dodgy astra

rio. · Post by **rio.** » Tue Aug 11, 2009 4:54 pm

my wife has a astra sri cdti diesel. its 9 months old with 9k on the clock.

on three occasions its lost power and billows out black smoke whilst being driven normally (ie not under excessive load).

it plays up for about thirty seconds and then goes back to normal

you cannot predict when its going to happen, it just does it.

ive taken it out for a proper test drive for her and red-lined the tacho in all gears

and it was fine? as ive not been in the car yet when it happens.

its been in the main dealers today on the diagnostic computer and they cant find anything wrong

any ideas please....

dewaltdisney · Post by **dewaltdisney** » Tue Aug 11, 2009 5:08 pm

The high pressure common rail diesel has a pressure release valve that opens if the pressure peaks above the safe level. The high pressure pump really pushes the pressure up to something like 2000 bar. It sounds like the valve might be opening and letting the pressure drop and this causes it to stutter for a second until the pressure recovers. Because it is an intermittent fault it is hard to diagnose. There are loads of sensors that check temperatures etc that the engine management system uses to control things and these can also cause problems.

This is just an idea though and not based on any expertise.

DWD

Raf · Post by **Raf** » Wed Aug 12, 2009 10:46 am

black smoke = too much air.

Vauxhalls are known to have had a period of dodgy EGR valves.... try driving the car very normally and light footed; this is when EGR is activated.

it may replicate the issue.

also those blimmin ECU's only record a fault if its present for a certain amount of time.... thats just daft to me!

but really we need more info... when it happens does the car rev passed 4k? is it jerky or just lacks power? what is idle like? if you turn the car off and then on again... does the problem go away (this usually points to a sensor)?

as its new you dont want to f0000k around with it too much as it may affect your warranty.

dewaltdisney · Post by **dewaltdisney** » Wed Aug 12, 2009 4:25 pm

black smoke = too much air

That is why I thought it was a momentary drop in fuel pressure at the injectors. The pressure release valve opening would probably be overwritten in the fault codes too quickly to be read after a period of normal running.

DWD

rio. · Post by **rio.** » Wed Aug 12, 2009 4:46 pm

thanks for the replys.

the car is a bit jerky and no power when it happens, you could be say driving at 40 mph and then it will lose power until it eventually clears itself.

no problems with it starting and it will idle fine.

the only thing that seems to be consistent is that it will happen on about a quarter tank of fuel?

I was thinking it could be contaminated fuel. I bought the car when it had 4k on the clock ( ex rental). so who knows whats been put in the tank?

the dealers did'nt even check the filter, I know on a couple of older diesel vans that ive had there was a little tap on the filter that you could drain the water out. or is it different these days

Raf · Post by **Raf** » Fri Aug 14, 2009 2:46 pm

could be the in line fuel tank pump giving up but i just cant see it at that mileage.... plus it dies quite quickly rather than very slowly.

get a leak off test done to test injectors but i would imagine that until the problem gets worse or becomes more persistent it would be hard (and expensive) to diagnose.

JOA · Post by **JOA** » Sat Sep 05, 2009 7:30 pm

Raf wrote:black smoke = too much air.

Vauxhalls are known to have had a period of dodgy EGR valves.... try driving the car very normally and light footed; this is when EGR is activated.

it may replicate the issue.

also those blimmin ECU's only record a fault if its present for a certain amount of time.... thats just daft to me!

but really we need more info... when it happens does the car rev passed 4k? is it jerky or just lacks power? what is idle like? if you turn the car off and then on again... does the problem go away (this usually points to a sensor)?

as its new you dont want to f0000k around with it too much as it may affect your warranty.

Black Smoke mean too much fuel so its over fuelling.

lockie · Post by **lockie** » Tue Sep 29, 2009 9:50 pm

I had a similar problem on a golf gtdi and it was the air mass meter located along the pipe by the airfilter box.Unplugged it and the car ran with more power but used more fuel as this is what the sensor monitors but it proved it as the faulty part.Turns out its been a world wide problem with them acording to the web searchs i did.
Might be worth some googling to see what comes up.