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My 997.2 C4 is a daily driver, about 15k miles/year, odometer currently at 76k. Over the past 18 months I have noticed a progressivly worse idle quality which I was convinced was due to a bad MAF. The condition continued to get worse and recently resulted in bank specific misfire codes, cylinders 1, 2, 3. This tipped me off that it probably wasn't a MAF sensor so I started thinking about things that would be bank specific, VVL solenoid or O2 sensors. I started with the VVL solenoid and was right.
The first thing I did was remove the VVL solenoid and tested it with a 12V power supply. The VVL solenoid has 3 ports, oil supply in the nose (P port, also contains the filter), a control port in the middle (A port), and a tank port on the top (T port). When powered with 12V the P and A ports are connected, when disconnected the A and T ports are connected. When I powered my VVL solenoid I could feel the armature inside the coil portion jumping and the hydraulic element moved out which connected the P and A ports. However when I removed the power supply the hydraulic element didn't return. I could push the hydraulic element by hand to get it to return but it took high effort.
I then disassembled the solenoid and found that the armature in the coil portion was binding inside the armature tube, (see attached image). I polished the OD of the armature to the point where it moved feely inside of the armature tube. I then reassembled the solenoid and re-installed into the vehicle and test drove. I have been driving it for 3 days now and its completely transformed back to when I bought the car with 29k miles. Perfectly smooth idle, no stumbles or misfires. I do plan I replacing both VVL solenoids with the updated part number, 9A1.105.308.03.
Hope this helps others with similar issues.
Coupla questions.... was a simple remove and replace? This is located between the plugs correct?
I have threatened myself to replace these in a hail mary pass.... I get a dropout at around 2700-3000 RPMs under slight load. I've had this for all 100K miles of ownership... one tech said he thought it may be a "lazy actuator". I swore I was going to change them out my last plug change, but like a dope, I forgot to order them. Did you have that dropout? I don;t have your other symptoms.
Coupla questions.... was a simple remove and replace? This is located between the plugs correct?
I have threatened myself to replace these in a hail mary pass.... I get a dropout at around 2700-3000 RPMs under slight load. I've had this for all 100K miles of ownership... one tech said he thought it may be a "lazy actuator". I swore I was going to change them out my last plug change, but like a dope, I forgot to order them. Did you have that dropout? I don;t have your other symptoms.
Peace
Bruce in Philly
Yup, simple remove and replace and yes they are located between the spark plugs, one on each bank.
See this is what I like, a guy who uses his head to figure things out and then his ingenuity to see if it can be fixed without just buying a new part and tossing the old one. This is how we used to do it before manufacturers and dealers decided it's more profitable to just hire parts-swappers to throw expensive new parts at a problem till they stumble across the right one.
03-04-2019, 08:21 PM
997.2 - rough idle, stumble, misfires, stall, finally solved
