91 floods out

My old plow truck is giving me fits, it idles great, put it in gear it floods out, put in park or neutral rev up and it clears back out, the temp sensor reads 85 degrees c on my scanner, has code 33, but i attribute that to flooding out causing erratic rpm, it lopes, I have replaced the spark plugs, wire cap and rotor, o2 sensor and map sensor, flushed and filled cooling system,I was advised a dirty cooling system can cause residule voltage, I also have switched throttle bodies and checked the fuel pressure and it is in specs, any thoughts on what I am missing? Also when put in reverse or drive it will run fine, but as soon as you crack the throttle it starts flooding out, the MAP sensor voltage at idle is 1.08 and the kpp is 31 and when it is flooding out it is 3.94 volts and 83 kpp
any insight would be great

My old plow truck is giving me fits, it idles great, put it in gear it floods out, put in park or neutral rev up and it clears back out, the temp sensor reads 85 degrees c on my scanner, has code 33, but i attribute that to flooding out causing erratic rpm, it lopes, I have replaced the spark plugs, wire cap and rotor, o2 sensor and map sensor, flushed and filled cooling system,I was advised a dirty cooling system can cause residule voltage, I also have switched throttle bodies and checked the fuel pressure and it is in specs, any thoughts on what I am missing? Also when put in reverse or drive it will run fine, but as soon as you crack the throttle it starts flooding out, the MAP sensor voltage at idle is 1.08 and the kpp is 31 and when it is flooding out it is 3.94 volts and 83 kpp
any insight would be great

you think the intake manifold has a crack. exhaust gas is getting into the engine intake .

at idle the MAP a little over 1 volt is good , 4 volts is WOT or very low vacuum....

I'd check the coolant temp sensor and the wires to it as well as the IAC and EGR valves. Any one or combination thereof can cause poor idle and stalling in gear.

I'd check the coolant temp sensor and the wires to it as well as the IAC and EGR valves. Any one or combination thereof can cause poor idle and stalling in gear.

if the EGR spring is weak it is very possible this is his problem. this would cause the map voltage to shoot up ..

Well, had an opportunity to mess with the truck today, unhooked vacuum line to egr valve and plugged off, runs great, now need to deturmine what is causing the problem, bad egr valve or something else, since this activated a check engine light
Thank you for your thoughts so far, gave me something else to check

Well, had an opportunity to mess with the truck today, unhooked vacuum line to egr valve and plugged off, runs great, now need to deturmine what is causing the problem, bad egr valve or something else, since this activated a check engine light
Thank you for your thoughts so far, gave me something else to check

egr valves don't last forever. the spring and diaphram do fail over time by small amounts . if the spring is weak the EGR opens too much. If the diaphram has a hole in it you get a large vac leak when the EGR is commanded to operate.

replace it ..