1999 S80 T6 low/rough idle

[DonVanhugenstein]

As the title says, the car at idle is very rough and shakes the interior.
The rpm also seems low @ 500rpm

To start the car I have to press the gas pedal and make sure it starts and let it rev up to 1k before I can let off the gas. Once I let off its back down to 500rpm on its own and that's both warm and cold starts.

It does stutter abit when you rev up (from 500rpm) until abut 800-900 then it's smooth and 100% seems fine at around what I expect to be the proper idle for that car.

I do have some CEL codes;
P1238 - This one I hear is a Turbo Control Valve code, however read that the actual issue for people is with their MAF and after replacing it the code and issue was gone.

P0031 O2 SENSOR CIRCUIT LOW BANK 1 SENSOR 1
P0037 O2 SENSOR CIRCUIT LOW BANK 1 SENSOR 2
P0134 O2 SENSOR NO ACTIVITY BANK 1 SENSOR 1 - This and as well as if you go down to P0154 below, These 2 Sensor #1 could be the issue?

P0051 O2 SENSOR CIRCUIT LOW BANK 2 SENSOR 1
P0057 O2 SENSOR CIRCUIT LOW BANK 2 SENSOR 2
P0154 O2 SENSOR NO ACTIVITY BANK 2 SENSOR 1

P0300 RANDOM/MULTIPLE MISFIRE (I think this is when I attempt to force the 500rpm up to where it gets smooth 800+ rpm and the engine stutters at times which I'm 100% sure its a miss, however at 500rpm it is NOT missing the shake and vibrations are steady and after 800+ rpm the engine is also steady its just stumbling as I attempt to force it up to were it should idle)

P0236 TURBO BOOST SENSOR CIRCUIT A RANGE/PERFORMANCE (I think this is because a hose was off my intake pipe when I bought the car. I will have to see when I test tomorrow)

Now, from what I read about the P1238 people put a new TCV only to get another code and in the end it seems it's almost always their MAF that was the issue the entire time.

The code for Turbo Boost Sensor A Circuit Range/Performance I believe shouldn't come back because later I saw a line that links to 3 spots on my intake and it was off nearest my MAF. (I guess I'll see)

The O2 codes for Circuit low don't bother me, the P1238 does a little as does the "O2 No Activity Detected" on the first 2 of my 4 O2.
The major bother is the P0300 "Random/Multiple misfire detected"

It doesn't sound like it's missing at low idle but when I start to force it up from its low 500rpm it stutters sometimes before I reach 800 rpm and it smooths out, I think that's where P0300 comes from.

I'm extremely upset that the car wont toss me more codes and it's probably because Volvo and their stupid DICE+VIDA setup.

All injectors read 12.5ohm so they should be ok, brand new bosch spark plugs.
Tomorrow I want to start the car, test my MAF as well as do the PCV glove test as well as after testing the MAF just unplug it and see what it thinks about that.

I read that the guys who discovered P1238 wasn't the TCV but actually a issue with the MAF diagnosed it by unplugging the MAF and they said the car ran 100% and after a new MAF all was jolly.
And a MAF can messup alot but I inspected it, it's clean, cleaned it anyways.

Also I recently replaced my alternator, And so I had my Intake manifold and Throttle body off and cleaned what I could see from the Throttle body which houses the ETM.
Now I did not clean it immaculately however #1 it had this issue before I cleaned it and even though its not immaculate and #2 I did clean it and the car has not come up at all in rpm and it's clean enough I think.

Anyways I want to get the info out for someone who's smarter than me to comb over it if they can and offer some input.

I'm leaning towards just buying 2 O2 Sensor for Sensor #1 in Bank 1 and Sensor #1 in Bank 2 because a "No Activity detected" doesn't sound promising and from what I understand they control my air/fuel ratios somewhat.

If that doesn't help, my #2 O2 on Bank 1 + Bank 2 only tossed "Control Circuit Low" and also from what I understand are just more of an emission piece for testing the Catalytic Converter. So I'll probably leave those if the #1 sensors don't fix it and move onto another culprit.

I'll have an update tomorrow when I start it up (need new battery) and I'll see what new codes will pop up for me.

[DonVanhugenstein]

Ok guys, So today the car still requires gas to start it and as before I still have to make sure that after its on it gets up around 1k before I can let off the gas and then it will go down to 500rpm and idle on its own.
A cold start should be idling around 1200rpm or so and it wont budge past 500rpm unless I am forcing it via gas pedal.

BUT
My only active codes today are;
P0030 - HO2S Heater Control Circuit (Bank 1, Sensor 1)
P0050 - HO2S Heater Control Circuit (Bank 2, Sensor 1)

P0136 - O2 Sensor Circuit Malfunction (Bank 1, Sensor 2)
P0156 - O2 Sensor Circuit Malfunction (Bank 2, Sensor 2)

The codes that I listed above this post I had pulled, written down, erased and went on with my alternator repair because It had to be done and I was eager to just open that up and change the alternator as well as inspect the Throttle Body and also my PCV system too.
Yesterday I did try to pull codes, there was none but my battery still needs replacement and I guess the car just didn't want to give me anything because the battery was so low.

But today I see that after I cleared the first set of codes in Post #1 I must have gotten some new ones because I also had 3 stored codes today ontop of the 4 active codes.
Stored Codes are all O2 related as well;
P0036 - HO2S Heater Control Circuit (Bank 1, Sensor 2)
P0056 - HO2S Heater Control Circuit (Bank 2, Sensor 2)
P0134 - O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 1)

So thankfully P0300 (Random/Multiple Misfire) has not come back (yet). Neither has code P1238.

It seems dodgy that all 4 O2 Sensors are tossing me these codes. Carbon buildup possibly, maybe some oil blew by and fouled them.
I am planning to take each one out when I have time and inspect them, clean them with a spray and if I can get enough access (I don't know how much play room I'll have) I want to test the O2 sensor wire loom up to the plug and inspect visually if possible.

Currently I cannot see any O2 sensors or wires any were I'm going to have to lookup how to get to them all.
I figure a good inspection and cleaning is worth a shot because the price of each sensor is around $200 here so id be looking at $800+ most likely and I still need a new battery for the car too so another $100 there.

I paid $800 for the car because of the list of codes I pulled in Post #1.
Add +$800 so far in parts (literally that $800 parts was just the alternator, intake manifold gasket, throttle body gasket, new O-Rings for the injectors and all that because I took the fuel rail off, a new air filter, and a new charged air pipe) Total $1600 Canadian with just 4 O2 Sensor codes remaining.

Another $800 for 4 O2 Sensors If I do still need them all after cleaning and inspection + test, And +$100 for a battery which is inevitable.

So a possible $2500 total cost for a 1999 S80 T6, They sell here for $3,500 no problem.
If the new O2 sensors fix absolutely nothing that's a large chunk of cash to be burning for nothing and just puts me closer into having to dump this car before I've put more money into it than its worth.
Which is why I want to Inspect+Test+Clean the O2 Sensors and try that before I do commit to buying new O2's.

I will post back when I learn how to get to all 4 O2 sensors and let you know how it all looks and that good stuff.
It may take me a little while.

I think the idle issue must be related to the HO2S Sensors #1 Bank 1 + #1 Bank 2 "No Activity Detected"

Oh and the upper engine mount ripped apart in front of me today. So I guess that's why the shaking was so intense, time to replace them all.

[Rucho26]

Did you ever get a solution on stored codes p0154 and p0050? My car is giving me the same code, and I can't seem to get rid of it. I just replaced the catalitic converters on mine.