DDK - Die Deutschen Klassiker

I just imported a 3.2 Carrera from Jersey where there's no MOT and on its first MOT in the UK the CO emissions are way too high. I asked if this is just on idle and they said "no" but I'm not taking that as gospel. What's the protocol for dealing with this?

On another note the engine sometimes hunts at idle and can be prone to stalling. My understanding is this is usually the "too rich at idle" problem and that the first fix to try for this problem is to twiddle the 3mm allen bolt on the airflow meter all the way in and wind back 2-3 turns in order to set the idle enrichment correctly. Does that sound legit? I understand there's a more sopisticated approach to this fix which involves fixing some relay across the ecu.

Assuming that additionally, the mix is rich across the entire range, does anyone know what's the protocol (in terms of easiest and/or most likely fix first) for eliminating possible causes of this?

Trying cleaning the idle air control valve re the stumbling and stalling at idle.

Hunting at idle and (bizarrely) high emissions can also be caused by an air leak.

It could just be burning off some oil.

What’s the mileage / has it been rebuilt / when was the oil last changed or topped up and did the person who did it know how to do it on a 911?

If it’s just been sat or is a smidge overfilled a proper hour’s hard drive might solve it.

Sam wrote:It could just be burning off some oil.

What’s the mileage / has it been rebuilt / when was the oil last changed or topped up and did the person who did it know how to do it on a 911?

If it’s just been sat or is a smidge overfilled a proper hour’s hard drive might solve it.

Thanks for the suggestions. No reason to think it may have been overfilled. I just did 200 miles at motorway speed prior to the test, which would have burnt off any excess, do you think? It's done 170,000 miles but had some new piston rings and related work at around 90,000 miles.

PeterK wrote:Hunting at idle and (bizarrely) high emissions can also be caused by an air leak.

From what I read there's some gubbins in there that reacts to a weak tickover and prevents the engine from stalling - so it stands to reason that's the thing that could cause high emissions. Where do I look for the air leak? I assume it's the entire vacuum system, particularly hoses and joins?

Chris_911 wrote:Trying cleaning the idle air control valve re the stumbling and stalling at idle.

ok thanks will give that a try... Now to find it!

RobFrost wrote:

Chris_911 wrote:Trying cleaning the idle air control valve re the stumbling and stalling at idle.

ok thanks will give that a try... Now to find it!

Worth trying - you can't miss it, straight in front of you as you look at the engine.

This should help you out from Heidi and Franny’s Garage


https://www.youtube.com/watch?v=MRZG-s_55CU

RobFrost wrote:

Sam wrote:It could just be burning off some oil.

What’s the mileage / has it been rebuilt / when was the oil last changed or topped up and did the person who did it know how to do it on a 911?

If it’s just been sat or is a smidge overfilled a proper hour’s hard drive might solve it.

Thanks for the suggestions. No reason to think it may have been overfilled. I just did 200 miles at motorway speed prior to the test, which would have burnt off any excess, do you think? It's done 170,000 miles but had some new piston rings and related work at around 90,000 miles.

80k on the rebuilt engine is certainly enough to mean the valve seals and rings may be worn and leaking again, but as you did those high speed miles, and since the idle isn’t right anyway I’d start with the fuelling.

This is how CIS works: https://youtu.be/a4fJAfXYxW

Not super complicated but it’s still easy to spend hundreds or even thousands getting KMI to rebuild all the wrong bits. I spent a couple of days chasing poor running on my 205 GTi, then rang Pug1off who correctly diagnosed it as a broken track on the TPS over the phone and fixed it while I waited for £150. I’d have never found it.

Whether you have a go yourself or just get it to a good specialist depends on your desire to learn and/or spend.

A specialist could also give you a good idea of the condition of the rings and valves by doing a leak down test.

Err...it's a 3.2 so. no CIS...

O yeah. Oopsie. Same logic applies, just replace CIS with LE-Jet.

Sam wrote:

RobFrost wrote:

Sam wrote:It could just be burning off some oil.

What’s the mileage / has it been rebuilt / when was the oil last changed or topped up and did the person who did it know how to do it on a 911?

If it’s just been sat or is a smidge overfilled a proper hour’s hard drive might solve it.

Thanks for the suggestions. No reason to think it may have been overfilled. I just did 200 miles at motorway speed prior to the test, which would have burnt off any excess, do you think? It's done 170,000 miles but had some new piston rings and related work at around 90,000 miles.

80k on the rebuilt engine is certainly enough to mean the valve seals and rings may be worn and leaking again, but as you did those high speed miles, and since the idle isn’t right anyway I’d start with the fuelling.

This is how CIS works: https://youtu.be/a4fJAfXYxW

Not super complicated but it’s still easy to spend hundreds or even thousands getting KMI to rebuild all the wrong bits. I spent a couple of days chasing poor running on my 205 GTi, then rang Pug1off who correctly diagnosed it as a broken track on the TPS over the phone and fixed it while I waited for £150. I’d have never found it.

Whether you have a go yourself or just get it to a good specialist depends on your desire to learn and/or spend.

A specialist could also give you a good idea of the condition of the rings and valves by doing a leak down test.

that video is giving me "video unavailable". Do you have the name I can search for?

Best advice is to get a copy of the Bentley manual for the 3.2.
It will rapidly pay for itself.

Chris_911 wrote:Best advice is to get a copy of the Bentley manual for the 3.2.
It will rapidly pay for itself.

Thanks for the tip. I have the Haynes manual already - is it far superior to that?