Audi 80 ACE 16v: Good when hot - Poor when cold

Posted: Wed Jan 31, 2018 4:08 pm

sometimes the flywheel marks can be difficult to see.

I'd recommend removing the distributor cap so that the rotor arm is visible. Turn the engine by hand until you have the rotor arm almost pointing to #1 cylinder - now look for the mark on the flywheel. Move it tiny amounts and keep checking window in the bellhousing - an assistant helping is recommended.

If you find the mark - use some tipex to make it more visible.

Once you've got that mark, remove the front cover and check your cam marks

Posted: Sun Apr 22, 2018 12:03 pm

Ok, I did a fuel pressure test. Not exactly by the book - I used the test port on the lower half of the fuel distributor.

5.5 bar when the engine is running and
3.5 bar after 30 mins.
3.9 bar after 3 hours (it was a warm day)
3.0 bar after 24 hours

A great result and within guidelines. I think...

I am ready to give the fuel system a clean bill of health - I will repeat the differential pressure regulator voltage check which had some odd results in the last post.

I will also adjust the air flap mixture setting, with Vagcom running live data -> to get the smoothest idle. I may swap back my air flap to my old one which has not been adjusted.

Really, after that it is back to the ignition system and the associated sensors that the ECU uses.

...and it may be worth considering major failures like piston rings, leaking valves etc. The engine is emmiting a lot of dark grey sooty smoke - leaving deposits on the wheelie bin behind it. I believed it to be incorrect mixture burning that gave this but maybe something else.

I have done a number of compression tests with varying results ->Perhaps soot buildup is giving more favourable results at the moment. The plugs a get sooty but not oily FWIW.

I am looking for checks/tests to assess general engine health - any tips on the ACE or similar engine?

Posted: Sun Apr 29, 2018 6:48 pm

I did a compression dry & wet test -> seems fine, happy to rule that out.
Fuel pressures seem flawless -> I repeated the tests. 6.1 bar when running & 3 whe turned off. Happy to rule that out too.

Yesterday it was running well once I got it warm. After all that still the same as it was last year! When hot all the nasty soot disappeared. I had the CSV disconnected.

Back to the CSV! The CSV is working alright but it seems to be dumping fuel, ruining the mixure. The CSV connector measures 12v continuously on priming. I read in a golf 2.0 16v motronic that it would prime for 12 seconds or less based on temp. Mine seems to stay on. My plan is to test it again when the engine is hot - to see if it is turned off then. Or run a live feed (backprobe) and see when it stops dumping fuel in normal circumstances. Thus show associated performance changes. That would confirm my thinking/hypothesis but not isolate the cause.

I was still not sure which temp sender feeds data to the ECU to control the CSV. There are many but it seemed to be between the multifuntional temp sensor on the side of the head or the G62 at the back of the head.

I tried to trick these sensors by putting them in boiling water hoping that the 12v feed would drop to 0v on the CSV, But no! the dash would confirm that the sensor was warm, but maybe not warm enough to switch the CSV off.

Anyway I am still loking for a complete breakdown of all the sensors my car uses to adjust csv mixture formation. It could be multiple readings because I am not getting much sense out of it yet.

Any pointers welcome!

Posted: Wed May 09, 2018 3:24 pm

Ehm - Fixed!

I had betted on the cold start valve but it worked perfectly. I blanked the port and started the car. I videod the spray and it worked as it should with a perfect spray. I cleared out the port to make sure the spray was actually getting to the bores in the correct dose.

I cleared out the crankcase breather, but that was pretty clear anyway.

Some iterations of the CIS system suggested that the fuel pump relay was also responsible for initiating the spray. The housing of my relay was loose anyway and it appeared that some of the contacts may not be connecting - I replaced the 208 with the superceded 372 relay.

Finally I heard a little bit of air release from the heater matrix ports - perhaps there was an air lock/bubble developing at the ECT temp sender.

One of those appeared to be the solution. I'll keep testing it. It flew through its test last week.

Thanks for the support