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Intermittent lumpy running - Cured
http://forums.tipec.net/viewtopic.php?f=8&t=22655
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Author:  Spot [ Sun May 28, 2017 9:08 am ]
Post subject:  Intermittent lumpy running - Cured

Thought I'd share my experience of an intermittent fault with you. My car is a 2003 996 C4S which, 14k ago had a full Hartech rebuild.
In March the car developed a problem where, on occasions, when up to operating temperature it would run really lumpy. There was no consistency. One journey would be faultless, the next would be a nightmare. Above 2500-3000 rpm the issue was less apparent, but occasionally under acceleration there would be a momentary stutter followed by normal performance. When the fault did decide to show itself, at idle, the revs would drop to a virtual stall then surge. Eventually the engine management light would flash followed by a 'drive to workshop' warning.
The description above is very condensed. There were many red herrings in the mix, including the fact that the first occurrence of the fault was immediately following an oil top up. The second occurrence was a few days later after ensuring that I'd refitted the oil filler cap correctly to make an airtight seal. The only OBD code was P0022 (Powertrain 'A' camshaft position timing over retarded, bank 2).
The fault was eventually identified by OPC Tonbridge as a cam position sensor.
I live over 50 miles from OPC and the nearest Indy is almost the same distance away. Two local and trusted garages were honest enough to say that they could rack up hours in fault finding to try and locate the faulty component or potential cable breakdown.
I had to wait a while for an OPC appointment, but the guys there could not have done more to sort the problem. Great service from them.
Now enjoying my car Porsche again but being economical with the mileage to keep within the maximum I'm allowed on the insurance. It's surprising how many miles you can clock up trying to find a fault and running to workshops and back!

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