Cold Start noise
12-29-2001, 05:05 PM
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Cold Start noise
I've noticed recently as the temperature has dropped (0=>+4degC) that when I cold start there is a very noticeable 'bop, boh, bop' coming from the engine for the first 3-5 mins after starting. Sorry for the vague reproduction of the noise but it is difficult to reproduce in writing...I think it is linked to engine rpm (the frequency of the noise that is (from idle up to around 3krpm which is the highest I use while the car is cold)) but it disappears quite quickly as the car warms up and is inaudible from inside the car with the windows up. It sounds almost like air being pumped through a rapidly opening and closing valve. Does anybody else get this? Is there something wrong with the engine? 
12-30-2001, 02:44 AM
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Mags;
It is normal, it is the electric airpump, and if you have condensation, the noise will sound like a gurgle. It is there to lean the rich mixture on startup.
It is normal, it is the electric airpump, and if you have condensation, the noise will sound like a gurgle. It is there to lean the rich mixture on startup.
12-30-2001, 02:27 PM
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Originally posted by Kevin:
<STRONG>Mags;
It is normal, it is the electric airpump, and if you have condensation, the noise will sound like a gurgle. It is there to lean the rich mixture on startup.</STRONG>
<STRONG>Mags;
It is normal, it is the electric airpump, and if you have condensation, the noise will sound like a gurgle. It is there to lean the rich mixture on startup.</STRONG>
01-05-2002, 03:21 PM
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Passed by a Porsche garage today to pick up some bits and pieces and had a chat with one of the technicians who said the 993tt didn't have an air pump . Was he speaking crap?
I described the noise - of course it wouldn't do it there because the engine was hot - and the technician said it could be a cold exhaust sound and if it was then that was normal. Does anyone else out there who drives a tt experience any interesting/different noises on cold start up?
. Was he speaking crap?I described the noise - of course it wouldn't do it there because the engine was hot - and the technician said it could be a cold exhaust sound and if it was then that was normal. Does anyone else out there who drives a tt experience any interesting/different noises on cold start up?
01-06-2002, 04:15 PM
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Mags;
You might need to find another shop. Call your local Dealer and ask him if part number 993-624-103-01 is for a 993TT. Mags you have one, unless it has been removed. Good luck.
You might need to find another shop. Call your local Dealer and ask him if part number 993-624-103-01 is for a 993TT. Mags you have one, unless it has been removed. Good luck.
01-07-2002, 05:14 AM
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Originally posted by Kevin:
<STRONG>Mags;
You might need to find another shop. Call your local Dealer and ask him if part number 993-624-103-01 is for a 993TT. Mags you have one, unless it has been removed. Good luck.</STRONG>
<STRONG>Mags;
You might need to find another shop. Call your local Dealer and ask him if part number 993-624-103-01 is for a 993TT. Mags you have one, unless it has been removed. Good luck.</STRONG>
M
01-07-2002, 06:22 AM
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Originally posted by mags993tt:
<STRONG>
Will do Kevin and thanks once again. Just for the record this was one of the biggest OPC's in Central London. If my past experiences with Official 'whatever' centres are anything to go by then nothing surprises me
M</STRONG>
<STRONG>
Will do Kevin and thanks once again. Just for the record this was one of the biggest OPC's in Central London. If my past experiences with Official 'whatever' centres are anything to go by then nothing surprises me
M</STRONG>
as you correctly stated in the first place.I'm really disappointed at the level of knowledge exhibited by the so-called experts where I bought the car and where I was hoping to have it serviced. Before I totally bin them do you think it is at all possible that UK spec cars do not have this part? When I suggested to the technician that I was hearing a noise that could be the air pump following your initial response, he said that only the older cars had air pumps. I specifically asked the parts department whether the part number was for all model years (mine is '98) and they said yes but just wondering whether they may have deleted it for certain countries (if indeed it is possible to delete) from a certain date - I can't think why they would though...but just trying to understand where the technician was coming from...
He seemed quite knowledgeable and said he had been servicing Porsches for 30 years...
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01-07-2002, 01:22 PM
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I might be able to explain the discrepancy, but let me add that I am not sure what hardware is on the 993TT.
On the older emission controlled vehicles (1970's) there were air pumps. These were mechanical pumps, driven from a belt, to inject air. In later years, most manufacturers changed to a vlave arrangement that pulled in air using exhaust pulses. This was a better solution, as you eliminated the mechanical drag of the air pump.
Most people still refer to these valves as air pumps, but strictly speaking, air pumps have not been widely used for many years.
BTW - I get the same burbling sound when first starting the engine. I have modified mufflers and it sounds great. If you let the car sit and warm up, you can hear when the air injection stops, as that noise goes away. Air is injected when the engine is cold, since the mixture needs to be richened. This add'l air lets the cats do their job, as they can not work efficiently with the rich mixture needed when cold.
On the older emission controlled vehicles (1970's) there were air pumps. These were mechanical pumps, driven from a belt, to inject air. In later years, most manufacturers changed to a vlave arrangement that pulled in air using exhaust pulses. This was a better solution, as you eliminated the mechanical drag of the air pump.
Most people still refer to these valves as air pumps, but strictly speaking, air pumps have not been widely used for many years.
BTW - I get the same burbling sound when first starting the engine. I have modified mufflers and it sounds great. If you let the car sit and warm up, you can hear when the air injection stops, as that noise goes away. Air is injected when the engine is cold, since the mixture needs to be richened. This add'l air lets the cats do their job, as they can not work efficiently with the rich mixture needed when cold.
01-07-2002, 02:02 PM
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Originally posted by Mark D - 993TT CA:
<STRONG>I might be able to explain the discrepancy, but let me add that I am not sure what hardware is on the 993TT.
On the older emission controlled vehicles (1970's) there were air pumps. These were mechanical pumps, driven from a belt, to inject air. In later years, most manufacturers changed to a vlave arrangement that pulled in air using exhaust pulses. This was a better solution, as you eliminated the mechanical drag of the air pump.
Most people still refer to these valves as air pumps, but strictly speaking, air pumps have not been widely used for many years.
BTW - I get the same burbling sound when first starting the engine. I have modified mufflers and it sounds great. If you let the car sit and warm up, you can hear when the air injection stops, as that noise goes away. Air is injected when the engine is cold, since the mixture needs to be richened. This add'l air lets the cats do their job, as they can not work efficiently with the rich mixture needed when cold.</STRONG>
<STRONG>I might be able to explain the discrepancy, but let me add that I am not sure what hardware is on the 993TT.
On the older emission controlled vehicles (1970's) there were air pumps. These were mechanical pumps, driven from a belt, to inject air. In later years, most manufacturers changed to a vlave arrangement that pulled in air using exhaust pulses. This was a better solution, as you eliminated the mechanical drag of the air pump.
Most people still refer to these valves as air pumps, but strictly speaking, air pumps have not been widely used for many years.
BTW - I get the same burbling sound when first starting the engine. I have modified mufflers and it sounds great. If you let the car sit and warm up, you can hear when the air injection stops, as that noise goes away. Air is injected when the engine is cold, since the mixture needs to be richened. This add'l air lets the cats do their job, as they can not work efficiently with the rich mixture needed when cold.</STRONG>
I think I may have to modify my mufflers too because it doesn't sound that great through the stock ones - Well, it's as good an excuse as any!
01-08-2002, 01:04 PM
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Mags & Mark;
The air pump in a 993 and a 993TT is an electric air pump similar to a electric heater fan. It is not belt driven, like the power steering pump. It is located roughly over number 2 & 3 cylinders.
The air pump in a 993 and a 993TT is an electric air pump similar to a electric heater fan. It is not belt driven, like the power steering pump. It is located roughly over number 2 & 3 cylinders.
