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z3 swapped, misfiring on #1

N

Nchristopherson

New member
I finished doing the z3 turbo swap and 60# siemens Deka injectors on my GT but am running into problems. It starts and seems to run fine, but there is a pretty consistent misfire on cylinder #1. all of them have missed at least once, but very seldom. The PCM has a bunch of L67 tables copied over to help it run safer and the IFR was scaled by 2.79 (60#/21.5#). The offset and other injector tables havent been tweaked yet. It has Autolite 103s gapped to .035, we tried swapping coil packs, ICM, ohmed out the resistance of #1 wire, and hooked up a wideband to view the AFR, but the problem persists. The AFR seems to be okay, but looks to be slightly lean, which I would expect given the deka offset is a bit larger than the OEM. At this point I am questioning if the injectors need a good cleaning. Any one have other ideas?

The tune is here: https://drive.google.com/open?id=0BzVFuTcJenYqZlZhQVF2Z3RWZ28&authuser=0
 


open the plug gap up some. make sure all your injectors are sealed and not leaking, spray with carb cleaner at idle.

and make sure you dont have a cracked spark plug.
 
Tried the carb cleaner at idle but it didn't stumble or give any hint to a leak there. Also swapped plugs 1 and 5 but the misfire still follows 1. Didn't see any cracks. When I originally installed them, they were at the set pre-gap but the problem was still persistent.
 
every set of plugs ive gotten were set at about 0.60.

im running my 104's at 50.

it could be tune related. you need a solid tune in there.
 
Gap seems small, swap injectors over see if mis follows..buddy has a set of 60s has a mis at.idle only, we swapped everything still missed..it was an injector that was bad...104s gapped at 50 as well no issues.
 
Turns out it was the injector.. Damn. Do either of you guys have any tips for cleaning them off the car? I am assuming that's a more thorough way to clean them.
 


you tube has some vids of how to clean em. its pretty easy to do, just need to power the injector up. search you'll find it fast on yt.
 
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Well this is upsetting. I haven't had time to post updates here. Unfortunately the problem is still persistent. I am really starting to run out of ideas. I'm going to try to summarize this to the best of my abilities but there is a lot going on.

So, just for peace of mind, I bought a whole new set of 60# injectors, but it didn't help at all, car still misses on #3. When first starting the car, it will misfire on all cylinders and not like to idle smooth, more of a quick oscillation. After maybe 30 seconds, it will suddenly smooth out and only misfire on 3 and 6, mostly 3. Since those share a coil pack, I tried swapping them and that did nothing. Tried replacing the ICM, didn't help. Thought maybe I messed something up with #3 cylinder so I did a compression test, as well as on the other front bank cylinders. All within 10 psi of each other at 160-170 psi. Tried using a whole new plug wire from my other car for #3. Even bought the Z3 tune from ZZP to rule out a tune issue, but the problem is still there.

Interestingly enough, while I was talking to Tim from ZZP about the tune, he recommended I gap the plugs to .054". After doing this, #3 will now miss under load. Also tried swapping plugs.

Given these conditions, I can only imagine at this point it is a fuel problem or a vacuum leak.. Any suggestions? I am at a loss.
 


Just to be thorough, the problem is the #3 exhaust valve is burnt. Did the exhaust test with a piece of paper and it sucked back up against it. Didn't show up with a compression test..

Time to replace a valve and determine the fate of this engine..
 
I thought so too. Kind of unfortunate, I ruled out physical damage and kept driving and it has gotten worse. Called a mechanic yesterday and told him all my symptoms and what I have done and he said pretty much the last thing was a valve. You can hold a piece of paper up to the exhaust pipe and if the paper sucks back towards the pipe instead of always positive displacement, then that's telltale of a bad valve.

Now I'm wondering if I should pull the rear head off too and check all of the valves and cylinders
 
This is concerning. Drained the coolant out of the engine by pulling the front knock sensor and there are a ton of tiny flakes that came out with it. I wouldn't assume this is normal at all
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