1991 NSX completely shut off while driving, complete power loss

I am the second owner of a 1991 Acura NSX. I’ve owned the automobile since 2001. It remains all stock. It was a daily driver for many years, but the last two years I’ve stored it in the winter time since I live in Minnesota. Last year, after taking it out of storage, I drove it only a few times. I want to say then on the second drive, it completely lost power and I had to pull to the side of the road. The engine light went on at the time of power loss, but then went back off. I was able to start the car and drive it home normally. I just went and picked it up from its winter storage today. It was sitting in a dry barn covered for the last seven months. I jumpstarted it, and it turned right over. After driving approximately 30 miles on the Freeway, it completely shut down and lost power, and the engine light went on. When I pulled in the side of the road, I simply let it rest for approximately 30 seconds, then restarted it. I was able to complete the additional 30 miles on the highway without problems. I’ve kept up on maintenance. I am not mechanically inclined. Last year when this happened, I had two different mechanics look at it, and they could not find a cause for the dysfunction. Anyone have any idea what may be causing this? Since no codes are likely to come up without lights being on, are there some basic maintenance issues that I can address without being sure of an exact cause?

Many thanks,
Andrew

Unless I’m mistaken, I think you have a main relay that is going bad. I am like you, owned the car for 15+ years and about 18 months ago had similar problems. I resoldered the main relay and haven’t missed a beat.
Alternate, but possible issue is with the ignition switch.
Main relay is early to replace and a great starting point.

Thank you very much. I’ll have a mechanic take a look.
Pretty unnerving traveling at 70 mph and your car completely loses power.
Have a great evening,
Andrew

This wouldn't be the cause of your issue, but the ~1.5 year old gas isn't doing your fuel system and engine any good.

There is a drain plug on the bottom of the tank if it's full of old gas. If it's only a little bit, then you can try filling it up with fresh stuff and add a bottle of Techron fuel system cleaner.

I wouldn't subject the engine to a significant load until you've gotten rid of the old gas.

Given the vintage of your car and the random nature of the failures you describe, I agree with [MENTION=11324]Miner[/MENTION] that the ignition switch and the main FI relay would be the likely first choice candidates to check. However, there are a lot of other failures that can mimic your symptoms so they are not the only potential candidates. The only problem with your plan to have a mechanic 'take a look' is that if the engine is able to run at the time, its almost guaranteed that they won't find the problem unless they can trigger the failure by whacking the relay or wiggling the key back and forth in the ignition lock cylinder.

I am not a particular fan of this method; but, with random failures you may have to start the diagnosis by replacement. If you are using an Acura dealership for the work I would be inclined to tell them to just replace the main FI relay and the ignition switch as a starting point. If you are not using an Acura dealership, I would acquire the parts ahead of time and have your mechanic install them. Fortunately, the two parts are not really expensive, particularly if you order them from Rock Auto (less than $100 US$ total if you follow my tip below). Not that expensive from Acura either.

A little tip, I think the 1991 main relay may no longer be available from Acura. They are available from Rock Auto and other aftermarket suppliers; but, they are more than twice the price of the main FI relay from the later cars (I think it changed around 1995). Thing is the relay is identical, only the mounting bracket changed. If you are inclined to save $50, you can pop the old relay out of its case, do the same for the new relay and switch cases allowing you to install the later relay in your 1991. A less elegant solution is to just attach the new relay to the old bracket using zip ties or that heavy duty double sided tape used for fastening automotive trim.

Neither the main FI relay or the ignition switch are 'technically' difficult to change. The ignition switch is a physical hassle because of the need to get under the dash on the driver's side. The biggest risk is damage to the plastic trim panels during removal and reinstallation because of the age of the plastic. R&R of both parts is covered in the service manual (and a few Prime posts) which is available on Prime if you search and are at all inclined to give it a try.

Mac Attack said:

This wouldn't be the cause of your issue, but the ~1.5 year old gas isn't doing your fuel system and engine any good.

There is a drain plug on the bottom of the tank if it's full of old gas. If it's only a little bit, then you can try filling it up with fresh stuff and add a bottle of Techron fuel system cleaner.

I wouldn't subject the engine to a significant load until you've gotten rid of the old gas.

Click to expand...

Question- how do you dispose of old gas?

[MENTION=18194]Honcho[/MENTION]

If it still combusts and hasn't turned to varnish you can use it in your lawnmower.