Motor blew up today.....need some tuning experts in here.

**mecanicman** · 10-10-2013

Look at your map signal, and the coresponding drop in cylinder air. Something mechanical was going on, maybe on the cylinder that let go? I added cylinder air in with map and maf and watched them dance with tps reading 100%, looks like an engine issue to me.

**lwrs10** · 10-10-2013

Originally Posted by EagleMark

I was thinking TM too. But can't remember it ever acting this way? Lag, lean then rich?

Can't really think of anything tune related that could do this if VE is dialed in, especially MAP and MAF?

What happens, or happened... if you were running Open Loop?

Bummer on the piston, but I don't think a 15 AFR lean spike during WOT caused it... unless it was some spark knock not being handled properly for a long time? Have you pulled the plugs and looked for specks/fly turds on the plugs?

Torque management is zero'd out in my tune, so not sure on that. I have ran it full open loop and it will still do it. Does not have to be WOT, it will do it anytime it is above 75kpa, and held there at a steady rate for 3 seconds.

I have even jumpered off an injector and hooked a portable oscope up to it in the cab, and the injectors just shut completely off when these lean spikes happen. So i would 100% say it is the computer causing it. Why.....i have no idea. That is why I am here.

Originally Posted by mecanicman

Look at your map signal, and the coresponding drop in cylinder air. Something mechanical was going on, maybe on the cylinder that let go? I added cylinder air in with map and maf and watched them dance with tps reading 100%, looks like an engine issue to me.

That was when it shifted into 3rd, so i would expect a slight dip in the MAP reading. I can post screenshots of this happening hundreds of other times not during a shift and the MAP kpa does not move.

**mecanicman** · 10-10-2013

From looking at the different logs you posted, I can see this stuff in everyone. Your koeo map value is 102kpa. You never hit that going wot, best I believe I saw was 98kpa. Is your air filter to small, or you have silicone elbow you are sucking shut? You have a map sensor "tick" in your steady state cruise with no tps fluctuation. Something was up with the engine. I have included 2 pics from your logs that are not shifts, and show the same thing I described before. Map sensor doing the funky chicken. Your issue is not tune related.

**EagleMark** · 10-10-2013

Nice use of scanner!

Could that be a intake valve? Lean pop?

**mecanicman** · 10-10-2013

I would lean towards valvetrain related, but with just the log its hard to pinpoint.

**lwrs10** · 10-10-2013

I need to post some screenshots of this lean spike when not WOT.

as far as the MAP sensor varying at WOT, what would cause that? Truck ran perfect everywhere else but that lean spike. I do have some logs from when the engine was bone stock, so I will compare those.

**lwrs10** · 10-11-2013

Here is that lean spike when not WOT. You can see everything is steady as can be when it happens. I have even hooked an oscope up to an injector, ran a jumper into the cab, and monitored the pulsewidths in real time. The injectors shut off for 300ms completely everytime this happens. I have also monitored voltage on the positive side of the injector plug, and it does not drop at all.

I am 100% sure this is related to the WOT spike, and 100% sure it is a computer related issue since I can see it stop commanding the injectors when it happens.