Mhave found the cause of my lumpy idle

[themanthatcan]

My car hasn't idled quite right since purchase; It's always been a little bit lumpy. I've been trying to solve it for ages cos it really niggles me So far I'd tried replacing the coil packs, spark plugs, coolant temp sensor, and cleaning the throttle body and MAF. That didn't leave many possibilities so I've been looking for a vacuum leak. Look what I found today:

The pipe is down behind the inlet manifold:

Does anyone know the name of this pipe? It seems to connect up to the left-hand side of the inlet manifold, connects to a T-piece which goes into the bottom of the inlet manifold, and then travels round to the back of the engine somewhere.

Any help greatfully received! Thanks!

 

[voorhees]

thats a coincidence
had my car data-logged today by Stealth Racing but it come up with nowt,done all the stuff you had plus a new maf and Vince had a look under the bonnet to find a leak in the same place as yours,I think its a dealership custom piece

 

[themanthatcan]

Just done some research and it appears to be part of the PCV system and apparently is quite a common failure.

Will pop down to Audi tomorrow and see what crazy price they want for a replacement. Bit annoying actually cos I was only down there this afternoon and could have got it ordered up ready for tomorow..oh well!

 

[themanthatcan]

Could be the same problem as mine. has it been spluttering when cold?

It hasn't no. The only problem is a slightly unstable idle, Im talking a 50 RPM wavering. That's not to say that your problem couldn't be caused by a split hose though. VAG vacuum hoses are notorious for splitting.

 

[HTC]

Mine went recently. Yes it's part of the PCV system. Didn't seem to effect my idle which is why I didn't notice it. Usually there is a build up of goo when they leak.

 

[themanthatcan]

Popped down to Audi this morning and they want a crazy £48 for the pipe!!!!!!!!

Has anyone ever made up their own vacuum hoses? This one isn't a fancy hose at all so can't be that hard to replace!

 

[1animal1]

feel for ya mate....when my T piece (vacuum system) went they wanted £60 - £70 for a pipe kit, which contained loads of lil crappy pipes that i didnt need

 

[HTC]

Breakers? Loads of busted TTs about with the same pipe.

 

[themanthatcan]

Breakers? Loads of busted TTs about with the same pipe.

Knowing how brittle these pipes become I wouldn't want to be using second-hand parts. Will probably pop down to Halfords or the local MotorWorld and see if they've got any.

 

[ash_s3]

Halfords etc.. sell rubber hose by the meter and its dead cheap, allsorts of sizes too.

Is your rocker cover gasket leaking or is that just spilled oil?

 

[themanthatcan]

Excellent, thanks matey.

As for the mucky rocker cover, think it's just a mixture of spilled oil and a previously leaking gasket. It's had a new gasket recently and there's no sign of fresh oil so once I get this pipe replaced and a new clutch fitted I might actually be able to afford some cleaning products and a pressure washer to get the engine bay cleaned out!

 

[themanthatcan]

Well I took the inlet manifold off the other day to see if I could replace the hose with some generic vacuum hose from Halfords but Audi have done a great job of customising the pipe as much as possible making it very tricky so I dug deep and ordered the pipe from the stealers. Have just picked it up and my wallet is £48 lighter The upside is that the part replaces all the PCV piping under the inlet manifold and it's made of much better quality stuff than the originals:

Haven't got time to fit it myself this weekend so it's being fitted by the garage when they do my clutch on Monday, along with a few other bits like a new thermostat. Only time will tell if this actually cures my idleing problem though..I ****** hope so!

 

[1animal1]

good luck Andy, hope it works mate

 

[simch]

Nice place mats!!

 

[themanthatcan]

LOL Was having friends round for dinner so the table was set. The missus wasn't too happy to see my taking pics of car parts on her white velour runner that's for sure!

Cheers Tim..will let you know how it goes!

 

[Dave B]

Im off to check mine now! same 50rpm blipping on idle

 

[Riley]

the same for a '99 S Plate do you think?

Mine's had the same problem since I got it and it's my only gripe so far (well, that and the missus telling me I don't "Need" new alloys...)

 

[themanthatcan]

There's a whole list of possible causes for lumpy idle:

MAF, Ignition Coil, Spark Plug, VAC Leak, O2 Sensor, TB, CTS

It's just a question of running through the list to see which one cures it! I get my car back from the garage today so will let you know if the new pipe fixes the problems!

 

[HTC]

When you say the idle is "lumpy" do you mean it's just wavering up and down or do you have missfires. Mine had an air leak past injector number 3 (now fixed) which produced missfires:
http://youtube.com/watch?v=bfny9Y3SBng
This is the usual symptoms of an air leak.
I've found that alot of 1.8T engine seem to waver up and down a little. I'd love to know the cause of it.

 

[themanthatcan]

Yeah my research has shown that the 1.8T isn't the most stable idler. I have what feel like little random missfires; nothing drastic enough to show up on Vag-Com but it's like the engine does a little cough every few seconds.

 

[HTC]

Which can be caused by an air leak. That pipe may well sort the issue out. Also have a listen to the injectors for hissing past the seals.

 

[themanthatcan]

I'll bear that in mind thanks. Funny you should mention the injectors actually because I had the fuel injection rail out the other day while I was removing the intake manifold. After refitting the rail the idle seemed to be stable (the rev counter would still flutter but there was no missfires). It was ok for a day or so and then returned to it's lumpy self.

Wonder if some new seals on the injectors would help as well then?

 

[HTC]

With the engine running, you can wiggle the injectors. You'll soon hear the engine note change if there is a leak.

 

[themanthatcan]

******. The pipe hasn't made a single bit of difference Got the garage to fit it while they were doing the clutch and it still has the odd hiccup occasionally.

HTC - Did you replace the seal on your injector to fix your missfire? I remember seeing the seals when I had the rail out and they looked easy enough to replace and I'd imagine they're pretty damn cheap as well?

 

[HTC]

Sorry to hear that. I was going to swap the seals from my old injectors to my new ones, but they were a little cracked. So in the end I ran a small bead of RTV sealant around the top after inserting them into the inlet manifold.
What I did notice that the genesis seals were slightly smaller than the OEM items, not that that helps you of course.
Try the wiggle and look for black oily deposits around them.