350Zzzz

I recently developed Multiple Cylinder Misfire at idle, however, it smooths out with increased revolutions. The service engine light stays on, then went off and reappeared after about 74 miles.

Nissan service diagnostics identifies the Multiple Cylinder Misfire, but is unable to isolate the cause.

Apparently, everything is within specs, except for the misfire below 2000 RPM; even the coils. Some have mentioned that the coils have known to have problems. But it'll cost me $500 + with no guarantee of the problem being resolved...therefore I am a little hesitant to replace the coils.

My NGK plugs are one step colder than stock and at stock gap.

Tomorrow, I plan to re-check the spark plug gap, and maybe even revert back to stock plugs but with closer gap.

I have been running the pro-charger for 7000 miles now, it was tuned last week, and yes the misfire & service engine light was on before the tuning.

Any, similar experience and/or fixes?

Thanks
Gerald

Borla dual exhaust
91 - 93 octane fuel

jesseenglish

I'd definitely check your gap on the copper plugs. I believe it should be .035, not the stock .044 that the LFR6A-11's come gapped at.

elektrik_juggernaut

Check all of your intake tubing.....an air leak in the intake tubing can cause it run rough.....make sure all of those clamps are hella tight.......i blew my intake hose off once and it ran just like that

jawbone

good call EJ the po300 code can be set by a vacuum leak causing a unstable idle condition. multiple lean misfires= P0300 code

jesseenglish

Yeah, good call. In addition to the intake tubing, I'd check the PCV hoses, vacuum tree and vaccum lines that go to the FMU and bypass valve.

jeffw

Could it be related to that pending Nissan recall on the crank sensor? Just something to keep in mind.
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Jeff

350Zzzz

Will wash the car first thing, Saturday early AM...brrrrrrrrrrrrrr

Followed with

1. spark plug gaps
2. air intake hoses
3. PCV hoses,
4. vacuum tree
5. vacuum lines FMU
6. bypass valve (what is the procedure for checking?)

Has anyone switched to the Vortech bypass (to atmosphere) valve?

I suppose that's another story

Does one still close the gap for spark plugs one step colder than stock?

Thanks
Gerald

daking350

please explain this for all...

jesseenglish

I explained exactly how to check the vacuum tree and vacuum lines on http://www.350zfrenzy.com/forum/show...&threadid=2224

That thread covers some common Procharger installation mistakes. Do #5 and #6. If you don't understand exactly how to do it let me know.

jeffw

Here's one of the threads that covers the recall:

https://my350z.com/forum/showthread....ghlight=recall

The most likely scenario if you had a faulty crank sensor would be that the car would not start at all. I just threw this possibility out to keep an open mind about what's causing the problem.
--
Jeff

MSGarrett1

I thought the Procharger installation manual insists on upgrading to colder iridium plugs. If you revert back to stock plugs and continue to have problems, or have a bigger problem, you might be up a creek w/ both Nissan and Procharger.

jesseenglish

Actually, they recommend colder copper plugs, not iridium.

DrCold

From what i understand, with a FI system, you need to have your plugs gapped smaller than stock (like jesse said). When i had my truck, i put a KB supercharger on it, and i forgot to gap the plugs properly. I had miss fires like there was no tomorrow. After i gapped the plugs smaller it was much better. What i've heard from the grape vine, is with the increased pressures, its harder for the spark to make the jump. Gapping it smaller make it easier to make the spark. I'm not exactly sure on this, but it kinda sorta makes sense i guess.

Darin

True, but his misfires are occurring below 2000rpm where there is no boost.

Another side note is that copper plugs at the same gap require MORE voltage to fire than platinums, because platinum has a much finer center electrode (easier for spark to jump gap). This increases the chances of misfires with coppers. I have seen it recommended to gap copper around .035 if your application required platinum at say .043, forced induction aside. However I would have thought the coils in the 350Z would have plenty of juice to fire coppers at .043. Personally I would go iridium 1 step colder, either NGK or Denso! Iridiums require the least voltage of all and so have the least chance of misfires.

A17Z

iTrader: (1)

had the same code but without a check engine light. took awhile to figure out, they ended up replacing all the coils which solved the problem. who knows maybe the code came back, i haven't check it lately.

daking350

did you have a slight "burp" at idle that caused the car to idle a little rough???

A17Z

iTrader: (1)

exactly. during idle you can hear it once in awhile. also the frst fix they did was replacing the fuel injector of the cylinder that was coming up as a misfire. that didn't work.

350Zzzz

That was what I was told, about the coils; did you pay for the coils or was it under warranty?

Were the coils detected as being faulty; and was it only at idle that the problem occurred. According to NISSAN, if it were the coils the misfire would be more pronounced at higher RPMs.

Thanks
Gerald

A17Z

iTrader: (1)

yes it was covered under warranty and consult did not come up with bad coils, just multi cylinder misfire. i think they mentioned that the code for bad coils was removed from consult for some odd reason so they could not pinpoint it at first.

first there the blurps at idle. then they switched they coils around to determine which one was bad. they thought the fixed the one coil that was bad but after that it started to have large hesitations at higher rpms. so they just replace all of them.

350Zzzz

What was the approximate duration from misfire at idle to higher RPM?

Thanks

Gerald