Bad hesitation, pulling hair out, replaced far too many parts, really need help pleas

jaffaz32

jaffaz32

Experienced Member
Joined
28 November 2009
Messages
997
Hi Guys,

I have searched and searched the forum. I have tried almost every suggestion there is with similar issues while searching old posts. It's not obd2 so i don't have the luxury of just plugging in to a computer.

What is happening is. The car did have a rough idle but that now seems ok upon initial start up and if left settled, it now seems better. not sure if related.

But.. I still have a hesitation under moderate - hard acceleration. If i feather the throttle the car is drivable. Any more throttle than being very gentle the car hesitates.

When i say hesitate, the power totally goes, throws you forward in the seat and then comes back and pins you back, does it couple times upon acceleration.

If you let the car warm up, drive it hard, you will get 2 pulls or so, any more than that it happens. Turn the car off and straight away back on. you get another 2 pulls before it happens again. Once it happens it happens every time you go near the throttle unless being mega careful or turn it off and on to get another 2 pulls or so.

The problem has also got worse over time, it started out being occasionally would happen it's now everytime i take it out. Infact i've avoided driving it unless testing it.

Fuel tank has been removed, cleaned and reinstalled

I get a TCS 1 blink occasionally when pulling codes, if related? who knows.


  • First off i have tried completely unplugging the TCS unit behind passenger side seat, still does it. Hoping it would bypass the TCS completely and causing the 1 blink code it throws with the TCS light.

Other parts i have swapped and replaced to try resolve the issue:


  • Coil Packs
  • Spark Plugs
  • Main Relay
  • Fuel Pump
  • Ignitor (Black box behind throttle body)
  • New Earths in engine bay
  • Throttle body with TPS and motor
  • Fuel pump resister bypass (paper clip)
  • Both O2 sensors
  • Crank angle sensor


I have new fuel filter coming and fuel resister however i did do the bypass on the resistor previously.

I don't think it's ignition switch as i have been reading can be a issue, i have rattled the keys about while normal driving and nothing, only happens under moderate to heavy throttle movement.

I have tried thinking back, i had changed my wheels and tires months before i had the problem. Nothing actually changed, it just seemed to start happening.

I know it seems i have thrown parts after parts at it but... although it may be a complete waste of money it can't be bad replacing older parts with brand new. I would like to work through and replace sensors anyway or parts along those lines with new. When i read scare or horror stories on Prime i replace the parts that have caused other people engine failures of other issues.

Any more ideas?
 
tbnsxt said:
do have any coils going out?
Click to expand...

Sorry, what do you mean?


Actually that reminds me, i have recently had coilovers fitted and it may have started since installing, it was very close.

The car has not been alligned yet, if the alignment was way off could this be causing perhaps traction control issues? Would traction control cause sudden lose of power and appear to hesitate?

Just a thought.
 
How many miles do you have on your car? Have you tried sending your injectors for cleaning at RC engineering?
 
I know this will sound simplistic but a very good mechanic taught me that you need three things for an engine to run properly.
Compression, spark and fuel.
In your case compression is not an issue.
You've changed out most of the spark side. The only thing left is the igniter. I had to replace mine about 10 years ago when I had an engine miss.
On the fuel side the only thing left is the fuel filter (which you are changing) or as lazyboy69 suggests, the injectors.
I recently sent my OEM injectors to RC for cleaning and it helped with a smoother engine.
 
The violent stalling is a clue for me. It seems like there is an interruption in either Spark or Fuel.

It's too bad you don't have a fuel pressure gauge or a Wideband O2 sensor. Fuel pressure fluctuations is very telling and can lead us the right way at a diagnosis. Also, if you had a way to monitor Air/Fuel Ratio then when the stall condition is present you'll be able to see if it's a rich condition or a lean condition when it stalls. A rich condition would mean either too much fuel or more likely no spark. A lean condition would likely mean little or no fuel. This is the only way i'd go about diagnosing this thing. Otherwise, you'll end up with a completely new everything and probably will still have the problem.

If I was to guess though... the problem is in the wiring harness. Shorted wire, melted wire, cut wire.... etc.
 
^1+ In cabin fuel pressure gauge and a vacuum gauge will help you see in real time if there are any issues on those ends. Also, if you have aftermarket headers/cats, there could be a crack or leak that throws the 02s off. Over time, the leaks get worse and more consistent hesitation occurs.
 
I agree with RYU, I would guess it is a shorted wire. I had a slight (not as bad as you) hesitation for years in my car and could not figure out why. One day I discovered that my O2 extension wire was rubbing against my oil pan and creating a short. I replaced the extension harness and the hesitation went away. Hope this information helps! Good luck!
 
Semnos_NSX said:
I agree with RYU, I would guess it is a shorted wire. I had a slight (not as bad as you) hesitation for years in my car and could not figure out why. One day I discovered that my O2 extension wire was rubbing against my oil pan and creating a short. I replaced the extension harness and the hesitation went away. Hope this information helps! Good luck!
Click to expand...

I have also had a similar issue. Alternator output wire was pinched under the intake manifold and frayed... the vibration of hard accel would cause it to short.
 
How did your spark plugs look when you changed them? I had a similar problem with my integra and it was the IAT sensor (intake air temp sensor). Basically, it was reading my air temp incorrectly and dumping fuel and running super rich. To the point that it was hesitating and misfiring upon acceleration. When I pulled the plugs they were really black. They should be a golden color.
 
^^ It could be that too. Good idea to check the spark plugs.

However, a rich condition in where the IAT sensor is malfunctioning will typically throw a CEL. If he had a AFR gauge he could tell right away and we can all stop guessing. The C30A likes to "sputter" starting around 10.9AFR. It falls flat on its face around 9.5. Ask me how I know...
 
I would think it would throw a cel too but it didn't in my case. The only way we found it was while tuning. It read a constant 15 degrees Fahrenheit which we knew was wrong. Swapped a new one and solved the problem.
 
jaffaz32 said:
Sorry, what do you mean?


Actually that reminds me, i have recently had coilovers fitted and it may have started since installing, it was very close.

The car has not been alligned yet, if the alignment was way off could this be causing perhaps traction control issues? Would traction control cause sudden lose of power and appear to hesitate?

Just a thought.
Click to expand...

Please don't take offence to my observations.

Based on the sheer number of part you have thrown at this car for this problem and the above comment I think you are in over your head.

Take the car to someone who can properly diagnose fuel/electronics.
I have been down this path before trying to pass smog.

Spend a few buck to find out what the issue really is. Maybe you replace the offending part yourself. It probably only costs ~$100 to have it diagnosed.

Good luck.
Later,
Don
 
I am going to echo the comment of some others, you need to check your fuel pressure under load (acceleration). You haven't said anything about misfires during acceleration, so what you are describing sounds like a fuel supply issue. If the fuel pressure checks out OK, I am going to offer an 'out there' suggestion. Most fuel injection systems that run off of MAP sensors use a combination of manifold air pressure and engine speed to determine fuel requirement (fuel injector pulse width). I am guessing; but, don't know for sure that the NSX EMS operates this way. The throttle position switch is primarily used to tell the engine management system that the car is in the acceleration (throttle opening increasing) or deceleration mode. Rapid throttle movement or opening past something like 70% also generally blocks the feedback loop from the O2 sensors so that you are running directly off of the base fuel map at high throttle openings. This is important because in the acceleration mode, the TPS signal causes the EMS to en richen the fuel mix set by the base map which improves engine operation during acceleration. Without this enrichment, the car will likely still run but performance during acceleration will be poor and the engine may stumble. If you accelerated very slowly, you might not notice the problem. You said that you replaced the TPS (I will assume with the correct part) so I will assume the TPS itself is working; however, as suggested by others, you might have a wiring issue between the TPS and the EMS which is screwing up the TPS signal. As I said' first make sure that the fuel pressure under load is good. The TPS wiring is something you could check out if the pressure is not the issue. Finally, as a matter of interest, is your car a '95 with drive by wire but pre OBDII? Seems to be some uncertainty about exactly when some of the NSXs started getting OBDII.
 
I am based in the UK.

I now have a Fuel pressure gauge i will hook up to the filter, setup a gopro watching it and go for a spin.

The spark plugs were pretty black and looked a bit burnt. Not sure how they should look after use.

I pulled apart the vacuum control box just out of curiosity as i keep hearing vacuum pipe being mentioned. Keeping in mind i haven't driven the car for a week, when i pulled the pipes off they hissed and released built up pressure. Is this normal?

I also relocated the pipes to the catch tank from the heads. so they didn't have a low point.


When i took it out for a drive i thought i had fixed it! seemed fine got allot further with no issue at all, then it started again once and was ok for rest of journey massive improvement it seemed. Now it's back to how it was again. Not sure if this is any help?


Also...

With the TCS plugged in, it does seem worse. maybe in my head?

When it's really bad you can actually pump the pedal and it appears to no respond what so ever then comes back in it's own time only responding to very gentle movement to the throttle, surely if it was fuel, it would still open the throttle body and bark or suck air? It's as if the throttle doesnt respond. I am wondering if it's the DBW system? the rear TPS has been swapped and i tried a spare motor. I then found the front sensor under the front hatch with the cable. I was hoping it was the same as a TPS sensor but it has more wires and bigger. This sucks as i can't swap it out to test it. I thought could it be a earth to the front TPS or APP, but it looks insulated with rubber grommets around the bolts.

But it does make me wonder why it seemed better after pulling apart and putting back together the vacuum system. Maybe it was just a freak incident and decided to behave for a bit.

The fact that it comes and goes makes me think it's perhaps electrical or maybe even vacuum, but i don't really know.

Also as suggest i have pulled out the AIT sensor, cleaned it. wasn't that dirty as it wasn't replaced that long ago.

Hesitation is probably a bad subject, when it happens the car appears to hesitate as the throttle does not respond and comes back again. within seconds so the car feels like it's hesitating as it comes and goes so quickly. but what i actually think is happening is that the pedal movement or position isn't being recognised and seen as having no load on the pedal. Maybe i'm wrong but that what it feels like the car is doing especially the last couple times it was really bad. and again turn the car off and back on and it seems to be not as bad.

I can't even find a replacement APP which is so annoying. the TPS is a whole assembly but you can buy the sensor separately from blox and other vendors but the APP i just can't find.

- - - Updated - - -

The weird thing also is, it doesn't always throw a engine light, hardly ever. even when it does when you turn it off to short the connector and turn back on the light has gone out and no codes are there.

i know you can't plug a obd2 reader in to a non obd2 car, but it has two blue cable surely they are there for a reason? what about those expensive machines garages have can they plug in to the older cars and give any information?

- - - Updated - - -

Yeah, my car is pre obd2 but it is dbw.

i originally had a blox dbw 72 mm throttle body installed with a blox tps.

i swapped back to the factory throttle body, factory tps and it had a motor attached also.

when saying check wiring, what does this actually mean? Check tps and motor plugs? But how do you trace the wires back without stripping them?
 
Did you check the DRW module located in the front (bonnet), this is connected to the throttle pedal via a cable. As it seem that you have checked everything else in the engine bay.

Just trying to help.

Bram
 

Similar threads

P
Chasing engine hesitation
2
Replies
25
Views
2K
Chris_Lum
Chris_Lum
Buddy
Auto to Manual Swap Questions, Need help
Replies
8
Views
580
drew
drew
Wild Turkey
Solved: Misfire, hesitating driving, stumbling idle, OBD 1303, new plugs & dirty fuel injectors cleaned
Replies
18
Views
3K
Wild Turkey
Wild Turkey
N
Emission / Smog test failed, O2 passed / Air Fuel failed.
Replies
1
Views
862
Old Guy
Old Guy
bogle
Help diagnosing a voltage drop under high loads
2
Replies
38
Views
4K
bogle
bogle
Back
Top