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Discussion Starter · #1 ·
Looking for some insight on what’s happening with my 07 XC90 3.2 AWD with about 191,000 mile.

Car was stalling out when shifting into reverse or drive after starting the car, both cold and hot. If I let it idle for a few minutes, it would shift into gear fine. Occasionally, if I pushed the accelerator hard I’d get some hesitation.

Volvo told me at my last service I needed a new cat and muffler, that this is where the check engine light was coming from. At the price of $4,000 I said I’d hold off.

Today while driving, I noticed some hesitation and heavy fuel consumption. As I was driving I pushed the peddle and felt the car start to not move. Got over to the shoulder, started it a few times in park and neutral and while it starts as soon as I push the pedal it dies out. If I start it and do nothing sometimes it idles correctly, but most of the time it’s idling erratically and just dies.

I have noticed some exhaust smell also.
 

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Do you have a copy of the Repair Order which stated which trouble code was read from the check engine light? How did the XC behave up to this event? You said you already brought it to the dealer, why? Fuel MPG?

Without knowing your maintenance history and assuming you are up to date with spark plugs, transmission fluid changes, fuel filter, etc...

It could very well be a clogged cat. It could also be an erratic fuel pump, fuel pressure regulator, bad O2 sensor (which should be replaced with a new cat anyways), bad crank or camshaft sensor, PCV valve, etc. A read-out of the codes using VIDA would give a better picture and if you could give a summary of your maintenance too.

Since you said you started in Park and it would die out if you pushed the pedal, you could rule out the transmission for now.
 

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Discussion Starter · #3 ·
I'll have to grab the Volvo sheet and see if they listed the code it was throwing.

Yes, I have someone that will do some smaller things for me in a pinch and he started with plugs and wires, worked great for a week and then the pressure issues started back up.

I let the vehicle sit for a few days while I drove my 07 V8 XC90 and decided to give the 3.2 another go, it started up and drove just fine out of the gate. Didn't want to push my luck so didn't test it extensively.
 

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If you did have a backpressure issue with clogged cats, then it would be apparent all the time. If you were able to drive mostly trouble free for a week after it sat, then it might not be the expensive catalytic converters.

This is where reading the codes is important. Some sensors, like the camshaft or a crankshaft sensor can get hot and begin to throw inaccurate readings. Sometimes the fuel pump needs time to cool and then can fire right up. Other areas which it could be are in the fuel (bad gas, regulator, venting, injectors), intake (throttle body, MAF), to ignition (bad coils, bad boots, wrong spark plugs).

Since you said someone did the spark plugs and wires, well the engine does not have spark plug wires. It has individual coils with boots. I would double check the coils and spark plugs, that the plugs are the correct ones (either Bosch or Volvo and not cracked), that none of the boots are torn or out of place, and that the connections are tight. If all good, then I would also swap coil locations (2 at a time) to see if the running slightly alters, which could mean you have a bad coil. 2.5t owners know very well a bad coil can give weird symptoms. The engine could run fine, but then run rougher at different temps, different loads, different RPMs, different gas, and sometimes for days at a time.

If an O2 sensor code was thrown, thus why the dealership suggested a new cat, it could be due to unburnt fuel with a bad spark plug/coil and/or fuel issue. If the engine is indeed running rich, you can try to smell the oil on the dip stick. Check if the oil smells a little like gas (it might not), if so, then I would start looking at the ignition first.
 

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Discussion Starter · #5 ·
Spoke with him and he said he put in the best NGK plugs, but did not swap the ignition coils. He cleaned the MAF, said he also cleaned the upper O2 sensors.

I'd tend to rule out bad gas, I only buy from BP and use premium religiously.

Thank you again for your insight, not as familiar with the XC90 as I am other models.
 

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Not sure why he would clean the MAF and O2 sensors unless there were codes for them. I typically do not like cleaning the MAF because more harm than good can happen, even when using MAF cleaner. Did he mention how the O2 sensors looked? Cleaning them might explain why it ran well for a week, but not sure. The MAF and O2 sensors could both throw codes if the readings were not within range, but the real cause could be something else. That means these parts could be in good working order, but fiddling with them could do more damage. An inconsistent MAF reading could be caused by an air opening after the MAF, such as a loose/cracked boot or loose/missing plastic thingy on the boot connecting to the throttle body. The O2 sensor can throw a code, well if it is running rich due to what I listed already. Both the MAF and O2 sensor coordinate with each other. The 3.2 also has variable length intake (VIS) via flaps and this not working could possibly affect the power delivery curve, but should not stall the engine.

Reading the codes would help very much in this situation. If you can't get a VIDA reading, go get a free OBDII reading at an auto parts store, that is a start. With your mileage, it could be a simple worn out part causing the trouble.

When you drove the car right after starting (it doesn't take O2 sensor input until the sensor is warmed up), what was the rpm you went up to? If you were running rich for quite some time, it could affect the cats, but it should be more apparent as you go up in the rpms. Clogged cats feels more like a chug than rough running.
 
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