P0305, P0172 and P0131, on a 1998 C70 turbo

Post by **jblackburn** » 18 Apr 2012, 05:57

The cat is glowing because of Unburned fuel from the misfiring cylinder.

I fear you may have a burned valve. Its happened to quite a few people. Run a compression test to see if that cylinder is still OK.

eddiecohoon · Post by **eddiecohoon** » 19 Apr 2012, 22:29

Didmt think this was relevant until reading some more posts on here today. But I do have an oil leak off what appears to be the back drivers side of the motor, towards the top. I know basics but not enough to go into detail with a part name. Its kinda righy under the heavy duty black pipe going to im guessing the turbo.

Post by **erikv11** » 19 Apr 2012, 22:40

This sounds like a leaky rear cam seal. Even though the rear seals are nearest to cylinder 5, that wouldn't correlate to the p0305 code. Can;t think of any oil leak that would.

The Autolite plugs are not a good idea in an 850 turbo and there is a chance they are the cause of the 305. But I sort of doubt it.

jablackburn's guess seems to be, unfortunately, a good one. If I was in your shoes I would next get a compression test. It is not a difficult job but to do it yourself you will have to do some reading and buy or rent a compression gauge. Still probably cheaper than taking it to the shop for one test, but your call. Any shop can do a compression test and give you accurate numbers, they don't have to be Volvo specialists at all. Get the numbers, post them back here. If there is a burnt valve then compression will be near zero in cylinder #5.

yevgeniy · Post by **yevgeniy** » 19 Apr 2012, 23:51

Autozone will let you rent a compression tester for a few $

eddiecohoon · Post by **eddiecohoon** » 20 Apr 2012, 00:18

I am gonna check with the parts stores in town tomorrow ti see if they rent them. Also forgot to mention the a couple months ago my gas mileage slowly began to drop. thought it was the o2 but apparently not. Dont know if that changes or strengthens the burnt valve idea.

eddiecohoon · Post by **eddiecohoon** » 23 Apr 2012, 16:21

the compression was 130, when i took the plug out it looks likes its not having any combustion inside the chamber. did a spark test and it does spark. so no gas getting into the cylinder? but still getting in the rest? Could it be a clogged injector or a fuel filter that needs to be replaced? Also ran a can of sea foam through and it seems to be running better. stutters and shakes less when accelerating from a full stop. could this be a fuel system issue?

Post by **erikv11** » 23 Apr 2012, 16:28

So does the gauge read 130 in all cylinders, or is that just #5? Post up all 5 compression numbers for clearest picture of the test.

To answer the fuel question: try eliminating fuel from that cylinder. If you unplug the electrical clip that runs injector #5 and drive around, does it run the same, better, or worse?

Yes, a clogged injector seems possible, good idea. Unlikely the fuel filter is the cause, it would misfire all of the cylinders.

eddiecohoon · Post by **eddiecohoon** » 24 Apr 2012, 09:03

yes the compression is even in all cylinders. unplugged cylinder 5 fuel injector, seemed just a bit worse i think but very close yet to if it was plugged in.

Post by **erikv11** » 24 Apr 2012, 21:47

OK no burnt valves, that's good! So it does sound like a bad injector.

Try swapping the injector in #5 with a different one. Then clear the codes and run it. If the code follows the injector then you know it's the injector - probably clogged like you suggested or could be some internal failure. You can get fuel injectors cleaned and flow tested, not a bad idea on a 14 year old car. I had this done once but I'd have to look up the name of the place I sent them to.

EDIT: sorry I was getting your thread mixed up with another one: It looks like you also haven;t tried swapping the plugs, to see if the misfire follows plug currently in #5. I'd definitely try that.

And what I said about Autolite plugs being ia bad idea is not just me being picky, these cars REALLY don't like anything other than OEM plugs or simple coppers (BOSCH copper is good).

A follow-up about your clogged cat idea: it is a possibility, except that you wouldn't expect it to just be #5 that was misfiring.

eddiecohoon · Post by **eddiecohoon** » 25 Apr 2012, 08:44

Fixed the misfire, faulty plug. I hadn't swapped them before but i had bought a new one and put it in so that was the second in a row. I will definitely get a set of Bosch but no where around here carries them so i will be ordering online. Thank you immensely for all your help.