my 99 360 5.9L truck is running real rich. it power surges at idle and It will stall out on me at lights while i drive. It blows out black smoke and the plugs are wet when i check them after it idles. IT origanaly had a 318 in it, but that wont do so i put the krate 360 in with a cam. I have changed the plugs, wires, distributor cap, and rotor. I took out my cat converter and have replaced the front O2 sensor and do have a simulator on the way for the second but i dont think that is causing it to run that rich. I took it to a stealership and my ignition timing is perfect and compression is at 115. My fuel pump is pumping at 53 psi so its real strong. I dont realy know what to think besides somthing in the computer? any suggestions? thanks.

 

I would check the plenum, the most common problem with these things. Look down your TB and if you see oil in the bottom, time to replace it. Also could be a blown head gasket. It MIGHT be some badly clogged injectors and they have to work really hard to get a good mixture, dumping way to much fuel in.

Welcome to DF

 

3 things come to mind beyond what you've fixed/replaced...

1st being the coil... it could be going bad but usually it's worse than what you have. I'm thinking weak spark on that. Plugs may not be gapped right, re-gap them down to .035~.040 max for stock ignition.

next would be the MAP sensor reading is incorrect. the map sensor is responsible for telling the pcm how much vacuum there is in the motor, if that's off, then your mixture could be off.

last is most likely the culpret is your fuel pressure... 53 is high but in spec. I bet you milage sucks big time. I think you can swap the fuel pressure regulator off the pump, check with the dealer on that one. If you think about it... higher pressure means more fuel at each time the injector opens causing it to run rich... drop the pressure and you milage goes up and your mixture goes lean

I would start with the regulator...

 

thanks for the responses.. I will check those out. Heres somthing else too.... not exactly sure if my wording is right but.. the programer is telling me that the degrees to my ignition is low. 1 degree at idle where it should be siting at 40 or so. did that make any sense? Im thinking a computer issue but i dont really know. any thoughts on that?

 

Still havent figured it out yet.... been too long since ive drivin it... gettin homesick. No oil pooling in Tb and my antifreeze never goes low to be my head gasket.... Mechanic wants to replace my computer and he's payin for it so i said go ahead hahaha but do you think that will help? its the surging at idle thats throwing me off from 400rpm (or dyinig) to 1200-1400. oh well i guess i will let him deal with it and see.