Strong hesitation when cold

CL65 Captain

CL65 Captain

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Here is the long story long... :tongue:

2000 NSX OBDII

At the track and the CEL comes on and I pit in. Car is purring like a kitten on the track and even after pulling the clock fuse the CEL comes back on and stays on steady. Figured it was 2nd 02 sensor and ran the rest of the day on the track. On the drive home while at cruise, the steady CEL turns to a flashing CEL and TCS light comes on and the car starts running crappy. This repeated itself several times on the 2 hr drive home. Getting the car above 4k rpms seemed to make it go away when it happened.

CEL codes were for rear primary 02 excessive volt range and bunch of rear misfires and a random misfire rear bank.

1. Jumped the fuel pressure resistor with a paperclip and the car seemed to run better, but the CEL stayed on. So I replaced the resistor with new.

2. Replaced both 02 sensors (primary) with new NTK sensors.

3. All 6 plugs and ignition coils were replaced.

Now I'm use to a lumpy idle and slight hesitation when cold, but now it has a strong hesitation when cold. Car bogs down and hesitates big time. No CEL flashing or steady. After 5 min and the car warms up it runs like a champ.

????
 
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If your fuel pressure is OK at idle and above 4K rpm then I'm going to guess it's the ignitor. Common problem on tracked cars and known to be intermittant. Misfire under accelleration, OK when cruising seems to fit with ignitor problems. My best guess. Good Luck!
 
CL65 Captain said:
Here is the long story long... :tongue:

2000 NSX OBDII

At the track and the CEL comes on and I pit in. Car is purring like a kitten on the track and even after pulling the clock fuse the CEL comes back on and stays on steady. Figured it was 2nd 02 sensor and ran the rest of the day on the track. On the drive home while at cruise, the steady CEL turns to a flashing CEL and TCS light comes on and the car starts running crappy. This repeated itself several times on the 2 hr drive home. Getting the car above 4k rpms seemed to make it go away when it happened.

CEL codes were for rear primary 02 excessive volt range and bunch of rear misfires and a random misfire rear bank.

1. Jumped the fuel pressure resistor with a paperclip and the car seemed to run better, but the CEL stayed on. So I replaced the resistor with new.

2. Replaced both 02 sensors (primary) with new NTK sensors.

3. All 6 plugs and ignition coils were replaced.

Now I'm use to a lumpy idle and slight hesitation when cold, but now it has a strong hesitation when cold. Car bogs down and hesitates big time. No CEL flashing or steady. After 5 min and the car warms up it runs like a champ.

????
Click to expand...

So, what was the fix to the problem :confused:?
 
pgilliam1 said:
So, what was the fix to the problem :confused:?
Click to expand...

Don't know yet. Took it up to my tech, went for a drive while he monitored the OBDII. Consistently, hesitation including flashing CEL (random misfires). Nothing on the scanner showed unusual. Here's the thing. It's not just a "cold start" in the am. If parked for more than 20 min, it has the hesitation for two to three minutes before returning to normal. If parked less than 20 min, no hesitation and runs like normal.
Trying a valve adjustment first, since it's never had one (way over due and my car has 20k + of track time alone). His guess is out of tolerance when cold, but good "enough" when the engine warms.

Then trying the fuel pump (replacing with a Walbro).
 
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The valve adjustment is indeed overdue and could be a factor. Also, check that #4 hose discussed in the other thread ...... given that you track it, the open end of that hose (drops down towards the ground) could be partially clogged and that seems to have fixed the issue Ryan.
 
what oil weight are you using? what specific codes were you getting?
 
Jim - I went thru a similar issue recently. I was having hesitation/misfire but only under load/boost. Classic igniter problem but of course I didn't know that at the time.

1. Replaced all plugs - needed to do them anyway
2. Replaced all coils - misdiagnosed repair but i guess it's "nice" to have new ones
3. Replaced fuel filter - needed to do it anyway
4. Replaced fuel pump - needed to do it anyway
5. Was about to replace the igniter - then low and behold.. I noticed the ground wire to the igniter was just slightly loose. It must have came loose from the vibration especially since iv'e been driving the car hard lately. It's now got a dab of locktite on that bolt.
6. Step 6 would have been to scrap all the comptech fueling and go full on EMS - going to do it anyway but just wasn't ready for it quite yet. Funny thing is.. I would have still had the issue with the igniter!

Step 5 was the one that fixed it. Simple issue. In retrospect I should have looked at the igniter before the coils. Lesson learned.

Hopefully it's something simple with yours.
 
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CL65 Captain said:
Read through that, but still no reference to where hose #4 is or page in the manual, etc? :confused:
Click to expand...

I'm going to go out on a limb here and say he's referring to the #4 vaccuum hose, that has the #4 stamped on it several times lengthwise, on top of the throttle body above the ignitor.
The ignitor has been known to be an intermittant problem, especially on tracked cars and can be affected by heat, whereas the fuel pump is rarely affected by heat. Also, if your valves were that far out of adjustment to cause misfires, I would think you'd be hearing a lot of clicking sounds back there and I don't think them warming up would be that noticeable. My $.02.
 
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Is the "ignitor" the ICM (Ignition Control Module) that sits on top of the intake?

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CL65 Captain said:
Is the "ignitor" the ICM (Ignition Control Module) that sits on top of the intake?

attachment.php
Click to expand...
Yes. Connector G103 was the loose piece on mine. On the CTSC it mounts to the CTSC snout not the stock manifold.

btw.. do you see the 4 vacuum lines right next to it? one of them is #4 if I recall.
 
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CL65 Captain said:
Damn, looks like on a N/A car the vacuum lines are in the way and you can't raise it more than 1/4" or so. :mad:
Click to expand...


Frankly, I don't think you need to but it doesn't hurt if you minimize the potential vibration. My igniter was not the issue - and I had some 100 track days on it at the time and it is still the OEM one from 1998. My bolts were tight; and even when I moved the ground that was not the issue so i brought it back to where it was originally. Try to clean vacuum hose #4 first, the simplest and cheapest first step.
 
When the STMPO RSTB was taken off to do the valve adjustment there was a hole in one vacuum hose and rubbing on the rest from the bottom of the STMPO RSTB. :eek:

Replaced the hoses. And the valves were all smack in the middle of spec and didn't need to be adjusted.

HOWEVER.... still getting a hesitation for the first few minutes when driving.

Oh, and one thing I forgot to mention was a few months ago I noticed a high pitched wining coming from the rear bulkhead. I'm not sure if I had never noticed it or it was a new sound. I'm pretty sure the later. Fuel pump going? After a few months of continuously doing it, it's not doing it anymore. ???

Next up.... replace the pump with a Walbro.
 

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Is it worth swapping a main relay with someone local to see if that helps:confused: Also If you are running a 50 wt oil since you track alot My car ran crappy and did not start easily with 20/50 with temps below 55 deg
 
OT
When was the last time you clean the engine bay? Look so dusty. I remember at the last nsx meet(source1) Brian mention you spend the entire Satuday or something like that, to clean the outside of your car..

Sorry for the OT.

Continue
 
docjohn said:
Is it worth swapping a main relay with someone local to see if that helps:confused: Also If you are running a 50 wt oil since you track alot My car ran crappy and did not start easily with 20/50 with temps below 55 deg
Click to expand...


5w30 Pennzoil Ultra

Temp has been in the 60s.

It starts fine, idles fine. Drives fine after 5 min. Hesitates once or twice when driving for the first min or two when you start driving ~ steady state in 2nd @ 25-30 mph while driving through the neighborhood. Even if you let it warm up at idle in the garage for 5 min. (a smoke or two ~ in the garage, don't ever smoke in the NSX. :wink:) AND once the other day it hesitated once while cruising at 40 mph when the car was already warm. NO CEL btw.
 
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IWantNSX said:
OT
When was the last time you clean the engine bay? Look so dusty. I remember at the last nsx meet(source1) Brian mention you spend the entire Satuday or something like that, to clean the outside of your car..

Sorry for the OT.

Continue
Click to expand...

I clean the engine bay once or twice a year. It's not THAT dusty.
 
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CL65 Captain, how do your spark plugs look? I've been fooled into a misfire diagnosis when I didn't even notice that the plugs were so far worn down (GFs car) that the center electrode was almost completely receded into the ceramic! The funny thing was that the car ran GREAT the previous day I drove it. Inspecting the spark plugs can tell you a lot about how an engine is running, that only takes a few minutes and might tell you something new.
I always try to check the easiest possible solutions before "shotgunning" parts to try and fix a problem. It's frustrating when I buy a part thinking I've solved the issue and it still persists.
The fact that this is intermittent points towards being an electrical issue of some sort (possibly vacuum leak). From what I know and what others have posted it seems that the igniter is the most likely cause of an intermittent hesitation given your situation (heavily tracked).

Shad @ Driving ambition had the right idea by allowing more airflow to the igniter and even a 1/4" could help alleviate this issue in the future.

Just my $0.02 hope it helps.

Edit: I wonder if all STMPO RSTB rub against that vacuum line? Does Ross know about this? Which RSTB do you have?
 
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Track Addict said:
CL65 Captain, how do your spark plugs look? I've been fooled into a misfire diagnosis when I didn't even notice that the plugs were so far worn down (GFs car) that the center electrode was almost completely receded into the ceramic! The funny thing was that the car ran GREAT the previous day I drove it. Inspecting the spark plugs can tell you a lot about how an engine is running, that only takes a few minutes and might tell you something new.
I always try to check the easiest possible solutions before "shotgunning" parts to try and fix a problem. It's frustrating when I buy a part thinking I've solved the issue and it still persists.
The fact that this is intermittent points towards being an electrical issue of some sort (possibly vacuum leak). From what I know and what others have posted it seems that the igniter is the most likely cause of an intermittent hesitation given your situation (heavily tracked).

Shad @ Driving ambition had the right idea by allowing more airflow to the igniter and even a 1/4" could help alleviate this issue in the future.

Just my $0.02 hope it helps.

Edit: I wonder if all STMPO RSTB rub against that vacuum line? Does Ross know about this? Which RSTB do you have?
Click to expand...


As stated above, all 6 plugs were replaced as well as all 6 coils. Old plugs looked fine.

Igniter usually has problems when heated up, not cold like my problem ~ ie first 2-3 minutes of driving and then fine when warmed up. As well, my problem isn't intermittent. Does it consistantly every time I drive the car for the first 2-3 min.

Yes, all the STMPO RSTB (NA2) probably rub. It goes right across the top of the vacuum lines and there is zero clearance (actually neg clearance as the bar has to push the lines down to fit). Ross knows about this now, as I sent him the above pics. His suggestion is to bend the vacuum lines (said they are steel lines and won't break by bending them down). I removed my STMPO and went back to OEM brace since I track the car often (I'm sure my engine moves quite a bit) and don't want to worry about this in the future and really didn't want to bend them because a little bit wasn't going to do it, they needed a good 1/2 to 3/4" more clearance.
 
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