Pinging

My '96 has always pinged (panged? pung?) on 87 octane but not on 91.

Yeah, but the engine in Miata's 91 doesn't require 91, does it.

Yes, apparently it does. ;)

Whether it's supposed to require 91 or not is another question.

In my experience, as engines age they seem to require higher octane fuel to avoid pinging. I presume it's due to the buildup of deposits in the cylinders that create hot-spots somehow or to degraded performance of engine management components.

I agree with Grant here, he's got a good point. I'm however, wondering if the OP is confusing pinging with HLA noise (a 91 miata's security blanket). He refers to it as "rattle noise".

The lifter noise is unaffected by octane and the OP says he put in the hi test and it didn't help. Allot of mechanics aren't familiar with the miata's lifter clatter. The OP should try a fresh oil change (maybe a high mileage blend) and pay close attention, he may find it disappears for about 25 to

Later, Chris

I'd agree with Chris, and suggest that a bit (few ounces) of "Marvel Mystery Oil" (or some automatic tranny fluid) be added to the oil. This did wonders for the tiny lifters in our old Mazda MPV 4cyl. with

Thanks Chris, I am very well be confuse, I don't even know about HLA, I will do fresh oil change and fill up with high octane right away.

HLA noise is unmistakable - very loud even at idle, and comes from the very top of the engine. Pinging (or pinking as we say over here) typically shows up only when the engine is put under load - such as driving up a steep hill, or under harsh acceleration.

If you think it's the latter, you should have the timing checked. A former owner may have advanced it to 18 degrees BTDC by mistake - it happens, as the timing marks are easily confused.

Neither does the '96.

Now I am sure it is pinging not HLA, I will have the timing checked.

there was a 4 cyl avail? I had the V6 once upon a time, wasn't aware they offered a 4.

Chris

Good luck, Chris

Well, sounds are tough in text ;-) but, if the high octane didn't help, it makes it somewhat less likely it's the timing issue. Not saying it can't be, just less likely. By the way, 10 BTDC is spec but I strongly recommend 14 BTDC for extra seat-of-the-pants low end torque.

Let us know the result! Chris

If the timing is really whacked, then it might still ping on 91 in warm weather. But, changing from 87 to 91 should have reduced it. OTOH, you'd think he'd have lost enough compression by now that it wouldn't be a big problem. :)

If it's louder at idle/cold, then it's lifters. If it's lounder when it's hot and you're trying to accellerate in high gear, it's pinging. If it's the latter and 91 octane doesn't help much, he might want to try a tank of 93 or 94 if he can find some.

He also might want to check the plug wires to make sure their not worn out, loose, or mis-connected. Bad wires will make an engine sound funny (though it doesn't usally sound like real "pinging").

Let's make this simple. Your engine won't ping when your foot's off the throttle. HLA clatter doesn't care what the throttle is doing.

My HLA clatter seems to come and go as it it pleases, though it tends to be worse after 2500-3000 miles and worse when the engine is hot (the opposite of what Grant said).

Thank you, the KIS principal!

Chris

I remember it being the way you describe also. The thicker / cold oil lessened the noise, the hotter / thinner / older oil, accentuated the noise.

Chris

It was actually the better of the two engines. Seems that it had the Japco/ auto tranny, instead of the electronic one used with the 6cyl. The tranny was (so I'm told) originally intended for taxicabs. The 4 cyl was a very good long lived engine, without many of the problems associated with the v6 engines. The 4cyl was also available with a standard tranny, although it was not very popular, and the length of the shift lever was something to behold.