I am in the process of tuning my LB9 running SUAJPV4, Cam is a comp 266H-r14 and ive got TFS 175 heads and shorty headers. When I first fired this thing the other day after completing all the mods I was having a problem where it wouldn't go into closed loop at idle, sometimes it would take 10 minutes of idling before the crosses would start moving and it would stay in closed loop. So i figured maybe the headers were to blame and I got a universal 3 wire (standard motor products) and wired it up, After starting it went into closed loop after only about 30secs and the BLM's were alot more realistic to what the wideband was telling me. The problem is that after idling for about 10 minutes the engine started to loadup, The wideband dropped into the 10's and when i looked at the o2 mv's in tunerproRT it was showing 70mv. After about 30secs of this the check engine light came on and it went open loop (and it cleaned right up and went to about 13:1 in the wideband) i scanned it the next day and there were no stored codes. If i let it cool down for an hour or so it goes back to reading normal o2 values again I've seen it happen 3 times now and its the same each time, First it st starts to get lazy and the cross counts slow down, Then the mv's start dropping and the engine gets super rich. Is it possible that it's overheating? It's located about 2 inches from the header flange. Or maybe it's just fauly. Has anyone else seen one wig out like this?

 

Sounds like the 100 Kpa SA that is used from the main spark table during cold startup is a good value. Once it warms up the SA is taken from the closed thottle table (unless it is disabled by the selection bit) or is using the main table value (If the closed throttle table is disabled).
Confirm your SA is not dropping once it gets warm causing the richness.

 

I caught the 'Event' in a datalog today, It looks like the timing stays more or less the same while it's happening so i don't think that is it. Hopefully someone can take a look and see something that i don't, This ones a bit of a headscratcher for me.

 

What program was that log made with?
Don't reconize by anything I have tried.

 

I used tunerpro rt, just checked and it's v4.13. I see it's a little out of date maybe that's the problem. If you do get a look at it the glitch occurs at about 400seconds engine runtime.

 

I'm watching it now but engine run time is messed up, how many samples into it does it happen?

Nevermind, what mask is that?

 

it's 8D based on suajpv4

 

I'd guess you got a bad O2 sensor with a leaking compression seal between the sensor and the case. I had a bad batch of those once - they'd fill the case with exhaust gas slowly, and the differential O2 would go to nothing and the voltage would drop. The only cure was a long deceleration, or drill a hole into the back case to refresh the oxygen.

 

That's interesting and it would explain my problem. I was leaning toward just getting a new one it just sucks cause they are not cheap and i doubt they will exchange it.

 

Use a one wire, only $17.

 

That is true but this whole thing started because my old one wire wasn't letting me go into closed loop at idle.

 

I just thought I'd update on this, I swapped in a new NTK 3 wire yesterday and the problems went away so it was a bad o2 sensor right out of the box. thx

 

Ooops, moved this post to the proper forum board - https://www.thirdgen.org/forums/tech...ml#post4213232


sorry to disturb anyone.