95 850 Stumbling / No power / Misfire issue

TwoOne · Post by **TwoOne** » 23 Jul 2012, 10:31

I recently acquired this 95 850 from a guy who was going to sell it for scrap, I have managed to piece everything back together to make it a good little car but I am still having one major issue which is this stumbling / lack of power issue.

Symptoms - Stumbling at idle, misfire and loss of power when it is under any kind of load especially up hill, exhaust smells very rich. The stumbling problem seems to smooth out when I down shift into low and as soon as it hits above 3k RPMs the stumbling goes away but it still has no power.

Done so far - Pressure tested at the rail and have 42lbs of pressure, wires have been tested and all work fine, if you pull them off one at a time the idle changes and it starts to stumble worse. I have replaced the plugs, checked and cleaned the MAF, checked and cleaned cap and rotor. Cat was replaced last summer and I have done a few more odds and ends to it but nothing seems to clear this problem up.

I also have a list of codes that I pulled off of A2 and they are as follows:

241
451
452
453
542
543
544
545
551
552

I have an appointment at the exhaust place that did the cat to make sure I don't have any blockage in the exhaust, that is for tomorrow at 3pm but I was hoping with the help of you fine Volvo owners that maybe I could pin point this issue and get it fixed before then. I deliver in this car for a living so I REALLY need it running in tip top shape so any help that you guys can offer is greatly appreciated.

Thanks!

Louis

Post by **jblackburn** » 23 Jul 2012, 11:07

Unplug the mass airflow sensor and go for a drive. Does it behave better?

TwoOne · Post by **TwoOne** » 23 Jul 2012, 11:09

I did that and it essentially acts the same as it did before I unplugged it, doesn't improve during driving and it screws up the idle even worse than it is now if the MAF is unplugged.

Post by **jblackburn** » 23 Jul 2012, 11:19

Hmmm.

Check for major air leaks in hoses. Idle control valve, intake manifold gasket, throttle body hose. Something's causing it to be off with the air/fuel ratio is what it sounds like. Take a can of carburetor cleaner and spray around things and listen for a change in idle speed.

I see a code there for an EVAP valve. Sometimes that can stick open and flood the intake manifold with fuel-rich vapors that can cause the car to stumble.

After checking for leaks in other hoses, try unplugging this hose from the intake manifold. Cover both ends with duct tape so as to not create a vacuum leak and/or have fuel vapors in the engine compartment. Take it for a drive and see if anything has improved.

Once you figure out where a leak is, you may have to reset the computer by pulling the negative battery cable to let it properly re-learn air/fuel mixture values.

TwoOne · Post by **TwoOne** » 23 Jul 2012, 12:22

I went through and checked vacuum lines and everything seems to be in order. One new thing I found is if I unplug the IAC it makes zero change at all, but when I take the hoses off it kills the car. Think the IAC is stuck at wide open?