The 1.8T diag thread

[David 8]

There's a few of us having engines issues lately with our cars.

I thought it would be a good idea if we pooled our resources and made a collective thread.

The 1.8T is strange one, it's a good engine but can be mare to diagnose faults on especially when there are no codes present.

I have an issue you need help with post it in here, with as much info as possible include any mods, logs or anything else you can think of that may help.

With a bit of luck this thread could become invaluable to users looking to fix those 1.8T issues.

[David 8]

I'll start us off with my heap of crap

Sounds like a boost from what I have been told , it will hit peak at around 19psi then drop back a little to around 14 then wobble around until dropping off as usual.

I'm losing a few mpg too but this seems to have improved a little since changing a few bits, I have replaced the boost pipe seal before the pancake pipe and checked all joins, I also changed the hockey puck valve on the inlet as mine looked solid. I had the wrong N75 on there which made it look worse but that is now sorted, I've tried swapping the AIT, the CTS numbers look good the stat is fine, MAF is less than a year old, coil packs are good as far I can tell, I changed the PCV valve which was solid too. I got no codes. Long term fuel trim is at around -5.5% which points towards a boost leak, Short term looks fine

It does feel a little bogged down at low revs where as before it hardly needed any accelerator to get moving now it does, when its first started the mpg runs as normal then seems to stick at 19-20mpg and then slowly rises but I have to drive miss daisy to get it up, any sort of power and it guzzles it.

I'll add any more as it comes too me

edit... Here my thread http://www.briskoda....slowly-i-think/

Heres a few logs if anyone wants a look

LOG-01-032-014-015.CSV

LOG-01-120-107-115.CSV

LOG-01-003-004-xxx.CSV

LOG-01-020-063-115.CSV

LOG-01-032-004-115.CSV

LOG-01-061-003-004.CSV

LOG-01-120-115-118.CSV

LOG-01-031-xxx-xxx.CSV

LOG-01-063-115-002.CSV

Help me Obi Wan Kenobi ........ You're my only hope !!

LOG-01-118-115-003.CSV

[G-slave]

how is your boost gauge connected?

[David 8]

Off the fpr top pipe. Been like that for years.

Changed the pcv elbow this morning .... no difference.

Noticed idle feels quite lumpy as well.

[Bodge]

I'm guessing you've already checked it, but what about the small vacuum pipe connected under the inlet, that runs to the one-way valve (that you already replaced)? Really common leaker.

Do you still have the suction spray pump fitted under the inlet mani? If you do, the plastic pump housing has a habit of splitting and leaking. You can easily remove the system and it makes no difference to the car. Can be a cause of vac and boost leaks. No sensors or junk, just requires the hole in the TIP and inlet manifold to be plugged.

How much vacuum are you pulling on hot idle? ~25inHg? Anything less and I'd get suspicious of a vac leak.

What about fuelling? New filter? Pump, injectors, injector seals, rubber fuel hoses in engine bay etc all ok?

[IulianE]

in 5 years of ownership I changed the ignition module and one coil...and that's it.

I never had any problems with DTCs,

1.8t AGU

[David 8]

I'm guessing you've already checked it, but what about the small vacuum pipe connected under the inlet, that runs two-way valve (that you already replaced)? Really common leaker.

Do you still have the suction spray pump fitted under the inlet mani? If you do, the plastic pump housing has a habit of splitting and leaking. You can easily remove the system and it makes no difference to the car. Can be a cause of vac and boost leaks. No sensors or junk, just requires the hole in the TIP and inlet manifold to be plugged.

How much vacuum are you pulling on hot idle? ~25inHg? Anything less and I'd get suspicious of a vac leak.

What about fuelling? New filter? Pump, injectors, injector seals, rubber fuel hoses in engine bay etc all ok?

Checked the s pipe which comes off the pvc. That was changed a few years back anyway.

Vac is sat at about -26inhg. I thought the suction pump thingy was connected to the brake booster as well??

I checked it out and they are now priced at £50 lol. Fuel filter was done late last year hoses all look good. No smells of petrol. injector seals look clean. Could a clogged injector cause these problems ?? car does like a drop of oil but there's never any smoke. fired it cold this morning whilst stood behind and nothing came out. I have read that a bunged pcv can cause oil use so I changed the pcv elbow off the crank today which fell apart in my hand as I tugged it loose. my weekly milage involves a lot of traffic and stop starting of engine so i could put the oil use down to that. Its funny every time I change something the boost gets a little better it's not dropping as much now but its still noticeable.

Long term fuel trim is now at -7 and seems to rising daily I'm not going to reset it again which hopefully should bring a code at some point, which can hopefully point me towards something. I've done a few more logs today of normal 30 mph driving I'll tidy them up and post them later.

Thanks for the input here. I said if anyone wants to post a running issue feel free.

Any typos above are due to the fact that I'm typing this on the mobile.

[marko pollo]

I really want to put up my nightmare of a vrs but im sure many good ppl are bored of it, you must be one of them?

lol

[Cossie1]

Unclip the pipe going into your charcoal canister, to see if anything changes.

[David 8]

Which pipe there's a few iirc. Unplug whilst idling or run with it unplugged.

[David 8]

I really want to put up my nightmare of a vrs but im sure many good ppl are bored of it, you must be one of them?

lol

Link your other threads and update what you have done since.

[Cossie1]

Which pipe there's a few iirc. Unplug whilst idling or run with it unplugged.

There is 3 on the drivers side, it's the bottom 1 of the 3.

Run with it disconnected.

http://i257.photobucket.com/albums/hh239/Bowders1_2008/VRS%20Mods/Charcoal%20Canister%20Delete/Charcoalcanisterdelete8.jpg

[Gonzaga]

in 5 years of ownership I changed the ignition module and one coil...and that's it.

I never had any problems with DTCs,

1.8t AGU

Because you have a older ECU which doesnt have at least 60% capability of a vrs ECU ME 7.5

[G-slave]

i reckon you need to give the ecu some time to learn. you have no major issue so no need for major intervention.

[G-slave]

is there a way to connect the boost gauge to the inlet manifold?

[David 8]

is there a way to connect the boost gauge to the inlet manifold?

I think it is, it's on the pipe that runs from the manifold to the FPR

i reckon you need to give the ecu some time to learn. you have no major issue so no need for major intervention.

It's had long enough lol, so in effect if I cure the issue, the symptoms could hang around for a while ??

[David 8]

Can you give me some blocks to log which may help ???

3rd gear runs, I can slip on to the M4 in a bit and get some clear runs at this time of night

[Cossie1]

I think it is, it's on the pipe that runs from the manifold to the FPR

It's had long enough lol, so in effect if I cure the issue, the symptoms could hang around for a while ??

Clear the fault codes (even if you don't have any) and it resets the trims.

[David 8]

Clear the fault codes (even if you don't have any) and it resets the trims.

I know but I was kind of hoping too leave them build up this time I've done them everytime so far lol

[David 8]

Actually looking at that engine diagram again theres a pipe missing from the actual engine layout

THeres a pipe which enter the TIP where I have circled, that pic is from the AUQ service manual too !!!

[RobClubley]

My modified version

[David 8]

Where did you get that one from Rob ??

[RobClubley]

Where did you get that one from Rob ??

I made it from the standard one and added the correct AUQ connections. Then did some colouring in.

[David 8]

I made it from the standard one and added the correct AUQ connections. Then did some colouring in.

Ok, show off lol.

This is getting more confusing by the day, I hope my leak tester turns up tomorrow !!

[David 8]

I'm really starting to think the O2 sensor is on the blink, shouldn't these figures match a little better

https://docs.google.com/file/d/0B4mPZKTTSOUFa28zeE56d2x6eTA/edit?usp=sharing