2000 S70 Still runs poorly after Xemodex upgrade

[draser]

If you get your hands on that scanner you could look at maf and engine % load which indicate engine flow, hence cat condition. If both maf and engine load are low then cat is plugged up. The oxygen sensor switching only show if cat is chemically operational. You don't have a cat efficiency code so it's more likely to be clogged. You should be able to check fuel press as well with scanner, at least I can on my s60. I'd also check fuel trims for better diagnostics.

[E Showell]

In theory, the o2 sensor should throw a code if it is bad, but they can fail gradually. In that case I believe (although I have no proof of this) that the onboard computers adjust to the output of the failing sensor without throwing a code so that it might be possible to drive quite some distance with a bad sensor. I had a sensor fail over time without a code and it cost me a burned exhaust valve, so if you have any doubts about the o2 sensors -- I'd spend the $200 and replace both as opposed to 10X that for an engine replacement.

[draser]

We had an extensive post on the s60 side just recently with ways to test both o2 sensors, waveforms, etc. The code was cat eff. below threshold however driveability was good, including fuel economy. The cat was not plugged but it did not "store" oxygen as it should. Kinda opposite to this case. First reaction of owner was replacing both sensors but it did not fix the problem. Using a good code reader one could graph both sensors and look at switching frequency on the time scale to make sure the rear one switches just a couple seconds slower. But in this case it's more like cat is plugged or fuel press is low like Mike said, however I'd think you won't be able to rev at idle. Fortunately both fuel pressure and engine air flow can be tested with a good scanner.

[1998v70xcbill]

A good scanner is key. I bought one for my bmw because of ems codes. I have one that let me gragh o2 or other signals. $100 back then. probably $20 BUCKS WITH A SMART phone. Sorry a can't help with your problem. But seeing the O2 sensors in action helps.

[Chapelgirl]

Ok, I borrowed a higher end scanner so I could watch what was going on although I didn't understand much of it. The co-worker I borrowed it from helped me out some. He was looking at fuel trims which I believe were hovering around 10%. He immediately suggested replacing the fuel filter if I had not done so lately. So, I changed out the fuel filter last night and now the fuel trims are hovering closer to the 1% range. Operation did not change, however. In viewing the o2 sensors bank one is remaining fairly constant at around the .5 mark. Bank two is not flipping between rich and lean like I would think. It stays mostly rich in the .7 to .8 range with only an occasional dip down to .1 or .2.
After all this I was speaking to a co-worker in our technical department (construction equipment) who is a very smart individual. He suggested a very simple test based on his experiences in side work regarding catalytic converters. He told me to simply drive the vehicle home and when I parked the car to get out and see if the cat was glowing red. Sure enough the thing was a glowing red hot. Perhaps we've been overlooking a simple test. I think I'm done with all the speculation and testing and reading everything I can find on the matter and fretting over it. I'll do just about anything on my car but I don't do exhaust work. If I were to break a stud out of the exhaust manifold, for instance, I think I would just about lose my mind. So, I'm heading to the muffler shop for confirmation and replacement. Even though it won't be cheap I'm ready to let my Xemodex equipped car fly once the engine can breath out. Merry Christmas to me I guess.
I'll post a final wrap up to this saga in the days to come. Thanks everyone for trying to help.
-Dave

[E Showell]

Dave. If you have a local metals recycler - aka scrap yard -- near you, a Volvo original equipment cat has a fair amount of precious metals in it. Get the fried cat back from the exhaust shop. I got $70 from my local scrap yard for mine. It takes a bit of the sting out of the cost of a new cat.

[northernlights]

After all this I was speaking to a co-worker in our technical department (construction equipment) who is a very smart individual. He suggested a very simple test based on his experiences in side work regarding catalytic converters. He told me to simply drive the vehicle home and when I parked the car to get out and see if the cat was glowing red. Sure enough the thing was a glowing red hot. Perhaps we've been overlooking a simple test.

Wow. That's hot. I think your muffler shop trip will do the trick. If you can any pictures of the carnage, I'd be curious to see what it looks like.

[mika]

Interesting read. I have been having similar problems with my V70: I have been thinking that my pedal cable /pedal assembly needs adjusting/replacing because it feels so "heavy" and hard especially uphill; with a headwind and an uphill forget about it. Good to know to take a look at the cat when its hot.

On a side note, is it normal for the exhaust manifold to have a hint of "red" color when it is cold?

I have also heard that using excess fuel injector cleaner can clog up the cat.....

[oragex]

A front oxygen sensor (no need to replace both) it's found for $100 off Ebay (I used NTK which is known to be a good brand). Replacing it can be a good idea any way if the car has quite some miles on it.

If the catalytic converter is clogged, I heard that it will heat up pretty much, so that might be a way to test it. To replace, no need to get a new part, a used one from a scrap yard will perfectly do the job. Especially since a new one is in the hundreds of dollars. Also, the issue that caused it to became clogged must be found. Look inside when removing it, if you can see through the honeycombs it's not clogged. The cat can also heat up if the fuel mixture is really out of specs.

How is the fuel filter? The fuel pump?

[EstVolvo]

Once I had a glowing catalytic converter and it was glowing because too much unburnt fuel got into the exhaust.
I can't remember what caused it but after fixing it, I used the car with the same cat for another 150,000 miles.