Three OBD codes - could they all be pointing to a singular cause?

[shelzmike]

I have a 2000 Olds Silhouette. Has about 140k on it. Runs really well actually. We recently took it to Tennesse and had no issues until about 2 weeks after we returned.

Every now and again (about 50% of the time) it will run at lower than usual RPMs at idle and while stopped. It never actually dies, but feels like it might.

It has always thrown a P0442 code, which everyone tells me is the gas cap, but it must be some other small leak because I have changed the cap 2 times with no changes.

I pulled the codes yesterday and they are the following:

P0171 - System Too Lean (Bank 1)
P0410 - Secondary Air Injection System Malfunction
P0420 - Catalyst System Efficiency Below Threshold (Bank 1)

To me, this seems to be pointing to a singular cause (hopefully anyway). I have not done anything to it recently except adding fuel system cleaner before we left for TN. It was not STP or anything - it was a better fluid, but do not recall the name. I didn't have any problems and we went through about 3 tanks before the problem started.

The issue does seem to be intermittant - but it is occuring a little more than it is not occuring. Any suggestions? Thanks!

Mike

[dewaynep]

Is that the order the codes appeared on the scan tool? Usual course of action is to reset the light and read the code at the first sign of the SES light. Let us know which one shows up first and we can go from there. It may be a problem with the air ijection system, but it's just a guess until we know which code shows up first.

[shelzmike]

That is good advice. I will see what I can do. I actually had Autozone pull the codes again because I am also having transmission issues as well and thought they could pull some codes on that as well; however, the only thing they discovered are the same codes repeated 2 times and then an additional code which was P0507 - I am pretty sure this is all related to a singluar issue.

As an updated, I did take the MAD sensor out and it was very clean. I did clean it and replace it and it made no difference - I understand it could still be a bad MAF sensor altogether, but unsure how to verify without spending like $200 on a sensor that I may or may not need. I suppose I could go to a junk yard for that if nothing else seems to be the problem.

I will reset the codes and try to determine which one comes up first. Thanks!

Mike

[shelzmike]

Problem fixed, or at least on of them is, so it seems. Rather than trying to get the codes in order, I decided that since I had been having the P0442 and I knew that it wasn't the gas cap, I decided it was probably a vacuum leak somewhere (the thing I was trying to avoid because sometimes they are hard to find!).

So I got my bottle of propane and started her up. To my surprise I was able to actually hear the leak. It was coming from around the throttle body/EVAP area. Though I could not tell where it was coming from. I held the propane to that area and it smoothed the idle out ever so slightly. Still, there are several place a leak could be coming from in that area, so nothing was definitive.

So I simply started gently wiggling some of the connection there. Nothing really noticable until I moved the plastic tube that connects the PCV valve and to the evap system. As soon as I touched it - I heard a much louder flow of air and the engine started jumping like crazy.

As it turns out there, is a plastic fitting that goes down into the intake that is midway between the pcv and evap side of that plastic tube. It is supposed to have a rubber grommet and mine had none at all - just plastic. I replaced the $8 part and she runs perfect now! (well, besides the nagging and even more frustrating transmission issue). Thanks for at least posting something, no one else did.

Mike