So I did a 3rd gear pull today both with Logworks 2 and Evoscan. Both show exactly the same result (minus my graph scale all screwed up on evoscan). As the pull starts my AFRs slowly decrease then at about the same spot they go through the roof? I can't be running that lean or I would have no engine left at this point. I re-did the free air cal today twice and I get fine numbers at idle and low power.

Does this seem like an exhaust leak issue? Or do I have a calibration problem or something else?





I can provide the full logs if need bee but I thought this might be enough info.

 

BTT for the morning crowd

 

That looks like a misfire or a bad power connection. The log will show lean like that when you have a misfire because when the fuel is not burned and the O2 is not used, that is what your LM1 is looking at. I ended up connecting directly to the battery because I couldn’t get clean power from the cigarette lighter.

 

that's what my sensors do when they go bad.. how old is it and are you running leaded race fuel?

 

Both of these are what the folks at innovative said too. IF I HAD to guess I would bet its a bad sensor. I say this because, though it is not old, I did a **** poor job marking the hole in my pipe on my old exhaust and it was just a bit off center so it was a tight fit in there between the pipe and the tranny tunnel, so under certain loads you could hear it rattling against the floor boards - not good, I shoulda pulled it then. Its mounted fine now, but it was that way for a while AND I have had it in and out a lot, so the ceramic COULD be cracked. And no race fuel.

I have a hard time understanding why a missfire would show lean and not show rich? I don't understand your explanation, isn't the sensor always used and wouldn't it sniff out the fuel and report rich?

I do have a second set of plugs in my garage I could swap in, but a missfire I would deffinately feel I would think. It should run pretty crappy if there is a missfire, but it pulls smooth and consistent. But its something to look at I guess.

I am installing a buddies wideband this weekend so maybe I will swap his sensor in real quick on mine to "test" it first and see what happens.


What do you guys replace them with? You buy the whole sensor and plug from innovative or do you just buy a sensor local and slice the wires?

Thanks!

 

No, the sensor measures oxygen not fuel. If the fuel is not burned (misfire) the oxygen in the air is not used and will show lean. More fuel = more O2 used, less fuel = less O2 used. Misfire won't use any O2.

I'm leaning toward bad 12-V supply.

Get the sensor for a VW part #021-906-262-B or Bosch # BS 17014 you should be able to get them for about $35 if you look around.

 

OK that makes perfect sense! I was a bit confused there. Anyway, if I have time tonight I'llswap plugs, if not for sure this weekend I will test my buddy's wideband in there before I dump the cash on a new one.

 

^^ smart man

 

bump 4 u

 

Even smarter if anyone is looking for one, the advance auto parts website lists the replacement wideband for $47! In store is $98, but I got them to match it. I didn't want to buy so soon but I wanted to do that before the price went back up. So, worst case now I have a $50 spare.

Should be here tomorrow.

http://www.partsamerica.com/ProductD...pe=291&PTSet=A


I thought about just taking the one out of my wife's VW, but I don't think that would go over to well!

 

wow...i actuallly might get one of those instead of paying double of that when i need one in future..thanks for the link!

 

Not to nitpick, but on the rich side of stoichiometric, it is the absense of hydrocarbons that convinces the sensor that the parcel is lean (infinite lambda) for a miss fire. This is the same reason that you get a lean shift near stoichiometric when you are downstream of a cat. The CAT removes hydrocarbons, hence the shift.

-jjf

 

O2 sensor doesn't measure O2?

 

I'm sorry, I explained that badly. See here:

http://www.megamanual.com/PWC/LSU4.htm

For a better explanation. The point I was trying to get at was that the sensor actually works differently on each side of stoich. That is, the chemistry actually changes.

-jjf

 

Didn't have a chance to play with mine this weekend. Ran out of time. But we got a lot done to another Evo. I'll do it one day this week and post up what happens for future reference