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Hesitation

Joined
29 March 2001
Messages
765
Location
Dexter, MI USA
1992 w/ 43k miles
relevant mods: headers ’99, injectors bench tested ’02, O2 sensors new with header install ‘99
relevant service: fuel filter, spark plugs ’99 @ 20k miles

symptom
slightly rough idle (missing) and hesitation between 1,500 – 3,500 RPM. No hesitation in this range at WOT. A road test can cause repeatable check engine light #1 (Front Oxygen Sensor Circuit)—closed throttle deceleration in 2nd gear from above 4k to idle.

History
Driving home from an end of season track event last year I noticed a hesitation under slight acceleration around 2-4k RPM. Unfortunately, the hesitation did not go away during the winter, even after refilling with a fresh tank of gas.

Diagnosis thus far
Compression check: ok
Valve clearance: ok
Visual spark plug inspection: ok
Injector coil impedance check: ok

Following the Service Manual flowchart for code 1 (pg. 11-30) then to (pg. 11-36), I cannot produce a 43 code while running engine at 3,000RPM for 2 minutes. I am suspecting a front oxygen sensor or front fuel supply.

Question
Even though front and rear O2 sensors have different part numbers, can I swap them to rule out the O2 sensor as the failure?

TIA,

DanO
 
Considering you have more engine knowledge than 99% of prime patrons, I'm not sure you will get your problem resolved here. And that's by no means a criticism of prime members.

Here are some other resources to try:
http://forum.aempower.com/bbs/index.php
http://www.honda-tech.com/

if all else fails, you can try: http://www.hotrodders.com/f5 I know it is primarily an american iron board, but there are many talented mechanics on board there.

How long have you had the problem and was any service/mods done close to the time the problem started?
 
I had an engine hesitation most of last summer. Larry B confirmed that I had a probblem at the New Hampshire event. It turned out to be the throttle body. I had sprayed cleaner in a couple times, but I didn't feel any difference. I finally had Acura service pull it apart and give it a full cleaning. The problem was gone after that. Also, I never got any check engine light.

John
 
O2 sensors

Yes, the front and rear O2 sensors are the same. The different part numbers are mainly for wiring length difference.

Eddy
 
Thanks for the input guys! Just to clarify, the only engine code I am getting is #1, (front oxygen sensor circuit). My plan is to switch my O2 sensors (front to rear) to see if I get a code #2 (rear oxygen sensor circuit). I don’t think I will, but I’ve already done most of the work switching them and plan to do a test drive later today…I hope.

If switching the O2 sensor still yields code #1, then I’ll test the TPS (actually I’ll probably do that right away, thanks BrianK). I’ll also check out the vacuum hoses going to the MAP and see if there is a test for the MAP; but it seems to me that the MAP would through an error if it were not functioning properly.

The only recent relevant “mod” is the RC injector blueprinting that was done a couple of years ago.

Thanks for the help,

DanO
 
DanO said:
I’ll also check out the vacuum hoses going to the MAP and see if there is a test for the MAP; but it seems to me that the MAP would through an error if it were not functioning properly.

Generally no, Honda MAP sensor can get sort of slow on the readings and not throw codes, I'd suggest swapping for a known good MAP sensor just to check. A laggy vaccuum reading can cause hesitation as the TPS is out of sync with the air readings, worth a shot anyway.
 
DanO said:
The only recent relevant “mod” is the RC injector blueprinting that was done a couple of years ago.

I have heard of 2 instances where new / rebuilt injectors (especially where leaking or producing lower flow) when immediately swaped will produce a CEL. I will verify on mine this Friday. In any event - resetting the ECU (forget which fuse) cleared everything up.

Just wondering if you have tried powering everything down and when/if the lights come back (now that you have the code).

Again - way below you on the engine knowledge ladder but sometimes from the mouths of babes...

Good luck DanO - let us know what you turn up.
 
Throttle Angle Sensor: ok
Pedal Angle Sensor: ok
* these can be checked for proper voltage range at the TCS connector and a good ground
manifold absolute pressure (MAP): ok

I’ve got the O2 sensors out and plan on switching them and putting everything back together for a road test later this week. At this point, I’m leaning towards a fuel supply problem. I’ll have to get a fuel pressure gauge (any ideas? Snap-on = $250)

Matteni – I’ve reset the ECU after each CEL occurrence. Thanks for the help!

Again thanks!

DanO
 
Hi Dano - what did it "feel" like?

Did you immediately suspect an ignition coil? Fuel filter? Plug(s)? I am having trouble conceptualizing the hesitation.

I am starting to lean towards the fuel filter. Had a very similar experiance with some bad gas and since it has been X years and 23K miles since the last time you changed it.

Changing the fuel filter is a PIA on an NSX but is a lot cheaper and easier then swaping the o2 sensor.

Only problem with my theory is why just the front? The NSX ECU is an enigma to many but I am holding out that it is something simpler / easier.

Keep us posted / sorry to hear about your woes...
 
DanO said:
[I’ve got the O2 sensors out and plan on switching them and putting everything back together for a road test later this week. At this point, I’m leaning towards a fuel supply problem. I’ll have to get a fuel pressure gauge (any ideas? Snap-on = $250)

Hey DanO, I had John Vasos purchase a fuel pressure gauge (which you are welcome to borrow) for me from his supplier and I don't think it was more then $50. It doesn't have a mfr name on it , but is is made in USA. It did bolt right up to the fuel line as specified in the manual. Anyway, just didn't want to see you drop $250 if it wasn't necessary. Good luck with the hesitation. When you get that resolved, you better get out to GingerMan this year!
Good luck with the sensor test.
 
Hi DanO,

Certainly if you can get it from Chuck by all means :):):), also, nice fuel pressure gauges are availble at AutoZone or the like for about $40. (make sure you get a 100 psi range) I also got a separate "Honda" fitting for the tap at the top of the fuel filter connection (Thanks JerryF:)). Not a bad tool to have in your box going forward.

HTH,
LarryB
 
Hey Dano
Your the man when it comes to the tech stuff, so all I can do is tell you what happened to my car with the same problems.
It had a rough idle (missing) and hesitation between 1,500 – 3,500 RPM. No hesitation in this range at WOT.
I had some of the same codes, I replaced all the o2 sensors with no luck.
Then I replaced the fuel in the gas tank, then took off my cats to see if this would help. No luck.
So then I replaced the plugs, and put a meter to the coil pacs. No luck.
I bought 1 coil pack from the dealer and swaped it around to all the plugs, No luck.
So I bought 3 coil pacs and replaced one side, LOT"S OF LUCK!
Two of the coil pacs were bad, from sitting all winter.
The meter said they were fine.

Iam sure you have allready thought of this, but everything you describe is the same problem's I had.
Just my 2 cents.
Brian.
 
Last edited:
prova4re said:
...Two of the coil pacs were bad, from sitting all winter.
The meter said they were fine.

Iam sure you have allready thought of this, but everything you describe is the same problem's I had.
Just my 2 cents.
Brian.

Very interesting Brian / good post - thanks for sharing...
 
Measuring the Primary resistance of the coils is a good check, but it does leave out the possibility of a problem with the secondary which I would think would most likely be high voltage leakage.

I have access to high voltage test equipment, Megger and high pot. Would anyone like to send me a known bad coil to test out?
If I can come up with a test procedure that will show a coil is bad it might help out the many people with unsolvable miss-fire problems.
 
Well I got the O2 sensors switched around and bolted everything back together and went for a road test. The engine runs beautifully, no signs of hesitation; not what I expected, but I’ll take it.

I’m not sure what cured the problem. Yesterday I tested the MAP and EGR by using a hand vacuum pump. I also pulled all the emission hoses off the t-body and sucked them with the vacuum. Then I blew out the emission hose inlets (into the t-body) with the air hose. I really should have done that first before going crazy switching the O2 sensors. Maybe there was a piece of debris in one of the hoses. Oh well, I’m at a loss.

Thanks for all the help everyone! Chuck, I think I’ll call John to see if he can order me up a fuel pressure gauge and I WILL see all you Midwest guys at Gingerman this year and hopefully all the rest at NSXPO!

DanO
 
Perhaps a lose or bad connection at the O2 sensor.. Switching it may have made it good. It would explain the code that you were getting.

Eddy
 
the front sensor was clean. The rear sensor had a little-not much carbon buildup around the base which I knocked off.

I don’t think it was a connection issue altogether; I was getting the hesitation before and after I did a valve adjustment, which entails disconnecting and connection the O2 sensor wires. It could have been a short in the O2 wire in which case it will probably manifest itself again in a code #2 at some point in time, and that would be alright with me.

DanO
 
Eddy said:
Perhaps a lose or bad connection at the O2 sensor.. Switching it may have made it good. It would explain the code that you were getting.

Eddy

Hmm...how much does the secondary O2 sensor actually 'do'? It's possible your front O2 was indeed bad and now that a good one is in there the code is gone...now your bad o2 is in the back but if it's like most secondary o2's on Hondas all it does is make sure there is enough flow and merely supplements the primary o2. It's probably still bad, it's just not making a big difference now, may affect fuel mileage though
 
Secondary O2 Sensor?

I’m not familiar with a secondary O2 sensor on the ’92 NSX. To be honest, I’m not totally sure what a secondary 02 sensor really is? I assume that the ’92 O2 sensors were equal and that the ECU can adjust injector pulse with individually to get good front bank and rear bank stoichiometric readings individually.

Note: I have RM (B&B) headers which have the O2 bung in one of the header tubes before they join—I think, ill have to lift up my car to verify this. If this is the case, then the O2 sensor is just reading the #2 (rear) and #5 (front) cylinder. Hmmm.

DanO
 
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