Under the hood I hear a slight sucking sound( with liquid being sucked in?) or its a squirting sound. Hard to tell with fan blowing and exhaust noise. I did the plenum fix. Im thinking maybe the o-rings are bad on injectors or I didnt seat them properly. Would that cause that sound? Or is there a vacuum leak possibly? i have looked everywhere under the hood for vacuum leak and cant find one( except broken CC vac line, CC still dont work after repairing it). Im lost on this one. replaced dist cap,rotor, wires, NGK v plugs, seafoam. And it still has a slight miss( random misfire OBDII reading) only when its cold. Any help would be greatly appreciated.

 

What plugs did you put in there?

Have you cleaned the throttle body?

Does the truck idle nicely? (correct RPM for temp.....)

Grab yourself a spray bottle full of water. Squirt a bit of water at places you suspect might be leaking... see if idle speed changes.

 

Yeah I did plenum fix. When I did that I cleaned the TB the inside of intake and all. Absolutly no oil in there at all. Also I did the TB mod ( shaving all the little walls down). I used NGK V-Power plugs. Now I just thought about this. Here is my screwup, I have Exact(name brand) plug wires, and a new bosch o2 sens. kinda low on money and didnt do much research. It shouldnt be a valvetrain problem because it only does it when its cold, right?

 

There is a TSB in the FAQ section for plug wire routing, might be something to look at. Could be the wires, could be the wire routing, could be the plugs....

Is is worse when warm, or cold? If warm... might be just the cheap O2 sensor. I would still spray around with some water (mist....), to check for obvious vacuum leaks.

 

I had an annoying sucking sound under the hood not too long ago and thought it was a vacuum leak. But after a bit of searching it turned out to be the IAC (idle air control) valve on the back of the throttle body was stuck open and sucking air when cold. I took it out and found carbon build up on the shaft the at extends into the TB. I sprayed it with some carb cleaner, wiped it down and put it back. Now when I start up when cold no sucking sound and it idles smoother. Hope this helps.

 

Thanks for the info. Ill check it out soon as I get time. I been working 7 10s . Dark when I get up, dark when I get home. No time for anything but work