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Discussion Starter #1
Hi all,
It's been a long winter here in Sweden, the van (2.5L Petrol AVT Syncro) has done a load of trips but I have never managed to stop the annoying occasional rough idle and poor running. Its equivalent MOT is up soon and one thing that is getting worse is the exhaust smell. It smells rough I can't see it passing emissions, often of Petrol. I bought a cheapish replacement exhaust several months ago and no doubt the cat in that is screwed now. Anyway, I had a MIL and felt what I think is s misfire / rough running, I broke down and replaced the coil, which seemed to work ok, got me home, but to solve the underlying issue I started looking at the injectors and plugs from the following guide

HOW TO - Test G70 AIR MASS METER (aka MAF Sensor).

The MIL and it came back, Id say that it feels a little rough driving, but warms up fine and copes pretty well given its cold here.

Readout:-

16804 -Catalyst System Bank : efficiency below threshold
16689 Cylinder Misfire detected

Ohms tested the injectors and all in order, plugs looked ok to me, I took off the mass air flow sensor to clean but in doing so I pull the oil breather pipe off and liquid came out of it. Inside it was caked with white sludge. The oil filler cap looks like the attached.

So, my assumption is it may be the head gasket, but what's the best way to check? I'm not losing Coolant, but have used a lot of oil, I think there is white smoke out the exhaust (Its smells bad) but difficult to know in -20oC. Could it be oil seals, or is it very likely the head gasket? No overheating, the temp has always risen exactly the same to middle gauge and not deviated (summer/winter).

Id quite like to fix it myself but struggle with no manual for the petrol engines. So I guess my question is, what's the best way to rule out a head Gasket failure, should I buy a compression tester for the likely failure in cylinder 5? there are also the liquid gas testers kits available, but as I'm not losing coolant could the break be worse than the gasket and potentially not include coolant? Is there another way to test that will be conclusive?

Thanks in advance, Laurence

Oil breather

189142


189143
 

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that doesn't look good for the head gasket I'm afraid. Unless there is an oil cooler that uses the coolant water I wold say that amount of snot in the filler cap is indicative of head gasket failure.

Do a compression test if you can
 

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Discussion Starter #3
that doesn't look good for the head gasket I'm afraid. Unless there is an oil cooler that uses the coolant water I wold say that amount of snot in the filler cap is indicative of head gasket failure.

Do a compression test if you can
Thanks for the reply - ill go get a compression tester
 

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I once had an engine with blown headgasket but with excellent compression.
Turned out the headgasket was only leaking between an oil way and the water jacket.
 

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That's definitely coolant getting into the oil! Sometimes with a busted gasket or cracked head you can see substantial air bubbles coming up into the header tank. Hope you get it sorted, good luck.
 

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Discussion Starter #7
Thanks everyone, I was hoping to have an update on the van by now but we had baby instead. I did manage to get the compression tester beforehand, but no time to go and check as of yet and quite sure Id be in trouble if I tried. However, today the van failed its Swedish MOT on emissions. Has anyone a feeling of whether this is well over spec and indeed mechanical failure or just a bit over and an italian service may do the trick? We have E85 on pump here and some colleagues reckon that cleans the injectors somewhat and may be worth a fast drive on the motorway.

CO 0,8 (0,5)
HC 135 (200)
CO2500 0,7 (0,3)
Lambda 1,02 (0.97-1,03)

Im thinking there may be an exhaust leak, as I fitted a new one 6 months ago and it sounds bad, but I certainly think it running rich as it smells bad. Tempted if the compression is good and perhaps not the head gasket to replace the MAF and do a full service on the ignition, swap the oil and so.

Interestingly, a colleague also said that the oil could be just condensation as the weather here gets so cold. Im really keen to troubleshoot myself for the purpose of learning, as the van doesn't owe me much and I don't technically need it, just a lot of fun in the forest.
 

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Discussion Starter #8
UPDATE - I measured compression today, which was a first time for me. It was a cold engine (And operator) and values below. No oil squirted in, i just unplugged the hall sensor and the coil pack wire. turned it over for 3-4 secs each time, then ran round to read the dial. Going to attempt to replace the hall sensor tomorrow, and then the ignition components. The values seem significantly lower than the diesel engines but as I understand it, the petrol 2.5 is a low compression engine.

(Bar)
CYL1 - 13
CYL2 - 14.8
CYL3 - 14.25
CYL4 - 13.5
CYL5 - 13.5

I have no experience on this, i read that 10% variance is expected but perhaps as the engine was cold perhaps these are ok? Going to look for the book values online.

Any tips or advice would be appreciated. Picture of the spark plug from cylinder 1 in case its telling something. Cheers

191143
 

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Discussion Starter #9
Just checked Erwin, it states for AVT engine

New - 10...13 bar (I'm not sure what the ellipsis means, I assume between these values)

Wear limit - 7.5 bar

Permissible difference between all cylinders - 3 Bar

So nothing to worry about here then. Other than mostly above 13!
 

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I know nothing about the T4 petrol engines, but does it have HT leads? A misfire could well be from an old or cheap lead shorting on the engine, and a misfire will cause your engine to run rich from unburned fuel and this will find its way into the Cat and burns there - to the point it melts internally. This would throw the 16804 code too as it would detect rich conditions at all times.

It's hard to call on that water contamination. Could be from tiny journeys or a very long time sat still - does the 2.5 AVT have an oil cooler like the diesels? This has been known to split internally or the gasket go and let coolant into the oil system.

Compression number look fine, well within wear values.
 

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Discussion Starter #11
Thanks for the reply, it does have HT leads, and I have new set. Plugs, leads, dizzy cap and rotor and Hall sensor. I thought I'd change every variable. Bought some injector cleaner and new filters, so will replace the fluids this weekend and take it for a hot run. Will get it retested and then look to investigate further into if there are any continuing issues. Having replaced the ignition components already, it started straight away, so I haven't broken anything. I don't believe it has an oil cooler, this usually has the oil filter off of it if I am correct, and my oil filter is straight into the block. Ill update after the retest, fingers crossed!
 
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