High Idle - Suspected Air Shroud? HELP!

Hello,

1991 DX engine code - With the air shroud injectors.

I've been chasing an idle issue (high idle and poor/no cold idle). It's not bad and liveable (Chrotle has inspected the car and didn't comment on it at all), but I'm a perfectionist so it's doing my head in.

So far iv'e changed:

- Throttle body (stripped, cleaned original and same for the new one with 52mm butterfly. it's has a very smooth action and snaps shut easily, but I did notice a small gap around the butterflies when fully closed; however it's the same on the x3 TB's I have so presuming normal).
- Throttle Body Gasket- Throttle body idle screw o-ring- Inlet Manifold Gasket
- Checked every vacuum pipe and replaced all the smaller 3mm ID pipes
- AAV works (squeeze the pipe after the AAV when cold and idle drops, when warm, no change).
- Removed the injector seats and inspected (I have the brass upper and plastic lower) with no cracks found and I replaced the seal with some o-rings I have whilst I was at it
- Replaced lower injector seals with o-rings I have - uppers look ok, although a tad deformed
- Changed WUR- CO2 set up
- Timing ignition and cam set up perfect
- Tried a second Suction Pump

The cold start works perfect now, but the idle is still high - The idle screw on the TB is fully would in and it's around 950-1000rpm on idle, unscrewing the idle screw does affect the idle so I know this is ok - The idle is almost there, but I know with the idle screw fully wound in it should be trying to stall, it's not.
I've sprayed WD40 around all pipes and joints with no effect - everything is leak free and sealed. I've tried squeezing all pipes when running and nothing changes. EXCEPT one pipe. The pipe which goes from the Throttle Body intake boot (front side, lower) directly to a fixed port on the back of the head for the Air Shroud, squeeze this and the revs drop to the point of wanting to stall.

Is this normal or does this indicate I have a leak in the air shroud system? Possible injector seals and injector inserts? If so, do I stick with the brass inserts with plastic lowers or do I change for the full plastic type?

Not sure I noticed any high idle…
Wasn't with the car long enough with engine on to notice.
What I did notice was you're missing the lower intake pipe from the bottom of the air box the air filter fits into.
Did you replace that yet…

These are older cars and as such don't really know true mileage or history as to what the PO actually did, said they did but didn't… Lol
Keep at it you'll get it sorted.



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That's what I mean, the idle is just about right, it's took me a good amount if time with the car to realise something isn't quite perfect. It's like 95% there, but it is the other 5% which is bugging me. I don't think anyone else would notice. It's me being anal. 

I replaced the airbox intake for a genuine elbow and pipe not long after you pointed it out on the day! You'd be really surprised the progress I've made with all the missing bits. 

I noticed this morning that the pipework for the air valve thingy (drivers side wing) had been swapped over. Putting them correct helped matters a tad, but I'm still not happy. 

I took the car out to Chatsworth House today, it's a good drive and I encountered some stop start traffic - and the weather was bloody hot, as hot as you'll ever get in the UK (indicated 27 on the MFA). The car never missed a beat, the idle never fluctuated, not once.

The idle screw is at its lower limit but the car seems to be running good. Maybe it's just in my head? Either way, I'll change the Injector seals and seats; then report back. 

if blocking the air shroud pipe makes idle drop then yes you have an air leak past the shrouded tips. the proper shrouded injector seat seals have a square profile, so if you replaced them with some random opnes you found that could well be why.

i assume the main injector seal and the wee ones on the top hats were all replaced?

rubjonny said

if blocking the air shroud pipe makes idle drop then yes you have an air leak past the shrouded tips. the proper shrouded injector seat seals have a square profile, so if you replaced them with some random opnes you found that could well be why.

i assume the main injector seal and the wee ones on the top hats were all replaced?

Yep, blocking the air shroud pipe makes the idle drop to the point of stalling.

I replaced the injector seat seal with round ones (however, I did screw a seal in, then out to test and the o-ring had squeezed so I'm confident they sealed). But for the sake of £1 each, i'll order some new ones.

Injector wise, the lower 'top hat' seal was changed but the uppers left as my o-ring kit didn't have any of the right size, they looked fairly new (they were nice and soft but deformed so maybe that's the issue?). Once again, I've found a kit on eBay for around £8 so might as well.

The injector seats were brass upper and plastic lower - no cracks in the plastic but they did appear old and brittle so hairline cracks are a possibility. For what it's worth i'll change these too. rubjonny should I change the lower seats only or replace the full lot for the one piece plastic type?

From removing the seats, changing the o-rings and replacing it made no difference to the idle, so suspect seats or upper injector seal. Unless there is something else at play?

i dont think the other type will fit your head, so keep it as is

Thanks!

I've ordered the seats and seat seals from VW Heritage - Pattern parts, but fingers crossed.

O-Ring kit for the injectors ordered too.

I'll report back at the weekend once fitted.

So, the injector seats, seat seals and injector seals turned up.

The seats and seals are in - when removing the old seats with the o-rings I put in place, the o-rings had crushed to form a flat seal anyway - So I think they would have been fine. Either way, the new ones are in. Did them as tight as I dared (didn't want the seats to crack).

The injector seals which arrived were very poor quality, I'm not sure what I was expecting for £7 delivered, but there you go. The lower seals weren't that bad to be fair, they are all installed and a quick push into the new seats was a nice and snug fit (much better than before). But the upper seals were terrible, very hard and two of them split just trying to get them over the top hat. They had no give in them at all. The two which I managed to install on the injector were impossible to push into the seat, they'd likely end up splitting getting them to sit…  Every seal I've replaced in the past have been a firm, but malleable rubber with lots of give - these were like the rubber on the end of a pencil, chalk almost.

So I've sacked them off for now and ordered some new ones from Mr Injector (proper Viton seals) - They were OE priced at around £2 a seal plus delivery, but having used Mr Injector before they'll be here by the weekend and will be excellent quality.   

To avoid the same mishap again, I've been led to believe the top hats pull off to slide the seals on. Is it a case of simply pulling off and pushing back on again? rubjonny , maybe one for you?

they do pull off yes, but not sure how well they go back on? maybe give a nip with pliers to ensure they wont fall off. i guess you must have to remove them to get the main seals on, unless bosch dont intend for this to be done, rather you must replace the injectors...

rubjonny said

they do pull off yes, but not sure how well they go back on? maybe give a nip with pliers to ensure they wont fall off. i guess you must have to remove them to get the main seals on, unless bosch dont intend for this to be done, rather you must replace the injectors…

Well, I don't want to split the next seals, but I don't want to ruin the injectors either! I've read a few places the top hats just pop off and back on again. Not so sure though, it sounds like a disaster waiting to happen.

Edit:  Found this… CIS Injector Cleaning, Seal and Holder Replacement

Looks like they are meant to come off. I'll give it a go, what's the worst that can happen?

cool recon you'll be sorted

Be carful they are fixed on well as in the engine I've just rebuilt I found 2 injectors caps floating about in the head just above the valves when I removed the inlet manifold.

mark1gls said

Be carful they are fixed on well as in the engine I've just rebuilt I found 2 injectors caps floating about in the head just above the valves when I removed the inlet manifold.

Managed to get one off last night as a test. It was bloody tight but a very simple design - just an interference fit… They need a slight tap with a rubber hammer on a soft surface to get back on. To be honest, I'm really surprised they'd every come off by themselves at all!

It was a second hand engine so I did not know a lot about it but you can see what I found when the inlet manifold was remove, one good thing is if you do lose one you can get it out with a pair of long nose pliers.

Bizarre,

Judging by how tight it was to get off, I would have thought to be impossible. However, that looks fairly mint and if it was in there a long time it would have battle scars from bouncing around. I bet when the injectors were pulled they were done so forcefully so the cap came off.

But when I removed the one last night, it pinged off and flew about 100 meters. It was tight!  

UPDATE…

The cars all back together and it's running like a dream! Perfect idle and pulls like a train.  

Good news, now get out and enjoy the sunshine and warm days.