Check engine light issues 98 v70 AWD

randrews80 · Post by **randrews80** » 15 Jun 2010, 07:21

Have a 98 v70 Turbo AWD with 153K miles and am experiencing Check engine light issues. Have been getting OBD codes of P 172 (to rich bank 1), 304 (misfire cyl. 4), 305 (misfire cyl 5) and 300 (misc. misfire). No not notice any driving issues. Have cleared the codes three times but they keep coming back.

Between 150K an 151K have replaced dist. cap, rotor, plugs, wires, PVC system, timing belt and components, radiator, thermostat, temp. sensor, MAS (altitude sensor), air pump, SAS valve, and other non related engine components.

Have just started getting the above referenced codes. Have reset three times and it keeps coming back. Any suggestions on diagnosis? O2 sensor? Knock sensor?, Cam position sensor?. Any help would be appreciated.

Thanks.

Post by **FlyingVolvo** » 15 Jun 2010, 07:29

Does the car run rough? If so, try unplugging the MAF (Mass Airflow Sensor) just after the air filter box and see if it helps.

Also check all your vacuum lines around the engine for leaks. It could be caused by the front O2 sensor too.

randrews80 · Post by **randrews80** » 15 Jun 2010, 07:33

Car runs a smooth as can be.

Post by **jblackburn** » 15 Jun 2010, 07:36

The P0172 is almost always the vacuum connection at the left side of the intake manifold has fallen off.

The misfire codes could be a crankshaft sensor on its way out. The cam sensor will almost always throw a code unless it dies outright. When (and do?) you notice the car stumbling? Low RPM, heavy load, high RPM?

randrews80 · Post by **randrews80** » 15 Jun 2010, 07:46

About a year ago I would notice that while at high speeds (50 to 60 mph) the engine would seem to cut out for a second - I would back off of the gas for a bit then it seem to resume to normal ops. Have not experienced that phenomenon lately but have not driven it long distances fro a while.

randrews80 · Post by **randrews80** » 21 Jun 2010, 09:56

jablackburn you had it right on the money in re to the P0172 code. After checking all of the vacuum hoses I got frustrated and just about have up but this morning went back with fresh eyes and found the leak right where you said it would be. There was a cracked 1/4" vacuum hose (going to a check valve and then to a 5/16th" Tee by the evap. canister control valve) coming out of the front drivers side of the intake manifold, just below the throttle control valve and toward the center of the intake manifold. Replaced both with new fuel line hose and solved the problem.

In re to the P0134 and P0135 (misfires on cyls. 4 and 5) I changed the Cam position sensor (Hall Sensor) and that seems to have taken care of the issue.

Thanks for your great help.

Post by **Ozark Lee** » 21 Jun 2010, 14:59

Make sure the cam position sensor wires and the crankshaft sensor wires are both well away from ignition wires. The high voltage from the ignition can interfere with the sensor signals. Volvo had a TSB where they advised to use a zip tie to secure them away from the coil wire.

...Lee