dodgy choke??

[marty_t3]

Hi ppl.....

I was hoping you kind folks might be able to help me out with a problem i'm having with newly acquired (read tonight) golf. It's just a '88 5dr 1.6CL that i've bought as a runaround while my other car is of the road. I'm afraid to say i know absolutely nothing about golfs and i haven't seen a carb for over a decade  :-[

The problem i have is with the idle speed. The car idles at cold just fine.... as the temp starts to rise the revs stay just where the should be and the car feels perfect. Then for some reason, just before the car gets to it's full running, temp the idle revs jump to about 2-3k (i'm guessing cuz it doesn't have a rev counter). This high idle revving continues for about 10 minutes at which point the revs almost instantly drop to a normal warm idle.

I'm guessing it might be a sticking choke or something?? I tried a search on the forum and found a reference to a "waxstat" and also a mention of a flap on the airbox??

Any hints as to what could be causing this would be appreciated as it's far too cold outside to go rumaging blindly in the engine bay.  

[mk1]

The waxstat is a water heated plunger on the carb. It is extended out to increase the idle speed when the engine is cold.As the engine warms up water from the cooling system acts on the waxstat to retract the plunger, reducing the idle speed to a normal hot setting. Check the coolant level is correct and the small coolant pipes to the carb are getting warm. If all that is ok, poss faulty waxstat, only held on with 2 screws so easy diy fix.
The hot air flap is in the air filter box, it directs warm air from the exhaust manifold into the air box to stop the carb from freezing up when the air temp is low. Hope this is some help.
Steve.

[golfvr6]

I would say the problem is the waxstat, try replacing that first.

[marty_t3]

Cheers guys... much appreciated.  

To be honest i haven't even opened the bonnet yet. Will have a good look tomorrow. At least i know what i'm looking for now.

[richy_b]

i had a similar prob with my 1.3 , do you know if its a pierburg carb......
if it is i was told that these carbs have a common fault, apparently as the alloy carb warms up its expands causing one of the jets to become slightly loose but when the get warms up it becomes fine again, when it does it next time switch the engine off for around 5 mins start it up and it will probably be ok, this is why i changed mine to a weber now its fine

[marty_t3]

I had a look under the bonnet the other day (not that good a look though as my tools were 250 miles away at the time).

I see what i think is the waxstat.... the silver coloured cylinder on the right hand side of the carb. It has 2 coolant hoses connected to it (both were warm and coolant level is fine) and one vacuum hose coming from the back of it. It looked like there should actually be 2 vacuum hoses plumbed into it??

There's also a small black disc shaped thing bolted to the carb just behind it. It has 2 vacuum lines attached. What is it?

Now that i've clocked up some miles on the car i've a better idea of what's happening. The revs jump up when the car is warm.... but when it's been sitting in traffic for a minute or 2 the revs will drop down again. It's almost as though the underbonnet temperatures are affecting it rather than the coolant temps??? When the car gets underway again and the underbonnet temps drop then the idle jumps back up again. I noticed that the radiator only takes up 1/2 of the grill area.... should the other half be open to the elements or should it be closed off??

Also... the car developed a slight misfire due to the huge amounts of water/spray on the motorway today. Ran fine again once it had dried out a little..... is there any particular part that is prone to getting waterlogged?? (this was another reason i thought the grill should be blocked off)