What would a fouled plug show up on with a datalog? Would it cause knock? Reason I ask is I am expierencing a miss at idle that was not present before. Also car is knocking via the logs, and it doesn't run like it did when tuned last Feb. Also seemed to trap low for the mods and hp (280 at Buschurs) when tuned. Same pump 93 and no other mods since tune, boost leak check is negative.

Any suggestions or comments?

I can post a log, but it is a vendor map, so not sure if thats allowed?

SQ

 

When did these issues start to develop? You need to address the miss at idle before you go any further. Any check engine light?

 

I was tuned in Feb 06, I never logged until around June/July 06 (whenever evoscan 1st came out). Back then logs looked ok, some small knock but it was not consistent. Some pulls knock free, other ones had some (2-3 counts).

Car seemed to be slower this spring/summer. Miss at idle was never really present until a month or so ago. These logs from this years have alot of knock (10 counts or better).

I have had a CEL for the past year due to no cat. So not sure on anything else? Evoscan nevers shows anything when trying to read the CEL codes.

SQ

 

I beleive that logs of vendor tunes are fine. Just don't post the actual ecu maps.

 

Fouled plug might show as a miss which supposed to be a a lean spike. A fouled plug can knock from unburned gasses in the following stroke

 

Are you sure that missfires show up as lean spikes?

I'm not doubting you just trying to make sure?

 

EDIT :: Smarter people than I have cleared this up and a misfire causes a lean spike, not a rich spike. So, ignore the "rich" rubbish I've posted here. Head down a few posts for a better explanation ...

I would think a misfire would show up rich instead of lean ... But, depending on how bad the misfire is it might not show up at all. If anything, look for a slight RPM dip or flat spot and rich mix. the problem would be the sample rate while logging ... if you only see around 4 samples/sec and that probably wouldn't catch a misfire at crusing RPM.

 

Thats more along the lines of what I was thinking. A bit of a rich spot as a miss is dumping unburnt fuel.

 

Also, you'll likely see the rich spike somewhere in the next couple of cells past the RPM dip based on sensor position and latency. Good luck with the issue. Post up a log and maybe we can help diagnose.

 

With innovate products, a misfire would show as a lean spike in the AFR. Klaus has confirmed that over on the innovate forums.

 

I've logged misfires before and mostly they dont show up at all. Mine was boost blowing spark out due to plug gap / foul. They did not cause knock in my case.

 

That is odd. Did he explain why? Is it the difference between burnt ad unburnt fuel?

 

misfires never showed up as knock counts on my car.

 

Its because an O2 sensor measure oxygen content. A misfire would show up as a spike in the O2 concentration.

 

Yep, sure do, not saying they will show with slight miss but relative O2 increases with miss.

Wideband sensor will only read the O2 from combustion, not the amount of unburned gas, if no combustion occurred then more O2 is read even though raw gas is in there