Failed emissions test

Might help if you posted the details of the test. Did it fail on HC, NOx, or CO?

Pinging can be caused by too much compression (carbon buildup) and/or bad ignition timing. But post up the results of the test in more detail...that may help.

The general tuneup also is a good idea...don't bother emissions testing a car that you know is overdue for service...do the service first, then test.

Find another mechanic before he sucks you wallet dry! Sounds like he's blowin' smoke...

"Matt B." emitted :

Yes of course... I didn't have the documentation when I posted. It is the CO emissions on which the car failed. Here are the results :

DESC LIMIT READING FAIL

ENGINE TEMP MIN 80 82

FAST IDLE : ENGINE SPEED 2450-2850 2720 CO MAX 0.30% 0.54% X HC MAX 200PPM 32PPM LAMBDA 0.97-1.03 0.98

SECOND IDLE TEST : ENGINE SPEED 2450-2850 2720 CO MAX 0.30% 0.57% X HC MAX 200PPM 41PPM LAMBDA 0.97-1.03 0.98

NATURAL IDLE TEST: ENGINE SPEED 650-950 943 CO MAX 0.5% 0.05%

Which is a very stupid mistake I made!!

So the mechanic ran a compression test and the 4th cylinder was 6% down. He suggests this was allowing fuel to leak past the piston and on into the cat, and that is what caused the very bad smells. [I hope I am repeating this correctly]. The spark plugs where changed, oil topped up, timing checked (reset?) - the 4th cylinder is now at 100% and holding 175 PSI - so the MOT was passed. He then gave the car a road test and was satisfied it was performing OK for now, but noted the idling wasn't as good as he would like - and that I should monitor the cars performance and return if the problem reoccurs.

Here are the post results :

DESC LIMIT READING FAIL

ENGINE TEMP temp gauge showed 'warm'

FAST IDLE : ENGINE SPEED 2500-3000 2905 CO MAX 0.20% 0.02% HC MAX 200PPM 24PPM LAMBDA 0.97-1.03 1.00

NATURAL IDLE TEST: ENGINE SPEED 450-1500 907 CO MAX 0.3% 0.04%

-- S i g n a l @ l i n e o n e . n e t

"none2u" emitted :

The timing has been checked and it's correct. There was a suggestion to retard timing to kill the pinking as a quick fix, but since this can affect performance I have stuck to using Shell Optimax which seemed to achieve the same.

A bit of both, mostly the former; based on past history. Let me explain : When he fits a tyre for me, he doesn't charge for fitting. He's done jobs free of charge to keep me running - eg. spot weld on the cat when it came loose (god awful metallic knocking), same for the exhaust, refitted a leaking alloy/tyre, adjusted clutch height.. all FOC. When the clutch died I *was* suspicious. I thought the cable / finger snapped (clutch went to floor and didn't return) and was surprised considering the age of the car. So I picked up the discs to inspect themn and sure enough, they were at the end of their life (posted the pics here). I blame the previous owner for this. When the exhaust went, he put the car on the ramp and showed me it had rotted through. I saw it for myself.

I hope this explains why I have some faith in this mechanic.

-- S i g n a l @ l i n e o n e . n e t

"Lost In Space/Woodchuck" emitted :

See my response to "none2u"...

Total bill came to £60 to get it through the MOT including a new set of spark plugs. As I stated elsewhere - a bill I may have avoided had I serviced the car before putting it in for the MOT.

BTW I now wonder if VW replaced the plugs when they were last scheduled. The pinking and the cat smell were occuring before AND after that service. I mentioned this to the VW mechanic - at the time I did not know what pinking was - his post service conclusion was that it was a loose part on the exhaust rattling - that the smell was harmless and would go away when the exhaust was replaced. Based on this, I continued to drive the car.

-- S i g n a l @ l i n e o n e . n e t

Blah, blah... Okay, look:

CO is a measure of how rich or lean your mixture is. Period. I can't see why someone would measure both CO and Lambda and I can't imagine what equipment you are using that does both, since CO is usually derived from lambda. That said, .98 means you running slightly rich, very very slightly. Still quite reasonable. Those CO numbers do not correlate to a lambda of .98 (especially post cat).

There is no legitamite way to restore compression to the #4 cylinder without removing the engine or at least cylinder head. So basically, I'm just not buying any of this. Adjusting the timing and replacing the spark plugs would have absolutely zero impact on compression. "Topping off the oil" I suppose might if your cylinder is leaking you might be getting a little extra sealing from the oil, but if that were the case your compression would be higher than the others. 6% low is not good, but its not outrageously bad, its probably still within spec.

Your first "fast idle" test shows a maximum CO of .3%, the next one has a max of .2%. Say what? Your HC levels which should be roughly proportional to the CO levels (at a minimum) dropped by 50%, despite your CO levels dropping

Either someone is feeding you a load of crap, or you're feeding us a load of it. Either way, I'm calling shennanigans...