I have here a SEAT Altea that has been to many different places to try and sort this problem, including both SEAT and VW main dealers and specialists. It even spent 3 weeks and an engineering college!
It will start first time every time when cold. But after it has been run and left for a while, on the first turn of the key the engine turns but fails to fire.
The original codes stored in the ECU showed P0171 [Fuel Trim Too Lean] (present and intermittent) along with P2626 [O2 Sensor Pumping Current Trim]. Both of these point to a faulty lambda or MAF reading, however these were shown to be functioning correctly under test. They have also not shown up again during the 5 days I have had the car.
The coolant temperature sensor was then replaced as a matter of course, due to this being a regular failure of VAG models and widely attributed to the symptoms of this vehicle.
Since that time, the vehicle has been tested on several cold to hot runs, both static and mobile.
The starting issue arose again on a few occasions. On each of these occasions the coolant temperature was indicated to the ECU at 66°c. This seemed about right, but it just seems strange that it was the same temperature reported each time.
During further testing, the vehicle was found to have a misfire on 2 cylinders, although this was not a fault reported to the ECU. This was shown on cylinder 1 and more predominantly on cylinder two.
Full sensor, switch and relay diagnostics have been carried out, and appear to be working.
The EVAP control valve has been removed, checked for leaks and retested.
On one particular scan, the CAN network reported a break in communication to the engine ECU that hadn't shown up before. It was also noted that this fault had been reset 22 times previously.
This fault may however not be related to the starting issues, and has not shown up when testing the car during fault conditions.
Any ideas? Anyone?