A6 tdi quattro high idle 1100rpm

**JamesSvr6** · 13-07-2011,03:52 PM

I have recently bought a 99 A6 2.5 tdi and when first starting the car from cold it idles at 750-800 rpm which is normal. After 5 mins of driving, or just sitting at a junction for example the revs will go from 750-800 rpm to 1100rpm. The engine will then idle at 1100rpm for the remainder of the journey. (It's a fairly high miler at 178k)

Any thoughts as to what could be causing this?

I am going to change engine oil, filter and oil temp sensor in sump (oil temp always reads 0) as previos owner did 15k without changing it. Car has limited/next to no history.

Thanks in advance

James

**bagpipingandy** · 13-07-2011,10:23 PM

does water temp sit bang on 90deg?

Andy

**JamesSvr6** · 14-07-2011,08:20 AM

Yes, the water temp goes up to 90 and just stays there. I havent scanned it, which I can do at a mates. Only things I can think of is air leak, MAF or ecu compensating when car gets to certain temp.

**bagpipingandy** · 14-07-2011,12:33 PM

what is the engine code? 3 letters found in the logbook & in the spare wheel well

My AKE has 2 temp sensors, one for the dash, sits on top of the engine, and there is one on the low pipe to/from the radiator, I think it is for the ECU, get a scan done and you may be able to check engine temperatures in the measuring blocks to see if its it faulty

Andy

**JamesSvr6** · 26-07-2011,11:43 AM

Originally Posted by bagpipingandy

what is the engine code? 3 letters found in the logbook & in the spare wheel well

My AKE has 2 temp sensors, one for the dash, sits on top of the engine, and there is one on the low pipe to/from the radiator, I think it is for the ECU, get a scan done and you may be able to check engine temperatures in the measuring blocks to see if its it faulty

Andy

This is really starting to p me off, I have replied to this thread 3 times over the past week and it never posts up!! It's an AFB engine. The soonest I can get a scan done is on the 13th Aug when im back from hols.
I got a water level beep yesterday so the water has gone down after 800miles.

Thanks for advice.

James

**adamss24** · 26-07-2011,09:51 PM

Change the coolant temp. sensor. It has dual outputs 2 pin for the gauge and 2 pins for the ECU. In your case the ECU part is not working well and computer defaults to high rpm as it thinks that outside is very cold and tries to warm-up the engine. Get a new seal as well !

**philmax** · 27-07-2011,05:24 PM

I had a very similar problem. 2 minutes after starting the idle speed went up to 1200 rpm.
Its not nice trying to hold the car back. I replaced the temp sensor and resetted the fault. I have a good 740 rpm idle and the problem has never come back.
I have a number of problems. One down a couple to go or may be one to sort all.
Good luck

**philmax** · 01-08-2011,10:31 AM

Hi James. Have you got anywhere with the problem. I bought a sensor from Ebay for about 8 pound. It was a genuine part.
Its easy to replace. It took 5 minutes.

**JamesSvr6** · 12-08-2011,01:20 PM

Thank you everyone for the v helpfull answers. I really appreciate it! I have just returned from holiday and I am going to sort this problem out asap. So the sensor I need is the 4 pin sensor as here on ebay:

http://www.ebay.co.uk/itm/AUDI-COOLA...item27b45c0d88

Thanks very much! James