2003 Mk1 vRS boost leak and wot hesitation

[Sissipaska]

So I've been looking for some kind of boost and vacuum leak for a while now. The symptoms have been erratic idle and vac pressure and loss of boost pressure during WOT runs. The car would build up boost, dump it, build again only to dump it. Almost like a slow machine gun. I ran some logging in VCDS on N75 duty cycle, MAF readings and requested vs actual boost (MAP sensor) and all seemed somewhat OK apart from the MAP sensor readings but this could've be down to a boost leak as well.

 

I've changed all the hoses before in the Creations motorsport kit (not really recommended, buy better kits, but it's still better than the original rubber hose). 

 

The other week I cleaned my SMIC (never been done before) and also changed all the intercooler pipes. This lowered the intake temps by over 5-6 degrees which is really nice so clean your IC's if you haven't. My had a cup full of oil that had collected over the years. The MAP sensor had gotten a good amount of oil over the years so it looked a bit wet. I decided to change it.

 

I ran the car with the N75 to wastegate actuator pipe clamped and the car ran good and could build boost (WARNING! this has the potential to cause a catastrophic engine failure - be very careful) so I ruled out the wastegate. The N75 duty cycle was normal so I ruled out that one for the time being. I also found a hairline split in the pipe so I replaced it.

 

I deleted the N112/N249 which made the recirc-valve respond much quicker.

 

Still, the issue was there and I had to find something else. Then it occurred to me that there was gunk on the intake manifold where the injectors sit. I started looking in to this and found that some people have experienced boost leak through the plastic injector cups so I decided to change the whole lot. Guide follows below (Note! this is how I did it, there might be easier ways to do it and I'm not liable for any damage you do to your cars).

 

1.8T AUQ injector cups, injector O-rings and intake manifold gasket replacement:

 

Part numbers:

Intake manifold gasket 058129717D (qty 1 x £5)

Injector cups 06B133555H (qty 4 x £4)

Injector O-rings 035906149A (qty 8 x £0,8)

Throttle body gasket 028129748 (qty 1 - might not be needed)

 

It might be worth changing these parts at the same time when the manifold is off:

Engine knock sensor: 030905377C 

Crankcase breather plastic elbow: 06A103213F

Crankcase breather pipes underneath the intake manifold (Look here)

 

Tools needed: 

Allen key 5mm, 6mm

Allen key 20mm for the injector cups (or use 17mm wheel bolt with lug nut cover or something else)

Socket wrench 7mm, 10mm (preferably 1/4" drive for ease of operation) and long extension.

Torque wrench (recommended).

T25 torx bit.

Needle nose pliers.

PH head and slotted screwdrivers.

 

Tightening torque:

Manifold to cylinder head bolts and nuts: 10Nm

Fuel rail to manifold bolts: 10Nm

 

• Start by removing fuse 28 inside the car (fuel pump 15A) and let the car idle until it dies.
• Disconnect the battery negative terminal.
• Remove all engine covers and the bracket holding the N112/N249 valves under the intake manifold (I've deleted this and the SAI and have only the bracket left).
• Use compressed air and remove as much loose dirt as possible from where the intake manifold meets the cylinder head since it might fall into the exposed intake chambers otherwise.

 

Follow steps below if you like to move the whole cable holder on top of the fuel rail to the side - otherwise jump down to "continue here"

 

• Remove the right hand side headlamp (UK drivers side/EU passenger side) and disconnect the MAP sensor cable.
• Disconnect the two connectors on the throttle body (temp sensor and fly-by-wire connector).
• Disconnect the camshaft position sensor cable (YELLOW arrow in picture below)
• Disconnect the knock sensor cable under the intake manifold (RED arrow in picture below)
• Disconnect the brake booster pipes from the intake manifold in the marked positions (BLUE arrows in pic below).

 

 

Continue here

 

• Remove the intercooler-to-TB boostpipe and remove all 4 Allen bolts holding the throttle body to the intake manifold. Put the TB to the left side out of the way.
• Disconnect the 4 fuel injector connectors by pressing on the silver clips (RED arrow in pic below)

 

 

• Unclip the cable holder on the fuel rail and move the whole cable unit out of the way.

 

 

• Remove the two 5mm Allen bolts holding the fuel rail and hard lines to the intake manifold.
• Remove the two rubber fuel lines going to the fuel rail hard pipes. There will be some left over fuel coming out (RED arrow in pic below).

 

 

• Lift the fuel rail with the injectors out of the injector cups (some mild force might be needed. lift them two by two straight up). Some fuel will come out.
• Now you're left with this. Be careful of debris and use a vaacum hose to suck up all as much as possible. Remove the eight 5mm Allen bolts and two 10mm nuts that hold the intake manifold to the cylinder head in a star pattern starting from the outside.

 

 

• Remove the 6mm Allen bolt holding the intake manifold bracket (to the left of the oil dipstick)
• Remove all 4 vacuum pipes under the manifold (fuel pressure regulator, recirc valve, crankcase breather pipes).
• Lift the intake manifold off the car.
• Now you're left with this:

 

 

• Remove the gasket and put something to cover the intake chambers. I used a vacuum hose to suck all small particles that fell into the chamber.
• I cleaned all surfaces and replaced the gasket.

• Here you can see the obvious leak from the injector cups on to the intake manifold:

 

 

• Remove the old injector cups with 20mm Allen key. I used a 19mm bar but It's easier to just hit them down with a hammer and pry of the threaded part that's left since you're going to discard them anyway.

 

 

• Two of the injector cups came out easy, two broke and were cracked before and probably leaking like ****:

 

 

• Clean the intake manifold. Now is a good time to polish it or paint it, like I did.

 

 

• My manifold painted and ready for the new injector cups:

 

 

• To install the new cups I used a 17mm wheel bolt and put on a plastic wheel stud cover which was perfect fit and wouldn't break the plastic since it was plastic against plastic.

 

 

• Tighten the cups so that they sit flush to the seats on the manifold. Do not over-tighten since it's plastic to metal and use some plastic to metal anti-seize.
• Clean the intake chambers before refitting the intake manifold. I was pleasantly surprised over the cleanliness of my intake valves considering my car has done 240,000 km. Use 98 RON fuel, that's my top tip. Always have and always will. This is the result IMO.

 

 

• Remove the fuel injectors from the fuel rail and replace the O-rings (two per injector). Remove the brass clips (notice the direction) and just pull them out. If you have the oppertunity then leave them to someone who can clean them in an injector cleaning stand and test the fuel pressure and so on.
• Installing is the opposite of removal. Take your time, label everything if you're not sure and be thorough. 

 

Results: I don't know if the MAP sensor was the culprit but firstly I now have stable intake manifold vacuum at 25 in/Hg at idle, whereas it previously jumped between 22-23 in/Hg and secondly I have no hesitation or loss of boost during WOT anymore. If you're looking for a vacuum and/or boost leak then change the bits listed above since the cost is low and it's easy to do. The plastic injector cups were almost disintegrating and it would not be fun times if it falls in to the intake chamber.

 

Hopefully somebody is helped out by this guide. Note that I've changed most vacuum hoses and simplified the system a lot, mainly following the guides posted on pimpmyskoda.

Edited 18 May, 2018 by Sissipaska
Forgot some info.

[Passeyfier]

Wow, what a post! I will definitely be referring to this in the future if my current leak extends beyond a split hose (which is to be replaced in due course). I've never thought about cleaning the SMIC. In fact, I've never really inspected it properly and judging by the things that I've replaced since I took ownership I doubt any of the previous owners would have done either!   I must also get round to giving my engine bay a spruce. Yours looks great, mine is far from clean!  

[Liverpool-Lad]

Great post.  The valves though will always be clean no matter what fuel used as these are not direct injection engines.

 

Super cant hurt though!

[Sissipaska]

20 hours ago, Liverpool-Lad said:

Great post.  The valves though will always be clean no matter what fuel used as these are not direct injection engines.

 

Super cant hurt though!

 

Yeah but I've opened some 1.8T cars which looked much worse than this so it was more a surprise for me.

 

But direct injection engines can look really bad. The 1.6THP Prince engine that needs to be decoked with crushed walnut shells. Fun stuff!

[Sissipaska]

On 2018-05-18 at 19:02, Passeyfier said:

Wow, what a post! I will definitely be referring to this in the future if my current leak extends beyond a split hose (which is to be replaced in due course). I've never thought about cleaning the SMIC. In fact, I've never really inspected it properly and judging by the things that I've replaced since I took ownership I doubt any of the previous owners would have done either!   I must also get round to giving my engine bay a spruce. Yours looks great, mine is far from clean!  

 

Don't be afraid to give the engine a proper wash. I've always used a pressure washer with distance and carefulness and then some citric degreaser that doesn't ruin plastic or rubber and agitated with a wheel brush. Just put a plastic bag over the alternator, mass airflow sensor, battery tray fuse box and you should be good to go. If you remove the main engine cover then be careful with too much water over the coilpacks. No issues whatsoever and it helps with troubleshooting since you spot an oil leak or a split hose very quick.