well like the title says my 92 rs 25th anniversary has a high performance 350 5.7L engine in it,i used the old intake,tbi,exhaust manifolds and the same alt.,water pump,ect,ect it has run great for about 3 years now,recently i took a 200 mile drive to see my folks,the car ran better then ever,i returned home 2 days later with no issues,next morning i got up to go to work and my car cranked with no start,being that i make my living working on cars i figured screw it i'll mess with it later and got a ride from a friend(was late for work),well when i got home i checked to make sure i didnt fry any wires or anything and everything looked fine,tried to start,it just cranked.....so i treated it like a carb and pumped the gas,cranked with no start,so i tried pumping it while cranking and it fired up on the first crank so i reved the hell out of it thinking maybe carbon build up and when i let off the gas the rpms dropped to about 200 for a minute then it died,it fires up and runs fine as long as i hold the throttle partially open at all times and it runs really rich(no smoke but very strong smell) i was wondering what everyone thought the problem could be?,i thought fuel pump(its the o.e. pump) but usually that means no fuel to the engine,any ideas would be great thank you.

 

A bad coolant temp sensor.
High fuel pressure.
Bad ecm grounds.

 

hello I don't post on here much but I have an 89 tbi 305 that has been beating the crap out of me lately with a similar problem I bought the car not running, rebuilt the stock 305 (had no oil pressure) but I could not and still cant get the engine to idle unless I hold the throttle like the original poster. I've done everything I can think, I have no service light and I was wondering where I could check the ecm grounds at? if you find your solution I would love to know.

 

Ecm grounds are at the back of the pass. side head & may have some at the t stat housing studs.