Been lurking here for a while as I've been doing TBI tuning on/off over the years. Searched a bunch on this forum, but haven't seen other treads with the same or similar issue.
Basic problem: Not running as rich as I'd like at idle when cold. Results in a stall if driver or reverse are engaged shortly after startup. Also the crank time is extended, but one problem at a time. Changes to the target AFR in the tune don't seem to have the expected effect. Idles fine warm, at the desired AFR (13:1). Cold it also tries to idle at 13.5-14:1 and does so poorly. I'd like to get that down into the 11:1 range when warming up, but changing the Open Loop AFR vs Temp table doesn't impact Actual AFR. I've tried lowering that table by 2 across the board and AFR doesn't appreciably change. This is after the choke tables should be out of the picture (idling for more than a couple minutes). Has this issue until about 70C coolant temp where the engine is warm enough it'll idle okay at 13:1.
Engine info: 355 w/ vortec heads, 9.5:1 CR, performer RPM intake manifold, carb to tbi adaper, headers, dual exhaust, 212/222 hydraulic flat tappet cam. GM 80 lb/hr injectors, stock fuel pressure.
I'm using a stand alone WB02 (LM-1) and watching it as I'm connected with an Ostrich 2.0 and ALDL using TunerProRT. I've used the WB02 recently on a carbed vehicle and it seems accurate (I free air calibrate when I move it between vehicles, engine behavior matches expectations when AFR is too rich/lean).
Latest bin and log file from cool idle (14C) where it is running leaner than desired attached. I'm thinking there must be something overriding the target AFR tables, but haven't found anything obvious yet. If I heavily skew the main VE map in the idle region, it will richen up some and idle better. However, that produces an overly rich idle when warm. Running exclusively in open loop (255 deg C enable value for closed loop).
Any suggestions would be appreciated!
Reply With Quote
Bookmarks