Hesitation issues with Charlotte.

[GreyHoundSteve]

By "Denso sensors" do you mean o2 sensors? I have Cantrell headers too and when i had them installed i think they messed up my o2 sensors because thats when my hesitation problem started.

I order two new o2 sensors from Honda and they were pretty expensive even discounted. What did you pay for yours?

 

[goldNSX]

By "Denso sensors" do you mean o2 sensors? I have Cantrell headers too and when i had them installed i think they messed up my o2 sensors because thats when my hesitation problem started.

I order two new o2 sensors from Honda and they were pretty expensive even discounted. What did you pay for yours?

Do you want to express that you messed the Denso ones up due to being Denso's? Or are Denso and Honda ones not the same?

 

[Hugh]

By "Denso sensors" do you mean o2 sensors? I have Cantrell headers too and when i had them installed i think they messed up my o2 sensors because thats when my hesitation problem started.

I order two new o2 sensors from Honda and they were pretty expensive even discounted. What did you pay for yours?

Make sure you have good connections, especially with the extension cables. Disconnect everything, spray the connectors with contact cleaner then load them up with dielectric grease before plugging them back together.

Sparkplugs.com offers 3 brands of O2 sensors for the NSX.

Denso OEM - $92 F and $56 R (I ordered these)
Denso Universal - $45 each.

NKG OEM - $53 each
NKG Universal - $29 each

And some German ones. We won't go there as German crap doesn't belong in our cars.

 

[Hugh]

Do you want to express that you messed the Denso ones up due to being Denso's? Or are Denso and Honda ones not the same?

Honda sources them from Denso and NKG. Are you in Switzerland or Belgium Gold? I forget.

 

[goldNSX]

Honda sources them from Denso and NKG. Are you in Switzerland or Belgium Gold? I forget.

SOS has the right sizes too (according to your list)? I'm in the earlier one, quite late here to write on a forum located in the US. :wink:

 

[Hugh]

I miss Switzerland. When I was young I attended summer camps in Crans/Montana and Villars. I remember races they had up the mountain. Francois Cevert won one of them in the Elf F1 car that had the 4 front wheels.

Can you send me a wheel of cheese so I make a nice Raclette? :biggrin:

 

[GreyHoundSteve]

I paid a little over the Denso oem price but i guess thats not too far out of line then.

Goof advice on the harness extensions, i'll check that.

Make sure you have good connections, especially with the extension cables. Disconnect everything, spray the connectors with contact cleaner then load them up with dielectric grease before plugginh them back together.

Sparkplugs.com offers 3 brands of O2 sensors for the NSX.

Denso OEM - $92 F and $56 R (I ordered these)
Denso Universal - $45 each.

NKG OEM - $53 each
NKG Universal - $29 each

And some German ones. We won't go there as German crap doesn't belong in our cars.

 

[Hugh]

Goof advice on the harness extensions, i'll check that.

Thank you.

 

[Hugh]

New Denso O2 sensors installed today. CEL/ECU reset. Problem is resolved.

 

[Larry Bastanza]

Great, we will talk again at 460K mile mark.

Regards,
LarryB

 

[goldNSX]

New Denso O2 sensors installed today. CEL/ECU reset. Problem is resolved.

Thanks for the feedback.

 

[Hugh]

Great, we will talk again at 460K mile mark.

Regards,
LarryB

I'm sure I'll need your sage advice before that happens. And besides, didn't you promise me the first dance at NSXPO2009? You'll love my Brunhilde outfit!

 

[Larry Bastanza]

You'll love my Brunhilde outfit!

Dude, you scare me.......

 

[goldNSX]

Hesitation UPDATE. My car has hesitation below 4k rpm also. Test scenario: 2nd gear, starting with 2k rpm, accelerating hard. The engine doesn't pull as hard until it reaches around 4.5k rpm where it releases all it's power up to redline like VTEC in an Integra.
I did an additional test today: Bypassing the fuel pump resistor which is only active below around 4k rpm. In the pic I've released the fuel resistor cable and shorted it so the fuel pump has always the power supply as above 4k rpm. Result: Hesitation gone! It pulls significantly stronger below 4k rpm.
Possible causes: Fuel pump resistor or relay, Ohm was ok. Or bad fuel pump like suspected earlier. This test is very easy to do. Just make sure the shortening cable is secured in its position. Otherwise the fuel delivery is cut.
Interesting fuel pressure measures.
with resistor: 39/46 psi
bypassed resistor: 42/52 psi
both with a AEM FPR installed!
So the engine won't end due to fuel washing down the cylinder walls.

Just to let you know.

 

[GreyHoundSteve]

Hesitation UPDATE. My car has hesitation below 4k rpm also. Test scenario: 2nd gear, starting with 2k rpm, accelerating hard. The engine doesn't pull as hard until it reaches around 4.5k rpm where it releases all it's power up to redline like VTEC in an Integra.
I did an additional test today: Bypassing the fuel pump resistor which is only active below around 4k rpm. In the pic I've released the fuel resistor cable and shorted it so the fuel pump has always the power supply as above 4k rpm. Result: Hesitation gone! It pulls significantly stronger below 4k rpm.
Possible causes: Fuel pump resistor or relay, Ohm was ok. Or bad fuel pump like suspected earlier. This test is very easy to do. Just make sure the shortening cable is secured in its position. Otherwise the fuel delivery is cut.
Interesting fuel pressure measures.
with resistor: 39/46 psi
bypassed resistor: 42/52 psi
both with a AEM FPR installed!
So the engine won't end due to fuel washing down the cylinder walls.

Just to let you know.

Please keep me updated on your findings. I am having the exact same problem with my car and am interested in knowing exactly what your issue was.

 

[goldNSX]

Please keep me updated on your findings. I am having the exact same problem with my car and am interested in knowing exactly what your issue was.

Will do. I'm running with the resistor bypassed from now on until the relay/resistor/wiring or (more likely) the fuel pump is fixed.

Sidenote: The hesitation is more pronounced at lower outside temps (<15 degrees Celsius) what we have now in spring here. During summertime it's much less but also recognizable if you have the colder temp behaviour in mind.

 

[GreyHoundSteve]

Will do. I'm running with the resistor bypassed from now on until the relay/resistor/wiring or (more likely) the fuel pump is fixed.

Sidenote: The hesitation is more pronounced at lower outside temps (<15 degrees Celsius) what we have now in spring here. During summertime it's much less but also recognizable if you have the colder temp behaviour in mind.

My car is gutless below 4500 rpm, then a sudden rush of power comes on until redline. This problem arose after i dropped it off for paint, headers, exhaust, test pipes, vale adjustment, and spark plugs were done. Everyones best guess was 02 sensors so i had those replaced last week as well as a new fuel pressure regulator and fuel filter but the problem is still there.

My car is a 91 with 135,xxx miles so my first guess was fuel pump but everyone said to check everything else first. I am going to drop it off again some time this week to have a few more tests done but since our problems sound similar i would love to hear what the solution to yours was since my mechanic(s) are just playing the guessing games at my expense.

 

[goldNSX]

My car is gutless below 4500 rpm, then a sudden rush of power comes on until redline. This problem arose after i dropped it off for paint, headers, exhaust, test pipes, vale adjustment, and spark plugs were done. Everyones best guess was 02 sensors so i had those replaced last week as well as a new fuel pressure regulator and fuel filter but the problem is still there.

My car is a 91 with 135,xxx miles so my first guess was fuel pump but everyone said to check everything else first. I am going to drop it off again some time this week to have a few more tests done but since our problems sound similar i would love to hear what the solution to yours was since my mechanic(s) are just playing the guessing games at my expense.

Your problem sounds very much the same as on my car. :wink:
The sudden occurence of your problem may also be correlated to the work done on your car. Here's my really just hypertheoretical guessing:
- valve adjustment -> not done properly, grounding?
- spark plugs?
But maybe it was happening just by bad luck.

The test of bypassing the fuel pump resistor is very easy and done within 5 minutes without throwing a cent at the car.

Prior to this I went through the recommended steps like
- checked sparkplugs (ok)
- coil resistance and condition (ok)
- checking fuel pressure (ok at that time)
- changed the FPR later
- checked and cleaned the injectors (ok)
- thought about the 02 sensors

Another source I thought of would be the VVS because it's acting around 4k rpm but found it unlikely to have such a influence.

In the SM there's description of checking the resistor but only for the case the engine is not running. Above I've mentioned the fuel pump relay to check. This is not correct as the problem would be in the upper rpm range then.

I hope I can tell more in a month or so. Good luck!

 

[GreyHoundSteve]

Your problem sounds very much the same as on my car. :wink:
The sudden occurence of your problem may also be correlated to the work done on your car. Here's my really just hypertheoretical guessing:
- valve adjustment -> not done properly, grounding?
- spark plugs?
But maybe it was happening just by bad luck.

The test of bypassing the fuel pump resistor is very easy and done within 5 minutes without throwing a cent at the car.

Prior to this I went through the recommended steps like
- checked sparkplugs (ok)
- coil resistance and condition (ok)
- checking fuel pressure (ok at that time)
- changed the FPR later
- checked and cleaned the injectors (ok)
- thought about the 02 sensors

Another source I thought of would be the VVS because it's acting around 4k rpm but found it unlikely to have such a influence.

In the SM there's description of checking the resistor but only for the case the engine is not running. Above I've mentioned the fuel pump relay to check. This is not correct as the problem would be in the upper rpm range then.

I hope I can tell more in a month or so. Good luck!

The last mechanic i took it to said that he thought it sounded like it was missing and it was probably a bad valve adjustment but he would have to open it up to check and since i just had the adjustment done less than 500 miles prior i'm hesitant to do it again until i have eliminated all other possibilities.

I going to do some more tests like the one you mentioned before i open up the valve covers AGAIN.

 

[goldNSX]

I going to do some more tests like the one you mentioned before i open up the valve covers AGAIN.

I didn't want you to point you in a (expensive) direction. I just mentioned what I've did to find the problem. I'm fully your opinion to check the easy to test things first and bypassing the resistor is one of the (if not the) easiest thing. :wink:

 

[NSX~PERT]

I have the same exact problem as Hugh but my OEM O2 sensors are disconnected already and I'm running an AEM wideband to my AEM computer but the car has been doing this way before FI every once in awhile. Any suggestions what else can be the culpret? Coil pack, map sensor, relay, any other sensor I dont know about?

 

[4AU4LIFE]

Reset the ECU.
Clean Throttle Body

Then start swapping out parts from your other NSX:
-Coil Pack
-Spark Plug
-O2 sensors
-Fuel Pack Resistor
-FPR
-Throttle Body
-MAP Sensor
-CVC valve,
-EGR control solenoid valve
-ECU

He said he has 2 nsx engines in the garage, not actual cars.

 

[sparky]

I have just resolved hesitation problem in my car, which started with fitment of top speed headers. it's a long story, but the end result is directly related to the themes of this thread:

- unbeknown to me the honda mechanic fitting the new headers used WD-40 to loosen the O2 sensors. This ruins the sensitive sensor materials... which I diagnosed out later following CEL light + codes + using LarryB's (Lar's?) trick of disconnecting O2 sensors to limp mode.

- replaced O2 sensors with spare used ones. CEL light removed, hesitation reduced but not resolved entirely.

- suspected factory ECU maps not tuned to new air flow provided by top speed headers = not right fuel map (later this theory proved wrong)

- spent months trying various options, including bypassing fuel pump resistor (runs pump at 12V all the time = higher pressure at low revs, per Hugh's fundings)

- decided to go AEM ECU + wide band sensors to both fix the problem, and satisfy my long term engine performance goals

- recently fitted the AEM dual channel wide band sensors (UEGO's) but to start with I have connected them to stock ECU using narrow band AEM optional outputs. (the AEM ECU will be fitted later on)

- hesitation gone! beautiful smooth torque from 1500 - 8000 ...

- diagnosis = hesitation most likely due to a fault in one or both replacement sensors (they were used) and was not due to characteristics of the top speed headers

- note there was no CEL light after I fitted those used sensors, this matches Lar's point that sensors can still be faulty even if no code

- bottom line IMO hesitations are most often due to faulty O2 sensors, after all they play a central role in the ECU AFR feedback loop.