Ive been doing a tbi conversion to my 82 malibu wagon

89 305 caprice harness
89 305 caprice computer with 89 350(police) chip from hypertech and 2004r trans from caprice
88 chevy truck 350 motor, Police injectors, tbi, distributer,knock sensor 12 psi fuel pressure, 0 degrees timing, headers, dual exhaust with xpipe, 4 wire o2 sensor hooked up.

Today i got the 350 chip pluged in and the car runs really nice other then when it warms up if i get on the gas lightly it misses and sputters and as soon as i let of the gas it smooths out. but when i push on the throttle more then 1/8 way it runs great. It just acts up when im on it lightly weather im driving or not.

Thanks for any help.

 

Anybody?

Any reasonable guess(sp?), Im completely out of ideas.

 

What cam are you using?

And have you tried temporarily using the factory 350 copcar chip? IMO the Hypertech chip is one of your problems.

 

Well i dont have a stock 350 prom for in the computer. It was the 305 computer that i put a 350 prom into. It is a 746 ecm which is the same for 305 and 350 caprices.

and it is a stock 30over rebuild i was thinking maybe one of the sensors is bad but i dont have a clue which one to start with. I have double and triple checked my wiring with many different diagrams.

 

Come on guys almost 100 veiws and no one has any idea. It only runs funny in closed lood mode when im on the gas less than 1/4 of the way.

 

do you have a ce light? can do do a diagnostic check at the aldl connection?

consider datalogging.

 

Well found out that 12-13psi is to high of a fuel pressure (89 caprice calls for 11psi and 88-89 truck calls for 9-11psi). My spark plugs are black and i could smell it running rich.

But i have another problem when i adjust my feul pressure regulator it was at 13.5 and i got it down to 12 and it runs a little better. I cut the spring a liitle but i cant get it under 12psi at idle. If i hit the gas it will go to 10 so i think the regulator is set to 10 but my fuel pump might be pushing to much.
I am running a http://store.summitracing.com/partdetail.asp?autofilter=1∂=CRT%2DP5001&N=307763+115&autoview=sku

anyone know if there is a way to fix this or do i need to buy somekind of external regulator and with ones do you reccomend.

And 3/8 feed and 5/16 return line is an ok size right?

 

consider buying a FP spring for the truck series and installing it?
other option is to go to a chip that has the BPW corrected for the lower FP.

 

I have a spring for a truck but lowest i can get the fuel pressure to is 13.5 with it.

What is BPW?

 

base pulse constant. determined by a formula : cid vs inj size vs fuel pressure. tells ECU what you have under hood...so as to allow somewhat close basis for fueling.

 

Yeah when I put a 350 in the RS I used stock 350 injectors and a hypertech chip. It ran poorly with the hypertech chip when warming up. It started and ran great, and ran fine when hot, but in between it would buck and surge and die.