Car Looses power and shuts off under acceleration.

[Jeff@Carbon6]

I wanted to post my experience on this to help any others.

On my home from the ALMS race at Road America, I was accelerating hard up a hill when the car sputtered a few times and shut down (felt like it ran out of gas). While the engine was still spinning in gear (before I pushed in the clutch) the oil pressure gauge was still reading good oil pressure. After I pulled over to the side of the road, I looked at my fuel pressure gauge on top of the fuel filter (I recommend adding one of those for everyone) and the fuel pressure was 0. My first thought was the main relay. Although it seemed unlikely that it would fail while driving (but possible). Second, I thought of the fuel pump itself. There are quite a few threads where NSX owners have had to replace their pumps. Generally, fuel pumps will not completely stop. The car would turn over but not fire and had no fuel pressure while cranking. I had the car towed back to my house. Used the flow chart in the service manual to diagnose the issue. I bench tested the main relay and the fuel pump resistor. Both were fine. There are 2 power feeds that run that system. One was fine. The second (fuse #2 in kick panel (15a)) had blown. I replaced the fuse and the car seems fine.

A simple fix, However, there is a reason why the fuse popped. That I am not sure of yet. For now the car operates fine. I'll be digging into the fuel and charging system to see if I can find the weak link.

Lesson learned: keep a few spare fuses on hand and always check the simple things first.

 

[BTL3.0]

Lesson learned: keep a few spare fuses on hand and always check the simple things first.

My thoughts exactly about keeping spares fuse in the car. I always have 1 of each in a small bag. Even though there are some spare fuse next to the fuse box, sometime it might need more then just 1 of the same fuse.

I hope you can figure out what cause your car to short ut a fuse like that. Kinda dangerous when it happen on the road like that.

 

[Jeff@Carbon6]

My thoughts exactly about keeping spares fuse in the car. I always have 1 of each in a small bag. Even though there are some spare fuse next to the fuse box, sometime it might need more then just 1 of the same fuse.

I hope you can figure out what cause your car to short ut a fuse like that. Kinda dangerous when it happen on the road like that.

The car seems to be fine. It could be as simple as a voltage drop when the engine is under maximum electrical load. My battery (Odyssey 680) was only at ~70% when I put in on the smart charger after the car came off the tow truck. It is reasonable to replace the serviceable parts in that system however. Including the fuel pump.

 

[Briank]

Fuse #2 provides control power for a lot of stuff. 02 sensors, gauges, main relay, srs ctl unit, Emission control unit, alternator and speed sensor so lots of places for a possible intermittent short.

 

[Jeff@Carbon6]

Fuse #2 provides control power for a lot of stuff. 02 sensors, gauges, main relay, srs ctl unit, Emission control unit, alternator and speed sensor so lots of places for a possible intermittent short.

You are correct. Looks like I have my work cut out.

 

[BTL3.0]

Wow, where do you start? Man that list is long.

 

[nsxiest]

You might try checking that the wires leading to the O2 sensor near the rear bank (looking down into engine bay from the drivers side) have not touched something they should not have, melted and shorted (on same fuse as mentioned). Happened to me one day at the track and I was perplexed. I have since encased mine in some insulating silver heat reflective conduit.

My 0.2

 

[davidf]

Generally I would run the car until it blows again. Could've been a fluke and very well may never happen again. You have fuses on hand if it does, then I'd be concerned but for now, I'd let it ride before tearing the car apart.

 

[Jeff@Carbon6]

it popped again yesterday. I'll run a service diagnostic and start drilling down the list of possibilities.

 

[Jeff@Carbon6]

I found the issue. The front bank O2 sensor wires had shorted out on the mounting clip near the top of the head. I cut out the bad wires, replaced them with a new section (soldered and heat shrink) and wrapped the area of the wires that are exposed to heat with a heat reflective foil sleeve.

I believe the heat on that front bank is higher because there is no turbulent air movement with the underbody being sealed up. It may be marginal. My future concern would be premature wear on the engine. I may look at doing a heat shield on the top of the headers and/or figuring out how to get some cool air movement in that front engine cavity without effecting the under side aero.

 

[RYU]

Nice to hear you've found the culprit. This morning I found the source to my own electrical gremlins this morning and it sure is a nice feeling.

The 02 sensor wiring is also a worry for me. I found a satisfactory way to route my 02 wires but it's not optimal. If you find some high heat split loom or another form of heat protective wire sheathing pls let us know. I'm contacting my friend in aerospace to see what they use. The standard automotive split loom melts with simply the amount of ambient heat back there. The factory installed split loom is now cracking, dry, and brittle. I'd like to replace most of them.

 

[Jeff@Carbon6]

DEI makes some of the best heat reflecting materials. They are used in military applications. Their gold material will take 675 degrees for a minimum of 8 hours. I had some left from the underside of my diffuser. I put a fiberglass sleeve over the wires first to eliminate contact then spiral wrapped the wire with 2" wide gold foil tape. "If it's worth doin', it's worth overdoin" I always say :biggrin:

<iframe width="560" height="345" src="http://www.youtube.com/embed/XjFzTJOuDQE" frameborder="0" allowfullscreen></iframe>

 

[jagtiger]

Hi Vroom...I may have the same issue as yours as this happened to me from the canyon drive yesterday. I have been driving the car hard up in the canyons and on the way back - on the freeway the car will sputter like it's out of gas, then check engine light comes on and engine shuts down... I pulled over on the side..turn the ignition to off then restart...the car runs and drives like normal but then starts to sputters again and shutdowns after a few miles but this time the car wont start..then after 10 minutes or so it starts like normal again but I had the car towed since i didnt want to damage anything in the engine..

Yesterday I was told that this could be case of a bad main relay but I wanted to check first if it's the same exact problem that you have.

Can you please tell me where exactly I can locate the front 02 sensors wirings? Would this be the one by the headers?

I appreciate the help. Thanks -Henry

 

[Jeff@Carbon6]

Hi Vroom...I may have the same issue as yours as this happened to me from the canyon drive yesterday. I have been driving the car hard up in the canyons and on the way back - on the freeway the car will sputter like it's out of gas, then check engine light comes on and engine shuts down... I pulled over on the side..turn the ignition to off then restart...the car runs and drives like normal but then starts to sputters again and shutdowns after a few miles but this time the car wont start..then after 10 minutes or so it starts like normal again but I had the car towed since i didnt want to damage anything in the engine..

Yesterday I was told that this could be case of a bad main relay but I wanted to check first if it's the same exact problem that you have.

Can you please tell me where exactly I can locate the front 02 sensors wirings? Would this be the one by the headers?

I appreciate the help. Thanks -Henry

It is best to refer the the service manual. The front bank of o2 sensor wires run above the front header along the area where the valve cover and head mate. There are 2 spring clips (if I remember correctly) that hold the loom/wire to the top part of the head.

 

[RYU]

Hi Vroom...I may have the same issue as yours as this happened to me from the canyon drive yesterday. I have been driving the car hard up in the canyons and on the way back - on the freeway the car will sputter like it's out of gas, then check engine light comes on and engine shuts down... I pulled over on the side..turn the ignition to off then restart...the car runs and drives like normal but then starts to sputters again and shutdowns after a few miles but this time the car wont start..then after 10 minutes or so it starts like normal again but I had the car towed since i didnt want to damage anything in the engine..

Yesterday I was told that this could be case of a bad main relay but I wanted to check first if it's the same exact problem that you have.

Can you please tell me where exactly I can locate the front 02 sensors wirings? Would this be the one by the headers?

I appreciate the help. Thanks -Henry

Hi Henry,

I'm glad you and the car got home safely yesterday.

I'm not sure your symptoms sound like a main relay problem but it is certainly worth a look that way. Typically, the main relay issues presents themselves as intermittent or completely off.

This sounds like it could be a heat related issue?

In terms of your question you can see in the photo I attached, I believe this is where the O2 plugs can be accessed. I'll have to look when I get home but i'm 99% they're there. Bad O2s will sputter the car below ~3.5k rpm if I recall. There's a good thread where LarryB chimed in. To test the sensors (quick and dirty way) you can unplug the sensors, the CEL will come on, but the car should run fine if the sensors are bad. If it runs the same (i.e. sputters) then it's likely not your O2 and it's something else.

It was a hot day yesterday... one thing to check real quick is your coolant level. I would also start looking at stuff like fuel pressure and fuel filter (if the pump and filter haven't been replaced yet).

 

[Na1 NyC]

any updates? seems like im having the same problem, only dies when the car warms up, like after 30mins of driving

 

[Jeff@Carbon6]

any updates? seems like im having the same problem, only dies when the car warms up, like after 30mins of driving

My issue had to deal with the O2 sensor wire on the front bank had fallen out of the clip and was to close to the header. Once the casing of the wire got to hot, it melted and shorted the wires together. When it cooled, the plastic then created some isolation and it would start fine.

check your O2 sensor wires and confirm they are not melted and are clear of the headers.

 

[NonStopReaper]

I think i have the same problems along this line. My car would start and idle but when you rev it up. it revs up once and that's it. It would die back down and not rev up again. I've already replace the fuel pump, main relay, fuel filter, check the fuel lines even replaced the throttle body and still the same symptoms. could it be a bad o2 sensor? or speed sensor? I'm stuck

 

[Briank]

I think i have the same problems along this line. My car would start and idle but when you rev it up. it revs up once and that's it. It would die back down and not rev up again. I've already replace the fuel pump, main relay, fuel filter, check the fuel lines even replaced the throttle body and still the same symptoms. could it be a bad o2 sensor? or speed sensor? I'm stuck

Ignition switch

 

[Jeff@Carbon6]

I think i have the same problems along this line. My car would start and idle but when you rev it up. it revs up once and that's it. It would die back down and not rev up again. I've already replace the fuel pump, main relay, fuel filter, check the fuel lines even replaced the throttle body and still the same symptoms. could it be a bad o2 sensor? or speed sensor? I'm stuck

That sounds like a different issue. I wouldn't think its a speed sensor. Could be a bad O2 sensor...

 

[Na1 NyC]

mines shuts off and no dash lights come on, im gonna check both o2 and ignition switch, thanks
if its the ignition switch, i just swap out the cylinder?

 

[Na1 NyC]

got part # for ignition switch? thanks

 

[Briank]

mines shuts off and no dash lights come on, im gonna check both o2 and ignition switch, thanks
if its the ignition switch, i just swap out the cylinder?

You swap out the switch part the cylinder stays in place.