thewilldog

Hi, my LS1 has about 110,000 miles on it. Last week the check engine light came on. I got it checked and the shop told me that I have an air leak and that it was no big deal. Then they tried to sell me every service under the sun (brake flush, radiator flush, transmission flush, fuel injector cleaning, new fuel filter, new pads, etc. about $1200 worth of crap ) They said the fuel injector cleaning *might* help (not fix) the air leak. I told them no thanks.

Anyway, the light goes on an off now. It's off more then it's on. Sometimes I notice the car idles a little rough, I'm assuming that's the air leak. Occasionally I think I can actually hear the leak. Yesterday afternoon it was really loud, like the sound of a slightly opened cylinder of compressed air coming from the engine block (I couldn't really isolate it.) I tried to hear it again this morning but it wasn't as loud.

So I'm wondering if there's anything I can do to isolate the air leak. I don't know where any of the vacuum lines are located or even what they look like. Is there a reference somewhere on line?

2001NBMZ28

Secondary air leak, vacuum leak? Do you remember the code?

Kraest

Does the car run differently when it happens? If not, it's not a main vaccuum leak anywhere. Did you look at the air pump? That will throw a code, but not cause your car to run differently.

Honestly, you need to simply drive to Autozone and get the car scanned to see what code it is, then come back with the code.

Me>you

Hook ,snip, leak is...

Please quit the posts like this. Some of the folks asking questions are tyros and might just try it and ruin their motor.

Me>you

sure hope he's not really doing that right now...Pretty much the worst advice ever given?

johnny6

He's on the way to PA right now looking for a driver of an 83 citation with a 572.

Me>you

LOL..good luck with that...I'm in AZ and on my private jet...

thewilldog

Hello again,

I went to Autozone today. The codes were P0171 and P0174 twice ( left and right bank). The hand held computer said engine was running lean. People behind the desk said it could be:

• O2 sensor malfunction
• Mass Air Flow sensor malfunction
• Dirty fuel injection system
• Air leak (loose vacuum hose or something along those lines)
• Dirty Fuel filter

One of the guys said that since both banks were showing lean, it probably wasn't an O2 sensor. I had the fuel filter replaced in Nov 2006, about 30k miles ago. Unless that's dirty again, I'm left with MAS sensor, air leak, or clogged fuel injectors. I've tried a couple bottles of that gum-out type fuel additive but it hasn't helped. Is there anything else I can do to narrow this down? I don't know enough about the air system to know how to check it. I've taken some pics of the engine bay (yes it's dirty). Can someone direct me where to look to check out the air hoses?

http://photo.ringo.com/258/258847496O001212930.jpg
http://photo.ringo.com/258/258847268O805896022.jpg
http://photo.ringo.com/258/258847156O026695835.jpg

The car started rough for the first time this morning, I think it's getting worse.

2001NBMZ28

Thinking P0171 and P0174 simultaneously points towards a vacuum leak, PCV valve/hoses or fuel delivery issue since you're lean on both banks. Don't think it's the 02's either but should be scanned. You might find some ideas here: www.gearchatter.com/viewtopic9154.php Another idea is buy some spray cleaner and clean the MAF yourself. Might be time to take it to another shop and have them do a proper diagnosis - test fuel pressure, injector flow test, etc. if you can't get it resolved yourself.

Marc 85Z28

Thoroughly inspect the PCV tubing for leaks. Nearly every LS1 lean code I've seen comes from a deteriorated rubber connection on the PCV tubing.

This problem is so common a simple seach on this LS1 tech board for P0171 or P0174 would have yielded multiple results, all confirming the PCV tubing as the cause.

thewilldog

One additional piece of evidence: I took a little video of the hissing sound under the hood when the engine is running. I wasn't sure if I could hear the hiss over the sound of the motor. Turns out that's all you can hear. Check it out.

http://www.youtube.com/watch?v=9TQrd57nahA

Marc 85Z28

That's a vacuum leak just like I said! Look at the PCV tube! I think I can see a huge hole even it that video.

Kraest

Ya think?

thewilldog

Hello again, thanks for the response. I took a second look at the passenger side of the engine (that's where I was when I shot the video). I didn't notice and glaring holes in any tubes. I'm not sure I'm looking at the right spot. Can you confirm that PCV tube is the one in this pic that I've noted with five red dashes? I'm not at all familiar with the vacuum tubes and most other engine lines.

http://photo.ringo.com/259/259168531O932638143.jpg

Marc 85Z28

That's the PCV breather hose. You want to look at the actual PCV hose itself, which is the larger diameter hose located just below that one. Judging by the video you posted, pay particular attention to the area on that PCV hose that is right next to where the hose you highlighted meets the valve cover. Look for either a hole, a tear, collapsing, or very soft deteriorated rubber.