91 auto has no power below 4k rpm

[sloblue]

I have a 91 auto, it will not get out of its own way below 4000 rpm but has great power from 4k on. I did not know if anyone has seen a problem like this.

 

[NSXrunner]

Hmmm dunno. I got a 92 Auto. Power seems pretty linear. Granted it doesn't pull like the manuals or hold the higher revs for longer at the lower rpms, unless I keep the throttle floored or shift manually. The ECU also tends to be a bit on the protective side for the transmission, that may be what you are experiencing. I seem to keep up with other NSX's during random mountain/canyon drives though, so I have never given it much thought.

 

[sloblue]

a honda fit would out run the car from a stop there is that little power.

 

[goldNSX]

It could be everything else but your simple description reminds me of a bad fuel pump.

 

[Jett]

your simple description reminds me of a bad fuel pump

I agree!

 

[sloblue]

but at 4k the intake note changes and the car feels like it is in vtec then at 6k the cars intake note changes again. after 4k rpm the car has all the power.

 

[Jett]

...at 4k the intake note changes...after 4k rpm the car has all the power.

The NSX has a dual-stage fuel pump that kicks into the second stage (increased fuel flow) at 4000rpm. Which is why we think it is the fuel pump.:smile:

I drive an automatic also so I know how your car should "feel".

 

[goldNSX]

Have a search here on prime. I did a description of bypassing the fuel pump resistor. The fuel pump is then in Stage 2 all the time. Easy and cheap to do.

 

[Jett]

Maybe it is the fuel pump resistor itself, part number 16717-PR7-A01 for 1991-96 NSXs, that is giving trouble. Have a look at post #4 of this thread.

 

[Larry Bastanza]

Maybe it is the fuel pump resistor itself, part number 16717-PR7-A01 for 1991-96 NSXs, that is bad. Have a look at post #4 of this thread.

If the fuel pump resistor is bad, the car will not run

I would disconnect the 02 sensors, get the CEL to light and go for a test drive. Follow post #5 in this thread:

http://www.nsxprime.com/forums/showthread.php?t=104320&highlight=02+sensors

HTH,
LarryB

 

[goldNSX]

Do both tests, o2 and fuel pump resistor, the later one first as you talk about 4k rpm. Both are easy to do.

 

[Jett]

So I did some poking around and found out that the connector for my fuel pump resistor had gone bad from sitting in the hot engine bay or in the sun or something and cracked on the inside, leaving the terminals a bit of wiggle room to where they would sometimes loose connection for a second causing the car to stumble (or not to start)

Based on this quote from another thread, I would remove the fuel pump resistor and examine it and the connector.

 

[GreyHoundSteve]

Sounds like almost the exact same problem i was having. It was a bad fuel pump. Got a new one the and problem is fixed now.

Have them test your fuel pressure. If it is low then the pump is probably bad. I was getting codes 1 & 2 which were o2 sensor codes. I made the mistake of replacing both of those before i tested the pump.

 

[sloblue]

When the car is cold it has double the power below 4k but as it warms up the power starts falling off. It had an o2 code 3 weeks ago. I am also having a problem with code 21 I think it is the ecm based on trouble shooting but that is another problem. I need to find someone local that will let me swap in there ecu:redface:

 

[Larry Bastanza]

When the car is cold it has double the power below 4k but as it warms up the power starts falling off. It had an o2 code 3 weeks ago. I am also having a problem with code 21 I think it is the ecm based on trouble shooting but that is another problem. I need to find someone local that will let me swap in there ecu:redface:

All the more reason to follow post #10 above. When the car is cold the 02 sensors are not in use.

Regards,
LarryB

 

[Jett]

Have you had a chance to check the O2 sensors yet?

 

[Jin1976]

I'm having the same symptom now. Also shows code 1 and 2. New oxygen sensors, new fuel filter, new coil packs and new spark plugs. Looks like bad fuel pump. No performance under 4K rpm but no misfire. Press on the gas but the car is not accelerating very slowly. There goes my budget for GT-wing.

Sounds like almost the exact same problem i was having. It was a bad fuel pump. Got a new one the and problem is fixed now.

Have them test your fuel pressure. If it is low then the pump is probably bad. I was getting codes 1 & 2 which were o2 sensor codes. I made the mistake of replacing both of those before i tested the pump.

 

[goldNSX]

I'm having the same symptom now. Also shows code 1 and 2. New oxygen sensors, new fuel filter, new coil packs and new spark plugs. Looks like bad fuel pump. No performance under 4K rpm but no misfire. Press on the gas but the car is not accelerating very slowly.

You don't have to have a code with a bad fuel pump. Well, I don't have but she's bad for sure. Easy to test. Don't your codes (1 and 2) point on the oxygen sensors?

 

[Jin1976]

Yes. But the sensors are new.

You don't have to have a code with a bad fuel pump. Well, I don't have but she's bad for sure. Easy to test. Don't your codes (1 and 2) point on the oxygen sensors?