1983 1.8 GTi DX Engine Running Issues

Hi all - I am having some minor running issues with my 1983 1.8 GTi DX engine which I am hoping you can help with. It appears there is an air leak into the engine somehow. Here are the symptoms:

Appears WUR not working correctly as the idle speed does not increase when the engine is cold (although UK temperatures haven't been that cold yet this year which may explain it)
Idle speed cannot be lowered below 1,000 RPM
After the car has been on a run and warm, the idle speed then increases to 1,200 RPM
Car struggles to start from cold (as if lack of fuel) compared to last year when started on a button

In the last 12 months I have:
Replaced the starter motor
Replaced the fuel pump
Replaced the fuel filter
Replaced all the injector lines
Had the timing checked by a competent garage (they cannot reduce the idle speed either)
Used brake cleaner around hose connections to test for leaks (made no difference)
The idle screw o-ring is in good condition and the idle screw is fully screwed in
Adjusted the exhaust gas readings from the metering head (using the Haynes manual)
Auxiliary air valve seems to be working

I have not yet gone through the whole K-Jetronic fault finding testing injector spray patterns or fuel delivery volumes and pressures. Somebody did mention that the throttle body butterflies may have caused a groove on the body wall causing air passing.

Any ideas? Thanks in advance!

 

I think the WUR should work on a stone cold engine, even if it is hot outside.

Is mixture ok? Maybe worth having it double checked on an MOT rig

Failing that, maybe rubjonny can put a link up to one of his K-Jet check guides - maybe there's something simple overlooked?

I have a similar issue on mine with the idle speed rising slightly when warm but I can adjust it down to 950 but when I start it next time it will be too low and about to stall, it's on my winter to do list. I don't have any starting issues though but I did have to go through my whole system earlier this year and some of the places to check for vacuum leaks include the breather system and the vacuum advance and MFA hoses including the small cotton braided rubber hoses. Also, there is a blank on a vacuum damper that the vacuum advance comes from, mine was missing and it had a screw in it which was leaking. All of these things are worth checking and maybe remove the various hose one by one and check for perrishing or cracking which may not show up when spraying brake cleaner on them.

Good luck and keep us posted.

Thanks for the reply guys. Yes the mixture was checked on an MOT rig to the spec in the Haynes manual I have (CO content at about 1.5 I seem to remember) and very close to lambda 1.

Ive checked all the vacuum and air hoses the best I can and I believe they are all sound, although I will re-check.

Saulty - where is the blank you were talking about? Any chance you can post a pic of your engine bay?

the basic checks in here all apply:
http://www.vwgolfmk2.co.uk/forum/viewtopic.php?f=37&t=25972

the AAV valve might be faulty or need adjusting. check if its had a later head fitted with the air shrouding system, if it has and the vacuum line between injectors 3 and 4 is plumbed into the system try blocking it instead, if the wrong injectors are used that will give you an air leak

If you look between the cream coloured part and the cotton braided hose you can see a screw. That is blanking off a hole. Mine is broken but there should be a small plastic tube there which has a blank pipe fitted to it. I used the screw which some sealant to stop it leaking. I will replace it when I find a replacement for a reasonable price 😉!
Good luck, let us know if you need any more info!

Thanks Saulty - I know exactly which one you mean. In fact, mine is the opposite. Where your braided vacuum hose connects, mine has broken. And where your screw is, my braided vacuum hose is connected. I have simply pushed the fitting further in so the broken hole is covered by the rubber hose with a jubilee clip.

Sounds to me more like the WUR is working all the time as opposed to not working.  Hence the 1000 RPM cold idle but 1200 RPM idle once warm.

Thanks for the continued help guys, really appreciate it.

So last night I took a few hours to go through some fault finding. Here is what I did:

Re-checked all vacuum hoses, air hoses and sprayed brake cleaner at the connections - no issues

Sprayed brake cleaner at the injector seals - no issues

Checked the metering head - FD o-ring was replaced last year, and the gasket appears in good condition so assume no issues

Checked the AAR - no issues

Checked the WUR - appears that the one fitted is for a 1.6 and so has a lower resistance. It was also loose on the block so I re-attached. I have a total of 5 spare so Ive dug out a 1.8 version to clean up and replace to try.

I am yet to test the injectors and fuel pressure.

On the throttle body, the vacuum on the rear is very very weak, in fact non-existent. Is that correct? Vacuum for the advance (above the head cover as Saulty described above) is very strong. Also could somebody give me the correct part number for the throttle body for a 1.8 DX?

This morning when starting the car the idle was 1,500 rpm initially lowering to 950 rpm in 3 mins. Looks like the WUR is doing its job (although needs changing for the 1.8 version). After a 10 mile run, the idle speed is 1,200 - 1,300 rpm.

To answer rubjonny's question - no it is not the later 'air shrouding' and no leaks on the injectors as confirmed by the brake cleaner test above.

And finally - if I pinch the hoses, the only hose to make the engine idle dip to almost a stall is the one that returns from the head breather to the intake manifold…

Hopefully you find the correct 1.8 WUR, fit it and the problem goes away.  (There is always hope, isn't there).

Just a slight update - refurbed the 1.8 WUR and installed it. Now the car runs like a bag of spanners! No power, almost missing and spluttering whilst taking up. The WUR also appears not to be doing its job. Although I can now get the RPM down to about 850 rpm with the idle screw all the way in.

On the throttle body, the vacuum on the rear is very very weak, in fact non-existent. Is that correct? Vacuum for the advance (above the head cover as Saulty described above) is very strong.

Thanks for the continued help.

If you've refurbed the WUR and it's now the correct one for your engine then you will need to set up the mixture etc. Just checking you've done it 😉.

Just went out to the garage and started mine, the vacuum on the throttle body has virtually no vacuum when idling but does have a fair bit if you rev the engine but the other one (the one I photographed) has a strong vacuum! I will point out though, the vacuum in the back of the throttle body does the vacuum advance and the other one does the mfa!  Reading your post it looks like yours is the other way round!

Thanks Saulty - I have the same results on the vacuum test as you.

And no, havent set up the mixture again - will have to wait to get it onto a gas test analyser.

Is the little rubber o-ring still intact on your idle screw?

I remember having erratic idle probs once and found the o-ring was completely missing.
I made up a small rubber ring from a piece of small diameter tubing so that a seal was created and it fixed the problem.

I don't think my WUR has ever worked. I have to tease the throttle for the first 30 secs when cold, then it will run on it's own until warm and then idles nicely.

Hi Al - yes the o-ring is still present, and it did cross my mind. It adjusts correctly, although the idle speed will not decrease even with the screw all the way in.

When setting up the timing run the car on super unleaded petrol and keep using super unleaded, I could never get mine to run right on normal unleaded petrol because of the lower RON.

Hi all - Ive managed to spend some time trying to tune up the engine today. Here goes:

Checked all the injector delivery volumes - all OK
Check the injector spray pattern - all appear OK
Checked the system pressure - around 78 psi
Checked the control pressure - rose from 20 psi to around 50 psi
Residual fuel pressure - all OK
Adjusted the idle to around 900 rpm (strangely enough I can now adjust the idle more than I could originally)
Then went to adjust the mixture to 1.8% using the Gunson gastester, which is where it all went wrong…!

So whilst adjusting the mixture I had the engine warm, oil temp around 70 - 80, idle around 900 rpm, air box side hose removed and the air box hole blocked.

To begin with the CO value was 3.6%, in reducing the CO value (screwing the mixture screw out) the rpm dropped, so far that the engine was stalling. In order to start the car again, I had to adjust the mixture (screwing the mixture screw in). The closest CO value I could get without it stalling was 2.0% at 500 rpm, but in revving the engine it was spluttering and once revved the revs dropped and the engine stalled. The mixture adjustment isnt as precise as I expected it to be and what makes it more difficult is the 3mm allen key fitting appears to be rounded slightly (somebody else has already had a go at adjusting the mixture).

Any pointers appreciated!

those gunson meters are garbage, take it to your local garage instead. I set mine to '1.5%, then when it was checked on a proper setup it was more like 0.2%!

this was a brand new gunson meter as well, being run over by my mate was the best thing for it

rubjonny said

those gunson meters are garbage, take it to your local garage instead. I set mine to '1.5%, then when it was checked on a proper setup it was more like 0.2%!

this was a brand new gunson meter as well, being run over by my mate was the best thing for it

Oh…!