As indicated in subj line, my A4 (Avant 1,8 TS, MY2001, though chassis
8D - same as B5 saloon, motor variant AJL) requires the starter motor to
turn over for ca 15 seconds before I get ignition. This is the case if
the motor is hot or warm.
Car starts immediately on cold engine. Plugs are clean and gapped to
spec (0,8 mm).
Where do I start?
/Robert, in Sweden where we finally got a little snow this morning.
Dump ECU error codes and see if there's anything that jumps out, particularly
fuel mix errors.
There may be a temp sensor at the root cause of the problem; someone good with
a code reader may be able to see if a sensor component has aged beyond its
useful life (looking for out of range adaptation values, for instance).
Either way, the best way to attack this kind of problem is through the OBD
'00 s4 6spd
Thanks Tony and Daytripper for your ideas.
Tomorrow I will buy the new temp sensor and see if it gives different
readings that might stop the warm start problem.
Going from the practical to the theoretical - assuming that my
temperature sensor is indeed faulty, how would a new one, reading ca. 5C
higher, solve my starting problem?
The ECU uses engine temperature as one of the variables in determining how much
fuel the engine uses to run properly for what you are asking it to do.
If it thinks that the engine is warm when it is actually cold it will not supply
sufficient fuel to start it. If the ECU thinks the engine is cold when it is
actually warm it will send too much fuel and partly flood the engine.
Indeed I have now replaced the temperature sensor, though I only get a
couple of degrees warmer. So this indicates to me that I may also have a
thermostat sticking open, not making it possible to close the access to
the radiator when needed (see earlier thread).
But the car restarts without hesitation, even when motor is warm or hot.
OK - we're now a few degrees colder here, so it's not absolutely certain
that my warm/hot start problem is solved, but I have had to warm start
it a couple of times today, and it seems to have behaved better than
before. In addition, I think I am consuming less petrol than before
despite the colder temps, which indicates that the resistance of the old
sensor had been unreasonably high (reading colder than it should have),
causing the ECU to order a richer mixture. This would explain the
difficulties in starting before (15 secs on starter motor) followed by
the excessive petrol smell - engine had flooded.
Let's hope that the car continues to warm start well, even once the
temperature rises back to what it was last week.
Thanks to all who contributed their advice.
Thank you all, this info is very helpful to me. My 99A6 Avant is
experiencing exactly same promlem. Please help me with the following:
1. did u change the sensor yourself, if yes, where is the sensor is
2. where did you buy the sensor?
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