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Discussion Starter · #1 ·
Hey guys, I'm working on tuning my VVE on a new engine build and started getting a little rough idle. The whole story is kinda long, but basically I built a new engine, had a previous casting repair (before me, either previous owner or factory) that started leaking oil above the oil cooler a few days after getting it in and going. Got a new block, had it machined, and threw all my parts in the new block. I had it idling great before, and was doing good for a day or two, then I started doing a little exhaust work welding in v-bands and after putting my lead pipes back in I found this weirdness in my B1 O2 sensor. Anyone seen anything like this? Already checked plugs and wires, compression test is consistent across that bank, and verified no exhaust leaks. I am about to grab a new O2 sensor to swap in for kicks and giggles. Just thought I'd throw this up here in case anyone has seen an O2 sensor act up like this. I though they usually just go dead and read one direction. I'm wondering if in my engine swap, and taking the lead pipe out a couple times I've kinked a wire in the sensor or something. I was only gentle with my wideband, which is in the other side. I'll let you all know what I find.

152345
 

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Swap it to the other side and see if it moves. If it does, replace the sensor.
 

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Discussion Starter · #3 ·
Just barely swapped the sensor, no luck there. However, I did just throw a P0351 so tomorrow I'll swap packs around and see what we come up with. I think it just took a hot minute before the coil pack registered bad.
 

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any pinhole leaks in that bank ? dosnt take much to do that, make sure headers or any joins are done up tight, also if u have changed header bolts make sure they arnt bottoming out in the head so u think they are tight but they are not, had that happen on mine took couple weeks to show as the gaskets warn in and loosened of a smidge
 

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Air leaks or maybe a leaking injector? The fact that you swapped sensors and your trims are significant different make me think fueling, or plugs as it's so cyclical it could come down to a single cylinder being off.

Moreso on a rebuild, any contamination in the fuel lines could have clogged an injector.

How did you check the exhaust for leaks?


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Discussion Starter · #6 ·
Well I think I'm going to order a new ECM. I had a buddy supply some good info from ProDemand on scoping out the ignition signals and testing everything. After swapping O2 sensors, plugs, wires, and verifying ground 136 on the back of the driver side head was good, and making sure my vband clamps were actually sealing I think we've landed at the ECM being bad. My P0300 and P0351 don't go away after swapping coil packs around and the harness has good continuity all the way through with good looking impedance through all my grounds. The combined P0300 and P0351 that doesn't move means high impedance on the ignition control circuits within the ECM.

Here's my theory: This wasn't happening on the previous engine build (before the old block's casting repair let go and leaked oil everywhere) and I had been tuning for a few days and a few hundred miles. It was going superb and I was a happy camper. After the new engine went back in for the second time I forgot the big ground on the back of the passenger head and tried to crank the engine but it didn't work so well because that ground was barely making contact. If that ground shorted out erratically I could see it causing some issues with other ground shunting components in there.
 

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Let us know if that fixes it!

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Discussion Starter · #8 ·
Well good news, all is fixed now. Events unfolded in this order: swapped ECM, got it programmed and synced up. The car ran much better, but I wasn't satisfied. I cut and re-welded my exhaust and got way more picky about it, I think I did have a slight leak in my vbands. Then I still had a code for P0351, but the P0300 was gone with the ECM swap. I tore apart the harness on the driver side and found a super bad kink in the 6v wire to the cylinder 1 coil pack. I fixed that and wrapped the harness again and the code is now gone and everything seems to be in order. Now on to tuning finally!

Also, random84, I'm using your tuning notes along with GRG. Between the two of you I am not nearly as scared as I was to tune my own vehicle.
 
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