knows, you hear opinions both ways all day long, so I do what has worked for me, when it comes to things like this.
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Unread 03-28-2002, 02:15 PM   #10
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</font><blockquote><font size="1" face="Verdana, Arial">quote:</font><hr /><font size="2" face="Verdana, Arial">Originally posted by 4wheeler4CJ:
[QB]That was me that uses Super for longevity, LOL </font><hr /></blockquote><font size="2" face="Verdana, Arial">Whups, missed that! Sorry

</font><blockquote><font size="1" face="Verdana, Arial">quote:</font><hr /><font size="2" face="Verdana, Arial">I disagree that it is wasted money to use a higher octane than "theoretically necessary". It is a personal preference, in a way. However, higher octane fuels ARE cleaner than lower octanes, and will sometimes offer a slight increase in mileage, depending on your motor and ignition system.</font><hr /></blockquote><font size="2" face="Verdana, Arial">Nope. Sorry, they're not cleaner in any way at all and they offer absolutely nothing in the way of increased gas mileage. The higher octane simply changes the ignition point so you can run a higher compression before the gas self-ignites. The higer octane number simply means that the fuel mixture has a higher percentage of octane (octane is an 8 carbon chain hydrocarbon) mixed with heptane (heptane is a 7 carbon chain hydrocarbon). Octane resists compression much better than heptane so the higher percentage of octane in a mixture allows you to run a higher compression. It doesn't aid the engine or performance at all.

</font><blockquote><font size="1" face="Verdana, Arial">quote:</font><hr /><font size="2" face="Verdana, Arial">In my opinion, one reason I have never changed injectors or had any problems with fuel, even on vehicles that have logged over 200,000 miles, is because I use Super. Many people I know have had to do injectors as early as 100,000, and they use 87. I can't prove or disprove my theory, but it seems to have worked for me over the years.</font><hr /></blockquote><font size="2" face="Verdana, Arial">Sorry again. The octane rating isn't helping you here. You just take good care of your vehicle. Take credit for it...the petroleum industry sure isn't helping you.

</font><blockquote><font size="1" face="Verdana, Arial">quote:</font><hr /><font size="2" face="Verdana, Arial">Who really knows, you hear opinions both ways all day long, so I do what has worked for me, when it comes to things like this. </font><hr /></blockquote><font size="2" face="Verdana, Arial">Read my comments above.
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Unread 03-28-2002, 07:43 PM   #11
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OK, LOL, I'm a structural engineer, not a mechanical like you, you're using "chemical warfare" on me now......LOL Just Kidding. <img border="0" title="" alt="[Wink]" src="wink.gif" />

I dunno, without getting into too much nitty gritty, I notice a difference in performance/mileage running super, however slight it is. Heck, when I take my snowmobile touring trips in Canada, we all use Super even in our Touring Sleds, and it really does make a difference, even on that small a motor. The sleds run super-smooth when we use super vs. regular. We used regular, and they run fine, but climbing mountains, etc., they are just that extra bit smoother on super.

Maybe I just notice because I am a "hard" driver (CJ, XJ, snowmobile, boat, whatever it is, LOL), and tend to pick up subtle differences?
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Unread 03-28-2002, 08:04 PM   #12
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</font><blockquote><font size="1" face="Verdana, Arial">quote:</font><hr /><font size="2" face="Verdana, Arial">
Maybe I just notice because I am a "hard" driver (CJ, XJ, snowmobile, boat, whatever it is, LOL), and tend to pick up subtle differences?
[/QB]</font><hr /></blockquote><font size="2" face="Verdana, Arial">LOL!

There is a possibility that there is some slight predetonation going off under a hard load that super helps...I'd try coming down a notch to mid-grade and see if that makes a difference. Could be an interesting experiment.

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Unread 03-28-2002, 09:03 PM   #13
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LOL, Hard Load, meaning my foot, eh?

I dunno, can't hurt trying I guess.
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Unread 04-01-2002, 10:16 PM   #14
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I was going to ask about my '83 258 pinging in fifth gear, but i am already confused...lol
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Unread 04-02-2002, 06:31 AM   #15
4wheeler4CJ
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Pinging in fifth gear is under a load. You can help it by either retarding your timing a little bit, or by increasing your octane.
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