Engine over-run

[macmillions]

Hi guys,

Have just bought a new(er) 1990 MKII Golf GL 1.8 carb. Engine code GU.

Drove it home last night and after having driven it for about 30 mins I pulled up outside the chippy in town, switched it off and it over-ran like mad. Hugely embarressing, especially when a load of chavs are standing there p*ssing their pants at this car that thinks its a V8 muscle car at idle!

I had to switch the ignition back on for a second, it fired up again, then switched it off and it cut out finally. (Then the starter motor broke, but thats just bad luck!)

Now, I've been researching through the forum and it seems it may be a mixture, or may be a timing issue. I dont think its had a full service since 96k, and its now done 130k, making me think the air filter is as black as the ace of spades. In which case, running too rich and possibly creating a lot of heat, thus igniting the fuel after switching off.

I don't know if this is linked, but I was reliably informed by the guy who sold it that once its switched on, it revs at 2000rpm, then once warm, it idles "normally". After driving for 30 mins, the temp guage reached about 3/4 of normal running temp, yet idled at around 1500rpm. Could this again be due to poor mixture? Or is this a different matter? And why did it only reach 3/4? There is a split in the air hose just after where the hose is attached to the wing of the car, but I thought as it's before the warm air feed, it wouldn't make a difference.

Sorry for all the questions, but I want to ensure its something simple which I could rectify, before looking simple by taking it to a garage. I know it needs a good service too, as the oil is very dark, so hopefully that could help.

Any comments would be great. Thanks!

[kenney]

If the engine has an idle speed of 1500rpm,that will cause an over-run

[macmillions]

Ah right,

So now then, my question is, why is my idle speed 1500rpm? is that due to not reaching optimum running temperature?

And if so, WHY is i not reaching optimum temperature?

[Crasher]

The Pierburg 2E2 carb is prone to this if the wiring to the shut off solenoid for the 3-4 point unit is faulty, the idle may be too high as well, it should be 750rpm. If fitted with a Weber carb, they can also be very susceptible to running on even with a 750 rpm idle. The cure is to fit a fuel shut off valve from an 80’s Ford replacing the brass bung on the front of the carb. Then with an earth to the carb and power to the shut off valve with the ignition on, you will have a fuel shut off system.

[macmillions]

Ok thanks. Should the idle speed drop if it reaches the optimum temperature? and if so, how can I get it to reach the optimum temp?

Want to make sure that it's because of the idle speed that its running on, not faulty wiring.

[Crasher]

The idle speed is raised by the wax stat on the front of the carb and also by a device called a Thermo Time Valve on the side of the carb, often the wiring to this device is broken.

[kenney]

If the engine does not reach 90 degrees the wax stat will not operate properly,resulting in a high idle.I would suggest you start by replacing the thermostat

[macmillions]

Ok I actually remember my dad's old Jettas he had years ago, one was actually a 1.8 GL, the other was a 1.6 (can't remember spec, just that it was a 1992 model) and both of these had high idle speeds (around 3000rpm until the temperature got to optimum, then it dropped down). Thge garage said that the thermostat needed replacing on both. My dad having deep pockets and short arms, however, felt that as the cars still worked, they didn't need fixing! So I don't know whether that was the cause or not.

I'll let my mechanic know to fit a new thermostat.

Crasher, is the Thermo Time Valve very obvious to a novice? i.e. clearly visible when the air filter is removed? Simply because I really wouldn't know what to look for.

I'll start off with the thermostat, and if no avail. I'll dig around for the Thermo Time Valve.

Thankyou both for your replies. I hope its something simple so I don't have to go down the Weber route just yet.

[davey670]

have a quick look at this picture break down of the carb.
it list most parts.
http://images.google.com/imgres?imgurl=http://vwtech.no-ip.info/images/golf/pierburg2e2/2e2vacuum.jpg&imgrefurl=http://www.clubgti.co.uk/forum/showthread.php%3Ft%3D124945&usg=__Zerhc2e_2WknJ8UjCXR0L3Kq2Vc=&h=558&w=870&sz=79&hl=en&start=19&um=1&tbnid=gjvX_Qlw2KCFFM:&tbnh=93&tbnw=145&prev=/images%3Fq%3DPierburg%2B2E2%2Bcarb%2Bpictures%26hl %3Den%26rls%3Dcom.microsoft:en-gb:IE-SearchBox%26rlz%3D1I7GPRE_en%26sa%3DX%26um%3D1

if you have a webber it won't look anything like that picture, it will have two square's under the airfilter housing.

to be honest i never had a webber run on in any golf i fitted one to.
if you do have a webber you can turn down the idle speed yourself with a screw driver its dead easy.

[macmillions]

Our one is a pierburg as its an auto choke.

I will check the diagram and see if it makes any sense.

Thermostat is being changed today (hopefully, if my mate has time), hopefully that will work. If not, I'll refer to the diagram and try and find this Thermo Time Valve.

Cheers.

[macmillions]

An update.

My mate had a look at the thermostat, and said its working ok, so no need to change it.

Also, I checked the wiring to the thermo time valve and the plug appears ok too. However, I peeled away some insulation tape on the wiring and there is a green wire soldered to a brown wire... Not sure if this is normal or not?

Another thing, my g/f's dad and I tried the Redex trick of removing the spark plugs and pouring 15ml down into the cylinders, leaving it for an hour, and cranking it a few times. Then fired it up to watch the result! (not a lot of smoke to be honest). Anyway, then poured Redex down the carb. This, during our journey, resulted in the idle dropping after a while to around 1100rpm for a bit. But then, we continued on our journey for 1/2 hour and when we came to a stop again the idle was back to 2000 rpm! :aargh4:

Anyone got any ideas? Or do you think its still possibly the thermo time valve?

[kenney]

There are a few things that can cause the engine to idle too fast,one of them is, there is an o ring in the innlet manifold which swells up and prevents the hot water circulating through the carb,http://images.google.com/imgres?imgurl=http://vwtech.no-ip.info/images/golf/pierburg2e2/2e2vacuum.jpg&imgrefurl=http://www.clubgti.co.uk/forum/showthread.php%3Ft%3D124945&usg=__Zerhc2e_2WknJ8UjCXR0L3Kq2Vc=&h=558&w=870&sz=79&hl=en&start=19&um=1&tbnid=gjvX_Qlw2KCFFM:&tbnh=93&tbnw=145&prev=/images%3Fq%3DPierburg%2B2E2%2Bcarb%2Bpictures%26hl %3Den%26rls%3Dcom.microsoft:en-gb:IE-SearchBox%26rlz%3D1I7GPRE_en%26sa%3DX%26um%3D1 the o ring is number 32 in the diagram,i have replaced lots of them

[macmillions]

Aw bloody Nora. That looks like a bit of a pig to do! I'm assuming thats a carb-out job to do?

I'll describe the symptoms from scratch to make sure I've mentioned everything.

I start the car from cold, it normally starts first time, but if the temp outside is cold it sometimes dies and needs a blip of throttle to encourage the auto-choke to cut in and it holds the revs at 2000rpm.

Then after driving, it's still idling at 2000rpm, but does occasionally fluctuate to 1500rpm, and the one time down to 1100rpm. But usually it normally idles at between 1750-2000rpm.

Also the car never reaches optimum temperature, only about 1/2 (the 1st line on the guage). Plus evidence of it running rich (dicussed in another thread, spark plugs being pale, but with soot on the cetral electrode, but I'm assuming this is due to not reaching full temperature so the fuel mixture is high).

And finally, even with the temp not at optimum, it's idling at 2000rpm, and when I go to turn it off, it runs over... badly, as in, for minutes! But occasionally, it will just chug and splutter like sound like a stalling diesel.

(thought I would make it all as clear as I could.)

[kenney]

The choke is automatic and there should be no need to touch the throttle,see if the choke is closed,when the engine is cold,and check the pull down unit according to the info i posted.It is alfa omega the engine reaches the proper temperature,as the waxstat expantion element will not heat up enough and the engine will not idle properly,the choke element is electricaly heated,in the first stage,then when the coolant reaches the the proper temp,a temp sensor stops the current to the choke element and the choke is then controlled by the coolant,hence it is impotant the engine reaches the right temp.check also the wiring from the bulkhead to the carb as these often break due to heat,you need to remove the insulation to check them properly

[kenney]

One other thing i forgot to mention,do not let the engine overrun,put it in gear and stall it,until you find out what is wrong

[macmillions]

Ok, thanks for all this information. This poxy carb is a minefield. However, I guess replacing the carb with a Weber would make no difference if it is my inlet manifold that is blocked?

I think 1st of all I'll check the 3-4 point unit as Crasher mentioned in an earlier post. Is this the part that basically controls the thermo time valve? Then I'll check the wiring from the bulkhead to the carb. I have a multimeter, so I guess I can just test the resistance of the wire to check its in good working order?

If that fails, then I guess it will have to be a manifold off job. Would you recommend replacing it with a new one, or just replacing the o-ring & gasket and flushing the coolant system?

I'll check the choke tomorrow at work when I'm leaving. This is basically the little flap on the carb which we poured Redex into yes? (Please excuse my ignorance, but I am honestly trying to learn about these carbs)

My final question is what damage is letting the engine run over doing? It doesn't sound good, so I have been selecting 3rd and stalling it with the handbrake on.

[kenney]

It is the valve which controls the 3-4 point unit.You do not have to replace the manifold,just the o ring and the gasket.You say the engine is not heating up properly(why?)are you sure that is the fact or are you getting a false reading from the gauge.You really need to find out if the coolant is hot enough,as that could well be the problem.Yes we can call it the little flat.You can learn quite a lot about this carb if you study the info i posted. And the answer to your last question the pistons can be damaged,

[macmillions]

Ok, I'm going to get the car, (manifold) checked out next week by my mate who's back from honeymoon, as when he serviced it he ran out of time to check the rear drums, also my clutch slips occasionally in 4th gear. I've heard it's most likely to be the auto-adjuster on the clutch, although the car has done 130,000 miles so I wouldn't be surpised if its the clutch plate itself.

What I would like to know is how do I check the actual coolant temperature? As I know removing the expansion tank lid can be dangerous when it's hot.

Didn't get a chance to check the choke "flap" when I left work as I needed to pick up my g/f quickly.
Is the auto-choke unit the part on the left hand side of the carb, close to the pull-down unit according to the diagram?
I obviously want to eradicate all these possible problems before I rip the manifold off needlessly.

I've been trying to take in the info on the link, its really good, but they are so complicated I keep kinding myslef referring back to the daigram in the Haynes and the one in the link to work out what part is what.

When the engine has cooled a bit more (I only got back from work an hour ago) I'll check the choke and auto-choke unit and post back my findings. Also, I have told my g/f to stall the car when she's turning it off, as I don't want to kill the engine!

[kenney]

An automatic choke is just a term for the complete,choke,the choke consists of the flap,the heater element,and the pull down unit.To check the temp,you can simply feel the top radiator hose,if the temp is right,you should not be able to hold your hand on it for more than a short period,the best way is if you have an infared temp gauge,which means,you can check the temp of the coolant,circulating through the carb,

[macmillions]

Ok I have tested the auto-choke unit's temperature. I started it from cold (i touched it and it was cool to the touch) let the engine idle (at about 1500rpm) and touched it after 3 mins of idling. It was boiling hot to the touch. Is that a good sign? According to the info I have seen it seems to be! :confused:

We went for a drive, came back. I had to run in to Tesco, so left the engine idling as I went in quickly. Was in there for about 5mins, came back and my temperature guage was at optimum (still idling at over 1500rpm. But as soon as I drove away back home and got to driving speed, after 2 mins the temp guage was indicating about 1/2 optimum temp again. :aargh4:

[kenney]

I don't know the reason why the coolant temp drops when you start driving,I can only imagine the thermostat is maybe leaking,due to a greater force of coolant with higher engine revs.You must not forget as i said before in the first stage the choke element is electrically heated,you need to feel the temp of the hoses to the choke element and the statwax expansion element.If the hoses are so warm,you can not touch them then the coolant is circulating.At the end of the statwax element you will see a rod,which pushes the part on which the throttle wire is attached to,were the rod pushes the throttle arm,push hard with a long screw driver,and see if the revs drop to normal

[macmillions]

ok, i'll check the statwax element tomorrow. do you think i should test it when the engine is hot?

i'll post the result tomorrow.

[kenney]

The engine must be hot yes.The unit controls the idleling speed during warm up.If none of the other adjusting screws have been tampered with,and the coolant is reaching the right temp,there could be something wrong with it.

[macmillions]

Ok, I think I have some progress....

I had a look at the 3-4 point unit when I was leaving work today. I measured the pushrod and it was extended 16mm when the engine was cold, with the accelerator flap (technical term I know) resting against it. I started the car and watched. The pushrod moved back slightly after a few seconds, bringing the flap down a bit, but only enough to sit at 1500rpm. I don't know If this has anything to do with all this, but the accelerator pedal is very stiff to depress, so I checked the flap (when the engine was off before hand) and noticed this too, was quite stiff.

Anyway, I got home from work about 45mins ago and checked the 3-4 point unit with the engine running (idling at around 1750rpm. The pushrod was in the same place as when I had 1st turned on the engine and the accelerator flap was resting agianst it. So I whipped out a long srewdriver and pushed the bottom of the flap against the pushrod quite firmly and the pushrod moved back into the 3-4 point unit with the force I was putting on it, and lo-and-behold, the revs dropped to 1100rpm! I tried pushing harder but couldn't get a good enough angle. So the car was idling at 1100 rpm then.

I tried turning the ignition off to see if it would run on and it just spluttered like an old diesel sucking in loads of fuel/air and stopped after about 2 seconds.

Not managed to find out what temperature my coolant is at yet as I haven't got access to an infra-red thermometer.

Is this all a good sign? Or at least showing me in the right direction?

[kenney]

3/4 Point Unit:
When engine is off, should be extended to 14.5mm. When engine is started should retract to about 8.5mm after a varying delay, depending on temperature.

[macmillions]

Ok thats what I thought.
I spoke to my mechanic today who serviced the car and he said he checked out the 3/4 point unit when the car was in and he noticed the unit not reacting as it should. He disconected some of the wiring and also bridged the thermo switch between spark plugs 3 & 4 to get the choke to work "normally". It didn't. So that left him a bit baffled too.
So I don't know if that means the 3/4 point unit is faulty, or whether something controlling it is faulty?

I have come across a company which reconditions pierburg carbs for around £165. Sounds a lot, but considering the auto-choke unit alone is £70, I don't think thats bad going, because he'll repair any defective parts or replace them, inclusive of the price.

I would rather do that than go for a Weber. But thats a last resort really if the problem turns out to be a costly repair, when something else could go wrong straight after.

[kenney]

iam sorry i don't understand,when you say the mechanic bridged the thermo switch between plugs 3&4.The fact the pushrod is 16mm out when the engine is cold,suggests the adjusting screw 14mm to the rear of the 3-4 unit,is screwed too far in.this is the adjustment screw for idle.

[macmillions]

This bit here is what he did.

http://www.hallvw.clara.co.uk/jettachoke.htm

I'll re-measure again tomorrow before I leave for work and double check it was definately 16mm. I'm pretty sure it was, but I may have been mistaken.

If it is I'll try adjusting the screw a few turns and see if that makes a difference.

If, however, the pushrod isn't retracting when the car has warmed up, do you know what the cause is likely to be?

[kenney]

With you now There are 3 things that cause the high idle,the 3-4 unit,the waxstat,and the wrong adjustment,,the choke element will not cause high idle,but on the other hand,unstable ideling and high fuel consumption.The 3-4 unit is an expensive part,and can be disabled,without any issues of the engines,performance,i have never understood the need of it to be honest.I feel now that you have 2 faults,(one the choke),you say you have to give a bit of throttle to keep the engine running when cold,this could either be the choke is not on,or the pull down vacuum unit is leaking.The fast running,is either the waxstat or the 3-4 unit I can go into detail later and tell you what to do to eliminate each part.

[Crasher]

Power failure (or failure of the valve) to the Thermo Time Valve can also cause high revs.

[kenney]

Agreed,but we are then talking about excessive revs ca 2500rpm

[Crasher]

True, what are the revs? I lost the will to live on this post a while back…

[kenney]

Never say die Steve,the rpm is around 1100

[Crasher]

Wind the 13-mm bolt on the 3-4 point unit out with the 4-mm headed M5 bolt on the wax stat cam slacked off. If the 3-4 point unit does not retract something is wrong, possibly in the vacuum lines area or if there is no slack on the wax stat bolt, the wax stat is u/s. If the wax stat has an ally body, it is pretty much certain it is dead, the later black plastic ones are more reliable.

[macmillions]

The 13mm bolt you are talking about crasher, is that the one that is one the "accelerator flap?" (as I call it) I measured the one I have on there and its about 17mm, so I'm not sure if I'm looking at the wrong bit.

As for the wax-stat 4mm headed M5 bolt cam. I know what the waxstat is (its black plastic by the way) I have tried looking for it, but cannot find it anywhere, as I don't really know what this cam looks like. I have a Haynes, but am unable to locate it. Do u have a photo to guide me?

Also, my car has developed a misfire on cold dewy mornings. It goes away after a few minutes when the engine has warmed up a bit. I have recently replaced the spark plugs and have a good set of Magnecor HT leads, plus new dizzy cap. My friend said its most likely to be moisture under the dizzy cap, so I nicked a shower cap off my mum (she doesn't know yet! :nana:)and covered the cap with it and secured it with an elastic band. What a bodge! Hopefully it will work, if not, I'll start yet another new thread. :o

And kenny, would you be able to guide me through the elimination process? As if it turns out to be something costly I'll get a recon carb. Remember to speak in Layman's terms, as unfortunaley, you may have noticed I don't know a lot about these carbs!

[kenney]

Crasher has given you the info.Look at the diagram of the carb,in the info i posted,beside the pic of the 3-4 unit there is what is called an idle regulating valve,screw it out 3-4 turns to see if the idle drops.The pic of someone holding the carb in his hand, his thumb is on the screw for the waxstat cam.The coolant must be warm when you try this,and the engine ideling

[macmillions]

Brilliant, thanks. Unfortunately as it's dark I can now see sweet f-a. So I'll have to check in the morning. Out of interest, how much would a 3/4 point unit be likely to cost?

[kenney]

It's quite a while since i replaced one,but they were expensive and as i said before you can disable it,but find out first what is causing the high idle