Lug.Nut59

2002 S4 2.7 V6 - Engine turns over fine, has spark, fuel pressure seems to be good (I can hear the fuel pumps come up to pressure and fittings spray when loosened). Does not back fire. Exhaust is rich smelling. Periodically, it sounds like one cylinder tries to fire. No codes present to be read.

I suspect that the cam belt slipped and the cam timing is off.

History: Car was being driven steady state at about 60 MPH. Car just seemed to lose power and fade away to nothing. When a restart was attempted in a parking lot, the engine would not turn over. The engine seemed seized. But I was able to turn the crankshaft backwards 3/4 of a revolution and then it would crank back to that spot. Pretty sure that a few attempts at this simply bent a valve allowing the engine to turn over normally as it does now. With cam timing off and with fuel and spark, I would think there would be a backfire now and then.

Any ideas would be greatly appreciated.

shawnoc2003

Time to pull the valve covers.

Lug.Nut59

I plan to do a compression check as soon as I get back to the car. What do you expect or think I will find when I pull the valve covers?

If there are bent valves, I would expect to see valves that do not return fully to the closed position. Will this be true for the Audi? I have plenty of experience under the hood of GM and Ford vehicles, this is my first Audi.

thanks for the suggestion.

shawnoc2003

You should be able to see a shredded belt. If it bent a valve, you may see signs of distress on the cam lobes and tappets.

Valve covers are just quick. No point in a compression test since it won't roll over.

Lug.Nut59

Belt is in great shape. We were told the belt was replaced just before purchase 18 months ago. From the looks of it, it was replaced. However, looking at the cam pulleys, there is clearly a difference in position between the two, maybe 15 degrees.

The tension on the belt is good as well. I do not have a clue as to how the timing could have changed, but that sure appears to be the case. Very odd due to the occurance at a steady speed as well.

I will not get back to the car for a few days. Thanks for the input.

shawnoc2003

Just a guess, but it sounds like the pulley wasn't torqued down correctly if it moved.

Lug.Nut59

I had the same thought. Finally had time to get the valve covers off. Both exhuast camshafts have been damaged. The tops of the lobs of two cylinders on the right and one on the left have been shaved. Lifters are busted. I will be pulling the heads this week. I assume the valves will be bent; is this a valid assumption or do the valves survive in this engine?

How difficult are the valve systems to work on? I have looked at the procedures for timing the cams to each other and the tools required. Are there any tricks to the valves or are they pretty straight forward?

odoboyusa

I have a pair of good heads for the 2.7.
PM me if you are interested.
By the time you replace valves and lifters, and pay for all the parts you will be in the same spot as just buying other heads. Unfortunately when valves hit pistons, parts break off and get chewed in the cylinder, damaging the heads beyond repair.