E437 DMX 90q emissions fail. Help please

iconauto · 20-09-17, 05:36 PM

Hi, I got the above 90q from Ken on here some time ago. She's been off the road for about 9 months and I took her for the test recently and it failed on the emissions. The CO was 4 times the max and the HC was over as well. I have tried changing the plugs (they were really black due to it running rich) and running some fuel system cleaner through it before the retest but it made no difference. The only thing which has changed since the last time it was tested is that I have replaced the brake servo which had a gaping hole in it. After fitting it the idle was rough as a bag of spanners so never having had a KV before, I adjusted the idle with the grub screw and locknut on the accelerator cable bracket on top of the throttle body which sorted out the idle. I've done a bit of research on here and I now know that the idle is controlled by the brass screw in the casting. Could adjusting the idle with the wrong bit make the engine rough very rich or does it have the same effect as adjusting it with the brass screw? Also I hear that the coolant temp sensor can affect the fuel/air ratio if it is knackered. Am I right in saying that it is the bottom sensor on the water flange on the front of the head with a spade connector on it? When I disconnect the connector the revs rise for a second or two then even out. The same when I reattach it.
Any help would be appreciated as I really want to get this car back on the road. Thanks in advance.

Kenquattro · 20-09-17, 05:44 PM

Good to see you still have it, Matt. Emissions problem apart, has the replacement servo sorted the brakes out on it? Be good see some recent pics of it.

John. · 20-09-17, 05:47 PM

Is there not an engine temp sensor at the back of the head?? Maybe that's been disturbed when doing the brake job?

iconauto · 20-09-17, 05:47 PM

Hi Ken, yes the servo you supplied with it sorted the problem out. It now stops! It is exactly the same as when I got it from you, I haven't changed a thing except the stereo as the display bled out on it.

iconauto · 20-09-17, 05:51 PM

Quote:

Originally Posted by John.

Is there not an engine temp sensor at the back of the head?? Maybe that's been disturbed when doing the brake job?

There is a large-ish sensor screwed into the rear of the head, the connection looks fine on it visually. The problem I have with the emissions is that I have no way of telling whether what I am doing is making any difference until I take it back to the garage. He's been pretty good so far as he hasn't logged it on before testing it but I don't want to piss him off by taking it in every day and asking him to stick the pipe up its pooper.

Kenquattro · 20-09-17, 05:53 PM

Quote:

Originally Posted by iconauto

Hi Ken, yes the servo you supplied with it sorted the problem out. It now stops! It is exactly the same as when I got it from you, I haven't changed a thing except the stereo as the display bled out on it.

Glad to hear the brakes are finally sorted. I am sure the emissions query will be sorted with some help from the technical bods on here. Shame about the stereo.
Glad to hear it has been looked after, I was sorry to have to sell it on, but it was the sensible thing to do for me at the time. Not many unmolested early B3 90 quattros about, now.

quattromnc · 20-09-17, 05:54 PM

There can be several reasons for this, here's a few suggestions you can try...

1. Fuel metering head issue (bit above the airbox), it could be an adjustment, there's a tiny allen key adjustment screw at the bottom of a small tube.
2. Injector leakage/bad spray pattern,
3. Bad fuel, if it's been standing, have you put fresh fuel in?
4. Idle valve issue (could be liked to your bad idle)
5. Air leak
6. fuel system issue, have you checked/changed the filter?
7. Ignition system, leads, rotor, dizzy cap & arm
8. Engine breather pipes, they can clog up with oil residue
9. Oil change, dirty oil can produce pretty bad emissions tests

Lots of stuff to check, hope this helps

iconauto · 20-09-17, 06:05 PM

Thanks, fuel is new, it does rev to about 2000 rpm on startup but then drops to normal idle after about 20 seconds or so. pumping the brake pedal causes the revs to rise to about 1500 rpm. I will change the oil this weekend.
I have readjusted the idle using the brass screw and backed off the other screw on the throttle.

quattromnc · 20-09-17, 07:14 PM

i meant the Idle Stabilisation Valve (ISV) a cylinder shaped object with 2 pipes and a wire attached, located near the back of the head, every one I've had has needed a good clean out with a solvent, that regulates idle.

iconauto · 20-09-17, 07:26 PM

Yes i'm going to whip that off and give it a soak. Do you know whether adjusting the idle with the throttle butterfly rather than the idle screw would cause it to run rich?

20-09-17, 05:44 PM	#2
Kenquattro 4 ring whore! Classic Audi Club Member Join Date: Nov 2007 Posts: 6,267	Good to see you still have it, Matt. Emissions problem apart, has the replacement servo sorted the brakes out on it? Be good see some recent pics of it.

20-09-17, 05:47 PM	#3
John. 4 ring whore! Classic Audi Club Member Join Date: Mar 2011 Location: Scottish Borders. Posts: 7,520	Is there not an engine temp sensor at the back of the head?? Maybe that's been disturbed when doing the brake job?

20-09-17, 05:47 PM	#4
iconauto Grown up member Classic Audi Club Member Join Date: Oct 2011 Posts: 63	Hi Ken, yes the servo you supplied with it sorted the problem out. It now stops! It is exactly the same as when I got it from you, I haven't changed a thing except the stereo as the display bled out on it.

20-09-17, 05:54 PM	#7
quattromnc Grown up member Join Date: Mar 2011 Location: Newton Mearns, Glasgow Posts: 177	There can be several reasons for this, here's a few suggestions you can try... 1. Fuel metering head issue (bit above the airbox), it could be an adjustment, there's a tiny allen key adjustment screw at the bottom of a small tube. 2. Injector leakage/bad spray pattern, 3. Bad fuel, if it's been standing, have you put fresh fuel in? 4. Idle valve issue (could be liked to your bad idle) 5. Air leak 6. fuel system issue, have you checked/changed the filter? 7. Ignition system, leads, rotor, dizzy cap & arm 8. Engine breather pipes, they can clog up with oil residue 9. Oil change, dirty oil can produce pretty bad emissions tests Lots of stuff to check, hope this helps

20-09-17, 06:05 PM	#8
iconauto Grown up member Classic Audi Club Member Join Date: Oct 2011 Posts: 63	Thanks, fuel is new, it does rev to about 2000 rpm on startup but then drops to normal idle after about 20 seconds or so. pumping the brake pedal causes the revs to rise to about 1500 rpm. I will change the oil this weekend. I have readjusted the idle using the brass screw and backed off the other screw on the throttle.

20-09-17, 07:14 PM	#9
quattromnc Grown up member Join Date: Mar 2011 Location: Newton Mearns, Glasgow Posts: 177	i meant the Idle Stabilisation Valve (ISV) a cylinder shaped object with 2 pipes and a wire attached, located near the back of the head, every one I've had has needed a good clean out with a solvent, that regulates idle.

20-09-17, 07:26 PM	#10
iconauto Grown up member Classic Audi Club Member Join Date: Oct 2011 Posts: 63	Yes i'm going to whip that off and give it a soak. Do you know whether adjusting the idle with the throttle butterfly rather than the idle screw would cause it to run rich?