98' V70 SAS / Misfire codes - sensor fault?

ChadHalstead · Post by **ChadHalstead** » 02 Jun 2014, 13:09

I've got a 98 v70 T5.

My obd2 scan tells me codes P0401 Secondary air pump malfunction , P304 cyl 4 misfire , P305 cyl 5 misfire and then P300 random misfire.

I recently replaced a broken vacuum line and checked the pump and pump works good. I have heard e pump running three days in a row, just before CEL came on. So I am pretty sure it is not the pump, hose, or check valve - those all proved to be working.

After doing the airpump work. Everything was great and had no lights and I probably went through the drive cycle which caused the CEL to come back on.

As for the misfires - Car runs GREAT. Smooth idle, good power, no signs of misfire ( I am pretty confident I could identify a misfire by sound or feel). It doesn't burn oil, and there is no current signs of a head gasket leak ( of course that's the biggest fear ).

Does anybody have experience with electrical issues causing this type of faults or problems?

I am going to try to clean plugs, injectors and check all the coils are in the right sequence but it just seems like there is a computer or sensor failure here.

Any other recommendations or ways to narrow problem down?

Thanks a lot,

Post by **kahl** » 02 Jun 2014, 13:54

I think it would be a good idea to clean or change plugs, are they the Volvo plugs? these cars really like the Volvo plugs. After the plug work erase codes then see if any codes pop back up.

ChadHalstead · Post by **ChadHalstead** » 02 Jun 2014, 16:13

I've checked the plugs. They are ngk but look pretty clean, no carbon, not wet..... Im going to swap out distributor cap/rotor right now But unfortunately I still have two opposite codes. So I have to keep returning to get an obd to see any progress on either the air pump side, or the misfire side.

Biggest mystery is why ( I suspect ) my secondary air pump decided to read a failure as soon as I put on the highway miles and completed a drive cycle after I heard it running just 10 minutes prior.

Will grab new plugs and swap them out regardless.

Post by **abscate** » 03 Jun 2014, 02:01

Plug wires too. Whe these go bad, since they are in close proximity to each other and metal, all kinds of nasties happen

Bougicord plug wires only is the lore here, sneers from ME7 owners aside.

ChadHalstead · Post by **ChadHalstead** » 09 Jun 2014, 14:03

Okay maybe someone can throw in a little advice......

So I have these two issues.

Secondary air pump code p0401 but the pump runs on cold starts. Could this be a faulty o2 sensor not recognizing the change in oxygen in the exhaust? Isn't this what causes the p0401 code to set off?

Misfire cyl 4/5
Ran a compression test on a loaner from an auto store.
My goal was to check if there was something obvious like burnt exhaust valves or dead cyl. Compression ran around 120 dry -145 wet on all cylinders except cyl 2 which was around 90 dry - 135 wet. I get no code on 2.

I think the gauge is a bit cheap as well but couldn't tell if it would make much of a difference.

The engine has around 198k so I get that compression will start to decline due to its age but the car runs GREAT. Turbo spools and it pulls hard.

QUESTION: knock sensors, cam shaft position sensors..... Can these be a cause of throwing a code?
I work on boat engines a lot, which are covered in sensors and throw codes and faults all the time so I have learned to build up a bit of a denial issue when I know the engine is working and it is most likely just an electrical thing.

I just need to pass smog. I really wouldn't care but I don't have the money to just hand my car over to a mechanic. Plus I am very capable of the engine work, I just can't solve this issue.

Thanks!

ChadHalstead · Post by **ChadHalstead** » 09 Jun 2014, 14:07

Note: the car now has new dist. Cap, , dist. Rotor ,spark plug wires, spark plugs ( oem spec Bosch ).

I've taken out and swapped injectors too.

Idle air controller? Could this really cause a misfire?

From what I've heard this is more of an idle issue. Car idles at 800 but I've heard it skip a fire before. I've never heard it studded or run rough under power.

layback · Post by **layback** » 17 Mar 2020, 12:28

Chad Halstead,and others,
I am having basically the same misfire code problem on my 98 non-turbo V70. This code only came up after we did the oil trap and hose. So we had to disconnect the fuel injector wires and unplugged the eng speed sensor plug. I thought it may be from these connectors on these old plugs so I cleaned all the terminals with terminal cleaning tools (sort of like tweezers with file like ends) and it only helped a little. I have put in a new cap and rotor and the wires are only 2-3 years old and they were orig Volvo part number wires when I put them in. I'll check the plugs but I pretty sure that isn't the problem. So does anyone have any idea what else could cause these misfire codes to keep coming back?
Car is 98 with B5254FS engine Motronic 4.4 with 232,000 miles

Post by **misha** » 17 Mar 2020, 17:27

Possibly a SAS valve is not working properly.
Misfire codes and actual misfiring and flashing CEL(when misfiring starts) can occur if SAS valve is not closing when it should,allowing moisture and water from condensation to be sucked into engine via air filter housing...instead of going through exhaust when SAS valve is properly closed.That's when misfiring occurs.

This will kill the MAF eventually because it will be covered with water.Air filter will also be wet.

layback · Post by **layback** » 18 Mar 2020, 09:49

I'll check the MAF and the air filter and see if they are wet. Thanks for the tip

layback · Post by **layback** » 18 Mar 2020, 11:04

I checked air filter and MAF sensor and they are very dry. So I don't think it is a SAS valve problem.
Does anyone have any other idea's?