Volvo S80 multiple misfire codes and misfire codes on all cylinders.

[ThommyKent]

Catalyst are very long lived, if the 02 sensors are bad and the car is driven a fair amount of miles, the Cats can lose life because the 02 sensors control the fuel mixture going through them. Running rich for a time is not the best thing for them. If the Cats are bad it doesn`t effect how the car runs per say, but emissions will be high. If I had bad cats but didn`t need to pass an emissions test I wouldn't bother replacing them. Eventually after many years and miles the catalysts can fall apart and clog the exhaust.

[Roger_850T]

The catalyst efficiency trouble code is set when the rear O2 deivates too much from the front one. VIDA lists possible sources as:
- Misfiring
- Air leakage in the intake system
- Air leakage in the exhaust system
- Faulty fuel pressure
- Uneven Compression
- Defective three-way catalytic converter (TWC)

I have only once come across a faulty catalytic converter, and in that case it all broke apart inside.

Also, every single time I replace one O2 sensor, I end up replacing it's companion in very short order. They age similarly, and now I just automatically do them both. Or, in this case, I would do all four together. So yes, I would recommend you replace the last one and make them all match.

Beyond that, I'd check for air leaks, and check the fuel pressure, and keep an eye on it. With the new O2 sensors getting it running properly, it might settle out.

Also, the VIDA codes are more detailed - if you can find someone with VIDA that can read it out for you, there might be more specific info to help pinpoint the issue.

Hope this helps!

Roger

[Axe]

Thanks for the responses! Much appreciated. I will replace the other o2 sensor as I figured the same thing about it being on its way out. That's good to know that the cats very rarely go bad. I do not have to pass emissions so if it ends up being the cats I will let it ride until it absolutely needs to be done. I have read about air leaks and a possible bad maf sensor. I've got a scanner, not a Vida but a bosch and iam going to see it if will read read fuel trims. Hopefully this will point me in the right direction. I wish I could find someone with a Vida around. The only place I know that has one is the dealer and they want $100 a pop to read off codes. Gets a bit pricey when you're chasing them down. Does anybody know what the fuel trim should read if I can get it too? I know ltft should be close to 0 and stft can vary a little. Also should I reset the fuel trims after replacing o2 sensors? Or is that necessary?

Thanks again!

[Axe]

I checked the fuel trims tonight. As far as I can tell they weren't too far out of line but I am certainly no expert. At idle stft was 0 to 3 on bank 1 and 2. At 2500rmp stft was -5 to 3. I'm sure there is a way to get an average but I haven't figured that out yet. The lowest it would go was -9 and that was when reving the car and it would quickly recover to around 0 when rpm was steady. The ltft was 7 for bank 1 and 10 for bank 2. I reset the fuel trims to see if this will help. I'm sure I'm missing something when it comes to fuel trim as this is my first time really looking at them so please be gentle!

[abscate]

These probably aren't new faults - without knowing the source code for the ECM this is just a guess, but Ill guess that the cat efficiency monitoring is disabled if the OXS error is present - why try to monitor something when the monitor is known to be broken?

Leave the cat alone - there are vacuum leaks and induction leaks to chase before you get into that.

When my VVT solenoid went bad, I got the MAP error, turbo error, and a knock sensor error - all spurious. NO VVT error either.

[Axe]

Thanks for the response! That makes sense if o2 sensors are known to be bad. I will check for vacuum leaks more thoroughly. I do have a digital manometer and tested for vacuum through the dipstick. It had vacuum but I wasn't sure on what the readings should be at idle and when engine is at a certain rpm? Called volvo dealer and he said as long as it showed a vacuum it was fine. It didn't sound like he knew what he was talking about or just didn't want to tell me. He couldn't give me any specifics on the subject.

[abscate]

Its not glamarous, but to look for vacuum leaks on an old car you have to pull each hose, inspect it carefully with a light, blow into it and listen for noise, etc. I wrote a thread on this in the P80 Forum based on a BMW experience...

https://www.matthewsvolvosite.com/forums ... le#p426011

[Axe]

It does not look like fun that's for sure lol. I will definitely look into it and give it a go. I may try the smoke test and see what happens also or just replace the hoses and oil trap since I'm sure it's never been done. Thanks again for the help and I'll report back what I find.

[Axe]

So I broke down and bought a cloned dice and vida program. I've got a few other things I wanted to look at with it and figured one trip to the dealer would cost the same. I looked at the fuel trims and the bosch told me ltft was around 8% for both banks. When I hooked up the vida program it read right around 0% for both banks. Anyone else come across this? The vida does give a lot more info on codes and is very helpful. I still haven't had a chance to go through vacuum system but with the info from vida sure looks like everything is spot on? Starting to think that the cats are actually bad. Also has anyone else programmed with a cloned dice? I've got a door module that is bad and needs a new one. Was able to test the window motor and door locks through vida and they are good.

[Barledge]

I agree, it is very nice to read about the solution instead of only 50% of it. But, did changing all 4 02 sensors solve your issue? I just paid 2500 4 weeks ago for this T6, I've replaced an incorrect replaced alternator, new battery, new throttle body new acceleration pedal and sensor, all new spark plugs, 2 coils that had codes, thought I had it beat but it is 3900 into it beating the crap out of me. Now all these misfire codes and efficiency codes. I've had it, not once has a car ever broke me but I'm ready to send it off a cliff? HELP PLEASE