OK, I have my fuel curve pretty much nailed down now - the BLM is between 132 and 124 everywhere, except for at idle. No matter what I do the BLM at idle is always 150+, usually 160. Does the ECM idle the car lean on purpose to save gas, or am I really running that lean? Any help would be appreciated.

BTW, I'm running the $6E code.

------------------
Black 88 GTA L98
261 RWHP, 345 RWTQ
13.406 @ 103.72 MPH
ZZ4 bottom end, Edelbrock 6085 heads, LT4 HOT cam, GMPP 1.6 RR's, ported stock TPI, SLP 1 3/4" headers, no cat, Dynomax cat-back, Stock PROM
E.T.F.A Member #11

 

I was under the impression that you want 128 at idle with the INT bouncing around. Then you want to adjust for light cruise (slow moving throttle) and still want 128. Then under WOT you want to do some major plug cuts and test and tune with a performance meter of some sort. As for the BLM going 150+, that doesn't sound right. I don't know about your ecm but my eprom for the 8746 (TBI) has a 150 max BLM so it couldn't go above it if it tried. Some guys lock the BLM and do nothing but plug cuts, it's usually the best way of getting a good VE table.
Back to your question, no, 150 BLM is WAY too high, you need to correct your BPW value for a good 128 BLM idle. Grumpy should give you a better reply so wait for his opinion.

------------------
, Jon (350 TBI!)
91 Red My website

 

Hmm, that's weird. Because I've been able to adjust down to around 128 from 150 at other points in the fuel curve by only adjusting 1-2%. But I've increased it 3% at idle and nothing. Also, the max BLM for my PROM is 160.

 

I'm having the exact same problem with an 88 Iroc w/ the $6E. I've got it between 126-132 everywhere, except idle. It will go into closed loop, and slowly climb towards 160BLM, and the integrator does not move. As soon as you give it just a little bit of load, it jumps to 128. The only thing I can think of, is the calibration is screwed up from having the screens removed, and having the MAF relocated because of the supercharger.

 

Yep, removing the screens (and fins) will throw off the MAF calibration and very low airflows. I had the same problem with my old internally-stock 305. You'll need to change some of the values in the first MAF table to correct for this. To do so, you need to find out the airflow value(s) where it's running lean.

Since your BLM is at least 160 at idle, I'd bump up those values by 25%, and maybe the values immediately above and below by maybe 10%. A previous thread describing this in great detail is at:

https://www.thirdgen.org/messgboard/...ML/000132.html


------------------
Greg Westphal
'87 IROC 355TPI/A4

 

Sweet, thanks Greg. That should help a lot. I didn't even think about having the screens out affecting it.

 

A vacuum leak will do exactly what you you describe. Take it from the been there done that guy.
Jason

 

Might try adding some injector timing correction vs Battery Voltage. Try going up 5-7 hex values at and around 14.2v and lower.