Engine morning start up idle drops

[davesingh]

Hi guys,
two morning start ups now i have noticed that when i start up the van ,starts fine but soon sounds as tho it is going to shut off and then a puff of smoke it regains good idle speed,and then everything is fine.this problem started when i started the van without allowing the the glow light indicator on the dash panel to shut off, i just started,think is was still sleeping.

 

[Dave]

Is the coolent temp sensor right or out of spec.

How does it go once the glow plug light has gone out ?

Dave.

 

[tweak'e]

what colour smoke?

i would suspect air bubble in the fuel.

 

[scottybobcat]

Run some fuel and injection cleaner through it as you may have a little bit of carbon build up and bleed the fuel system,also check your glow plugs that they are working.
Does the engine check light come on when it runs rough

 

[davesingh]

The smoke is whiteish blue no check lights the problem only happens on morning start ups ,van is doing 72000km.how to bleed the fuel line?

 

[Dave]

There is a primer pump, push that a few times and see how many pumps it needs to get hard.

Dave.

 

[pointblank5]

Ive also experienced this problem,
it starts and idles normally for a second or two, then idle speed drops around the time the oil light goes out and some white smoke comes out the exhaust.
then it runs as fine as ever after that.
seems to only happen on cold mornings.
(zd30 also)

I changed the glow plugs and made sure there was power to them for the right amount of time, it helped a tiny bit but didnt solve the problem.

I have been thinking it could possibly be the coolent temp sensor?
any advice would be much appreciated

 

[Old.Tony]

The glow plugs are supposed to continue glowing after the engine has started until the engine coolant temperature rises above 50C. This is called "after glow". It's designed to prevent rough idling when cold. A problem with the temperature sensor will result in the glow plugs not doing what they're supposed to do.

Is the temp gauge in the dash displaying the expected temperatures?

If you've replaced the glow plugs and verified that they're operational, I'd suspect that temp sensor as well - as long as fuel was getting in. By the sounds of it, the fuel delivery isn't a problem, so it may easily be that coolant temp sensor.

 

[pointblank5]

thanks for the reply Tony,
yeah i'm pretty sure the after glow works, got 12v at the glow plug rail for about a minute after start up (not sure on the time but i remember it was what the manual said it should be)
so i think i can pretty much eliminate glow plugs.
yeah the temp gauge seems to work fine, on these cold mornings obviously its hard against the bottom.
Not sure why there is white smoke directly after the drop in speed, it doesnt happen immediately on startup or any other time, and clears up right after.

 

[Dave]

I haven't looked much into the engine management side of things but does the computer semi close a butterfly in the intake to make it run rich and restrict air. ?

Dave.

 

[Old.Tony]

White smoke is usually an indication of an injector staying open. A semi-closed butterfly might cause an issue with it running rich, but that'd cause more soot (black smoke).

I'd suggest a bottle of injector cleaner in the fuel tank, if those glow plugs are fine and generally fuel is delivered okay, then it's just while it's cold - and a cold injector with a little varnish could also be the culprit.

 

[pointblank5]

not sure about the engine management either Dave, i did the egr/butterfly mod ages ago without any problems.

Tony, i have tried injector cleaner both in the tank and the liqui moly one straight in the fuel lines.

the problem seems to me like a management issue, because it runs fine with no smoke at normal idle speed immediately on startup for a few seconds, then drops for a few seconds and returns to normal.
I really wanto get it sorted before it gets worse
thanks for the replies guys