2008 Cayenne S 4.8 - low RPM knocking, smoking and all plugs fouled within 50KM

[Jmcmilli]

I'm at a loss what to even try next ... ANY suggestions appreciated !!

 

Compression 240-245 in all cylinders except for #2 which is 200. I think these are good numbers for a 10 year old engine. When the lifters were replaced so were a pile of gaskets, seals and hoses.

 

Very very minor scratches in multiple cylinders. This doesn't look related to scoring, so common in these questionably designed 4.8l engines. 

 

Rough idle, knocking and heavy smoking at low RPM acceleration – often car struggles after coasting in gear 5 or 6 then having to accelerate. Shreds oil and spark plugs even when stuffed with Lucas high mileage additive.

 

Toronto's best independent Porsche shop did all but the AOS:

• The lifters were replaced
• Camshaft and tensioners out
• Carbon cleaning of valves and intake system
• New actuator solenoid for the 2^nd stage valve lifters
• New vacuum pump
• New ignition coils
• New top engine mount
• All AOS parts and hoses
• New spark plugs every 50 KM 

 

After all that work cylinder 2 or 3 fouled right away so the shop said it was scoring and doomed. They filled it with Lucas and replaced plug 2 suggesting I should trade it in ASAP. Once I realized how absolutely worthless these cars are after 10 years I figured I'd just hang, onto it until I could see if it was fixable. If you drive it hard in manual the car seems perfect with tons of power - that's my main reason to try and fix it.

 

If only I could drive the local 40km/hr streets in 1st and 2nd gear at 2500-3000 RPM without drawing angry stares from the noise and occasional light roll of coal.