MOT Fail HC Emissions

[westy303]

Hi,

I've just had my 1.9 waterboxer fail its MOT. Its a 1985 German Lefthooker and the HC Emissions have come in at 1237 ppm (pass would be 1200ppm). Its not the only thing that its failed on, and it has a lengthy list of fairly minor issues, including headlamp not working on dipped beam, tyre, and a couple of bulbs out. Nothing to really lose any sleep over.

The one thing that I'm stumped on is the HC Emissions. Its only a midges kahunas over the limit, and I'd like to suss a way of bringing this down. It runs brilliant, despite the mechanic saying "it sounds like its a bit low on compression when starting". Its a daily driver, and never gives me any hassle.

To be honest its due a service. Would this make a vast amount of difference. I'm thinking oil and filter change, plugs, leads and air filter, with an additive like wynns formula gold????

When I had my MOT done last year by another local garage, they told me that my cylinder heads were leaking, although 12 months down the line the van is still running (albeit with no MOT).

I'm toying with the idea of a new engine next year, and I dont know whether to save the cash and keep the car off the road until then, or try and get it thru another year until the new engine can be sorted.

[kit]

Not sure on petrol but I got my diesel through by filling the filter with injector cleaner and taking out the air filter.

[Hacksawbob]

WHS, take out the air filter and make sure you take it for a good burn up the motorway firs, also disconnect crank case breather from the air box temporarily.

[kevtherev]

If it's petrol and a carb not injection...
Then a full service would rule out misfires due to plugs, leads cap and arm... clogged air filters richening the mixture.
High HC is either unburnt fuel or oil.... or both
What was the O2 reading?
the emissions test tells you quite a bit about how sick or well the engine is

When I had high HC it was an air leak causing a misfire, which is neat unburnt fuel thrown into the exhaust.
My pal had blue smoke and high HC ... snake oil didn't cure it... piston rings did

[westy303]

There's no O2 reading on the print out that they left me with. CO2 reading is 1.63%, which is well within tolerance levels.

[kevtherev]

So what engine... is it a DG?

if it is and thats a CO reading.. it's running weak

Shame you didn't have the O2 that would tell you if it was an airleak.
if the mixture correction doesn't cure the HC then it's oil I would think

[westy303]

Tbh I'm a bit of a novice. How would I find out if it's a DG engine?

[weimarbus]

Hi, the high hydrocarbons on my waterboxer were caused by a perished hose that feeds the brake servo, to check this remove the plug lead from cylinder 3 start the engine a see if it idles the same switch off the engine and repeat the process with the other cylinders, if the engine idles the same with plug leads 3 or 4 disconnected and drops when plug leads 1 or 2 are disconnected then this hose is leaking and is causing the engine to run lean at idle on cylinders 3 & 4. This means incorrect combustion and un burnt fuel creating high hydrocarbons. There were no other symptoms with this fault and it only showed at idle speed the engine ran well and had no flat spots and the brake servo still functioned correctly. Hope this helps and good luck.

[kevtherev]

Tbh I'm a bit of a novice. How would I find out if it's a DG engine?

It's on the engine under the breather tower or the service book

weimarbus... that's exactly what I had... the servo hose was a better water sprinkler..

[California Dreamin]

You are so close it won't take much to get the HC under:
New air filter
New oil filter
Oil change 15W40 mineral
New spark plugs

I would bother with oil treatment or plug leads unless you have a misfire or irratic idle.

Give it a good sustained run (motorway for half a hour would be good but whatever you do take it in to the station hot and hope they test it straight away.
High HC could be it's burning a little too much oil, if this is the case then try a 20W50 oil to minimise oil by-passing the rings.

Martin

[westy303]

I've had a butchers and it turns out its a DH Engine.

Anyone any idea which spark plugs I would need for this. Just Kampers sell WR7DC which they say is suitable for all VW T25s. The Haynes Manual gives a variety of different plugs for different engines, but not a DH engine. The sensible side of my brain makes me think that the DH was a later version of the preceding DG engine and was presumably not that different, although wikipedia suggests differently.

As the GW engine was out at roughly the same time as the DH, and is also an injection model, would a W7CC 0 plug be ok?

[California Dreamin]

Bosch W7DTC (triple electrode) or the newer Super 4
Plain W7DC+
Bosch W7CCO
NGK BP6ET (multi electrode)

Mine runs well on multi electrode W7DTC (2.1MV)

Martin

[paul66beetle]

Mine also failed on High HC by very low CO2 levels so would appear running lean.

I gave it a little tweak before retest but it was still out, MOT station got it through emissions but it now runs worse than ever.

Pretty sure its not service items as I gave it a full service recently, only thing I didn't replace was HT leads.

I have a 2.0 CU Aircooled. Any tips on tuning this engine? I could only find one mixture screw on the n/s carb? How do you alter the mixture on the o/s carb? How can you easily balance these carbs?

[..lee..]

did they test the emissions at idle or did they increase rpm to 1200. if its still over 1200hc @ 1200rpm then you really need to get it sorted. if it passes @ 1200rpm it will buy you some time.

if its been suggested to you that it sounds low on compression then i`d start there.

[paul66beetle]

did they test the emissions at idle or did they increase rpm to 1200. if its still over 1200hc @ 1200rpm then you really need to get it sorted. if it passes @ 1200rpm it will buy you some time.

if its been suggested to you that it sounds low on compression then i`d start there.

Increased revs and passed ok. Only a 50k mile engine. Compression good c02 very low and hc high so running lean as above.