Black Smoke Normal?

[205*31* 0]

Hi ok when gti is cold and I fire it up if I rev it hard say to 5k get quite abit of black smoke out of exhaust could this be normal think its running abit rich still but not mega bad I got near 90 mile on £20 of unleaded all town driving and in traffic.

[DrSarty 90 1 Cars]

Well smoke is not normal on any engine really (except a diesel).

 

And why are you rev'ing a cold engine hard?

[2-Pugs 57]

Sounds like you might have an air leak in the inlet area. This has the effect of richening the mixture, making the engine run badly (may not idle), and will also throw smoke out the back as you describe when revved

Edited July 6, 2010 by 2-Pugs

[j_turnell 137 3 Cars]

Sounds like an ecu temp or afm problem to me. I deffinately wouldnt advise revving a cold engine to 5k though, wont do it any good atall! Not sure how an air leak would richen the mixture.....

[2-Pugs 57]

Because depending upon where it is, it raises the pressure in the inlet manifold which in turn means the fuel pressure regulator allows a higher fuel pressure, which means more fuel is injected every time the injectors fire hence richening the mixture.

 

This exact same thing happened to me on a previous 1.9 GTI. It turned out the bolt holding the oil filler neck was missing, allowing air in.

 

Good shout on the temp sender though. Could be a cause and definitley worth a try, should be less than £20 from a factors

Edited July 6, 2010 by 2-Pugs

[ben_kilpatrick205 0]

I'm having the same sort of problem. When i rev high i get black smoke

 

Not when i first start it up tho lol.

[Simes 248 2 Cars]

Hi ok when gti is cold and I fire it up if I rev it hard say to 5k get quite abit of black smoke out of exhaust could this be normal think its running abit rich still but not mega bad I got near 90 mile on £20 of unleaded all town driving and in traffic.

 

Although £ / mile isn't the most accurate way to work out mpg, it's £50 to fill up a tank which works out that you're getting 205 miles from a tank - that's pretty bad, in fact it's 20.5mpg.

Definitely over fueling.

 

As 2-pugs mentioned there is that bolt but without it your car will barely idle.

Edited July 6, 2010 by Simes

[welshpug 1,657]

its a bit more than £50 to fill a 205 up, more like £60.

 

though that aside, its still overfuelling.

 

DrSarty's E-reg gti that has just gone to a new home puffed out smoke and drank like a trooper (15 ish MPG! ) due to a properly fiddled with Air flow meter.

 

dumped that unit and fitted another known OK-ish unit and it was up to 40 mpg after a good service, I would suggest checking out the AFM following the data shown in the haynes workshop manual.

[205*31* 0]

hi guys thanks for replys. Its not the ecu temp sensor as this is brand new recently fitted so looks like im looking at the AFM, where abouts in haynes does it tell you about afm testing?

 

also what if the ignition timing is too advanced this would cause overfueling wouldn't it?