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Discussion Starter · #1 ·
Hi folks,

Cross posting the same thread from MVS...

Well, I bought that 2009 S60 T5 that I asked for opinions on earlier... and it's testing me by giving some running issues. No codes - that would be too easy.

Here are the symptoms (and my thoughts on each):
1. Idle is rough feeling - vibrations in cabin in drive/park/neutral. I've replaced the upper torque mount, lower trans torque mount, and passenger engine mount with Lemforder/Hutchinson OEM parts.
2. Throttle 'dead spot' when setting off or general lack of sensitivity. It's extremely laggy, and when it finally does respond, the car often jumps forward suddenly.
3. Odd transmission behavior - around 40 mph or below, when I'm off the gas and coasting, the rpms drop to neutral. I don't think my 2009 auto should be doing this?

I think it's the MAF. I've done some data logging using an iCarsoft Volvo reader, and have these values:
- Idle speed in neutral, AC off, at temp : 650 - 677 rpm
- Fuel trim, bank 1, short : 0.99
- Fuel trim, bank 1, long, lower : 0.99
- MAF reading, neutral, idle, at temp : 10.5 - 10.8 kg/h
- MAF correction factor : 0.99

I know the later model P2s have the Bosch throttle units that tend to be better, which is why I'm starting with the MAF. Looking for any other guidance folks can offer. Thanks!
 

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Start with cleaning the throttle body. Remove it from the engine, but leave it plugged in as to not disturb the connector. Clean it with GUMOUT and some scotch brite. Replace gasket and see if that helps. When the throttle body is off, operate the butterfly with you fingers. When its in the closed position, see if you can push the butterfly freely. It's gear driven and sometimes the plastic gears can become worn (in which case you replace the throttle). Usually if the throttle is dirty enough it will set MAF flow too low codes as well as a throttle actuator code and LTFT code. Regardless, eliminate the fact it could be dirty.
 

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Discussion Starter · #3 ·
Start with cleaning the throttle body. Remove it from the engine, but leave it plugged in as to not disturb the connector. Clean it with GUMOUT and some scotch brite. Replace gasket and see if that helps. When the throttle body is off, operate the butterfly with you fingers. When its in the closed position, see if you can push the butterfly freely. It's gear driven and sometimes the plastic gears can become worn (in which case you replace the throttle). Usually if the throttle is dirty enough it will set MAF flow too low codes as well as a throttle actuator code and LTFT code. Regardless, eliminate the fact it could be dirty.
Thanks for the response. I'm 99% sure the throttle body was cleaned by the shop before I bought the car - they said it was done when they serviced the PCV system. Perhaps I can pull the hose off and see inside with a stethoscope to see if it's dirty before going through the effort of pulling it. Looks to be a PITA with being mounted upside down on the manifold.

Just looked also at the fuel pressure sensor values - right around 400 kPa +/- probably 20 kPa. I don't know if there's a threshold on how much this can vary, but that doesn't strike me as abnormal. Maybe I'll get a test kit from an auto parts store and compare to what the sensor is seeing.
 

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Without any codes to go off of definetly make sure you have a solid base line. Start with all the typical "stage 0" type of stuff. Make sure Plugs and air filter are new. Throttle is good and cleaned. Make sure there are no vacuum leaks - Spray the intake/all associated vacuum lines/hoses with carb cleaner and see if the engine RPMS change - if they do, remedy that. Be sure PCV system is clean and you have vacuum in the crankcase. You've replaced all motor mounts already so thats a good thing. Sometimes a "rough running" depending on who is describing it could be associated with a vibration from a mount, but then again it could be what we call a "fish bite" type of misfire. This will feel like a minor skip/hesitation but isn't bad enough to set a code. Your MAF readings at idle are a little low - Per VIDA "Normal value with the engine at operating temperature and idling, neutral and air conditioning (A/C) switched off: approximately 12–20 kg/h."
 

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Everything that Importservice mentioned is exactly what I was going to recommend. The MAF is easy, but the butterfly is a culprit along with spark/vacuum.
Super difficult to diagnose over the internet so if the suggestions don’t work, there’s plan B: take it in and get a guarantee on work performed.


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Discussion Starter · #6 ·
Follow-up on this... It was indeed a vacuum leak, right by the intake going to the turbo. The shop found it and fixed it. I always forget just how quickly a vacuum leak can drag these cars to their knees. Many times better!

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