Oxygen and Mass Air Flow Sensor Replacement
 

I am getting the following trouble codes for my 04 xc90. P0103 Mass Air Flow Sensor and P0150 Oxygen Sensor. Im also getting a P0740, P0299, and some misfire codes. Is it possible the bad oxygen sensor could throw codes for other things? Also it seems like most people recommend I use Mass Air Flow Cleaner on the MAF Sensor instead of replacing it. Good idea? Is there an alternative option to replacing the oxygen sensor too? There definitely seems to be issues with intake etc. Its running rough at times and eating up gas. Stalls after starting and or idles super high before settling down. Figured I would address these codes first and then move on. Any advice would be much appreciated I'm new at the DIY mechanic stuff. But excited to learn. Thanks in advance!

I start with a cleaning of the MAF with the correct type of cleaner. If that doesn't work, I typically change the MAF.

The oxygen sensor cannot be properly diagnosed until the MAF is clear (unless the sensor is dead).

its not uncommon for a mixture issue to throw a happy meal of codes. Start by cleaning the MAF, idle air valve etc using something like CRC MAF cleaner (standard carb cleaner may damage the wire grid in the MAF). Next I'd look around for air leaks - vacuum lines, torn boots etc. After that, reset all your codes and see what resets. Generally speaking O2 sensors fail when either the heater element breaks down or if the sensor itself goes (typcially via an open circuit). I discount the advise that suggests you can clean your sensor or that it goes off by a little... The error codes will tell you if the sensor is not found or that the heating element is open or shorted or if the O2 sensor is "out of range". This last fault means that the sensor's input into the ECU can not fully compensate for the mixture issue. If your MAF is bad or you have a major intake air leak, the O2 sensor can't adjust enough and throws a code. Fix the upstream issue and the O2 sensor is happy and the code won't reappear.

I have only had maybe one out of six MAF cleanings do any good. Most of the time we end up installing a new MAF and with the cost of those coming down so low, it probably is best to install a new one anyway.

On any of these vehicles with more than 50k miles, we recommend a thorough off-the-engine throttle body cleaning.

2002 S40 1.9T Idling low, must rev to keep rolling :mad:
 

So yank the TB off the intake plenum and clean her with TB spray? Any specific orifices I should pay close attention to?

I'm on the fence about replacing or cleaning the MAF and the IAC also, but this car is really trying my patience.

Been trying to track down and repair oil leak leaving spots on accessory side of engine. Exhaust cam is dry after replacing the o-ring inside the cam. Still wet down below on the oil pan from what appears to be the oil cooler o-rings. Replaced those and still have spots....hoping the ebay parts did not fail!

I'll be getting under her again tomorrow morning to solve this spotting problem...before moving on to transaxle mounts and front struts.

Don't know should I blame my GF for buying the car or myself for being so determined to correct issues on a 16YO car?

You need to remove the throttle body and clean it both sides. Don't just spray it down the throat. That method is so 1992...

Takes me back...
Rode my Honda from Chicago to Phoenix to learn motorcycle repair.
Riding across the US with a bad ignition coil making it impossible to run on 4 cylinders in moist air....so 1992.
Well over 20 years working on bikes and other assorted toys. Yamaha Silver Certified Technician.

I hope cleaning the TB makes it better...losing my cool with it.

It is a starting point, not a cure. Start with a clean throttle body and then check the engine operation.

+1 on what Tony said. The ETMs are also a common problem area - usually caused by contacts going bad. Check our ARD's web site for their ETM repair kit and look at some of the ETM rebuild services like Xemodex. There is some good discussion online about the various symptoms to consider when diagnosing. Replacing the MAF or rebuilding the ETM is not cheap so its best to start with the cleaning - but the parts may still need to be replaced.

Afternoon update: Cleaned TB, no change. disco all air/fuel sensors, reconnect and fire up. Idle in park is 2K, right about 900 while in gear. Take her out for 2.5 mile test drive, seems to run okay, notice slight oil smell as I'm turning back into my neighborhood. Then we see this when we park her in garage:
https://cimg5.ibsrv.net/gimg/volvofo...0b594b8149.jpgDrippy!
https://cimg7.ibsrv.net/gimg/volvofo...036a64f9f5.jpgOh No!

I guess we'll be taking a closer look at that oil leak now!
FOUND!
Intake camshaft seal pushed out and there's the oil leak! From what I've read on this forum the PCV system on this model can get clogged and cause excessive pressure....so, ordering parts and we'll put her back together soon. Would have just thrown some sealant around the seal to prevent it pushing back out again if I didn't have to lockdown the cams to put her back together, doesn't look like that actual seal failed at all.

Can anybody point me in the direction of where to find this PCV system and how to clean/repair/replace?

If you have a seal pushed out then you definitely have a clogged PCV system. It will also cause erratic running and idle since airflow is coming into the engine that does not go past the air mass meter (combustion backpressure).

PM me and I can walk you through the process.