Last year i replaced my high pressure fuel pump with a cheap one (was in a bind). Now its really loud. I have a cherrybomb on my truck and i hear the whinning over that. Yes its that loud. Also i removed my fuel res/tank switch for a while, i replaced it yesterday. Ive been having a really bad misfire at the low rpm range and at idle. Im running lean as well. Could this be because of this cheap and possibly bad fuel pump? Also i replaced my plenum a few months ago and it is full of carbon buildup, could that be the problem instead?

 

Need to do a fuel pressure test in order to come to any real conclusions.

If you're wiping out fuel pumps you may have crud in the tank.

 

I will do a fuel pressure test today. Do i just turn the ignition on and test it when the fuel pump primes or during operation?

 

You get the prime readings, then the readings while running. Have to rev the engine to make sure it doesn't drop off with rpm, a bad pump can often supply enough pressure at idle and not be able to support loads.

 

i figured it out. it was my darn dizzy rotor. it was all corroded so i took my knife to it and cleaned it up. fired right up and no misfire. every time ive had this misfire ive always thought it was a vacuum leak so when i would change my plenum gasket i would remove the cap and rotor to make more room and in the process clean off the cap and rotor with my knife. when i would start it then she would run great and all along i thought it was my plenum gasket. cant believe something as simple as a corroded rotor can cause this big of an issue. and it would get worse over time

 

Yeah, they corrode pretty good easy.
I clean mine off every oil change.

 

Mine does it after a month. Mu timing is off so maybe thats the problem...........