85 lesabre engine problems.

I JUST PUT A NEW 307 OLDS MOTOR IN AND I CAN't get the motor to run right. the motor will run at a high idle but then when it kicks itself down it idles ruff like a misfire or chokes it self out. also has a new carb, can anyone help? :confused:

I would be looking to the distrubutor. The motor itself is new, not off of a car? It's also possilbe the choke isn't right.

The Motor Is A Ac Delco Rebuild. W/ A New Carb. I Have Just Checked The Timing And It Is Correct. The Motor Will Crank Over Like It Wants To Start But Then It Either Back Pressures Fuel Out Of The Carb Or Shoots A Flame Out. I Had It Running Before At A High Idle And Ran Farely Smooth Till The Car Warmed Up. Runs Will Rough At Low Idle And Or Chokes And Or Shuts Itself Out. Car Is Computer Controlled And Has Sat For About A 1 1/2 Before The Guy Ask Me To Put A Motor In The Car. I Am Stumped With This Problem . Could It Be The Computer ?

Something similar happened to me. It would start and run at a high idle, and die. Hold the throttle open, and it would keep going, but sounded funny. let go of the throttle: instant death, won't start. I spent a whole month sitting out in my car 8 hours a day, testing sensor voltages, replacing the computer, checking the coils, ect. I finally noticed that the spring connection in the exhaust kept on releasing. So, I tightened it thinking that was the problem. After that, the thing wouldn't start. I took it off, and the car fired right up. So I drove it around with the exhaust off to make sure that was the problem. It turned out that the catylitic converter was plugged up, which sounds as if it is a similar case here.
The car sat for that long, so something may have crawled in the exhaust and died, or maybe the catylitic converter plugged. What I would do is disconnect the exhaust right in front of the catylitic converter(s) and see if it runs better then. Be careful, as the hot exhaust can be damaging.

[you said something about a design flaw causing weak psi. the car will run as long as you hold the key. it has a new fuel pump on it, mechanical. what was the fix for the weak psi? it now is back pressuring or spitting fuel up through the carb.