Metering Heads

Worth checking with a timing light (to be 100% sure) - in other words, while the light is shining at a timing mark, pull the vacuum connection off and observe the change, it should retard when its pulled off.

Yep, I'd say a tweak on the mixture should solve the problems. I've always had mixed success with DIY CO meters, they're really only accurate to 0.5%.

An engine can run happily (ie no misfires or drastic performance differences) at a range of mixtures, so using a 1600 metering head on an 1800, or vice versa, or with the 16V metering head too, shouldn't cause running issues as you're describing them. It will affect the fuel economy and peak power achievable, by around 10%, though.

Now your saying something that is worrying me…. I went through all this just before Christmas when I broke the halls sender unit.

When I put on the new dizzy I checked the vacuum pipes and they were piped up wrong, however I put the light on and when you take off the vacuum pipe to the dizzy there is NO difference to the timing mark, stays put.

The way the vacuum pipes are setup is:-
1. Throttle housing goes to the dizzy
2. The other two go to the vacuum sensor/dashboard and the diaphram mounted on the airbox.
The two that go to the sensor and diaphram are very strong but the one that goes to the dizzy is very weak if anything.
I took off the pipe at the throttle housing and cleaned it and it goes to about 1mm hole into the housing just behind one of the butterflies. Also cleaned the pipe and even when you rev to say 3000rpm it's still very weak.

Any ideas? and would this be a problem up to 3000rpm's?
I would have thought if it was ignition it would be all the way thru the rev range.

It don't sound right. So long as its after the throttle valve, the vacuum should be the same from wherever its taken, so the actual position of the different connections aren't so important. Without a vacuum meter, you can't really measure them except roughly.

At wide open throttle a (non turbo or supercharged) engine's inlet manifold will have little/no vacuum, so it will run fine when at high load. But if there's little vacuum when there should be some, then it could cause your running issues.

Are you able to swap them round, or perhaps blank off the dodgy one and use a T piece, so the dizzy uses one of the good vacuum connections?

The other thing to mention is that there's a one way valve too, and the servo takes its vacuum after the one way valve (and I think there's another vacuum connection for something else at this point too??).

Paul.

So if I take the one that goes from the vacuum to the sensor/dashboard (doesn't work anyway) and put that onto the dizzy then that should hopefully advance/retard.

If I remember rightly I did this last time and it increased the rpm as soon as I added the pipe, does that sound right?

Also just looking the the flywheel, stood at the passenger side front wing if the notch moves toward the front of the car (left) is that advance or retard?

The other thing to mention is that there's a one way valve too, and the servo takes its vacuum after the one way valve (and I think there's another vacuum connection for something else at this point too??).

Just had a quick look at the car, front of the intake manifold, there's a small length of pipe that comes out of the intake to a connector for the 2 x small vacuum pipes then you have a non-return valve which is joined with that grey Y shape which is connected to the servo pipe.
(I don't know how to add photos… sorry). If that makes sense.

Prid said

Paul.

So if I take the one that goes from the vacuum to the sensor/dashboard (doesn't work anyway) and put that onto the dizzy then that should hopefully advance/retard.

If I remember rightly I did this last time and it increased the rpm as soon as I added the pipe, does that sound right?

Also just looking the the flywheel, stood at the passenger side front wing if the notch moves toward the front of the car (left) is that advance or retard?

yep sounds about right.

I'll give that a whirl on the way home.

Paul_c can I say thank you very much for your help and support, I know you've spent quite a while taking to me, so thanks.

I'll let you know my findings tomorrow or later tonight.

Paul P.

Paul_c

Hmmm I swapped the vacuum pipes over and first thing it did was throttle up to about 1800rpm, so I just adjusted the idle screw and brought it back down to 950rpm. On my way home I didn't really notice any difference the problem is still there, a little throttle fine, little to half throttle pants and full throttle ok, takes a bit to get it going but liveable, I will have another go tomorrow and check some other things.

One thing I did notice was it's hunting like mad and I think it's to do with the idle stabiliser valve, you can hear air passing through and it sounds like there's a solenoid pin going up and down, I disconnected the electrics and it runs better, still hunting a little tho.

Any ideas?

Check mixture first of all
Check/clean the ISV, they get bunged up
Check the electrical connections and the other wires on teh ISV controller - there's a little module somewhere.

Will do, I'll get it to a garage this weekend.

Where's the controller situated?

Sorry to keep asking you questions.

Prid said

Will do, I'll get it to a garage this weekend.

Where's the controller situated?

Sorry to keep asking you questions.

TBH I've no idea, I didn't even think an 88 has an ISV……

OK..

Well nothing suprises me with this car, it's had an hard life I think.

I'll have to look in my Haynes.

Cheers, I'll keep you posted.

Thanks again.

First the apology for the reference to a possible O2 sensor failure. Yes the DX does not have one it is the JH that does and I was to quick with typing before thinking in this case. But the problem still seems to lie in that area, too much fuel before the engine can use it. I know that you have stated that you checked the cold start system and the control pressure regulator (and those figures do say it?s OK), but maybe check again. This whole thing really seems strange and I doubt it is in the ignition. I do have the following thoughts to relay which maybe you can confirm or check.

You have stated you changed the fuel metering head a few times with different ones. Did you only swap the fuel distributor itself or the entire fuel mixture unit (air sensor and distributor)? I ask because almost every time you only change the fuel distributor the combination has to be adjusted for it to work correctly. Or if say the o-ring seal is forgotten then that throws things off also. So the question is; did you only swap the metering head or the complete unit?

The rest position of the air sensor is important on all CIS systems (or zero position). The air cone and sensor plate are what controls the mixture depending on the air intake. If say the sensor plate is set too low in the cone at rest, the plate will raise too high and could cause a rich mixture until the cone shape widens and more air than fuel is mixed. Again, the question is this; have you checked or reset the sensor plate rest position when doing these metering head swaps?

Fuel lines? What, if any, real problems would happen if the control pressure regulator (WUR) return line was mixed up with the cold start line? Both are the same size I believe, the main return is a size bigger, and could get reversed.

As this is strange, I think something is going to have to jump forward to shed some light on the problem before it?s really found. So enough on that, which brings me to the numbers game we have had. Although one might think so, I don?t pull these things from a hat or make them up as I go along, they come straight from Bosch. Yes, Bosch number 0 438 120 035 is a 1.6L Gti metering head, as in EG code engine and others too, but so are 0 438 120 100 and 0 438 120 128 and 0 986 438 100 (newest number). I can?t recall any DX engines using an ISV, have to check to be sure, so just how did the mechanic re-plumb it or did he/you mean the AAV? You can install a 16v KR stand alone idle stab system on any 8v, but that would not be ?re-?, that would be converting in a way.

GrimyFingers,

Thanks for your reply, I see you have spent sometime on the subject I thank you for that.

OK will start at the top.

Cold start system, I have check thermotime, fires for about 6 secs and then switches off, 5th injector works fine, no leaks good spray. AAV took that off cleaned it up and put current through for 4 mins and it closed up, I even checked it on the vehicle and all worked fine (pinched hose, revs went up/down can't remember which) I have also tried another unit and that works same way, so I think I have 2 good ones. So I think cold start systems is fine…. Also car works really good when the AAV is open. Don't know if that helps at all.

Fuel distributor, my first one was identical to the one I took off 0 438 100 150, so I just replaced the metering head, everything was great until the garage stripped it down, then I lost all pressure. I bought a complete unit from a member and put that on (airbox and metering head) I understand that they are setup flap/cone and plunger (maybe I'm wrong, read that somewhere). I had to set the flap up, cos it was quite a lot lower than the smallest point of the cone….. Please tell me if I have done something wrong.
Basically I have bent the small strip under the flap so that the top of the flap is level with the leading edge of the cone…. the edge that is the smallest point). The metering head was taken off and cleaned, but always returned with the 'O' ring in situ. I have also checked all pressure with both units and both units show the same symptoms.

Whenever I changed anything, like WUR, I left the gauge in-line and checked the pressure so that whatever happened I could see if there was any change.

I checked the layout of the fuel lines, especially the 5th injector with an old manual I have and I'm certain that is ok, but I'm sure the 5th injector is the outlet closest to the engine (metering unit located to the right hand side)… I'm going off memory, but I will check tomorrow.

The Bosch numbers don't mean much to me, I am using 0 438 100 100 I don't really care if it's 1.6 or 1.8, I'm not into getting 110% performance, I just want her running sweet. Any help on this would be great even if I have to get another metering head.

I think your right, something is very strange, regarding the ISV, when I got it originally it's was only partially plumbed in, what I mean by that is, the outlet/inlet that is plumbed into the rubber boot on the throttle housing was blanked off and then they had put a bolt and jubilee clip into the pipe that should have been connected, so in effect no air was ever flowing. So the mechanic kindly put this back in and it's been hunting ever since.

If you send me pm me your email, I can take some photos tomorrow of the plate, ISV, anything you need to help me… Or if you fancy a run up to Leeds at anytime, let me know?

I think I have covered your questions, but if I've missed anything off then let me know.

Paul.

GrimyFingers….

Just looked at your profile, location Germany… I think you can scrap my last comment.

Cheers

Paul.

Just an update….

Following on from a few discussions, I managed to get on the car this weekend.

What I have done is taken all the air hoses off and cleaned them all up and replaced any worn pipes, put new jubilee clips on and checked them all.
However with all this is not made a bl**dy difference.

I have found out a few things tho, the idle valve is on all the time and I don't understand what switches it on and off….. If this continues to be a problem I can take t out of the system altogether like it was previously.

Also I took the airflow meter off the airbox and started to rev the engine and I noticed that the airflow meter anly starts to move when you really put your foot down, ie when the second butterfly valve opens in the throttle housing….

Does anybody know if this is right? Maybe this could be the cause of the stuttering.

Please help?

The flap needs to be centred and set at a particular height, I think its 2mm or 0.75mm or something, below the start of the cone. There is a nut in the middle you can undo to centralise it; and a spring which can be positioned underneath, to set its height. Other than that, then it should lift reasonably smoothly in line with airflow requirement, bearing in mind that a typical engine only consumes 1/85 of its air during idle, as it would during WOT and max revs (a maximum power situation). So going by throttle position alone is only half the issue. You'd need to be able to look at it under load too, etc.

The best way to evaluate it all is to measure air/fuel ratio on a wide range of operating conditions, since this is what you're 'tuning' for anyway. The flap position is merely an intermediate along the way.

MoT testing stations now have wideband, also you can buy a standalone kit which can be adapted to the Mk1 Golf (tailpipe attachment); and any rolling road will also have one for diagnostic/tuning/info.

Don't rule out weak ignition, or wtong ignition timing, tho im sure its already been mentioned in this thread!

Paul_c

Firstly let me say thanks for coming back to me.

I think I have set the plate up as per Haynes/Ben Watson, it's central, best I can get it and it's just lower than the cone so I am hoping that is correct or near enough.

I will have to take it to a garage then to set up the air/fuel ratio/mixture etc…. I just don't want to go buying anything else, unless they are cheap as chips (probably not to do with this car)

You indicated that it could be weak spark/timing.

I know that the timing has been setup by the garage when they put a new cam shaft in, but I can check it with my timing light, however just to put me out of my misery, if the timing was out, wouldn't it be right thru the range from 1000 - 6500rpm?
I'm not too clued up on advance and retard? maybe a quick summary would help?, I assume that the dizzy works fine, it is from a working car (not that makes any difference) and it is the third second hand dizzy I have put on and the symptoms are still the same.

Regarding the spark, my understanding of this is that the dizzy sends a signal to the coil and that then send a high voltage line to the centre of the dizzy cap, which in turn goes to the plug via the arm. The coil is new so I'm ASSUMING that this should be spot on, however if the coil isn't getting the right voltage could this have an adverse effect on the high voltage line?
If I replace the dizzy would this help or not?

Going back to the metering head, when I put this on with no fuel pipes attached, it's totally free, fire up the car and you get 50 PSI when warm and you have quite a bit of pressure when you try to lift up the flap.
So going from this would you ASSUME that the airflow and metering head are fine?

I have checked the WUR for pressures cold/system/warm/rest and everything appears to be as per Ben Watsons book or Haynes.
So would you ASSUME that is working correctly?

Sorry Paul for all the questions, I'm just really fed up with this car, it's cost me a lot of money and I just want the dam thing to work and I really need help?

In your oppinion, where do I go from here? I'm just after a best guess situation, you are probably a million miles away from me, but I'm totally stuck!!!!!!      

Any help would be grateful?

Cheers

Paul P.

Measure the air/fuel ratio in the areas where its running funny and also clean/check as much as you can of the ignition system.

Daft question but how do you measure the air/fuel ratio?

I'll clean the igniton circuit again and see what happens.