Engine stumbling when warming up.

[bigbadbob76]

So I'm gradually working through the issues with my 1.9DG engine.
Latest problem is that If I pull away too soon after starting from cold she stumbles and stalls. like she's running lean.
By "too soon" I mean 10-15 mins at idle, she's fine at idle, plugs are a bit sooty so she's rich enough there
and she's fine once warm, plugs are a nice tan colour after a good run.
I've ruled out ignition timing by sorting the dissy.
It's almost like the choke is coming off too soon but I doubt that.
So I'm thinking there's an air leak that closes up as she warms up.
If this is a common fault or anyone else has suffered from it I'd love to hear your experiances.

Tweaking the mixture screw has no effect which backs up the air leak theory.
I know it's been messed with so if anyone can suggest a base setting for the mixture screw that would be great.
Standard 1 1/4 to 1 1/2 turns out?
The fast idle screw allows me to increase idle speed above about 900 rpm (by ear) but won't let me go below that, is this normal?
I'm used to bike engines without all the vacuum stuff so would expect to be able to drop the revs till it stalls but maybe the carb vacuum unit takes care of that?
Time for cheese and contemplation.

[CovKid]

Its not uncommon amongst v-dub owners to have a winter and summer choke setting, despite it being automatic. Plenty on here about adjusting autochoke but it generally involves slackening the three fastening screws and turning it just a little so the choke stays on longer. Most are lumpy when the engine is very cold.

[itchyfeet]

I'd say after 15 mins of idle choke should be pretty much off but then again you do live 500 miles north of me

idle it for 15 mins then pull the pancake off and take a pic of choke flap position.

acceleratior pump not adjusted right or broken can also make if hard to pull away.

check idle bypass valve click when connecting it.

check manufold heater and choke heater and carb heater has 12V and is pulling current.

[bigbadbob76]

Thanks for your suggestions guys, i'll try them all one by one.

On first start engine will rev happily, after a few minutes it stumbles and or stalls if you blip the throttle, after 15-20 mins it revs happily.

300ce- continued from dizzy thred- screwed mixture screw all the way in without any drop in revs, hmmm....
vacuum pipe is new and not leaking.

Covkid- will try this next.

Itchy- connections checked, all correct, getting volts and all heaters less than 1ohm.
throttle body and manifold heater supply turns off after a few minutes so looks like thermoswitch is ok.
engine dies when bypass valve is unplugged so seems ok.
after 15 mins idle, choke plate is fully off (vertical) Photo to follow.

E D I T- found the vacuum pipe wasn't wuite home on the choke pull down, mixture screw now makes a difference so set it as per 300ce's instructions, screwing it further out (richer) didn't improve the stumbling so I screwed it back in until revs dropped and backed it off 3/4 turn.
Then tried Covkid's choke adjustment, one of the three screws was far from tight so someone's been in there before.
Anyway, I adjusted it for a bit more choke and it seems to have improved, i'll have to let it cool overnight and check agin tomorrow but I think I've got it licked. Thanks guys. you've saved me again and tought me stuff too. never too old to learn.

[bigbadbob76]

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[itchyfeet]

checked choke pull down unit?
have you heard of carb cleaner?

[bigbadbob76]

checked choke pull down unit?
have you heard of carb cleaner?

I was just editing above when you posted, cheers. checked pull down as above, that helped.
Oh, yeah, carb cleaner might help too.

[tobydog]

I'd strip the carb right down and clean everything.

[itchyfeet]

+1 carb rebuild kit first

https://club8090.co.uk/forum/viewtopic.p ... 0#p8168579" onclick="window.open(this.href);return false;

https://club8090.co.uk/forum/viewtopic.p ... 68&start=0" onclick="window.open(this.href);return false;

[bigbadbob76]

Yeah. good plan!!

[Smosh]

Just a side point, do you run your van every day prior to driving? I thought you weren't meant to leave them idle whilst cold. I was under the impression you should just drive them. Nit scream the bejesus out of it or anything but drive and low to mid revs till I warms up?

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[multisi]

Yeah you dont need to warm the engine up before you drive, just start the engine and get going.

[itchyfeet]

Thanks for your suggestions guys, i'll try them all one by one.

On first start engine will rev happily, after a few minutes it stumbles and or stalls if you blip the throttle, after 15-20 mins it revs happily.

choke is coming off too quick, need to adjust it as covkid says.
your op was easily misinterpreted.

[bigbadbob76]

Yeah you dont need to warm the engine up before you drive, just start the engine and get going.

That's my problem, it stalls if I don't warm it up.

Have adjusted choke so will check tonight from cold.

[multisi]

Get the problem fixed and you can have an extra 15 mins in bed !