truck wont idle all of a sudden

[donw1986]

1986 chevy c 10 with 305 4 barel e4me calif model has been running fine and all a sudden today it started to not idle it idles fine until it gets warm then just dies starts back up and runs as long as you hold the pedal down carb was rebuilt a few months ago its getting gas so not sure what the problem is i know my starter is going out but that shouldnt have anything to do with it i got a code 34 which is the map sensor but as long as the rpms are high it goes away

[tucsonjwt]

Vacuum leak?

[donw1986]

okay i will look for that thanks

[donw1986]

Okay no vacume leak but if i unplug the mixture control solenoid it idles and runs fine but check engine light stays on with it unplugged

[f.monroe]

I would check the EGR valve. If it sticks open it will cause a rough idle as well as other issues.

[beamn7]

Check the vacuum line to the map (baro) sensor. They used to use a black plastic line that was prone to cracking and leaking. It connects to the passenger side rear manifold vacuum source on the carb. Seen the line to the sensor full of fuel before which would sometimes happen during a full throttle application. Usually only on ones that the line came out and dropped down low before heading up to the sensor on the firewall. Easy fix is to "T" the sensor into the manifold vacuum source port on the manifold behind the carb and plug the port on the carb. For a quick check, unplug the vacuum line to the MAP (baro) and the carb, and then blow through it to make sure you don't have any fuel in there. Then plug one end and blow to see if you have a leak in the hose.

Could be a failed MAP (baro) sensor also. If the ecm looses the MAP (baro) signal the mixture control solenoid pulls the metering rods down causing a lean condition via the idle air bleed valve and the vehicle stalls at idle. Unplugging it like you did causes the mixture control solenoid to stay in the "rich" position which will allow it to run / idle. The 85-86 CA emission trucks with E4ME carbs use what looks like a MAP but is actually a baro sensor and works opposite of a MAP. If you plug a standard MAP in (plug is the same) the truck will not run properly either...

Hope this helps.