Is this normal? I went froma very good tune to a lean tune just by switching from standard AC/Delco single wire to Denso 3 wire. My engine now goes into closed loop after 32 seconds, and the fuel is showing LEAN, very lean all of a sudden. When I drive it it is popping through the exhaust till it warms up to about 180 degrees water temp.
There are no vacuum leaks, plugs are new NGK TR55, DELTEQ ignition, 396 LT1 with XE 230/236 Comp Cams. No header leaks, everthing mechanical is SAT.
Any advice would be appreciated.
I can email a TTS file too, if you want to look at it.

 

If the old O2 wasn't functioning correctly, and now the new one is, then yes, things would change alot.

BTW, every once in a while, I've gotten a tank of gas that's done that.

 

I looked at some old data and the sensors were moving pretty quickly, voltages were adjusting quite a bit, with the old ones. I heard DENSO's can make you run real lean. But, regardless the old ones were functioning, when in closed loop. Since it wasnt going into closed loop before, and my tune was done to adjust the idle , so it would, then the new sensors went in and they obviously put the engine into closed loop, the ecm may be compensating too much as there is a huge difference on this when you go to closed loop.

 

Steve,

I had the same thing happen to me. I would trust the heated O2. Found that I needed to drop the O2 Idle Window Terms. If you have a cam with a good amount of overlap, you may want to do a search on NB v WB. Traxion talks about how he lowered the O2 voltages for idle. I did the same and motor seems to idle much better now. You may also want to look at the Prop Gain in Idle.

 

Thanks, I was thinking there was a mechanical issue/header leak etc at first, as it made no sense, as I thought that when it is in closed loop, it Was Closed Loop, wether it was heated or single wire.
Well, maybe my tuner can adjust the idle etc. Maybe I just need to go drive it and datalog all over again, since the O2's are different and the Ethanol gas may be a little change too.
My cam is a Comp Cmas 230/236 with 112*+2 . Lopes pretty good, and its an auto. But its a stroker so it helps a little
Also, did it make any difference elsewhere with in the driving? After idle?

 

Steve,

Is that a roller? And what are the advertised duration numbers. My cam is smaller, but I'm running a stock block 350 Xfire. However, my LCA is 108d. So overall, I have a 54d overlap. The thinking is that fresh air is passing by the NB, due to the overlap, and so ECM thinks its lean. Now my WB tells me its running pretty close to stoich. So I dropped the voltages for the O2 sensor at idle, so it "thinks" that the lean condition is within the the correct parameters. The BLM currently sits at around 129. Also, look at the Idle Prop Gain if your defintion has that. You may need to increase that particularly if the motor has been increased in displacement.

 

Heres the camshaft
Camshaft Specifications

 

Steve,

Looks like the overlap is about 64d.

 

So, due to the overlap, it is causing it to think its lean?