Cold Start - High Idle

[ikorraks]

Hi everyone, just another issue with the Rocco unfortunately! I only do short journeys to work (10-15 mins) and over the last 2-3 weeks I've rarely seen my car idling less than 3k-3.5k RPM. Obviously going through town making this sort of racket is getting on my nerves.

The thing is some days it will just randomly drop down to normal and drive perfectly, you can actually feel the accelerator pedal push slightly more against your foot at this point and when I next stop it will idle between 800-1k

Only seems to have been happening in the last few weeks since it's got colder. So I'm linking the 2 together. I've seen people mention similar issues and say that the TTV is wrong or the Wax thing on the carb? But I don't know what either of these things are or how hard they would be to fix myself one evening/ weekend

I drive an '88 GT 1.6 and it has the pierberg carb in still

[unknownmale]

Sounds to me like ether the choke is stuck wide open or maybe the return spring on the carb is disconnected? Depends how the pedal feels.

I removed my pierburg last year as there was too much going wrong and it was too complicated for me to figure out, but from what I remember, it takes coolant lines off the hvac to warm up the choke to close it when the car is up to temp...You could confirm this by taking off the air box and see what position the choke is in.

[Little_bro]

The auto choke is heated off the coolant system. Does your car idle ok when it's heated up?

[ikorraks]

Yeah once its going or on a warm day it idles fine, no issues at all.

The best way I can describe the pedal, is that it feels the same as it does when the engine is off. It seems to drop back a little when the engine is off and when I started the engine before these problems, it sort of lifts back up. But now it doesn't lift up when you start up it stays sort of half way down, and either randomly lifts up a little while into the journey if I'm driving long enough

I guessed getting a Weber would be a good way forward cos I've heard how complicated the peirberg ones are and they tend to go wrong eventually. If getting a Weber is likely to sort my issues I'll get one asap

[unknownmale]

Yeah once its going or on a warm day it idles fine, no issues at all.

The best way I can describe the pedal, is that it feels the same as it does when the engine is off. It seems to drop back a little when the engine is off and when I started the engine before these problems, it sort of lifts back up. But now it doesn't lift up when you start up it stays sort of half way down, and either randomly lifts up a little while into the journey if I'm driving long enough

I guessed getting a Weber would be a good way forward cos I've heard how complicated the peirberg ones are and they tend to go wrong eventually. If getting a Weber is likely to sort my issues I'll get one asap

A Weber is a good way to go, but best to verify before condemning the pierburg...They're actually a little better than the weber when working well in my opinion...The main reason I switched to a weber is so I could confidently service and diagnose it.

Check the rubber mount the carb sits on. If it's damaged your air fuel ratio will be wrong, causing sporadic idling. I've had a couple go bad and noticed once the intake had warmed up the leak seal due to it expanding...Only £20 or so to replace.

It sounds to me that it's most likely a bad waxstat - https://www.vwheritage.com/shop/0261292 ... tta-caddy/

I'm not sure if VW would be cheaper?

[the edmundator]

A Weber is a good way to go, but best to verify before condemning the pierburg...They're actually a little better than the weber when working well in my opinion...The main reason I switched to a weber is so I could confidently service and diagnose it.

You're quite right - the Pierburg is a better carb, it's just much more complex and very few garages these days have a grip on them (even back in the day they struggled), so for home maintenance the Weber is often much less of a headache. Nate has the Pierburg manual as a PDF and most (if not all) of the parts are available from Gower & Lee, so if you fancy a challenge it's still feasible.

[Lukeh17]

Hi,

I drive exactly the same car and year too!! I had a similar problem apart from my car would rev up randomly and then after awhile would settle down and I would get that where you feel the car accelerating away from you. After awhile it just stopped and this was during the summer when mine started

[ikorraks]

Found a garage reasonably close where one of the guys owned a mk2 scirocco so I figured he'd have a better understanding straight away and took it to him.

I like to try do things myself but with no garage and it getting dark early, this is my only car and daily runner and I need it working. He reckons the auto choke is getting stuck but I'm not sure myself. Anyway he'll have the utter displeasure of trying to get it to start and move tomorrow when he looks at it so hopefully that will give him some idea of what is wrong

[ikorraks]

They weren't specific about what they did but they said they couldn't find anything wrong or broken. They've drained the anti freeze and water and refilled it all and taken the carb off and cleaned it out. It ran okay bringing it home but nothing special. Felt like it was holding back a bit. Taking it to Banbury in a minute so will give it a good run and see how it goes

[hiltow]

For the Pierburg 2E2 carburettor, the Haynes Pierburg Manual suggests the following as causes of 'high idle speed':

- Defective choke waxstat (these can be easily and cheaply sourced and relatively easy to fix)

- Defective choke pull-down assembly (again, easy to source)

- Defective thermal time valve (TTV) or throttle actuator

The TTV is quite an expensive part, but there's one on eBay at the moment for about £40 and will be easy to fix as it can be swapped over easily - it's the black round thing to the left hand rear of the carb when viewed from the front. It's located next to the throttle plate actuator, which is the large metal disc-shaped mechanism in the same place as the TTV that has the piston in the middle of it. This will be more expensive to replace (about £140 when I bought one).

To test the TTV, you should listen out for a very faint 'click' sound when you turn on the ignition. I think this may be more down to your actuator because it's the actuator mechanism in operation that actually does impact on the movement of the accelerator pedal, which you've referred to.

Don't give up though on the Pierburg. It's a better carb. You can get the parts, but it's tracking down those who were working on them in the '80s and '90s who have the knowledge and expertise. If you're based within travelling distance of Northampton, I know a place there that rebuilt my Pierburg and did a very good job on it.

[the edmundator]

I'd be very interested in that place in Northampton as it's not that far from me.

[scirockirb]

I'd appreciate the contact details for the garage in Northampton if possible... Every item checked on mine and it still idles high. Time to admit defeat and take it to an expert! Apologies for the hijack.

[hiltow]

Both PM'd.