Metering Heads

Got some running issues with my Golf 1988 and I think it's the metering head, tried 2 from older models cars, no idea what the difference is, but running upto 3000rpm is pants, it idles fine and over 3000rpm is goes like…. a MK1 should go.

Just wondering if a MK2 16v metering head is the same as the 1.8GTI MK1

Please help?

Firstly….its definitely a Mk1, right? Secondly, Mk1 8V and Mk2 16V metering heads are different. Best way to check for differences in the 3 you've tried is to look at the part numbers to compare - post them up if needs be, and someone will be able to decipher them for you.

paul_c said

Firstly….its definitely a Mk1, right? Secondly, Mk1 8V and Mk2 16V metering heads are different. Best way to check for differences in the 3 you've tried is to look at the part numbers to compare - post them up if needs be, and someone will be able to decipher them for you.

Paul_c
Yeah it's a MK1 Cabby 1988 1.8GTI DX engine 8 valve

The first unit that was with the car was 0 438 100 150 it was working fine until the garage stripped it apart.
The following units were from an older car about 1983 ish 0 438 100 100 and I have that fitted to the car right now.

I have checked the fuel pressures, cold/system, warm and rest and everything checks out ok according to the data. Plunger is free one both units, they give the same symptoms, under 3000rpm half throttle and it's sound like it's miss-firing, the only thing I can't check is CO2.

Any helps would be good.

They're Bosch, not VW part numbers. I'll have a look in the shed, I have a couple of metering heads lying around.

Sorry I thought that's what you meant.

Oh ok, if you have that would be great.

Do you think it could be the metering head?

Prid said

Sorry I thought that's what you meant.

Oh ok, if you have that would be great.

Do you think it could be the metering head?

Bosch part numbers are fine, if others are able to look at their own metering head and report back what numbers they are!

TBH I don't think there's enough info to say if its the metering head or not - I'd be tempted to do more checks, for example give the ignition system a good going over. Clean the dizzy cap inside and out, make sure the plugs are new(ish), clean the ignition leads and/or replace them if dodgy, etc etc. Then get the mixture properly set up.

Paul,

I know you have a vast of knowledge about this, I've read so many posts on the subject, I will give you a very brief summary.

Bought this from my father in law in 2008, it never run right it was always coughing and spluttering, therefore first job to do was the filler neck, which led to so many other things. Replaced tank, both pumps, fuel lines, injectors… everything, the only thing that is not new is the metering head and airbox.
I have serviced the engine, oil, plugs, dizzy, arm, leads everything you would normally do to service your car, I managed to get the car going properly just before Christmas, took it for a spin up to the shops and whilst putting my foot it was fine but then took my foot off the throttle and then it just sounded like it was running on 2/3 cylinders. Straight away thought it was the dizzy and timing, finally struggled to get it home Sunday and I bust the dizzy… oops!

I had to replace the dizzy cos I broke the hall sender off it, so I bought one from one of our members working car and put that on, same issue still running rough….. That was it I'd had enough.

Took the car to a garage and he reckoned it was a sticking valve, ok ?400 later he rebuilt the top end, new cam followers, new cam, setup the valve clearances, clean the metering head and he got it working absolutely spot on. Went to pick it up the next day and it was running rough again, the guy was doing his head in, thought it was an injector…. anyway agreed to take it away and it was driving on three cylinders and it was still quite good.

Monday replaced the injectors and for one day it was spot on…. The following day couldn't start it, the only way was to take the relay out, burn off the excess fuel, put the relay back in and start it…. the only problems was you had to run half or full throttle, as soon as you let you foot off it was over fueling.

I then set out to check everything, AAV, thermotime, WUR, metering head etc… Richard Masters told me to buy a book "How to tune up Bosch" by Ben Watson… cracking book.
So I set off to check everything, first job was the pressure, put on the old gauge and b*gger all…. It appeared to be the pressure relief valve, rather than mess about I got one off another member 0 438 100 100 put that on and yes got it working but I am at the same place today, all the other items, AAV, thermotime etc… appear to be working great.
Pressures are (going off top of my head)
cold 16 PSI - Done when cold with jumper cable
System 75 PSI - Done when cold with jumper cable
Warm 52 PSI
Rest after 20 mins is 37 PSI

Basically that takes me to today… I have brought it to work today and found that during warm up it's spot on but soon as the AAV closed or when it's warm that when my problems start.
Little bit of throttle and it works ok, half throttle and it's propper pants, full throttle of 3000rpm brilliant.

One thing the garage did do was pipe back in the idle stabilising valve, don't know if that has any relevance.

I have got 3 WUR, tried each one, pressures are ok to data so I'm thinking they are ok, so that kind of puts me to the metering head.

If you can help me that would be great.

If you need anymore info, please give me a shout.

Check the air flap for the metering head is set up (centred and not sticking). Take off the metering head and check the plunger on the bottom is moving freely. Check for any air leaks allowing in unmetered air.

Also what dizzy did you fit? Not that it will make a lot of difference, but there are a few different advance curves out there.

Both fuel distributors are fine, the first ... 150 is probibly the original as it is used on DX engines along with other engine and the second ... 100 is from a 1.6L GTi engine, also other engines. From what you say you have done I would think that the fuel system is in fine shape. Only area I have not seen any testing or work done on is the Lambda system. It is a CIS w/Lambda right? Are you maybe on to the full throttle switch when it seems to run good above 3000 RPM? Have you tested the O2 sensor?

DX engines do not run Lambda mate

Dubboy.

I have done the airflow sensor, it's centred and is not sticking, I have tried the 3 units I have and all three have the same symptoms.

Taken the metering ead off and when you have pressure it flows up and down freely, also when you release the pressure the plunger is free as a bird, so I don't think it's that.

The dizzy is the same as what came off when it was working ok…
The Bosch unit has part no, 0 237 020 158 or 026 905 205 AK

GrimyFingers….

Slow down there…. I know about Lamba it something to do with exhaust or something, but I didn't think mine had a Lamba sensor on it.
Can you give me some more advice as I don't know where to look?

Well at first I thought you might have been onto something there…. also got me a bit worried.

Thanks Dubboy.

GrimyFingers said

Both fuel distributors are fine, the first … 150 is probibly the original as it is used on DX engines along with other engine and the second … 100 is from a 1.6L GTi engine, also other engines. From what you say you have done I would think that the fuel system is in fine shape. Only area I have not seen any testing or work done on is the Lambda system. It is a CIS w/Lambda right? Are you maybe on to the full throttle switch when it seems to run good above 3000 RPM? Have you tested the O2 sensor?

Bosch part number for a 1600 metering head is 0438 120 035.

I'd suggest someone with an 1800 metering head; and someone with a 16V metering head, post their part numbers up.


I think the issue could be a fault with the air flap; or a weak spark; or maybe a sticky plunger valve within the fuel metering unit.

Paul.

I'm kind of going down that route myself, something to do with the airbox/metering head.

I have given everything a good clean and tried it all it situ, everything apears to be free, the plunger is ok on both units, the air flap appears to be free when you lift up with a magnet or tape and it's central.

I know I've read bits and pieces to do with the 1.6 vs 1.8GTi metering head, if you say that I have the 1.6 then that shouldn't be a problem.

Just a quick one tho, why does it work better when its cold? Did you see if you had another metering head?

The part numbers don't match, I don't think yours is a 1600 metering head. Still need BOSCH part numbers to confirm!

Paul.

I went to pick a unit up (0 438 100 100) and it was definately taken from a C reg VW Scirocco 1.8 DX engine.

Don't know if that helps? Probably not.

1600 metering head: VW part num 049 133 353J, Bosch part num 0438 120 035

16V metering head: VW part num 027 133 353, Bosch part num 0438 120 195

1800 metering head(s): VW part num ??? ??? ????, Bosch part num ???? ??? ???


All it needs is someone to confirm the correct 1800 metering head part numbers. (I don't have one to physically check, and I don't have ETKA installed to look up the VW number).

Paul_c

Just going back to one of the previous notes, weak spark!

On the ignition side I have replaced the dizzy, cap, arm, leads, plugs, coil and module and when you take a plug out and run the engine the spark is ok, but I don't know how you check if it's good or not.

I can say from experience that it gives you a kick but I don't know if that's good enough.

Without proper measuring tools (which are beyond the scope of the average DIY mechanic) its not really possible to measure how strong the spark is. You'll know when an ignition 'miss', or a series of ignition misses, occurs, though. Also there are some areas where it is more difficult to light the mixture within the cylinder and a weak ignition system will 'track' across, eg, a dirty component or loose connection, rather than producing a spark at the spark plug. Examples include starting, areas where the engine is running particularly lean (or rich), etc. With no load, revving the engine gently to 2000-3000rpm will be in a zone of lean running, so if you start to experience misfires here, it can point to a weak ignition system.

Pragmatically, once things are cleaned, most ignition faults need to be solved by swap testing known-good components. By the looks of the things you've replaced, you've already eliminated this - so I'd say it was a mixture issue rather than ignition, here.

Thanks Paul.

Hopefully I don't think it's the ignition circuit, but you never know.

One think I have noticed, when you remove the vacuum pipe to the dizzy, it's doesn't change anything, it stays at the same revs. I did think it maybe to do with advance/retard.

I have just bought a CO2 unit, so hopefully when it comes I can get the mixture somewhere near.

To be honest, I have learnt so much with this car, but it's this last leg, I'm struggling and I just want her humming.

Paul.