Mot emissions question

[sierraman]

In my usual Friday night routine I search Autotrader for cars, notice a fair few seem to have failed the MOT on 'dense blue smoke emitted' which I'd take as it's burning oil so the rings or whatever are goosed. So how are they then passing the MOT upon representing it a few days later, might I add a lot of these are £500 stuff so unlikely to have had the engines overhauled.

[garbaldy]

STP oil treatment has worked for me in the past,

Although the smoke comes back in a few miles.

[Kiltox]

It's amazing how many cars have the exact same emissions output as a garage's courtesy car

 

Crate of beer in the boot to weigh it down for the test works wonders

[sierraman]

For blue smoke to be coming out it must be going through oil at quite a rate...

[Richard]

It can be valve stem seals too, and they are easy to change.

[michael1703]

I use this in my customers cars when they fail and it's worked every time

 

[r.welfare]

I wonder how much of it is down to people not getting their engine properly warmed up. My 2.0 Mazda had buggered rings and/or stem seals (loadsablue smoke from cold, oil consumption of a litre every 500 miles) but it was ok when warm and at the 3,000rpm they use for the emissions test.

[SiC]

^^ This.

 

Car fails MOT on emissions.

 

MOT man drives it hard round the block, getting the engine toasty. Pistons and rings warm up - so expand, gap now smaller.

 

Retest emissions immediately.

[andy18s]

Because VW?

[taxi paul]

My ex wifes focus failed the other week on the emissions. Was qouted circa £500 for new cat. Her dad took it to his garage. Couple of bottles if redex finest whatever and a good run and it passed next day.

[meggersdog]

I failed a van the other week for black smoke (amongst other things).Don't know why but I checked online before putting my results in and the van had failed elsewhere three weeks earlier on exactly the same things.Maybe they thought as I'm an MOT station in a small village I'd let it go, but hey.

When they came to collect the driver said it had been in one garage in Stamford,then a mobile mechanic had been to it and neither could fix the smoke issue.I told him to remove the fuel filter (it looked new) empty it,refill with injector cleaner and refit the fuel filter.Then take it for a run.

He worked to my failure list and brought the van back two days later and it was as clean as a whistle.Although he did say he'd cleaned the egr valve aswell.No doubt the garage and mobile mechanic both started the van revved it a bit and said "yeah s'fucked mate" and walked off.