Engine management light on with no loss of performance, tick over higher.

[rhencullen1989]

Hi, as per heading really, driving my 1.8 T BEX eng code the other day and the engine management light came on, there was no loss in performance and no mis fire, drove it 100 miles or so, got home and disconnected the battery, when reconnected and started the light was out, drove 70 miles the next day with the light still out, although I did notice the tick over was a bit higher sometimes, it would tick over at 800 revs as normal, then at the next set of lights would tick over at 1000' and so on.

Today the light has illuminated again, still no loss in performance and still an irregular tick over, some times it feels a bit lumpy as if its missing but it's not.

Any input will be great, I suspect some sort of air valve or a air mass meter issue, gonna get it scanned tomorrow and see what that brings up. but in the meantime if anyone has had the same issue please feel free to elaborate.....Ta.

[zollaf]

cts maybe

[rhencullen1989]

Sorry, what's cts!

[Guest 2]

coolant temperature sensor

your fault scan should tell you tomorrow

[rhencullen1989]

Ah of course, I assume this would be the green one at the back of the engine, new o ring and clip also required if this turns out to be the problem.

my temp gauge reads crack on 90 degrees though, would that be right......

[pauldazzle]

The CTS has 2 seperate outputs. One to the gauge & the other to the ECU, it's common for one output to fail without effecting the other.

[fourringsrus]

Only buy e-bay cheapo if you want to do the job again in the near future.
The genuine Audi part complete with new clip and o ring is only £40, been there, done that. 1.8t AVJ code

Stuart

[adamss24]

There is a throttle body adaptation to be made, you need fully registered vag com/vcds in order to perform basic settings though !

[rhencullen1989]

Hi again, thanks for the info so far.

Right had the scan done this morning and came up with the following Fault Codes:-

16891 (P0507) Idling speed control, revs above specification sporadic

17544 (P1136) Bank 1, Additive mixture adaption system too lean Sporadic - MIL ON

18010 (P1602) Power supply terminal 30 voltage too low sporadic - MIL ON

16804 (P0420) Bank 1, Catalyst system Efficiency too low sporadic - MIL ON

ok, so a few fault codes which i guess are probably linked to one problem, the 1801 power supply terminal 30 voltage too low i assume is battery related and probably due to me disconnecting the battery to turn the emissions light out.

The scanner did say it could be down to cheap supermarket fuel or an air leak somewhere, and to fill up with some decent esso or shell and to take it back for another scan in a week or so, he did clear all codes and re-set the throttle valve position as i removed this last year to replace the alternator pulley. So far today the light has stayed off but i dont expect it to stay out for too long.

Can any one descipher the codes that we have, thanks, Rhen.

[pauldazzle]

It may take a few driving cycles for the EML to come back on.
I would advise that you get your scanner/mechanic to look at the temp the ECU is getting from the CTS in VCDS measuring blocks as the ECU won't throw a code if it's getting a signal from the CTS even if it's wrong. Usually CTS failure only causes a code if it's shorted to ground or become intermitent. A goosed CTS will cause the ECU to fuel incorrectly which could well be responsible for your codes. If the CTS is at fault replace it with a genuine VAG part only or you'll probably be buying twice as cheap aftermarket CTS's rarely work properly.