Correct, Iam sorry I meant the MAF sensor and not your Oxygen Sensor that connects to the 'mass air flow' portion of intake tube prior to getting to cover for air filter.

Also heard to clean the MAF carefully as well as check the Fuses under hood
As well as told to replace 'fuel filter' is common here.

1. voltages on the front two oxygen sensors
?Where are these located to do this?

2. having the top intake off it may not have resealed correctly
?What would suggest to check if a leak exists with the gasket on upper intake?
-or at least see if this is causing any type of leak-

Does seem when idle position I can smell faint fuel odor.

So I am going to do the following:
-Check fuses under hood
-Clean MAF
-Check plastic connections on MAF to mass air flow and if anything out of alignment
-Check hose connections on upper section for wear
-Check voltage on front oxygen sensors [request location pic if have]
-Check resealing of intake manifold upper [based upon your suggestion best way to]

I thank you very much. It crazy I did the plugs and wires to attempt of better efficiency and now all this crap! arrggg...but I love the disco.

 

It can and that would be part of it's job. You just need to look at everything that is going on and try to make a picture in your head. Obviously you can interpret things differently and that's why nothing is cut and dry.

The thought process is generally if two of the same part in different systems are failing in exactly the same way it's likely something else common between the two systems causing those parts to indicate that. Especially with sensors. So you look at all the other codes and see a lean code and a misfire code. Now think about how it all relates.

You have two oxygen sensors that are failing for the exact same thing, circuit malfunction. This means the computer is seeing readings it thinks are inconsistent with what it should be seeing. For instance it reads how much air is going in the engine by using the MAF and it knows how much fuel it's dumping and it's doing so with pre-defined tables in the computer. It just knows for some reason the oxygen sensors aren't reading the correct AFR that it is expecting to see under ideal running conditions and it throws this code to flag them.

The misfires could be ignition system related and it's a possibility since he just messed with this system, but if this is the case then you wouldn't have lean codes, you would have system too rich codes from the unburnt vaporized fuel going into your exhaust system. So we need to consider other things.

Another code you have is system lean. This IMO is a the problem code. When you run too lean you create misfires because your mixture is messed up, so that is a possible explanation for the misfire code. Additionally, now you will have O2 sensors reading lean continuously. Since the computer doens't just run the engine lean, it will see this reading and throw the lean code along with flagging your O2 sensors as mentioned above.

Now with all this knowledge you have to figure out what caused your lean condition; aka too much air for the amount of fuel. One scenario that could cause it is the MAF sensor. If the MAF sensor is reading the air coming in but reporting too little to the computer, the computer will put too little fuel in for the actual amount. This would be a lean condition. Your engine is always the same size and efficiency for the most part so at idle it will always suck in the same amount of air +/- a small variation for different variables. Anything outside of this tolerance and the computer will throw a CEL for your MAF because it see it as providing incorrect data.

You don't have this happening in this case, so move onto another scenario; a vacuum leak. What happens with a vacuum leak is your MAF is reading the correct amount air coming by it and sending the correct value to the computer and the computer is happy. The computer looks at it's fuel table and puts in the amount of fuel it should for the amount of air. What a vacuum leak is, is the engine sucking in air AFTER the metering point. So now you have more air entering your engine than the computer is fueling for. Now your AFR will run into the lean area and your MAF sensors will detect this. Well your computer will look at all the inputs, determine the MAF is seeing what it expects, but your oxygen sensors aren't falling in line with all the other sensor readings. This is where they get flagged as mentioned above.

That's my thought process and why I recommended what I recommended. Also, checking for a vacuum leak and fixing it is often times way cheaper than just replacing sensors because they are called out by the computer or because they could cause the problem. Now if you don't find one of those you can go back to the steps above and revisit them for other problems that will cause the symptoms or look for new fault codes they may get thrown.

 

Brandon, thank you so much for that explaination, I really appreciate it.

Although I don't know a lot about the working of the newer sytems, I had wondered why the codes were showing both O2 sensors on the front... now I may know!

I will look for leaks at the locations you mentioned before replacing my other front O2 sensor.

Gromeo, thanks for starting this thread.

 

Thank you Brandon for the last post. It was excellent in understanding the overall codes collectively.

As you state the main issue can be a vaccum leak after MAF initially reads and the correct amount of fuel utilized but more air introduced into the system and throws the oxygen sensors off.

Besides the MAF point of connection into the mass air flow piece, I would need to chck the arm of intaske tube going into manifold, main hose area going into the intake manifold but how would I test or check if the new gasket I put on the intake manifold has sealed properly when put back on and torqued?

 

After inspecting all the areas being discussed this am here is what I discovered:

1. The inside latch to clamp down the 'cover lid assembly' over the air filter has cracked the actual location whereas it is suppose to clamp to on the lid.
--Which in turn 'unlatched the other side rear latch'
*So, now the air filter on the inside section is not properly sealed by the cover lid*

2. On the tube section of 'cover lid assembly' where it connects to the 'mass air flow' whereas the MAF plugs in there are two clips on the sides of the 'cover lid' section as the mass air flow fits into the tube and clips together. Both these clips are broke and this is the section that the previous owner has zipped tied to hold together and fits inside tightly.
--However, at the area where the clips are broke off you can see part of the plastic tube from the mass air flow.
*Could these two sections offer a leak as well?*

3. One of the top the 'breather hose' clamp was not clipped but the hose was on securely.
*Could this movement in breather hose even though on but not tightened fully at end of connection allow for any slight leaking?*

4. I did a visual inspect of the forward oxygen sensors and wiring harnesses. All seems to be connected fine. However, I did see some excess newer oil on the wiring on the right passenger side cable from Oxygen sensor to wire harness where it connects.
*Would this disrupt reading with wire continuity?*

Whatever, excess oil under engine after have it cleaned. Does that mean head gaskets need to be replaced and all cleaned while in there and re sealed properly. argg

 

Question that I am stumped on... If I resolve / repair an issues that is throwing a code(s), in this case the lean codes on the front O2 sensors, but I don't clear the codes, will the vehicle then still not run properly?

I installed a new MAF today, made sure all connections after the MAF sensor were tight, no cracks in any plastic, checked the connection at the throttle body gasket, etc. I didn't find any issues unless the connections were not tight enough.

In any case, The first couple of start ups the vehicle seemed to run smoother and then after a couple more I have a slight shudder, idle hesitates, when in drive with the brake on. I can notice a difference in the smell of the exhaust also.

Would not getting the codes cleared after the above mentioned now cause th idle to be "off"?