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Old 11-07-2015, 08:11 PM   #1
92redturbobrick
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Default Car sounds lean?

Hey guys, I've been lurking around here reading up everything I can for a few months now, ever since I bought my first brick, a 1992 940t with 155k.... anyways when I'm getting into he gas it sounds as if the car is pinging or like a fast paced tick.... this only co.e along when I get above 3k or so.... the car is still completly stock. I started looking under the hood replacing cracked vac. Hoses ect... I found that the rubber boot that goes fro. The am to the turbo with the whatever sensor it is has a hole about the size of a dime right under where the sensor is (about the middle of it) and where it goes into the turbo it's all sort and cracked looking. I just ordered a new one from fcpeuro... is this why the car sounds like this when I get on it? I suspect it's leaning it out? I was pisses when I seen it seeing as how my mbc and gauge should be in on Tuesday and I'm completely siked about turning it up to around 10 psi or so...
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Old 11-07-2015, 08:17 PM   #2
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If it's after the AMM, it's unmetered air, which will lean it out. I'd try to stay off the boost or just not drive it. You may get detonation and the kool-aid man loves 940s
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Old 11-07-2015, 09:11 PM   #3
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Thanks for the reply bud, maybe this also explains my poor fuel mileage as well... I ordered it with two day shipping.... should be here Tuesday along with my mbc..... what is the best way to check for vac leaks on a b230ft? Thanks in advance, I love this site
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Old 11-07-2015, 10:46 PM   #4
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By stage zeroing it before you start changing **** on the engine?

All vac lines, throttle body gasket, intake manifold gasket. Check EVERY INCH of your intercooler piping/hoses. Check the hose going inside the car to the boost gauge, etc. What grade of fuel are you running?
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Old 11-08-2015, 12:11 AM   #5
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ticking on accel can be exhaust manifold gasket leak.

Without hearing it, can't say.
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Old 11-08-2015, 01:16 AM   #6
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Sigged.
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Originally Posted by centason View Post
You may get detonation and the kool-aid man loves 940s
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You may get detonation and the kool-aid man loves 940s
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Old 11-10-2015, 11:44 AM   #7
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Ok, I got my amm to the inlet boot changed. It surely does ping like it was. It seemed to do it the worst at 3-4k. I run 93 octane, sometimes 89. I will look into the exhaust manifold gasket, and yes I surely won't be adding nothing until it's cherry. Almost there. Thanks guys
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Old 11-10-2015, 12:31 PM   #8
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Get a can of starter fluid. Spray it around injectors, gaskets, vac lines, etc. If idle changes, you found your leak. And do a boost leak test to make sure the turd system is sealed too.
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Old 11-10-2015, 04:51 PM   #9
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Only run 93, and as centason said boost leak test it. Does it sound like a tick or marbles in a tin can?
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Old 11-11-2015, 12:48 AM   #10
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Quote:
Originally Posted by ZVOLV View Post
ticking on accel can be exhaust manifold gasket leak.

Without hearing it, can't say.
This x100

Mine sounded so bad, like unbelievably bad before I replaced the gaskets. It sounded like a combination on detonation (on accel) and super misadjusted valves. Replacing the manifold gaskets made a huge difference.
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Old 11-11-2015, 12:49 AM   #11
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Doubtful that it's pinging on stock boost on an all stock car on 93 octane.
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Old 11-11-2015, 08:56 AM   #12
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Originally Posted by 93Volvo240 View Post
Doubtful that it's pinging on stock boost on an all stock car on 93 octane.
Why? A failed gasket or loose connection after the meter will cause a lean issue without a doubt.
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Old 11-11-2015, 09:31 AM   #13
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- the exh gasket on number 4 is often the first to fail.
When you are going to replace those gaskets make sure that you do not lose the rivets (o-rings?), these are special and are needed to allow the manifold to expand/contract when heating up/cooling down. Also check the mating surfaces of the ports for warpage. < you do not want that.
- the 90+ turbo exh manifold has a tendency to crack at the bottom of the collector part, could be the cause of those ticking sounds. It is hard to see it with the manifold in place but maybe you can use a mirror? Welding up those cracks is not easy. Best to pre-heat the manifold before welding.
- the nuts which hold the turbo onto the exh manifold also have a tendency to work lose. These nuts are made of special black colored steel (iconel?) that can withstand very high temps. On older cars these might have been changed at some point for nuts that are of lower grade material.
- the nuts that hold the downpipe onto the turbo also have a tendency to work lose, specialy when the bracket that holds the downpipe attached to the bellhousing has broken.

any exh gas leak upstream of the lambda sensor can cause false lambda input to the ECU which leads to false injection pulse timing.
In other words, in order to have good lambda input your exhaust side must be free of leaks upstream of the sensor.
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Old 11-11-2015, 10:58 AM   #14
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Quote:
Originally Posted by centason View Post
Why? A failed gasket or loose connection after the meter will cause a lean issue without a doubt.
Actually, post turbo, an airleak will cause RICH during boosting. Air escaping.

Go shove a length of hose in ear and listen around for leaks. Feel around when cold.


Prob time for some fresh high quality gaskets! You may break studs if it's the first time it has been apart in years! Soak in penetrant for as long as possible before doing the job.
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Old 11-11-2015, 12:36 PM   #15
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Quote:
Originally Posted by ZVOLV View Post
Actually, post turbo, an airleak will cause RICH during boosting. Air escaping.


engine sees a certain amount of airflow and then gets considerably less. ECU meters out the appropriate amount of fuel for that airflow, and then some of that air leaks. that means too much fuel.

A leak before the AMM just means it'll see less air to the AMM but should still meter and run correctly otherwise.

+1 on check for boost leaks, replace gaskets and generally stage 0 the car before proceeding.
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Old 11-11-2015, 12:51 PM   #16
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I derped that. Rich on boost leaks yes. Thinking too slow.
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Old 11-11-2015, 12:58 PM   #17
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Quote:
Originally Posted by centason View Post
I derped that. Rich on boost leaks yes. Thinking too slow.
OTOH though a dirty or malfunctioning AMM can read too little air for how much boost you're making though, which can cause a lean condition.

So get a can of AMM cleaner and hose that ish out.
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