My truck is having issues with not staying started. When I put it into drive it will stall but when its in park and Im on the gas it will be fine.
It has a 4.3 TBI.
Any suggestions??

 

Need a little more info (make model,etc) as it could be any number of things. Have you done the regular maint. on it? Filters, oil, plugs, etc.? Possible MAF sensor, bad catayltic convertor. Try taking it down to Autozone and have them check for DTC's. (Trouble codes)

 

Its an 89, 4.3 ltr. I just did plugs, wires, oil, distributor and fuel pump. There is no check engine light and my buddy took a computer to it and nothing came up. Could it be some kind of idle sensor??

 

take off your brake booster vaccume line and plug it with a big bolt, then put your foot on the brake and put it in gear (you will have no power assist, so push HARD). if it stays running then you need a brake booster. had the same problem on my 89 4.3l. when your engine loses all its vacuum it will stall.