Engine missing -- problem found.

[matt_shover]

"Engine missing" is a bit misleading -- after a quick check I did confirm that, indeed, the engine was still in the bay where it belongs. Should I rather say "misfiring?"

Had a problem with the engine misfiring on the NSX that cropped up right before pre-paid NSXPO (unfortunately, missed it due to the problem) Anyway, I wanted to share what the symptoms were and the solution for anybody else that may have the same:

-Car started and ran fine for the first few minutes.
-Upon hard acceleration in 4th or 5th gear the car felt as if it was stumbling/missing.
-After about 10-15 minutes the car would start missing noticeably if I were accelerating at all.
-After about 20 minutes it was missing even at idle. Soon after, it would feel as if it were dropping a cylinder.

Changed out spark plugs as I heard from the dealer that non-stock plugs (I was using Bosch Platinums) may cause problems after 6-7K miles. This did not solve the problem.

Ordered new coil packs (all 6) and this DID solve the problem. It made perfect sense that a coil was perhaps overheating and was not working correctly. Coils were about $75/ea from Niello with the crucial NSXCA discount (thank you, NSXCA). Also ordered the factory plugs for around $13/ea.

The car runs baby smooth now. One thing I did notice is that the stock plugs seem to fit a bit more snugly in the boot of the coil assembly. It's possible by cheaping out on plugs that the coil went prematurely.

Lesson learned: Buy factory NSX spark plugs!

FWIW, car has about 117K miles.

BTW, this came a few months after replacing the ignitor. Symptoms of that were driving on 5 cylinders (car sounded like 1/2 of a Dodge Viper). Although, from what I've read, the ignitor problem can take on a couple of different symptoms.

Happy NSXing!

-Matt

 

[matteni]

I have what I would call a rough idle - even in comparison to other NSXs and was thinking about changing out the plugs. That said my symptoms are no where near as severe as yours.

Did you notice a CEL or was it all seat of the pants?

I do have Honda NSX plugs and am under the miles one would change them.

Just curious...

 

[sjs]

Thanks for sharing!

Do you still have the bad coil(s)? Did you measure the impedance per the shop manual? I'm curious to know if your problem would even be reflected in the only published test of the coils.

 

[BryanZublin]

ODB2 NSX's (95 and up) can directly detect if the engine is misfiring and should illuminate the check engine light (CEL) within a short time.

94 and older NSX's will not directly detect engine misfiring, but could still illiminate the CEL after some time with an indirect error. For example, "bad O2" sensor because the exhaust will always have unburned hydrocarbons and the engine will never go into closed loop mode.

 

[spdntckt]

As an interesting side-note -> a few years back my '95 (ODB2) did the same thing - it was a bad coil pack (#4). Replaced and car ran great... -BUT- the check engine light never came on..

go figure

--s

 

[matt_shover]

SJS: I still have the coils, am trying to find the multimeter to test them.

Nick: I never did get a CEL -- as Brian stated. You can't go wrong starting by replacing the plugs with OEMs, then if that doesn't clear it up I'd replace coils (or take a look at the ignitor). I'll get back to this thread once I find the MM and test results from the coils.

-Matt

 

[Spencer]

You can definitely have a bad coil and not necessarily get a check engine light on an ODB1 NSX. But it's pretty apparent when it's "missing" (even if intermittent) because of a coil pack and at least with mine, eventually it developed into the CES showing when it "did" it.