Nissan GT-R 2009 misfire

bsh · Post by **bsh** » Fri Jan 01, 2021 9:03 pm

Hi!
Car is misfiring espacially when cruising say at 3500 rpm at very light load. WOT also, but prefer not do to many WOT pulls because something isnt right... Idle are nice.
Leakdown- and compression test fine. Afr and fuel corrections are fine. Cam timing are fine. Have checked for bent rod. Replaced with new original coils and sparkplugs gapped to 0.6 mm. New fuel. Loaded every ecu gnd and +12vsupply with about 7-9A. About 0V voltage drop. There are some voltage drop to the coils, max 1.9 Volt drop. Have hardwired coils just to eliminate that.
Car have COP and had to remove intake manifold to remove coils and put some spark plug cables between coils and plugs to be able to put on the inductive pickups. I have not scoped secondary before, only primary on a couple of cars aand have no experience with it. The primarys I have scoped on other cars have been "normal" with amp rising steady til coils is charged, just like the books tells it to be. The first "test 1" I have the primary on coil 1 as well as secondary on coil 1, 3 and 5. Primary are not what I have seen before and expected. Spiking towards end of dwell. Really weird... Secondarys arent as expected either... Really, really weird... Any idea? I have some notes on each file so you can see what I have measured.

EDIT: I think I must log one more time because it seems like I have setup the sampling too slow... Will try with 1-2 ms per divider.
Update 3 jan: I tried capturing some seconday voltage coil 2 at idle and 3500 rpm stationary. Idle seems ok I believe, but at 3500 rpm, the graph are weird... See attached pictures. What am I doing wrong..?

Thanks:)

kona · Post by **kona** » Mon Jan 04, 2021 1:52 pm

HI,

----------It would be nice to connect to these points:

----------Lay out the records in files / not in pictures /.

bsh · Post by **bsh** » Mon Jan 04, 2021 2:09 pm

Hi, I have a R35 with VR38DETT, not RB26.
Any idea why the secondary are weird looking? Can a partially clogged cat on one bank cause weird looking secondary voltage?
Thanks

Technician · Post by **Technician** » Tue Jan 05, 2021 9:12 pm

Leakdown- and compression test fine.

Many years ago I had an engine problem that would not start, going back to the 1980's. I carried out a cylinder compression test using a conventional gauge and nothing showed up. I've also carried out many engine leak tests over the years with these air fed testers, sometimes seeing as much as 100% leakage. The problem with those tests is that the compression test does not always show a problem, and a leak down test will not ever show a restricted or blocked exhaust system. Back in the 1980's thinking back to that problem of a none start which I never found the cause of, I've always assumed afterwards that the exhaust was blocked.

The point...

In your ignition waveforms you have a lot of hash where the spark burn time occurs. Some of the waveforms are difficult to assess due to the amount of hash. Suppose and I am only supposing because I've no idea on your engine what the true cause is, but lets say the inlet valves were not opening or opening correctly? Would that not cause an inrush of exhaust spent gasses back into the cylinder and create hash on your traces because of dirty combustion?

Thanks to Pico on this site I was introduced to some very advanced professional diagnostic equipment that I'd never heard of a few years back, and one such tool is the WPS500X pressure transducer. Now I respect the cost of the initial investment is not cheap, but the rewards are much greater than the cost of the kit. Having used this pressure transducer now many times and researched the waveforms produced I've learned that I can see many areas of an engine operation from that one 720 degrees waveform, from loosing peak compression's in any cylinder, to valves not opening/closing, blocked exhaust systems, valve timing seen too advanced and or retarded, inlet manifold depression problems and exhaust valves leaking during running engines.

This is a very advanced tool and may open your minds eye to a much better way of testing engines if you choose to invest in the kit. Compression gauges and in cylinder leak testers for modern engines are a little dated in my opinion and not very reliable in their results and conclusions.

Just my tuppence worth.

bsh · Post by **bsh** » Wed Mar 17, 2021 1:15 pm

It seems like what felt like an engine "misfire" was caused by a faulty ETS-unit in gearbox...
Thanks

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