pinging (?)

[Tom239]

I'm sometimes hearing what sounds like pinging (detonation). It only happens when accelerating, and only in the range of 4300-5000 RPM. It is more likely to happen when driving uphill, and more likely to happen in 3rd gear than in 2nd. I'm using premium of course (91 octane). The car is a stock '95 NSX-T (manual transmission) with approx 34,000 miles.

I just bought the car, and know of nothing wrong with it. I don't know for sure that this is detonation, but that's what it sounds like to me. I can only notice it with the windows shut, otherwise the exhaust noise masks it.

One more thing: I'm noticing this on roads at about 4000' above sea level (which is where I live; I haven't had a chance yet to see whether it also happens near sea level).

I read the article at http://www.nsxprime.com/forums/showthread.php?s=&threadid=19744
which suggests that pinging is potentially very bad for engines with high specific output, so I'm concerned.

Any thoughts?

 

[Yellow Rose]

Tom - you raise a very good question. Since you do not mention it, I am assuming that your NSX is naturally aspirated. Let's talk about your car for a moment. Does it always "ping" at the same engine speed / load? Ditto ambient temperature? Ditto throttle position? Ditto engine temperature?

There are a few supercharged NSXs (elevations above yours and elevations below yours) that emulate the sound you describe; however; the "pinging" is not always at the same engine speed / load. It seems to be a function of not only throttle position, but how fast the throttle plate is opened. In other words, given a degree of experiencing the "pinging", a driver could in fact intentionally induce pinging. Or said another way, they can modulate the go-fast pedal in order to "work around" the point where pinging occurs.

Assuming of course that the noise really is pinging. This is one of those nasty gremlins that can disguise themselves in making you think it is pinging, when in fact it could be something else. Or is it?

 

[sjs]

Every detail of your description, with the possible exception of elevation, is classic of ping. One of the greatest sudden load changes is when trying to accelerate up a hill in higher gears at around max torque RPM, and that’s when ping is most likely. You should also find that warmer days are worse.

If it is easily reproduced, try a decent quality octane boost to see if it lessens the problem. (It will take a LOT since when they claim something like "increase octane 4 points" they really mean 0.4 which would only put you at 91.4) This is not a solution to the problem but can help confirm what is happening. As Andy said, ping can generally be modulated with the throttle which is another indicator.

If you believe it is pinging then start with the following:

Check/replace your fuel filter. If it is restrictive then the fuel pressure will be low and may cause a lean condition on sudden demand.

One or more injectors may be spraying poorly causing a lean condition. I've never had much luck with injector cleaner but others swear by it and it's cheap. Either of these first two may have been caused by running the tank empty and sucking up some crud.

Check all the small lines and hoses for vacuum leaks and listen in the engine compartment for hissing.

Check the timing. Someone before you may have messed with it such that it does not automatically correct.

Clean/replace spark plugs

Check inside the ECU for an aftermarket chip installed by a prior owner.

Pinging can also be caused by carbon buildup in the cylinders or on valves, but with so few miles on an unleaded car that seems unlikely so the old internal steam-clean trick may not be warranted.

 

[Eddy]

You can also try 100 octane unleaded race fuel. 76 makes it and are commonly sold through pump stations. You might about to call 76 to find out a station near you. It should reduce if not eliminate the pinging. You just have to try it for about $5/gal to see..

The other thing is to try a set of colder spark plugs. The service manual recommends heat range 7 spark plugs if high heat or high speed driving is common. It should also reduce pinging.

Eddy

 

[Tom239]

Thanks for all the responses.

The car is normally aspirated; as far as I know, it is 100% stock. The previous two owners were good about saving service records and have passed them on to me. I could double-check that I have a stock ECU (I found the page on this site with tips on how to access it) but I'll probably look into some of the other suggestions first.

The fuel filter was replaced 4000 miles ago as part of a 30,000 mile service last summer.

Trying some injector cleaner seems easy enough.

I'll check the ignition timing soon and look for vacuum leaks. If all that looks okay, I think it's spark plug time. By Honda's schedule, the spark plugs are overdue (not because of miles, but because of years).

 

[nsxtasy]

The higher elevation should help, not hurt...