Rare nsx with a pre-4k rpm issue

[VBNSX]

Situation: Before the car gets to around 4k ish, the engine is boggy and sluggish... around 4k the car picks up, then in vtec range, the car is good to go... i've changed the fpr, fuel filter, and have had the injectors cleaned... still no change...

Here's the kicker. It's a 91 nsx with 8k original miles. The car looks like it was literally in a time capsule. Any ideas?

TIA,
x

 

[C-speed]

Change the spark plugs too.. and coils.

 

[angus]

cam timing?
did anyone do the timingbelt/water pump?
maybe if it's old , it skipped a tooth?

edit;
Is your other car an 800hp big block?

 

[Briank]

Right off the top of my head I would say O2 sensors, unplug them and see if you get the power back. If that does not cause a change then I would say fuel pump issue but check the fuel pressure to see if it's out of spec b4 replacing it.

 

[01blacks4]

02 censors

 

[C-speed]

02 censors

I'm assuming he's having this issue at WOT? If thats the case, the O2 sensors are not being used (open loop), so even if they were bad, it wouldn't affect the drivability at WOT.

 

[Briank]

I'm assuming he's having this issue at WOT? If thats the case, the O2 sensors are not being used (open loop), so even if they were bad, it wouldn't affect the drivability at WOT.

Situation: Before the car gets to around 4k ish, the engine is boggy and sluggish... around 4k the car picks up, then in vtec range, the car is good to go...

C-Speed, you assume wrong.

 

[C-speed]

C-Speed, you assume wrong.

The kicker is that he states "in VTEC range..."

VTEC does not engage unless you are beyond ~75% throttle, in which case the ECU is also in open loop.

So I think my assumption is correct

 

[goldNSX]

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

Please follow Larry's test procedure. Seems to be a more frequent problem on older cars.

 

[Briank]

The kicker is that he states "in VTEC range..."

VTEC does not engage unless you are beyond ~75% throttle, in which case the ECU is also in open loop.

So I think my assumption is correct

then in vtec range, the car is good to go...

You think wrong :tongue:

 

[VBNSX]

To inform everyone of the finale to this, it was the fuel pump...

Since the car sat around forever and ever, the tank formed a weird 'gunk' which clogged the fuel pump.

 

[tom4416]

To inform everyone of the finale to this, it was the fuel pump...

Since the car sat around forever and ever, the tank formed a weird 'gunk' which clogged the fuel pump.

How did you insure there is no more of thank "gunk" in the tank? Be a shame to burn out another fuel pump because the tank is not clean. It's an ongoing problem if the gas has been in there a long time. Even draining it may not capture all the crap.

 

[swerve2007]

correct, i deal with that issue quite a bit (old cars). the only real solution is reconditioning/replacement of the tank. if you don't, you run a risk of doing the entire exercise again- not fun.

 

[goldNSX]

It's an ongoing problem if the gas has been in there a long time. Even draining it may not capture all the crap.

How long would you consider 'long'? Most of the owners here in Europe let the car sit during the winter for 4-6 months.

What about fuel stabilizer? Does it help?

 

[swerve2007]

for the gas to gel it does take more than 2 years or so.

 

[VBNSX]

yeah. this car was a bit rare...

it sat around for years at a time...

if u say it was driven every year it was driven about 500 miles a year. However realistically the owner drove it around a lot during the first few years, then it just tapered off from there.

 

[gdae]

Pics?:smile:

 

[goldNSX]

To inform everyone of the finale to this, it was the fuel pump...

Thanks for the update.

Today, I've measured the fuel pressure. It got lower over a year or so. Now it's 39 psi (last time measured 41) psi with and 43 psi (last 51) without the vacuum hose connected. The FPR was replaced within last year (AEM).

The engine hesitates a little bit below 4.5k rpm, then delivers full torque. At 4.2k rpm the fuel pressure is raised, maybe the reason. I'll check out for the rest but all other components have been cleaned (inj.) or replaced (filter).

 

[Thanhnsx]

Great topic and answers. I also feel that I have the same issues. Time to clean out my fuel system

 

[VBNSX]

Pics?:smile:

next time I head over there I'll try to get you some... if you could ever imagine an nsx back in 91 in the showroom, that's what you have.. :wink:

 

[RON98]

correct, i deal with that issue quite a bit (old cars). the only real solution is reconditioning/replacement of the tank. if you don't, you run a risk of doing the entire exercise again- not fun.

how long does it take for this little miracle to happen? I got a project car on the rack for a year now.... i can smell the bad gas... definitely time to get the ball rolling! :biggrin:

btw can you PM me the answer... i might never find this thread again.