Mods done - LT1 cam, carb intake/adapter, headers, 416 heads ported/polished 1.6 intake 1.5 exhaust valves, gutted cat. Got her put back together. Haven't touched TBI unit - it's stock.

Had to set timing to 10* BTDC to even get it to run, but ran bad, backfired through TBI, no power, died at redlight. Set it at 12* - little better. Set it at 14* - better still - no backfire, no dying. Figured mark on balancer is off, so set timing by maximum vacuum on manifold - runs better still. BUT - I have this erratic idle - like the computer is adjusting for something, then back again - and it's throughout throttle. At stop, it wants to die. When at steady speed, any speed, it jerks enough to feel a slight slack in the U-joints. EGR is working, I can feel the diaphram move under throttle. Replaced MAP sensor - it doesn't seem to change anything, whether plugged up or disconnected, old one or new one. Cleaned IAC.

I don't know where to start - I wasn't looking to win any race, just run decent and get HP to a fun level. Would fuel pressure problem make surges like this? I haven't checked any of that yet - I figured that would remain constant, whether good or bad. I know most tune custom chips for maximum performance - but get decent results without - I'm not ready to play with chips just yet. Any ideas greatly appreciated.

 

You're having computer freak out problems like I did when I installed my 350 H.O. crate motor. My timing is way advanced, I think 12btc or something. I ran the stock 305 TBI chip and it ran like crap, then I put in my 305 JET stage 2 chip and it ran a little better (driveable) till my 350 prom came in from tbichips.com

You might go to tbichips.com and e-mail him with what you have done and try and get him to burn you a custom chip.

 

yeah, you def. need some computer tuning.

at the least, get a scanning tool, and adjust yoru fuel pressure.

 

Chip tuning would be the best idea. Or you could try a vafpr but it wont be as good. Mine did the same stuff till I got a chip in it.

 

When you set the timing are unhooking the ESC wire? I ran 8 degrees of advance when I was running a ZZ4 camed 305 TBI.

 

Yep, I disconnected the EST wire. I'm thinking the balancer slipped. If it wasn't for slippage on those things, no one would ever need a new one.

 

Are you sure the timing marks on the cam and crank were lined up? Sounds like somethings mechanicaly off. Back firing through the TBI doesnt sound like a chip isue. It only takes one badly adjusted lifter to make the motor run like crap. That cam will run ok on a stock chip. It will definantly run rich, but it will run strong with about 6-8* advance on the timing.(if everything else is correct)

Dont get me wrong. Chip tuning is a good thing, even on a stock motor. But if its running that bad, chip tuning alone aint gona fix it.