moneyshot

Hi guys.

I recently bought an 05 6 speed with 138000KM on the clock.
The car runs beautifully and is pretty stock except it has a heavy duty clutch and 2kw starter. It starts within 2 turns of the engine hot or cold and pulls nicely.
I decided to remove the factory cat and resonator and fit it with a 2.5" pipe through the mid section. When i did this i spaced the second o2 sensor slightly away to try and prevent the CEL. I live in New Zealand and this is perfectly legal here. It made the car a bit louder and raspier which is fine, it also gave it quite a bit more power which is great. The only thing is that now it has this odd missfire when driving the car under load. The CEL IS NOT FLASHING or even coming on and the car pulls nicely but as you accalerate you can clearly hear the odd miss. Ive cleaned the MAF and performed a seafoam treatment and the idle is a bit smoother now but its still doing this. Seems to mainly be in first and second. The leads and plugs have definately been changed but im unsure of the age of the coils. The CEL definately works as it came up after the seafoam but dissapeared again.

Can anyone give me any ideas? Ive done a lot of searching but cant find any info really relating to a similar issue. IS it possible the second o2 sensor could cause this? i was under the impression it wouldnt. maybe the SSV, fuel pump or ecs? Or is it likely to be more of a remapping issue? Or is it simply a chance that you hear the valves going through their stages (i doubt but worth the ask)

Thanks in advance

BigCajun

iTrader: (1)

Did you reset the NVRAM?
(20 brake pedal stomp)

moneyshot

Yes I did although I will clean the ess and do it again today and go from there.

40w8

Stock coils are good enough to deliver car only. One can't ever tell when they go bad, and sometimes you learn about it when cat fries.

I put on the BHR Yukon coil kit, and it might last life of car.

My over eager scanguage horspower went up 9 hp or a corrected 6 extra hp when I put on kit at 23k miles.

I only changed coils and wires at that time to test any more power. Put plugs in at 33k miles.

moneyshot

It's just odd to me that all the threads I read about misfires start with flashing CEL and I don't have any CEL

9krpmrx8

iTrader: (46)

The factory ECU won't detect everything. It's smart but thousands of misfires go undetected.

moneyshot

Ok all sorted now. I cleaned the ESS on a cold engine and forgot to reset NVRAM before I started the car so I warmed it up and still doing the same thing, pulled over. Did the brake press thing except this time I just kept pressing until the oil light moved (read somewhere an 05 wouldn't do this but it does and hadn't been for me last time I did it) and now she's purring perfectly. Thanks for the help guys 😀

BigCajun

iTrader: (1)

Awesome, thanks for the update.

moneyshot

Ok so this is the final chapter now, promise 😀. On the way home it started again. I thought man this is really strange, NO engine hesitation when it missfires car pulls beautifully but this wiered erratic misfire. No CEL cars running beautifully. So I got home and did a KAM reset and while I did that I checked the ignition leads were all tight and connected properly, checked vacuum lines and thought I'd add a couple of extra ground wires to the engine while I was waiting since I had the gear lying around and then I took the car out again but it was still doing it. I was baffled. So I thought I'd keep driving until something consistent showed up. And what do you know I noticed this "misfire" was only happening when I was hitting bumps. Now New Zealand roads are bloody aweful. Especially where I live. So I started to realise that the new exhaust I had bent up was touching the body somewhere. So I raced home eagerly and looked underneath and sure enough the new exhaust was just sitting on the front brace that sits under where the resonator used to be. It wasn't doing that when I fitted it so it must have moved a bit throughout driving around. So I ripped the brace off and went for another drive, nothing! Amazing. 6 hours to figure out I need to be abbetter fabricator!

So to sum it up what was happening was every time I would hit a rough patch of road it would just touch the cross member and in the car you would get this effect like it was creating the sound of a missfire when in fact it was absolutely fine! What a way to start the day. I'd like to say this might help someone in the future but truth be told there's probably never going to be someone that has this problem again 🤓

moneyshot

Sounds stupid but yes. I truly did sound like a missfire in the car. Embarrassing, but true.