G37 started misfiring cylinder #2 it just hit 100k so I assumed spark plugs or coils I told my mechanic to do all coils spark plugs and to throw a new belt just cause it needed it anyways but still misfiring he does compression test and it’s fine on compression he says fuel is fine they do everything all over again I hear a small rattle from the catalytic converter at low rpm’s. My question is can a clogged cat make your car throw a misfire? It’s weird because I would think if it was the cat it would throw misfire on the whole bank 2,4 and 6 but it only throws on number 2. Also no substantial oil or anything we’re 2 days into diagnosing and I’m just wondering what y’all think could be wrong

 

Did you try a compression test?

 

yes the compression is fine, I already ruled out spark plugs coils compression and fuel I’m confused

 

If the injector is fine than it's your wiring or as was in my case shorted transistors in my ecu.

 

okay how much do you think it would cost to do those repairs? I’m just asking to make sure the shop doesn’t try to up charge me

 

Unless you take out the injectors there is no way to determine that they're actually clean and firing evenly. Look up What_Wires on instagram, i posted a video of OEM VHR injectors that were cleaned by hand and "looked" good but were way off.

What type of spark plugs you used, where did you get them and were they legit. You should be using OEM Denso, Ebay or Amazon will yield a lot of fakes. You can check that same page and see a comparison between fake and real VHR plugs

What kinds of coils? Any broken coil connectors, coil boots? Any oil in the tubes?

 

If your mechanic has ruled out fuel,air and injectors than it's a wiring or shorted ecu. My ground wire began rusting and didn't provide enough ground and shorted two transistors in my ecu. The cost to fix it was 250 from an online company I sent it to in florida. But make sure your mechanic knows what he's doing diagnosing

 

Now throwing code P0420, but i thought that this would happen anyways. I can hear the cat rattling sometimes when its quiet outside but why throw some stock cats on what should i buy some HFC or something? I want to get some of that vq sound but i dont want to damage my engine doing tunes and all that extra.

 

How did the spark plugs look? Any decent tech would have done a quick read on them to tell if he was actually fixing the problem. But yes, I have seen a plugged cat cause a misfire, cylinder cannot evacuate the exhaust gas, so it cannot have an efficient combustion cycle.
As for cats, a pair of high flow cats won’t need a retune, and I actually just ordered a set from Kinetix, on back order for 4 weeks I’m told.

 

Yeah the mechanic called me next day after I made this thread and said that they fixed it. I don't know anything about my coils or spark plugs all I know is I replaced them all. Hopefully fixing this P0420 with some HFC will give me some better sound and kill 2 birds with one stone cause its really quiet. I cant hear it at all unless I step on the gas 3,500 rpm or higher even with a muffler del. Cats are the only code being thrown now. how do the Kinetix sound?

 

What did he do to fix it?
I’m not sure about the sound but I plan to do a before/after cold start and post it here if I can……my car is pretty loud though, all it has is a Top Speed (off a 370z, modified to fit) catback, which is full dual with two resonators and mufflers, so not sure why yours would be so quiet with muffler delete.

 

I saw some videos on yt it sounds dope I’ll look into some hfc the ones I saw like berk are 550$ usd for some pipes I don’t know

 

I just got an order confirmation today from Kinetix, and I only ordered them 2 weeks ago I think, so they’re ahead of schedule, woot! From them they were $449 I think, with a lifetime warranty it said, they were the same price from Z1, but they weren’t gonna be shipping till summer, so I went right to Kinetix.

 

well I’m going to do the same thing but a lot of shops are telling me even if I buy new hfc it’s still going to throw cel ? On kinetic website it says they bypassed that

 

HFC may throw a cel, but because their site claimed they don’t have that issue, and because of the warranty I went with them. I also have had great communication from Jason there anytime I had a question about my order…emails replied to in a day or less.