Yes, I did search, and came up with MonteC's thread about his truck running rough and it ended up being the pre-cat O2.

Well, in my case, my truck will sometimes make this odd sucking noise. More often than anything, it's when I accelerate that this noise is made, but occasionally at idle, I can hear it as well. Here lately, I hear it when the truck's tranny is acting up, and as the RPMs drop from it redlining (or close to redlining), the noise is made all the way down the range. The truck seems to be lacking in power when I hear the noise and doesn't want to accellerate that well. But whenever I don't hear it, it runs great.

I could almost agree that it is the O2 giving bad readings, causing the fuel/air mixture to be off and opening up the IAC, but the whole tranny part of it confuses me a bit.

So what do you guys think?

By the way.. the truck has 238k on it, so I'm sure the 02 should be changed soon anyway. I haven't checked for a plenum leak, but I don't think that's the problem. My dad swears up and down that it's the 14x3 setup, but it's not all the time that the noise is made, and thats why I rule that out. Thanks for any help.

 

vaccum leak?

 

Wouldn't a vacuum leak be more constant?

 

maybe, maybe not.......can you hear where its coming from?

 

Usually I hear it only on the road, and when it happens while I'm idling I'm usually in a rush, so I don't have the opportunity to inspect under the hood. And under the hood is the only good description I have of where it's coming from.

 

Pickin up wheels and tires bblw

 

What kind of air cleaner are you running? If you are still running the stock or the K&N, it is real easy to get them crooked on the throttle body, and you could be hearing air being sucked in through there.

 

I've noticed mine do this occasionally at idle too. It acts like it's trying to idle around 700 rpm instead of around 900. Never does it at part throttle. It will do this under the following conditions:

* Engine fully warmed up.
* Engine at idle for a few minutes.
* High ambient temperature.
* A/C on Max

It has to be something related to engine load and temp that the computer can't compensate for. If I blip the throttle, it goes away temporarily. I'm not too worried about it now because it's intermittent and hasn't thrown any codes yet.

 

Mine does this too. It is just the Air cleaner sucking in large amounts of air like it should.

 

Yea but its not really consistent which has me wondering