Just drove down to the shop to get some oil and you can feel its running better. The old oil stank, was definitely heavily contaminated with fuel which wouldn't have helped those emissions readings at all. Pulled a plug and its cleaner than it was when it went in and I only drove 10 mins down the road.

 

I think all of the times I've thought i'd fixed the rough running while fiddling with the earths I probably inadvertently 'restored' the sender earth with an accidental wiggle or something

good stuff 

 

some folk add an extra to the o2 sender for good measure too 

16 minutes ago, steveo3002 said:

good stuff 

 

some folk add an extra to the o2 sender for good measure too 

 

Don't see why not - wouldn't want to waste all that nice new wire in my parts bin now would I?

Just came back from the emissions re-test and it failed again but definitely going in the right direction:

Fast idle

Temp 91

CO 5.53% (down from 12.22%)

HC 442ppm (down from 996ppm)

Lambda 0.851 (up from 0.669)

Second test

CO 5.02%, HC 457ppm, Lambda 0.850

Natural Idle

CO 0.62% (down from 10.73%!)

 

Considering I drove with an ECU that thought it was -40C down to Corsica and back, in fact probably for the whole of this year, I've probably got a melted cat. Looking in the old middle silencer that got pulled out recently tells a story:

https://drive.google.com/file/d/11Og03-J_kAc0mjC1Ie9B1MbOV0sMwH2l/view?usp=sharing

You're seeing it right - thats the inner baffle bent inwards! God knows what the catalytic monolith looks like.

 

Got a new cat to put on and a proper Bosch lambda to use in it (second-hand but working - mainly bought it so I wouldn't have to try and prize the old sensor out). Thankfully the mechanic did this test for free and will do the official re-test once the cat is on.

 

Can't think of what else to do really - any ideas apart from pop the new bits on and hope for the best?

 

 

natrual idle seems much more like it 

 

so it has fresh oil in  it and you wire brushed the plugs ?

11 minutes ago, steveo3002 said:

natrual idle seems much more like it 

 

so it has fresh oil in  it and you wire brushed the plugs ?

 

Yep - new oil (although no new filter as its only about 3k old but more that I was pushed for time in the rain yesterday) and cleaned plugs (or rather a cleaned, spare, new-ish set I had spare). Air filter is about 3k old and looks fine too. Before the first fail I cleaned the throttle body (although it was pretty spotless anyway) and have disconnected the crank case ventilation from the air box - empties into a catch can.

 

yeah sounds good , nothing else i can think off to help

 

in the past its been a trick to take the air filter out to get it down a bit more for the test ...maybe an option ?

3 minutes ago, steveo3002 said:

yeah sounds good , nothing else i can think off to help

 

in the past its been a trick to take the air filter out to get it down a bit more for the test ...maybe an option ?

 

Not a bad trick and certainly one I'd be willing to have a go with. I'm pretty confident It'll pass with the new cat and lambda. Got a weekend of wriggling around underneath the car to look forward to now eh...

guess a good hard run with plenty of revs might shift any carbon build up in the valves etc

 

cross your fingers the manifold studs dont snap 

7 minutes ago, steveo3002 said:

guess a good hard run with plenty of revs might shift any carbon build up in the valves etc

 

cross your fingers the manifold studs dont snap 

Gave it a right thrash this morning before taking it in to the station but could probably do with another if its still running a bit rich.

 

Thankfully I've got new studs and brass nuts on the downpipe - had to replace the gasket a little while ago. By the way is the little spar that runs across the exhaust gully on the chassis (secured with two M8 set screws) removable? My guess is its there to protect the cat from being thumped rather than to hold the chassis together - would make taking the cat off heaps easier!

yeah it comes off...4 13mm bolts on mine

Had a couple of hours to spare so got cracking on the exhaust while its dry out. The lambda sensor was so coked that the airways to the element were blocked:

Cat monolith wasn't melted but doesn't look particularly good. Hard to tell but I can see various hues and some shiny parts which I assume isn't fab:

 

New cat next to old cat. The old one has a VW part number stamped on it, might even be the original?

That lambda sensor looks like my granddad's coal fire poker.

Getting there though.

Did you get an HC at idle figure with the fresh oil?

Check all the spark plug lead contacts and coil contact are clean/corrosion free?

 

6 hours ago, dvderlm said:

Did you get an HC at idle figure with the fresh oil?

Check all the spark plug lead contacts and coil contact are clean/corrosion free?

 

Didn't unfortunately, would have been handy eh. Lead contacts are all new and perfect (new Bosch leads - the old ones were too long in the shrouds and didn't grab the plug contacts consistently).

Had a bit of time today so finished off installing the new cat and joining it up with the rest of the exhaust. As per their instructions I 'ran it in' on idle for 10 minutes and then went for a normal drive around the block. Put in a second-hand but presumed well-working Bosch lambda probe (although I have a new one coming just in case this one isn't up to the job).

 

Well it sounds better - guess the exhaust is that much straighter than it used to be and a heap of it is stainless now, got a nice throat to it on a rev. Can't tell if its that much better than before or not but I can't smell the exhaust at all now. Plenty of action out the back of it but its probably all just steam given how humid and weird the weather is today. It definitely pulls even better than it did when I sorted the oxygen sensor and the engine vibrations are totally different so something has changed!

 

Try and squeeze it in tomorrow or Monday for a retest, fingers crossed.

 

 

Result! It passed! Not that I should be surprised considering its got a new cat and lambda but relieved nonetheless.

Fast idle

CO: 0.13%

HC's: 76ppm

Lambda: 1.007

Natural Idle

CO: 0.04%

 

Also only got 3 advisories for rusty springs too.

 

Thanks for the advice and pointers! Interested to see what the mpg is like now - I got 40mpg with that crazy over-fuelling, would be nice to approach 50.

 

good news i would hope to see a little more mpg and hopefully the cold chugging has gone away?

 

 

17 minutes ago, steveo3002 said:

good news i would hope to see a little more mpg and hopefully the cold chugging has gone away?

 

 

Gone entirely - it idles steady at 1k when cold and slowly drops down as it warms. No loss of power when cold either - it used to hesitate or almost die with quick throttle changes (must have been practically flooding!), pulls fine whatever the temperature now. Plus it doesn't sound like a misfiring lawnmower or fire petrol-scented vape out the back - much better for the neighbors.

 

Its interesting the economy was actually alright given how poorly it was running - i assume that running that rich I was having to open the throttle less? Who knows. Consign that problem to the history bin!

yeah good stuff ...hope the aftermarket cat lasts you a few years 

So this hole problem was the cat and lambda ? 

15 minutes ago, 1vw2many said:

So this hole problem was the cat and lambda ? 

 

 

Good point - could do with a recap to properly close this thread in case anyone needs it in the future:

The failure was caused by an earth fault between the coolant temperature sender and the ECU. This caused v rich running for an extended period which then destroyed the cat and the lambda sensor. The temperature sensing fault was rectified first, making sure both the correct resistance and the earth were seen by pins 10 and 8 of the ECU. Once that was done and it was confirmed the primary casue of overfuelling was fixed (new plugs came out clean rather than sooty after a run) then the cat and lambda were both replaced.

 

 

athe broken earth made the car think it was freezing outside , car ran overly rich and ruined the o2 sensor and cat by running so rich

 

the blue temp sender and its wiring are key to these cars running right - any problems go straight to this , cheap and easy to repair and always use a genuine  part