I have a 95, 850GLT, non turbo wagon. I've been fighting with a CEL since I bought the car. I keep getting misfire codes, mainly for cylinders 4 and 5. I started with a complete tune up, cap, rotor, wires, air filter, fuel filter, and even replaced the coil. All are VOLVO parts. It still misfired! Then I got a couple of new codes, that the O2 sensors were not working or not present. They have been replaced with BOSCH parts for the front and rear sensors. Still misfires! I bought an OBDII scanner to see what was going on. It tells me there is an open loop fault, and my MAF reading is 0.00 at all times! Oh yeah, I've also already changed the thermostat, cleaned the throttle body, serviced the EGR, ( cleaned out the totally clogged port in the intake), swapped the injector order, found a vac leak at the tree and replaced the missing o-ring! It STILL misfires! I even went as far as getting ahold of another (used) pressure regulator for the injector rail, and another EGR control to try, and still, I have the misfire on cyl 4, and cyl 5. On the highway, the car seems FINE! At idle in park, it runs a bit rough, but in gear, as you come to a complete stop, the engine runs rough! it has never stalled on me though. I even reset the ECU by disconnecting the battery for over an hour! I really need to get this CEL off so I can pass Massachusetts State Emissions! Thanks in advance for any and all your help!

Did you check the accordion hose between the TB and the air filter? They are notorious for cracking and letting in air.
Other than that, it is vacuum, vacuum, vacuum.

Klaus
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1995 854T and 1998 V70R

I'd lean towards an intake manifold leak also. Maybe connect a vacuum gauge to the intake manifold. Make sure the ac is off. Should be pretty steady and read around 15-17 in HG.

Hmmmm... haven't checked with a vac gauge yet, just the old carb cleaner sprayed at hoses and connections! I'll give that a shot by Friday, and post the results! THANKS!!!
Warren

Hi, engine runnig rough at idle but is fine on highway. I didn't have codes but rough idle with slowly ramping rpm up to 1500 and then coming down at once to 900 level and going up again.
Here the vacum leak was not in the hoses etc but in the air input manifol gasget started to leak after 10 years good operation.
br Tapsa

I have a '95 850T and had a similar CEL issue.

Engine ran well at highway speeds, but if decelerating from speed to a stop, the RPM's would go very low ~500RPM and the car would studder a bit before recovering to a normal idle of 900RPM's.

I also replaced the O2 sensor, plugs, filters, etc. I finally replaced the Mass Airflow Sensor, ~$175 from fcpgroton.com and the CEL went away. This may be your issue since your ODBII is indicating a flatline value out of the MAF.

Good luck,

Phil
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'86 740T Sedan 235k (RIP), '96 850T Wagon 80k (sold), '95 850T Wagon 103k (current)