Having a little problem, diagnosis please.

[1991NSX]

Nothing has ever been amiss with my 1991 for over 4 yrs. This week, it's been acting a tad weird. It makes a stumbling noise and power is slightly affected in low gears. The exhaust is making small burbles like on overrun. Very smooth at idle and driving, just when you say downshift to 2nd around a tight corning, when getting on the throttle at around 2k rpm it makes a blat, blat, blat from the exhaust and once I get past 2,500-2700rpm it goes away. If going under 30 and I coast and then hit the gas a little, it very subtlely does it. Any ideas?? It has 55K and I had the "major" done on it last year. It's been flawless until this minor hiccup.
Thanks for the help.

 

[Russ]

It could be an O2 sensor going bad, pull trouble codes from the ECU to see what's going on.

 

[1991NSX]

Thanks for your response! Can an O2 sensor go bad without tripping the check engine light?

 

[docjohn]

Thanks for your response! Can an O2 sensor go bad without tripping the check engine light?

not sure about obd1 but on obd2 cars the answer is no.Has your engine bay seen more water than usual?Funny electrical/coil issues can arise particularly after an engine detail.

 

[1991NSX]

No water whatsoever. Could it be a plug or plug wire? It only does it down low in rpm while accelerating though.

 

[Russ]

Thanks for your response! Can an O2 sensor go bad without tripping the check engine light?

Yes, this was the case on my '91. IIRC the code for bad O2 was set yet the CEL was off. Computers, sheesh

 

[BATMANs]

I had something similar to ur symptoms and started with replacing the spark plugs with the NGK Iridium ones.

Problem fixed.

Make sure u use a nice synthetic grease for the threads so in the future it's easier to unscrew the plugs.

 

[1991NSX]

Will look into these suggestions, thanks for the feedback. Could it be a MAF sensor? Maybe spray some mass airflow cleaner on the sensor? That was suggested by a friend here at work.

 

[Briank]

Will look into these suggestions, thanks for the feedback. Could it be a MAF sensor? Maybe spray some mass airflow cleaner on the sensor? That was suggested by a friend here at work.

Honda/Acura's do not use Mass air flow sensors.

 

[mknmoves]

Nothing has ever been amiss with my 1991 for over 4 yrs. This week, it's been acting a tad weird. It makes a stumbling noise and power is slightly affected in low gears. The exhaust is making small burbles like on overrun. Very smooth at idle and driving, just when you say downshift to 2nd around a tight corning, when getting on the throttle at around 2k rpm it makes a blat, blat, blat from the exhaust and once I get past 2,500-2700rpm it goes away. If going under 30 and I coast and then hit the gas a little, it very subtlely does it. Any ideas?? It has 55K and I had the "major" done on it last year. It's been flawless until this minor hiccup.
Thanks for the help.

Clogged catalytics.

 

[PrideExhaust]

Mentioned above are very good pointers. Try to maybe back track it, did you do anything to your car right before the problem started? Installed anything? Use cheap gas? Washed your car.....

 

[FelonyRuckus]

coil packs are my guess

 

[tbromley]

coil packs are my guess

If it's coil packs it should get worse with time.

 

[1991NSX]

Hmmm. Thanks for the suggestions guys. I really appreciate it. I haven't done anything at all to the NSX this year - no mods, cheap gas, washed it, etc. Sounds like it could be a number of things, I'll have to take it to the dealer I suppose.
Thanks all.
Jim

 

[pgilliam1]

Could be your fuel pump is going blinky. Try jumping the fuel pump resistor to bypass the low pressure stage. This is an easy DIY from the engine compartment. It only takes a minute. Good Luck and Happy Motoring!

 

[LJZ]

Echoing one of the above posts -- had very similar problem with my NSX that I bought last November (1994 w/18,700 miles) -- prior owner had either never or not in a long time replaced plugs. My Acura mechanic buddy replaced all 6 plugs w/OEM pllugs and problem gone immediately. Symptoms were slight miss in lower rev range -- from 1500 - 2500 or so. Nothing that rose to the level of serious stumbling but there and perceptible nonetheless. I characterized it as being "barfy" at low revs upon acceleration. Sorry for the technical term! At any rate, the plugs cleared this up and the car generally ran much better with the new plugs.

Best,
Jeff

 

[nsxtasy]

It has 55K and I had the "major" done on it last year.

The "major" should have included the spark plugs, which are specified for replacement every 60K miles or 6 years, whichever comes first. On a '91, that means they should have been replaced three times by now.

 

[1991NSX]

Yes, the plugs were changed. It runs fine most of the time. Only in the lower rev ranges when the car it is too high a gear. I tried it at 35mph, and shifted into 5th and took off from that. bunch of small hic ups and small detonations coming from the muffler with blap, blap, blap, then once I get closer to 3k rpm's all is fine. I did this as a test, it mimicks the 2nd and 3rd gears around turns that are sharp and I'm down on rpm's there too. It only does it under load at low rpm's. Most people I've asked say O2 sensor, but they aren't sure. I don't think it's the cats since it only does it at this particular time. I have no idea how to bypass the low pressure stage. Could you point me in that direction by chance on how to do that?
Thanks!

 

[1991NSX]

Anyone able to tell me how to pull codes from the car? I have no ideas where to even do that.
Thanks.

 

[nsxtasy]

Anyone able to tell me how to pull codes from the car? I have no ideas where to even do that.

Click here.

 

[1991NSX]

Thank you, nsxtasy.

Now the car has a very loud (sounds just like a sprinkler) clatter that doesn't go away. Click, click, click. I called the dealer and am waiting a call back. An exhaust leak wouldn't cause all this, could it?

 

[nsxtasy]

Now the car has a very loud (sounds just like a sprinkler) clatter that doesn't go away. Click, click, click. I called the dealer and am waiting a call back. An exhaust leak wouldn't cause all this, could it?

A small amount of valvetrain clatter is normal in the NSX. If it has gotten louder, it is not normal.

 

[mknmoves]

What is the diagnosis?

 

[BadCarma]

Pull codes, check plugs and o2 sensers can get crap on them, ohm out coil packs....how long since changed fuel filter....all good things to check. good luck!

best regards david

 

[Jin1976]

Clogged catalytics.

I have had similar issue that was fully solve late last year. Mine is also 91 and driven daily. Several things we did which include removing the clog in the catalytic convertors, replacing one of the corroded ignition coil and the real problem was the clogged injectors. It had similar symptoms like yours that is the idling was normal but upon accelerating between 1K to 2K rpm it was having a bit misfire and stumbling. At higher rpm it becomes normal again.

If you have not clean the injectors probably that should be the first thing to do.