hello folks as im sure you all can see im fairly new to the sight. i have had my 1988 gmc truck for about 2 years now bought it used and its ran like new up until the other day when it just stalled out on me riding down the road. now normally i would say fuel pump quit but i had a friend of mine turn the truck over while i looked into the throttle body and it seems like it was getting plenty of fuel. so again i tried to start it and it started but stalled immediatly. so i unplugged the map sensor and the truck stayed running but runs real rough and stalls every time i hit the brake. i replaced the computer but did not replace4 the prom or calpak(i used the old ones) because i thought that was the problem so i plugged the mapensor back in and tried to start the truck again it started but stalled immediatly. unplugged the map sensor and starts but runs real rough so as you all can tell im back to square one. my question is has anybody on this site had this problem before or can anybody tell me the steps to diagnose this problem? or if you think you know what the problem is please tell me? thanx for all your help. Steve

 

Does it have a CEL (Check Engine Light) on? Have you scanned the computer for codes? My guess is its a bad M.A.P sensor..........as far as testing....you have done that already......change the M.A.P sensor

 

changed the map sensor today still doing the same thing. check engine light is on. havent scanned it for codes yet guess that the next step.