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Discussion Starter · #1 ·
General driving and idle seems to be a lot leaner as of late and WOT seems to have gone really rich. Car is running MAP sensors so it's not TOO bad but I've been trying to pinpoint the exact problem for a while now.

I've checked all of the boost pipes for splits and made sure they're connected to the intake manifold. I've checked all of the connections on the intercooler to the intake plenum and found nothing.

Does anyone have any suggestions on how to find a vacuum leak or whether this is actually a vacuum leak?

A car doesn't just go rich at WOT and lean at idle for no reason. I've seen people suggesting to spray carb cleaner or WD40 around the intake throttle bodies. It's a GREDDY intake manifold with individual throttle bodies.

Thanks!
 

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The servos leaking are not unheard of but seldom checked.
 

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Rather than spraying wd40 around I get a propane blowtorch (unlit) and spray gas all around the suspect pipework/gaskets - any leaks will give an increased idle when you get near as it's sucking the propane in and burning it up.

Only works when it's not too windy mind!
 

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Discussion Starter · #5 ·
Ah, I was always a little weary of spraying onto the manifold etc.

So, smoke tests, can any decent garage do that or is it more of a specialised job?
 

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Discussion Starter · #7 ·
Also is there any definitive way to know whether I actually have a leak? the car seems to drive fine, just the AFRs seem a bit weird. Just checked again, unplugged pretty much every boost tube and checked for splits. Nothing; the manifold looks pretty solid too.
 

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Discussion Starter · #8 ·
Update

1. Sprayed carb cleaner all over the place! No change in idle/engine sound.

2. Connected a boost leak tester to the turbo air intake feed and hit it with 0.5bar through to 1.5 bar within the specification of the engines parameters. As soon as the compressor stopped, the gauge just dropped to zero. Checked the gauge on a tire and works as expected. No hissing at all....

3. Car behaves as it did previously, drives fine, just a bit lean on standard driving and pretty damn rich on full boost. It seems to make the boost pressure required though but this is probably down to he turbo being quite powerful and the greddy protecB boost controller.

4. Whilst doing the boost leak test, 1.5 bar on the gauge read as 0.1 bar on the defi gauge and the protecB


Really confused to be honest and any advice would be really helpful. I can't understand how the car can be going rich if the gauge is showing the correct boost pressure but it never used to go rich and this isn't just a change in the weather, it's been quite cool and that doesn't explain why idle and gentle driving has gone really lean.
 

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When you say it's going rich or lean, are you reading this off a wideband gauge? What sort of AFR figures are we talking?

For point 4 above, aren't your defi gauge/boost controller pressure sender plumbed in like the factory unit? If so they'll be reading the pressure post - throttles so it's perfectly normal not to see any pressure whilst doing that test with the throttle shut :) if your pressure gauges normally read vacuum at idle/on overrun then you've got nothing to worry about there!
 

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Discussion Starter · #11 ·
Hey, thanks for the reply!

So due to the cams that are in the car, the idle sat at around 13,9 and 14.1 with air con on. With no changes to the map, currently, idle will now start at around 12 and raise to about 15,5 and then with air con on, sometimes as bad as 16-18. I've actually had to change the tune a little to stop it from actually going this lean.

Furthermore, the car used to, at full throttle, hit about 11.5 on the AFR however now it hits 9.1!!!!

When driving off boost, the car does sit at around 14,7 but then a slight squeeze on the accelerator, (still off boost), results in the car going slightly lean, (15,5-16,5). Coming on to boost seems quite normal although also a tad bit rich.

So I can retune but I don't think that's the correct answer because to me, there's a problem. I don't really know whether it's a vacuum leak but as I've said I pinched all of the lines, used carb cleaner on the joins, used a compressor to listen for leaks to no avail.

I suppose the AAC/IAC could need cleaning? I've seen a few maintenance posts online for them.
 

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Have you checked all the large intercooler pipework buddy? We use hairspray to help seal all joints from leaks.
Also are you running uprated intake gaskets or OEM paper gaskets?
look for blown gaskets around this area, if so is there any oil residue on the throttle bodies?
;)
bob
 

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Discussion Starter · #13 ·
Hey,

Yeah, checked all the intercooler pipe work and tightened the clamps. I definitely couldn't hear any hissing. Hairspray is an interesting one though!

The intake manifold is completely custom, it's a six branch greddy intake so I would imagine the gaskets are uprated. I certainly see no oil, it looks extremely tight and snug. I sprayed a load of carb cleaner down at the joins and no change in the idle.

Any thoughts on whether taking the AAC/IAC off and cleaning would be of any use?
 

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Quick question when you did the smoke test where did you put the smoke input hose and what did you block off bud?
;)
bob
 

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Discussion Starter · #15 ·
Hey!

Haven't done a smoke test, I don't have the kit unfortunately. I've contacted a few places, RB Motorsport said that they don't do it but were great at finding leaks. I've got a compressor and a device that connects to the end of my turbo that allows me to push air through the system and it seems like that's not enough to find this one. I didn't block anything off, I'm not really sure what I need to block off actually :(

I read posts like using a paint can with a burning rag in it or a cigar to blow smoke through the intake but I'm not sure whether this is a good idea to blow dirty smoke through the system.
 

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Yeah we use a snap-on smoke tester much safer!
;)
Bob
 

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Discussion Starter · #17 ·
Any recommendations on where to take it? I'm near Milton Keynes. A smoke test would probably clear things up. I can fix the problem myself if I know where it's leaking.

Although according to what I described with the AFRs above, does that sound like a leak to you guys? The car does hold vacuum on overrun and Drives fine which is the weird thing.

Idle is set in the powerfc at 1000 due to cams however it does idle at 1150 which I also thought it could be attributed to a leak. It's running map sensors which is probably why the car is not suffering badly from this.
 
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