Running issue

[Brenjacques]

Hi all bit of a long post but I'm still having some oddish things going on with the 'rocco (1985 GT S EX engine)

Last few days the idle has been a bit off, it was sitting around 900 normally, took it for a drive and it rested for a few hours but since restarting it was idling at around 500rpm. Started it a few times from cold and it was just stalling unless I kept my foot on the accelerator until it warmed up a bit. Had some parts for the ignition system so fitted new plugs, HT leads, dizzy cap and rotor arm as they were all past it and changed the fuel filter. After fitting fiddled with the choke a bit and slight adjustment on the mixture screw it seemed fine. Started from cold and acted was as it should.

Started it today and it was fine cold but revs dropped again when warm to about 500rpm, this time it would fluctuate, sometimes idling at normal speed then idling low again. Had another look at the carb and whilst looking I noticed some air flow coming from the oil breather not any high pressure but a steady flow that I can feel, the pipe to the air intake looks a bit oily too. Just wondering if this is normal for this engine, or if there's a problem such as worn piston rings or a hg blow.

Not had any noticible oil loss, no blue smoke but I have noticed some blackness from the exhaust on the rear valance. Spark plugs I removed look fairly normal no oily deposits but some carbon on the outer thread ring of the firing end and the usual grey/brown deposits from age. Also been getting pressure in the cooling system and higher than normal temp as mentioned on another thread but no noticible coolant loss either and no actual overheating.

Other than that engine seems pretty happy when driving but it just seems like something isn't quite right. I've ordered a coolant head gasket tester kit to check what's going on there. I'm wondering if I should get a compression test just to see if there's anything off.

The dodgy running may just be due to the pierburg which I am going to replace with a weber when I can but if more is wrong then that is pretty low priority. The engine only has 62k on it so I can't see the rings being bad unless it has been abused but I doubt it has. Am I looking at a possible HG blow? Should there be some slight air flow from the breather or is something definitely wrong there?

[hiltow]

Sounds like something more likely to be carb-related, but I wouldn't bin the Pierburg without consulting the Haynes Pierburg manual first, as it's quite good at diagnosing faults and faulty components.

Before doing that, check ALL of the 3mm diameter rubber vacuum hoses for splits / deterioration (including the smaller ones down the back of the carb unit).

[Brenjacques]

I think it is to do with the carb really, some more adjustment this evening and it is fine again. I've recently replaced the vacuum hoses along with the waxstat but never had it working 100%.

Just a bit concerned about the oil and air coming through the breather too. Had a few old motors that do it but I'm new to these cars and don't know whether it is a normal thing with them.

[GT_II]

I don't think you need to worry about feeling an air flow from the breather - that is what it is for. If my calculations are right, your engine is throwing out 13.5 litres of air per second at 900 rpm, so a small flow of air from the breather is a tiny fraction. The air will carry a fine mist of oil, coating the inside of the breather tube and air cleaner housing. This is also normal.

I am a great fan of the Pierburg 2E2, but unfortunately, it is not something you can easily fault find and set up unless you put a lot of time into learning about the equipment on it and how it is supposed to function. I found the official Pierburg 2E2 manual really useful when trying to sort out a problem with low idle speed during warm up. There is a copy here - well worth printing off for future reference:

http://vwa1.dadoghouse.com/wp-content/u ... uction.pdf

After I had changed the wax stat on my carb, because it had sprung a minor coolant leak, the idle speed during warm-up plunged right down to around 500 and like you I had to blip the throttle to keep it from stalling. After warm up, it idled absolutely fine. I realised then that the old wax stat had probably not been working properly, so to compensate for that someone might have incorrectly adjusted something else. I had the luxury of time off work recovering from a knee injury, so I decided to bite the bullet and try to get my head round how everything on the carb was supposed to work.

It took me quite a few hours over several days to work my way through everything, but in the end just one adjustment was needed - to adjust the angle between 2 levers used to control the throttle gap during warm up. Luckily the factory setting screw had not been tampered with, so I was able to just release the locking screw, squeeze the levers to close the gap between one lever and the setting screw on the other and then re-tighten the locking screw. Officially, this adjustment requires the carburettor to be removed, but I did mine in situ. (Section B, Para 2.2, Fig 25 of manual.)

[Brenjacques]

Thanks for that link! I'll spend some time to work my head around all the operations of the carb, it is definitely something on it that is causing the revs to drop and rise. I've already had it off once to change the waxstat and look it over, it does run better than it did originally but I never got it spot on.

On another note, I bought one of these head gasket testers off of ebay:
https://rover.ebay.com/rover/0/0/0?mpre ... 2514603676

The test has came back as a positive cyl to coolant leak, there's no oil mixing which is a silver lining I suppose but it will definitely need this doing now and confirms the rising temps and cooling pressure. What's peoples experiences with doing a HG on the EX engine? Done a couple of HGs before but I think I'd rather just pay if it's going to be too much of a chore, not one of my favourite jobs really if I'm honest, suppose I better pull my finger out and get cracking....

[scirocco_ne]

Your symptoms sound similar to ours except we fitted and weber and its the same.

Yesterday ours was idling low at times and although running lovely since set up it still drops to a low idle it seems occasionally. The engine is so happy it holds it fine but its set to 900 so it should never drop below, minus electrical load.

I am doing another carb set up in the next few days and if the behaviour is still there at times it shows something is effecting idle intermittently even with the weber on.

Mick

[Brenjacques]

I'm wondering if it is something to do with the fuel being used. I remember with a previous car I had with an SU fitted the same problem occured. I was told the float chamber would burn off petrol but not the ethanol. Eventually the float chamber would be full of ethanol and the revs would drop, although with revving it would clear the float chamber and return the engine to a normal idle speed.

The only thing is the symptoms of mine are a little different to that as with revving it should return to the normal idle speed. It hasn't had a 'proper' carb service since 2014 so chances are it's getting a bit gummed up inside I reckon, especially as it only has occasional use.