So this is a problem ive had for a few YEARS now. I never drive the car too much, cause I ride the bike everywhere.

The car is throwing a Code 44 = Left o2 sensor running lean.

Changed both O2's and switched them, same code....

This means something is causing my O2 to run lean, such as a vacuum leak before the o2, correct?

I replaced the left(driver) side header gasket twice, no change. Ive taken off the intake and redone the gasket once, no change.

Where else could I be getting a vacuum leak on there? I dont know how to check vacuum, other than visually inspecting the hoses on that side(which I have).

I do have an LT1 Scanmaster, and have looked at all the numbers. From the page that tells you what they mean, I have gotten that there IS a possible vacuum leak, due to my IAC numbers being much lower than normal.

"At idle, you should see roughly "20" to "40" (this is fomr my M6, idling at 800rpm). And, it should be steady. Any lower and you probably have a vacuum leak, or the throttle return stop screw on the throttle body is preventing the blades from fully closing." ----Mine are around 9 at idle.

Coil and opti were changed, no improvement. Also I have replaced plugs and wires a while ago...still persists.

Car runs rough on start up, then calms down once the engine gets to like 170*...then once its hot(such as sitting in traffic) the RPS drop, oil pressure drops, and it starts to run really rough. RPMS drop to like 550. Ive also taken out the TB and cleaned it all out. I cleaned the IAC, but it looked pretty coated in crap.

Change IAC next or look for vacuum leak?

Help.

 

sounds very similar to what im experiencing do your brake take longer than usually to stop too?

 

No my brakes are fine...If its effecting your brakes, couldnt that be due to a bad opti? I've heard when opti's go out, the car will sort of surge forward when you're stopped/stopping and on the brakes? hmm not sure.

have you replaced/fixed anything on your car yet?

 

If ya can't hear a vacuum leak and ya think ya have one spray around all the gasket joints and hose plug in with starting fluid. The engine will increase in RPM's if it sucks it in through a leak.
Could be an exhaust leak too.
Opti won't cause it,the lean condition that is.

 

Okay if i remember there was a guy on this board that knows all about vacum leaks i think you need to plug up a laptop and see by your map sensor readings.... not your maf but maf he could tell by looking at it...

 

I'm pretty sure you can see your MAP readings with a Scanmaster. Get those readings at idle. They should be like .4 bar or 20 in.Hg (whatever units your using). If the reading is higher, adjust the throttle stop screw to get your IAC counts back to normal and see if that helps the MAP reading. If not, you may have a leak. Just pull and plug each intake orphis until you find the reading gets normal, then there's your leak. Or, just spray starting fluid around each hose to see if the RPM goes up, like 1racerdude said. If you have RR's, and if they're out of adjustment, that can cause your vacuum to be low. There's a few things for you to do.

 

When getting the MAP, I thought you you take that number, and its supposed to be 1/3 of the BAR.
So if BAR = 30, MAP = 10 or a little less?

 

An old standard for tracking down leaks is to use a propane bottle. Don't fire it up (or do, it'll be entertaining for me ) and snoop the suspect areas. If it's an exhaust problem then you'll need a data logger to see the change on the O2 sensor.

Do be careful and don't saturate any one area with the gas. I'd like everyone to retain their eyebrows.

 

I actually made the mistake on the 20 inHg (inches of Mercury), it should be reading like 10 in.Hg (30 in.Hg -20 in.Hg). 20 is that actual amount of vacuum it's pulling. I guess 1/3 is a good rule, but you have your units goofed. The MAP (pressure) is taken in bars, kPa, or in.Hg. The 30 in.Hg is approx. atmospheric pressure and the MAP reading 10 in.Hg means that it is pulling 20 in.Hg of vacuum (refer up a couple of lines). Hope this makes sense.