Solved: Misfire, hesitating driving, stumbling idle, OBD 1303, new plugs & dirty fuel injectors cleaned

[Wild Turkey]

This seems almost embarrassingly simple to have a thread, but I could have used a similar thread a few weeks ago...

Symptoms:
1. Normal start and idle while engine cold
2. When warm, stumbling rough idle almost stalling every 10 seconds or so
3. Hesitation while driving at slow steady speed, but not at >50% throttle
4. CEL & TCS warning lights on. Service Manual :“flashes during misfiring and stays lit afterwards, storing the code(s).

Issue? Fuel issue like the fuel pump, bad gas, clogged injector, or an ignition problem like the igniter, coil, spark plug, ECU? OBD II gave code 1303, cylinder #3 misfire. I should have cleared it & repeated to rule out a random cylinder misfire just happening to be on #3 . BTW, cylinders are 1,2,3 from R to L in back; front cylinders are 4,5,6 from R to L.

I removed spark plug #3 , and compared it to plug #2 ; both perfectly gapped at 1.10 mm.
https://photos.app.goo.gl/3QUJkeThVpEeWjJ5A
If anything 3 (right) looked better than 2, but I haven’t looked at a lot of spark plugs. The coils looked pristine with supple seals and no sign of carbon arcing or moisture from a failed seal in the on the cover. Intact cover seals F & R. (I just installed ddf’s awesome coil guard, but it was absent for the last 27 years.) #1 , #2 , and #3 coil resistance on spec at 1.1 Ohms.

I switched moved spark plug #3 to cylinder #2 , and coil #3 to cylinder #1 to see if the missfire would follow the coil or plug or stay with the fuel system on #3 . Test drive: CEL, TCS, stumbling, and rough idle. OBD 1302, cylinder #2 misfire. Diagnosis: spark plug.

To confirm, I switched the offending plug for a new NGK iridium plug. Result: normal idle, noticeably smoother acceleration, and no CEL or TCS light. (No double platinum plugs available locally and I was too impatient to wait. But that may be a good thing if the iridium will last any longer?) I replaced the other 5 as well.

It's now running great! Problem solved.

Because I can't stop myself, I reviewed the old service records; 6 new 3142’s January 2016 for a similar problem on cylinder #6 that eventually led to stalling while idling, and it’s gone ~5k miles since then. That seems early for double platinum plugs to go, but the service manual does say 6 years or 60k miles? Hmmm. Maybe I just had a bad plug. The only engine mods are the ’98 headers and ARC stainless exhaust. Thermostat was stuck open for a bit – would running cold accelerate spark plug demise? Perhaps the Iridium plugs will last longer?

Trouble code with Honda service check connector, MIL code 72, agreed with OBD 1302, but not as specific.

Why the TCS light came on with CEL each time? Also, why only misfire at idle and low throttle but work at higher throttle openings? I would have thought low RPM’s would mean longer time between firings, leaving more time to build up charge? But more fuel/air and higher pressure?

Related codes for searches: 1301, 1304, 1305, 1306, MIL 71, 73, 74, 75, 76
Sort-of related threads. I started a new thread because the title of these threads would not be helpful for search results:
http://www.nsxprime.com/forum/showthread.php/146531-Cel-73-Need-a-little-advice
http://www.nsxprime.com/forum/showthread.php/184307-Misfire-need-help!!! (1200 codes)

 

[Honcho]

Just a thought- have the fuel injectors ever been cleaned?

 

[Old Guy]

Misfire at idle / low load; but, not under significant load is very odd for an ignition related misfire. As the density of the fuel mixture increases in the cylinder (higher engine load) it takes a greater voltage to fire across the plug gap. If there is an external weak spot in the high voltage insulation path (inside the coil 'nose' or a problem with the spark plug) the spark current will follow the weakest insulation path) and not spark across the spark plug gap - leading to an ignition misfire. If you don't have any signs of external arcing on the plug insulator or the coil nose I find your symptoms confusing.

I can't deny the empirical evidence that replacing the plug appears to have fixed the problem. Having said that, spark plugs do wear and as they wear the voltage required to fire across the gap increases. A fresh plug may have fixed the problem; but, may be disguising the true cause. Perhaps like @Honcho I am thinking that you might have a fuel injector problem. All injectors have a time delay in opening after voltage has been applied. Variability in the timing delay affects the fuel mixture at idle the most and has less effect under high engine loads. If you have issues with the fuel injectors which are skewing the fuel mix slightly lean at idle / low load this could be inducing a misfire caused by a weakness in the ignition system. Your symptoms
1. Normal start and idle while engine cold
2. When warm, stumbling rough idle almost stalling every 10 seconds or so
would be consistent with a fuel problem. While cold the ECU is altering the fuel mix to below 14.7 which makes the mixture burn more smoothly and easier to fire. Once you are up to temperature the ECU tries to run at 14.7 which is perhaps when your fuel / ignition problem materializes.

Since the engine appears to be running fine now, I might be inclined to let sleeping dogs take a short nap - for now. When it come time for the NSX's winter nap, I would be inclined to remove the injectors and send them off to RC or WitchHunter or whoever, to have them cleaned and flow tested. If they do the flow test correctly (high frequency PW as opposed to continuously open) that will highlight any issues with injector opening times.

If your misfire problem persisted up to high engine load I would say ' yep, ignition problem - plugs fixed that'. Since the misfire goes away at high load I am thinking underlying fuel problem at idle which creates a problem that shows up 'first' at one worn plug. Replacing the worn plug makes the symptom go away; but, does not address the root cause That is my current morning caffeine induced analysis.

 

[drew]

> I would be inclined to remove the injectors and send them off to RC or WitchHunter or whoever, to have them cleaned and flow tested. If they do the flow test correctly (high frequency PW as opposed to continuously open) that will highlight any issues with injector opening times.

I'll pile in on the bandwagon: get injectors cleaned. It is likely you have the fuel dribbling out, the common symptom is less power and misfires.

If you like: number them with some sort of light scoring or heavy duty marker on the injector exterior if you wish to do some hardware to symptom tracking.

 

[Wild Turkey]

I'll probably add the injectors to the list for this winter along with the EPS rebuild.
I'll see how the car goes this summer. Just got back from a 600 mile road trip to Michigan International speedway & the car was flawless, so I'm hesitant to mess with it.
With respect to the coils, I checked VERY carefully for any sign of arcing. The coils looked brand new and no sign of arcing on any plug insulator either: the misfire code followed the spark plug, not the coil.

 

[drew]

It's hard to say exactly what is going on without detailed photos and possibly some testing equipment. So heuristics.

A lean or poorly mixed fuel air can run hot and can overheat spark plugs.

When a small symptom occurs millions of times, the effect adds up and you get a misfire. The swapped plug may exhibit the same systems as it too starts operating in the same enviro as the failed one.

The NSX injectors are known to clog and/or dribble fuel out, it is pretty much inevitable.

So rule that out as cleaning needs to be done regardless.

 

[Wild Turkey]

Fuel Injectors Cleaned:
Follow up: Winter snow arrived and I sent the injectors down to RC. Good call @Honcho, @Old Guy, & @drew.
Flows were 243, 229, 205, 198, 161, and 235, "fair" pattern, with dripping noted on #3, #4, & #5, as @drew guessed.
35% reduced flow on #5 & 20% on #4, with balance >50% from the mean!
Post clean all between 249 & 251 with "excellent" pattern. +/- 1%!
Hopefully no more fouling plugs (or bad cat CEL's)
We shall see when I get her out when the snow is gone. Hopefully noticeably more power!
Thanks for the input guys! Wonder how many more of us need our injectors cleaned and don't know it.
(Go to amayama or the upper and lower seal grommets will cost more than the fuel injector cleaning, but if you get them cleaned by RC, they replace all 5 disposables.)
Addendum: No return of the hesitation, no problems at all after driving the entire summer.

 

[Old Guy]

Good follow up. At large throttle openings the ECU switches to open loop so you would have been running significantly leaner than design on the front cylinders at high engine load.

How was the turn around time from RC? I may finally get around to doing my timing belt / water pump / coolant hoses this summer and if the turn around time is short enough that it fits into that maintenance window I might do the injector cleaning at the same time.

 

[drew]

FYI, our overseas brethren engineers have created a Home DIY injector test/clean machine currently under the name Autool CT150 at about US$300.

A YT review

Not much more than the cost of having it sent out. And you get a bonus tool cluttering up your garage too.

I have no financial interest, but for somebody like me where shipping and/or downtime is an issue.

 

[docjohn]

I think anyone still on original injectors could use a good cleaning...I was lucky to have an OBD-2 throwing lean codes that told me..

 

[Wild Turkey]

How was the turn around time from RC? I may finally get around to doing my timing belt / water pump / coolant hoses this summer and if the turn around time is short enough that it fits into that maintenance window I might do the injector cleaning at the same time.

RC Fuel Injection was good & fast, US$29/injector for analysis & cleaning, including new O-rings & fuel strainers. Once they got them, they had them heading back on UPS in <2 days. They shipped to me on vacation in FL. Witchhunter is cheaper, but promises a 2+ week turnaround and they never answered my emails.

RC Fuel Injection

It's so easy to pull the injectors, (except the connectors...), you might not even need to make it part of another job.

Solved: How to disconnect the fuel injector electrical connectors?

Can't believe I couldn't find a thread on this or a useful video on U-tube. Perhaps not too many other folks are having their fuel injectors replaced or cleaned by RC? Anyway, following the service manual, but can't get the electrical connectors off the fuel injectors. There doesn't seem to be...

www.nsxprime.com

TT

 

[Wild Turkey]

RK includes all 5 consumables!
I just put the fuel injectors back in. Note that RK supplied not only new top and bottom o-rings (bottom o-ring is called a seal ring in the SM) but ALSO installed a new cushion ring (top rubber ring) and fuel injector insulator (bottom rubber ring) as well as replacing the tiny fuel strainer at the top of each injector. All 5 consumables for each injector were replaced. I guess I didn't need to order the replacements from amayama.
So if you're doing it in the future, the injector cleaning is almost free! (If you consider that the consumables purchased separately cost almost as much.)
The only consumable you need is the crush washer on top of the fuel filter (and 2 crush washers between the fuel hose and the fuel rail if your NSX has crush washers, some have o-rings there.)

 

[asylum]

To confirm, I switched the offending plug for a new NGK iridium plug. Result: normal idle, noticeably smoother acceleration, and no CEL or TCS light. (No double platinum plugs available locally and I was too impatient to wait. But that may be a good thing if the iridium will last any longer?) I replaced the other 5 as well.

It's now running great! Problem solved.

I also had a problem like this with new Denso spark plugs. I replaced them all with 6 other new ones I ordered at the same time for another car and same problem again : one began to misfire after 100 - 200 miles. I ended up buying new NGK plugs and everything went fine. Were the Denso fake or damaged during the transport ? I will never know.

 

[ekhonda87]

I think anyone still on original injectors could use a good cleaning...I was lucky to have an OBD-2 throwing lean codes that told me..

Is this the general consensus among other owners too? Should we be having our injectors serviced every X number of years/miles. I have 135k miles on my 32 year old injectors, and I am sure they have never been cleaned.

 

[drew]

Yes, the NSX should have the injectors cleaned every X years.

We don't know what exactly the value of X is. And it seems to be more related to time over distance, this is to be expected as NSXs aren't driven a whole lot.

32Y > xY

 

[docjohn]

Is this the general consensus among other owners too? Should we be having our injectors serviced every X number of years/miles. I have 135k miles on my 32 year old injectors, and I am sure they have never been cleaned.

just do it....I think you will notice a difference..

 

[acuhon]

Is this the general consensus among other owners too? Should we be having our injectors serviced every X number of years/miles. I have 135k miles on my 32 year old injectors, and I am sure they have never been cleaned.

You will be surprised how much power is lost by dirty injectors. Just send them to RC . They will also send you new O rings . Follow manual for installation and change the fuel filter.

 

[Honcho]

I also had it done on my 91 with 90,000 miles. Made a big difference. I'd say the "X" is anywhere from 50,000 to 75,000 miles.

 

[Wild Turkey]

Your's were pristine compared to mine. I had 4 below 230 and 1 reading 160, all dribbling!
My math says down 10% on power?
Any idea where to find the torque spec for the ignition coil covers? Service manual doesn't say but notes the coils at 9 ftlbs (23-94). Similar bolts on the manifold covers (11-134) also don't show torques for the covers but the fuel rail nuts look similar and rate 8.7 ftlbs.