Misfire on boost / high rpms

Post by **Cams** » Sat Apr 05, 2008 10:45 am

Hi, all. Im starting a new topic because I wasn't able to find a specific answer to my issue searching thru the archived ones.

I'm having misfires at high rpms kicking in randomly between 4k rpms up to 6k rpms. In the video below you can see the behavior standing still, but a similar misfire is felt while moving. I don't think its fuel cut because its not like hitting a brick wall. Boost gauge doesn't show any spikes and vaccuum sits nicely around 20 once throttle is released. Issue has been present for about 4 months now, so you can compare the timeframe with the things done below.

http://www.youtube.com/watch?v=6sXAXmSQ5To

Things checked that could be related include:

- NEW Walbro HP installed 1 year ago. (Don't know if it will give a similar failure if gone bad)- NEW Fuel Filter (changed less than 2 months ago)- Injectors (standard 370cc, sent to the lab, internal filters changed, flow tested, 2 months ago)- NEW Nismo FPR +gauge (installed 7 months ago, pressure checked every 2 weeks, set to 37psi using relay trick, holds properly when accelerating from the cable.- RX7 Dropping resistor (1 week ago, fixed my rough idle issues)- NEW Engine Temp Sensor (1 week ago, fixed my high idle and cold start issues, ECU still shows code 13, waiting for that 50 starts to recheck if code is gone)- T25g + FMIC (rebuilt turbo + IC, boosting 8.5psi with standard wastegate, installed 7 months ago, rechecked all clamps for possible boost leaks)- Coil Packs (cleaned yesterday, fixed small cable ground at the end of the bracked that was about to snap)- NEW Sparkplugs (BCPR6ES-11 changed yesterday, gapped at 0.9mm, also tried with grade 5 ones before)

As soon as I replaced the plugs yesterday the car was pulling beautifully for about 6 or 7 hard pulls but after a while it started failing again, which is when I took the video shown above.

Things I haven't been able to check, because I'm really picky about the mechanics who would touch the car, and the ones I trust don't have the equipment to do it either, are:

- Timing (CAS has been sitting nicely in middle of the range since I bought the car)- Compression Test (I believe valve springs are weak because I blow white smoke every now and then, but the IC pipping is oil free, so I guess the turbo is fine.)

This dude who does SR20s took a quick look at the issue the other day and told me to double check the Fuel Pressure or to check if the Wastegate had gone bad, but I don't know if a bad WG would give a similar symptom and/or show steady Boost on the gauge. He also told me to lower the boost to see what happens, but I don't have any sort of boost control. I'm also using a 1G DSM BOV recirc from cold pipe, but again, don't know the behavior of a failling dump valve.

Since it works OK for a while after the new plugs I was looking into replacing is the Power Transistor (aka ignitor, right?) to discard spark issues. I'd appreciate a part number for this if you have it handy. Bad coils would give idle issues too, right?

I thank you all in advance for any inputs on this. I grade my mechanical knowledge 3 out of 10, but I love all the new things I have learned with this car, even if it doesn't work right most of the time.

Sorry for the long thread.

Post by **r34 gtr** » Sat Apr 05, 2008 11:02 am

Pull those plugs out and check them! If you aren't running 20psi on a big turbo theres no need for a plug that cold!

It sounds like you are fouling the plugs because they are not getting hot enough to self-clean. Try some 7's.

Post by **boost_boy** » Sat Apr 05, 2008 3:34 pm

You possibly have a serious issue with the wiring at your ecu. That code13 (water temperature sensor or circuitry) will have your car running as rich as Bill Gates. If you don't fix that issue, complaining will be senseless. Good luck..............

Dee

Post by **ca18detgabby** » Sat Apr 05, 2008 4:39 pm

both boys are right...... two things worth checking.

after that I would go back to checking vac lines and make sure your riding around didnt shack something loose

Post by **r34 gtr** » Sat Apr 05, 2008 4:52 pm

Sorry, I meant to say try some 5's, but apparently 6's are the standard. Definitely check out that temp sensor circuitry like Dee said. If it works for 6 or 7 pulls, it means the plugs are getting fouled up because its running too rich, causing the misfire. You might want to re-run the wiring to that sensor and see if it goes away.

Post by **USDM Silvia** » Sun Apr 06, 2008 4:27 am

would this also be the culprit to y my car is choking out at 2k and not wanting to any higher?

Post by **ca18detgabby** » Sun Apr 06, 2008 7:57 am

USDM Silvia wrote:would this also be the culprit to y my car is choking out at 2k and not wanting to any higher?

nope your ECU is in limp mode. something is not readng into spec and thus your ECU does not want to perform because the run conditions are not being met.

check your ecu for CODE(s) and see what it is reading is not in check.

Post by **USDM Silvia** » Sun Apr 06, 2008 7:58 am

its reading code 55

Post by **ca18detgabby** » Sun Apr 06, 2008 6:33 pm

USDM Silvia wrote:its reading code 55

I would try another ECU..... as that is about the only thing that would stop it from reving up and locking you at 2k...... other things would affect other run conditions or just stall you near 2k and eventually make it through the RPM band(such as a bad coil)

Post by **Cams** » Sun Apr 06, 2008 7:40 pm

Ok, rechecked the Temp Sensor and the connector needed some cleaning. Now I'm getting code 55 at the ECU, which I guess is a good thing.

Was not able to pull the sparkplugs today, but I should asume that they have gone bad already if I'm still getting the failure, right??

I'm not planning to boost any higher in the nearby future, so should I use Grade 5 plugs for the 8.5psi Im running, or should I keep using grade 6 in order to stay on the safe side? Or should I better get some Platinum ones (PFR6-11) ???

And to be completely sure, here is the noobie question of the day. When tightening the plug, once Im done tightening by hand, should I go for 1/4 turn or 1/2 turn with the socket wrench??

I hope it gets solved with the new plugs. Thanks again. I'll keep you posted.

Post by **Cams** » Mon Apr 07, 2008 6:50 pm

Could it be a st*pid mistake such as not tightening the plugs enough??

Post by **Vaikis_** » Wed Apr 09, 2008 10:24 pm

try to reset computer

Post by **Cams** » Thu Apr 10, 2008 7:12 am

Small update, hopefully someone can shed some light on this.

Getting Code 55 at the ECU. Installed brand new Grade 6 Cooper sparkplugs, gapped at 0.95mm. I was indeed not tightening them enough. Torqued them to 15 lbs/ft, Service Manual states it should be between 14 to 22 but I'm afraid to tighten them anymore than that.

Now the car revs happilly up to 5500 - 5700 rpms, after that it has minimal misfire until around 6400rpms at which it wants to stop reving up. If I take it to 6500rpms and slightly release the throttle it gives a really loud metallic backfire heard from the muffler, as if someone had hit a metallic can with a stick. Is this Detonation??! Or simply a louder backfire since it is at a higher rpm??

Will use the car for a couple of days and see if the issue degrades and moves down the rpm range.

Comments are appreciated.

Post by **ca18detgabby** » Thu Apr 10, 2008 8:04 am

back fire is a common issue with a non-recir bov.....maybe the recir line is leaking or leaking else where? idk what happens when a BOV fouls........

any boost gauge telling you what kind of PSI you are pushing when you are lagging or having issues.

there are people who have had issues with boost dropping along the RPM band with a basicly stock engine..... might try a MBC and leave it fully open to try and smooth the boost out and see if that resolves your issues.

Post by **Cams** » Sun Apr 13, 2008 8:43 pm

My boost gauge reads solid 8.5psi even when the misfire is present. Gabby, following your advise, I was able to get a friend to borrow me another 1G DSM BOV (recirc) to see if I might be leaking boost there, but in the end got the same results, with new plugs ran fine for a while but then failed after some hard pulls.

My biggest finding is that I was able to narrow the issue down to the sparkplug on Cylinder 2.

This is the plug from Cylinder 2 I installed 3 days ago

This is the plug (Grade 5 selected by mistake) installed yesterday

This is the plug from Cylinder 1 installed 3 days ago

By the looks on the plug from cylinder 1 the car might be too lean?? Should I retard the timing a bit? (No timing light available )

Going back to the actual issue, I did a couple of things today:- Replaced plug on cylinder 2- Switched Coil Packs between Cyl 1 and 2- Tested the Dropping Resistor, in which 3 pins gave a 6.2 Ohms reading and 1 showed a 6.6 Ohms reading

Same behavior, boosted nicely up to 6000+ rpms and then started to fail 10 minutes later. Was not able to pull the plugs out again today, but I will be checking it as soon as I have some time.

Just to be checking my options, if the issue follows the coil pack thats done deal. But, if the issue stays on cyl 2, could it be that I need to replace the injector?? Or is it possibly because of the 6.6 Ohms at the DR? Or something in the wiring of the coil/ignitor??

Again, all comments are welcomed.

Post by **biosehnsucht** » Mon Apr 14, 2008 4:21 pm

keep in mind if one or more holes aren't firing then the unburnt fuel is going to throw off the o2 reading, leading to the ECU going as lean as it can to compensate, driving the otherwise working cylinders to very lean conditions. then it reads way lean, and waffles back to normal or possibly over-rich. rinse, repeat.

the dropping resistor being slightly high is not going to cause a measurable difference. it may slightly increase initial open time of the injector by requiring more time to build the field to drive it open, but once it's open it no longer matters. this would not affect it enough for this drastic of a difference, either, and would affect all cyls equally.

- swap injectors between cyls in case one is sticking open- test/replace the ignitor and wiring to/from it

Post by **Cams** » Fri Apr 18, 2008 6:47 pm

Thx for the reply.

Unfortunatelly, issue is still present in Cylinder 2 after swapping the Coil pack and after installing a replacement (2nd hand lab checked) injector.

Any other opinions? I guess testing the Power Transistor (and maybe all the electrical system towards that cylinder) is the next step, but since it's on high boost, and I haven't been able to do a compression test, has it been reported that oil leaking from the valves or the ring lads could damage a sparkplug this quick?

Im running desperate now.

P.S. my car is a Latin America edition, so it doesn't have an O2 Sensor. Need to sort that out once I get a Wideband.

Post by **biosehnsucht** » Sat Apr 19, 2008 4:34 am

Yes, test/replace ignitor (aka power transistor), and check the wiring to/from it. You're definately getting either too much fuel in cyl 2 or too little spark ...

Without an O2 sensor, that does rule out it's own self-adjusting as causing a problem beyond the original problem. Is yours a 4 or 8 port head? I wonder if it's the same 4 port ECU as some parts of Europe got (they don't have an O2 sensor on some of theirs too).

Just because its better generally speaking, might consider trying to get a JDM / EDM ECU (depending on engine type) w/ support for O2, then install an O2 sensor in the elbow pipe (or get an aftermarket one already fitted).

If you go wideband, get a wideband controller that has a narrowband output, run that to the EDM/JDM ECU. Best of both worlds!

At least that way the ECU can *try* to self-adjust, and it might help. But don't go doing this just yet, your car should run ok 'as is' first..

Post by **Cams** » Sun Apr 20, 2008 8:03 pm

Thanks for the pointers.

Tested the Ignitor with the multimeter for continuity (as stated in the Service Manual), but was getting values of 500 to 760, instead of the corresponding beep sound. I don't know if this is right or not, but will try to get a loaner for testing or get one cheap around here. (Hate having to wait for shipping times)

Found a good price for a new PTU unit at Rockauto.com BECK/ARNLEY Part # 1800180 for Wholesaler Closeout. Will go with it if mine is indeed bad.

Will keep your other pointers in mind for when the Wideband time comes.

Post by **biosehnsucht** » Sun Apr 20, 2008 8:41 pm

Sounds like it could be a bad power transistor (igniter) then. Where is yours mounted?

Post by **Cams** » Mon Apr 21, 2008 5:28 am

On the engine wall next to the driver's side strut mount. I think this factory location, and bet it would take a severe amount of heat coming from the Turbo.

Post by **r34 gtr** » Mon Apr 21, 2008 6:30 am

Yeah, thats the proper location. I don't think it would go bad with heat. They do crap out occasionally though, due to being older than Christmas.

Post by **Cams** » Sat May 17, 2008 1:22 am

Hi, sorry to bring back my demise again but I haven't been able to solve it. First of all thx for the comments and specially The_Chosen_One for hooking me up with a replacement Ignitor.

After swapping the ignitor and bypassing the Hot Start Solenoid the issue is still present. Oddest thing now is that it seems to be triggered when the car is fully warmed up. I took the car for a spin on tuesday night as the car hadn't been used in a couple of days, and for the 10-15 minutes it took me to get to the restaurant I was heading the car behaved like a champ. Not a single studder nor reving issue. Was smoking quite a lot of blowby near idle as I was parking the car and so, but Im used to that. 20 minutes later I leave the place, and as I floor it it will give the stupid Sputtering exactly at 4000rpms on every single gear.

Tonight I took it out for a quick spin, and again reving happily up to 6,800rpms without issues. What could be causing a studdering issue when warmed? Compression? Timing? PCV? Hot Start Solenoid (already bypassed) ? Vaccum? Boost Leak? Something else?

Again, comments are welcomed.

Post by **boost_boy** » Sat May 17, 2008 1:26 pm

Cams wrote:Hi, sorry to bring back my demise again but I haven't been able to solve it. First of all thx for the comments and specially The_Chosen_One for hooking me up with a replacement Ignitor.

After swapping the ignitor and bypassing the Hot Start Solenoid the issue is still present. Oddest thing now is that it seems to be triggered when the car is fully warmed up. I took the car for a spin on tuesday night as the car hadn't been used in a couple of days, and for the 10-15 minutes it took me to get to the restaurant I was heading the car behaved like a champ. Not a single studder nor reving issue. Was smoking quite a lot of blowby near idle as I was parking the car and so, but Im used to that. 20 minutes later I leave the place, and as I floor it it will give the stupid Sputtering exactly at 4000rpms on every single gear.

Tonight I took it out for a quick spin, and again reving happily up to 6,800rpms without issues. What could be causing a studdering issue when warmed? Compression? Timing? PCV? Hot Start Solenoid (already bypassed) ? Vaccum? Boost Leak? Something else?

Again, comments are welcomed.

Let me assist you a bit! All these parts you are changing are not the cause of your lean issue. First of all, did you check the codes on your ecu? Muy importante. Your timing is more than likely too advanced and that's why it gives you a few minutes of happy time and then goes to crap. You need to find you a real timing gun and check to see where your timing is at (no more guessing). Looking at those plugs and listening to you say you're blasting your engine to 6800rpm while being problematic is a recipe for a cracked ringland or even four; or better yet, a or some melted pistons hence the reason why you're having blow-by and smoke.

Your next issue would be the changing of your water temperature sensor. Very important piece and has a lot to do with engine performance throughout the driving range. And lastly for the rest of you guys, the power transistor is a spark amplifier/converter and has nothing to do with the engine going lean. If anything, it will drop voltage to a coil or two which in turn will decrease or eliminate a particular cylinder's spark which in turn leaves a cylinder with unburned/partially-burned fuel which in turn will produce a rich condition. Injector resistors either work or they don't work. They rarely fail unless there was a bad wiring job or something to that effect, but they rarely fail. So please dude, read this and try to cover some of the areas I touched-on so you can stop spending money foolishly. Good luck with this..............

Dee

Post by **Cams** » Sat May 17, 2008 3:20 pm

Will definetly look into getting the Timing right and will also do a compression test before replacing any other parts. I appreciate the scolding as I do know I'm missing these important bits.

Checked ECU codes and its giving Code 55.Temp Sensor already replaced (solved cold start)Dropping Resistor replace(solved jumpy idle)Power Transistor replaced, looking into the Cyl2 plug being darker than the other ones (which do seem like a lean condition) but haven't checked further into this.

Thanks for the comments.

Post by **Ca_Silvia** » Tue May 20, 2008 6:38 am

I have a similar situation as you. I believe my issue is book leak related however after googling for answers on my problem i stumbled upon something that may help you. I read on nissansilvia.com a hack job method to fixing high rpm misfires.

Use electrical tape and wrap your coils above and below the black brick looking thing and re gap your plugs to .8mm

Its ghetto but it works. The Aussies swear by this (it seems) and it did in fact work for me so...

Post by **Cams** » Tue May 20, 2008 4:09 pm

hehe, sounds ghetto indeed. Will check the timing and if no go will give it a try.

Have any pics or a link to check further? Plugs already gapped to 0.9mm.

Thx.

Post by **Cams** » Fri May 23, 2008 1:48 pm

OK, timing was way off, at maybe 6 or 7 BTDC. Set now to 15°.

Replaced plugs, gapped to 0.8, removed coil packs to clean them thoroughly with Eletric Degreaser. Used electrical tape around them, althought I'm not entirely sure of what was supposed to be covered with it to prevent the arcing, if that is the case.

Now with the proper timing the failure is still there on mid to high rpms, but there is also a small misfire when idling, which would sound like a coil pack going bad, right?

Anyone selling a working set of coil packs? Maybe with the coil packs harness too?

Im out of ideas here. What other things would go bad once warmed up?

Post by **boost_boy** » Fri May 23, 2008 3:23 pm

Cams wrote:OK, timing was way off, at maybe 6 or 7 BTDC. Set now to 15°.

Replaced plugs, gapped to 0.8, removed coil packs to clean them thoroughly with Eletric Degreaser. Used electrical tape around them, althought I'm not entirely sure of what was supposed to be covered with it to prevent the arcing, if that is the case.

Now with the proper timing the failure is still there on mid to high rpms, but there is also a small misfire when idling, which would sound like a coil pack going bad, right?

Anyone selling a working set of coil packs? Maybe with the coil packs harness too?

Im out of ideas here. What other things would go bad once warmed up?

Sound like you got a bunch of coils that are going down together. I have a good set that I'd be more than happy to part with? I'll drop you an email.

Dee

Post by **ca18detgabby** » Fri May 23, 2008 6:00 pm

boost_boy wrote:Sound like you got a bunch of coils that are going down together. I have a good set that I'd be more than happy to part with? I'll drop you an email.

Dee

agreed.

to the OP

glad to see you are working through all the issues and solving your problems one by one. much better than people just giving up

ps I now have 3 extra sets of coil packs in my garage..... just in case.

Misfire on boost / high rpms

Misfire on boost / high rpms

Re: Misfire on boost / high rpms (Cams)

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Re: Misfire on boost / high rpms (Cams)

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