So I'll post my latest dilemma from another thread here before I get to my main question, maybe it can shed some light on my problem. Figured this would be the best sub forum to figure this out the rest of the way

https://www.thirdgen.org/forums/tech...ackfiring.html

Long story short, I swapped what I was told is an L69 into my car last year. I'm not positive but the casting number on the carb was correct so as far as I can tell, that's what I've got. Problem is, I didn't want to keep the carb and have to bypass the OBD system so I modified the TBI unit intake to fit the l69. Now from my last post, after I fixed everything, I just can't get it quite dialed in. I'm not sure where to set the timing mainly. It runs better than ever after I replaced the parts in my previous thread, but I still get some slight missing at idle, and it seems to idle VERY low, although I can't tell where snce my tach is broke. I get a code 13 every now and again on the highway, but I doubt the 02 sensor would cause a miss at idle, if at all. I tried setting the timing at 6* and bumped it down in 2* increments until it would hold as steady of an idle as possible in gear without stalling. It's now at 0* and if I go any lower before reconnecting the EST wire it'll stall just setting the base timing. Any ideas? I know the ECM I have is looking for a completely different cam at the very least. Should I get my PROM tuned to emulate the L69 one with added parameters for the TBI? I'm new at this side of things so any help would be appreciated.

 

Well I drove about 15 miles mixed highway city with the ALDL grounded and it's not going into closed loop for more than maybe 10 seconds, and that's only just after i give it gas or let off the gas, although the light flashes seem to indicate a perfectly stoichiometric mix unless it's just a base table and always open loop, I'm not sure how the ECM works like that. Anyway, I checked the 02 sensor again, and i guess it is bad, it gives a higher reading as temp goes up but it stays at that voltage, there's no swing, unless it's too fast for my DMM to see, but it's pretty constant at about .9v when warm. So considering everything else I've replaced, it would be the 02 and CTS preventing closed loop operation correct? I dialed in the idle and it's perfect now so I may have solved my own problem there, but i'm still interested in ideas for tuning for optimal performance with this combo if anybody would like to help me out.

 

If the o2 is not swinging it is either poisoned or faulty or installed in headers and not reaching to 5-600f and you would need to install a heated o2.

 

Definitely requires tuning. If anything, with the exception of x-fire set ups, all TBI engines came with swirl port heads. With that the spark advance is going to be too low for use with the L69 heads.

RBob.

 

Is that something I can tune into the PROM? I was thinking about getting a custom tuned one if it would help get this dialed in better.

 

IIRC the crossfire uses a 82s181 prom