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Robertjp

Original Poster:

2,279 posts

111 months

[news] 
Monday 3rd September 2012 quote quote all
For a while now i have been noticing rough running at idle from cold (almost like a very slight misfire), but that quickly goes after a few minutes. I put it down to TADTS...but it just didn’t feel right.

A niggle more than anything but its been bugging me – it was noticed during my 6k service but it quickly disappeared so nothing more was thought of it – there were a few other minor things that could have been causing the problem and they were resolved, so quite rightly we thought the problem had gone.

Anyway, about 400 miles on and this slight misfire was back....now i already have roller bearing throttle bodies, and with such a recent service ii hadnt suspected a problem here – but i did check them again recently and they were out of sync!! furious

A bit confused, i reset them all AGAIN, and next start up – car was perfect. Thought it was problem solved...until the bloody thing started again less than 100 miles later!!!

Getting frustrated at this point and suspecting the throttle bodies were leaking in some way – i purchased a set of Power’s Performance Throttle body gaskets. A lot of money but i decided to bite the bullet and take an educated guess that air leakage under the throttle body flanges was the problem.

Fitted them on Saturday...the car decided to fight me all the way while installing the job took about 5 hours, but at least an hour of that was spent looking for a bolts...word of advice, get a telescopic magnet with torch and a light coloured sheet for under the car BEFORE starting the job...believe me you will need it several times. Oh, and some thick gloves to prevent getting burned if you have run your car first wink.

When i inspected the flanges on the throttle bodies once they were removed, i was very reassured to find oily residue across most of the mating faces...indicating that they were in no way air tight, and yet they had previously been sealed with hylomar. After bolting it all back together, looking for more bolts and several adjuster arm springs that have a mind of their own....a throttle balance and throttle pot reset...initial signs were that they have made an incredible difference. Idle is smoother than it has EVER been, pick up is silky smooth, its quieter and just feels so much better.

I have only had a quick spin round the block with them fitted, so weather permitting i will be in the car tomorrow to give some proper feedback...just hope the start from stone cold is without a hint of a problem!!!


Basil Brush

4,195 posts

149 months

[news] 
Monday 3rd September 2012 quote quote all
I'm hopefully fitting the bearings in my throttle bodies next week and have some gasket material to make my own. Sounds like the work will be worthwhile.

clive f

7,028 posts

119 months

[news] 
Monday 3rd September 2012 quote quote all
fitted these to mine as well, helps keep the t/bodies much cooler too.

DAVEY DEE

624 posts

40 months

[news] 
Monday 3rd September 2012 quote quote all
clap This IS good news...I ordered a set today to be fitted as part of the rebuild.

PetrolHeadPete

495 posts

75 months

[news] 
Monday 3rd September 2012 quote quote all
Hylomar just washes out over time
High temp rtv works perfectly
Have refitted bodies 3 times with it and it works every time

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Robertjp

Original Poster:

2,279 posts

111 months

[news] 
Tuesday 4th September 2012 quote quote all
pete it was your threads that made me think of the leakage, but i decided to go for the gaskets in case they ever have to come off again and its not me that puts it back together wink
anyway, used the car for work today and early signs are woohoowoohoowoohoo its been fantastic, its an absolute pleasure to sit at idle now and then pick up is so smooth. Still early days but so far Im v pleased i spent the money on these smile

PetrolHeadPete

495 posts

75 months

[news] 
Tuesday 4th September 2012 quote quote all
I made my own with a laser cutter. But then (as it turned out) foolishly added a smear of Hylomar...they failed the same way. That was "the moment" I switched to RTV and no gasket. You can't use too much though else it makes a rubber band at the inside edge that you have to carefully extract later with long nose pliers wink

My mod with the direct coupled shafts seems to be holding up nicely...must post those pics.

Basil Brush

4,195 posts

149 months

[news] 
Tuesday 4th September 2012 quote quote all
PetrolHeadPete said:
My mod with the direct coupled shafts seems to be holding up nicely...must post those pics.
What mod is that?

s6boy

1,001 posts

111 months

[news] 
Thursday 6th September 2012 quote quote all
Any of these symptoms similar to yours Rob - Poor/non starting from very cold (below 10 degrees), uneven idle and PITA to drive until a little temperature in the engine, spitting back from one or more cylinders when blipped cold?

Cheers




Robertjp

Original Poster:

2,279 posts

111 months

[news] 
Friday 7th September 2012 quote quote all
s6boy said:
Any of these symptoms similar to yours Rob - Poor/non starting from very cold (below 10 degrees), uneven idle and PITA to drive until a little temperature in the engine, spitting back from one or more cylinders when blipped cold?

Cheers


Pretty typical of a poor AFR IMHO...i would check your throttle bodies with a syncrometer and reset them, then do it again in say 500 miles - if they have changed its a good indication.

If its spitting it suggests its running too lean - i.e. too much air...i had the same when trying my 'first' throttle body balance and was pulling way too much air. Its needs to be round the 6-8kg/min mark (or whatever the units on the syncrometer are wink )

s6boy

1,001 posts

111 months

[news] 
Monday 10th September 2012 quote quote all
Robertjp said:
Pretty typical of a poor AFR IMHO...i would check your throttle bodies with a syncrometer and reset them, then do it again in say 500 miles - if they have changed its a good indication.

If its spitting it suggests its running too lean - i.e. too much air...i had the same when trying my 'first' throttle body balance and was pulling way too much air. Its needs to be round the 6-8kg/min mark (or whatever the units on the syncrometer are wink )
Thanks, I was coming to the same conclusion before reading your thread good to have another opinion. However it's the fact that when hot the engine behaves perfectly which has been puzzling me. Now thinking a leak is being affected by a bit of thermal expansion when up to temperature.

Robertjp

Original Poster:

2,279 posts

111 months

[news] 
Monday 10th September 2012 quote quote all
s6boy said:
Thanks, I was coming to the same conclusion before reading your thread good to have another opinion. However it's the fact that when hot the engine behaves perfectly which has been puzzling me. Now thinking a leak is being affected by a bit of thermal expansion when up to temperature.
Thats another indicator its the flanges IMO...thats why i was getting the rough 'cold' start - i think as soon as they had some warmth they were closing up and reducing the leakage...

s6boy

1,001 posts

111 months

[news] 
Monday 10th September 2012 quote quote all
Robertjp said:
Thats another indicator its the flanges IMO...thats why i was getting the rough 'cold' start - i think as soon as they had some warmth they were closing up and reducing the leakage...
thumbup thanks Rob given me something concrete to work on rather than faffing around trying to find a fault that disappears after 5 minutes!

Night Rider

431 posts

89 months

[news] 
Saturday 22nd December 2012 quote quote all
What exactly is the gasket thickness and type?
Is it a special paper?

clive f

7,028 posts

119 months

[news] 
Saturday 22nd December 2012 quote quote all
thickess is about 2mm, so you dont have to replace the bolts holding the bodies on, material type escapes me, composite stuff, whose name I cant remember.banghead tuffnol?

Geoff Ashcroft

303 posts

92 months

[news] 
Monday 24th December 2012 quote quote all
I'm sure it's a multi-layered gasket that acts as a thermal barrier in addition to creating a proper, air-tight seal. I thought there was some bakelite-type plastic resin in there too and is not just paper. Best £80 I've ever spent on mine and is a no-brainer of an upgrade and means no more cold start/idle or spitting issues for my S6. But the increased gasket thickness does push the airbox up a bit, making it more of a PITA to wriggle on and off under the bulkhead.
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