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Jun 29, 2020 | 03:40 PM

BLUDICE

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Drifting

Joined: Apr 2014

Posts: 1,396

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From: Plainfield IN

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Will a DIY hand held scanner inform you of a vacuum leak?

Jun 29, 2020 | 03:48 PM

aaronc7

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Joined: Nov 2013

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From: USA

A generic bluetooth OBD scanner from amazon with an app like Torque pro can give you a lot of the basics for really cheap.

Yes, you can monitor manifold pressure/vacuum, and fuel trims with that setup. I would expect to see high positive value long term fuel trims with a vacuum leak at idle.

Jun 29, 2020 | 04:34 PM

C5 Diag

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Joined: Sep 2013

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From: Cape Coral, Florida

Quote:

Originally Posted by BLUDICE

Will a DIY hand held scanner inform you of a vacuum leak?

Yes, if you had a vacuum leak you will have elavated long term fuel trims...if you increase the RPM’s to 3000 RPM’s and long terms start decreasing you have a vacuum leak !!..video below !!...earlier this month didn’t you have some issues with idle ????

Last edited by C5 Diag; Jun 29, 2020 at 04:37 PM.

Jun 29, 2020 | 05:34 PM

BLUDICE

Thread Starter

Drifting

Joined: Apr 2014

Posts: 1,396

Likes: 129

From: Plainfield IN

Mine is a Hyper Tough HT309 OBDII/EOBD
I’m not 100% sure I have an issue - it just seems to me to be a little high to me.
So I bought this thing when I had my ‘08 C6 and know enough to be extremely dangerous lol - so can I this thing pick up a vacuum leak or is this not “big” enough?

Jun 29, 2020 | 05:40 PM

C5 Diag

Moderator, Tech Contributor

Joined: Sep 2013

Posts: 15,319

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From: Cape Coral, Florida

Quote:

Originally Posted by BLUDICE

I am not familiar with this scan tool but if it can read fuel trims you’ll be OK...if your long terms are over +10 % you should be concerned !!...these scan tool are not dangerous !!

Jun 29, 2020 | 05:51 PM

BLUDICE

Thread Starter

Drifting

Joined: Apr 2014

Posts: 1,396

Likes: 129

From: Plainfield IN

Quote:

Originally Posted by C5 Diag

I am not familiar with this scan tool but if it can read fuel trims you’ll be OK...if your long terms are over +10 % you should be concerned !!...these scan tool are not dangerous !!

Sorry I’m lost of what you’re saying “fuel trims” & “long terms” - the car starts and runs great - bought it 3 weeks ago - has 37000 miles on it.
thanks.

Jun 29, 2020 | 05:58 PM

aaronc7

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Joined: Nov 2013

Posts: 2,048

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From: USA

Googled that thing real quick, manifold pressure, fuel trims are all "standard" SAE defined OBD params so I'm 99 percent sure that will work. Plug it in and see what LTFT is. Like he said, +/- 10 percent is a good place to be. If it is a bit off, it could be a vacuum leak, but it could also be something like a dirty MAF sensor. But at least with a scan tool it gives you some data so you know where to start if you have an issue (or maybe no issue at all).

Long term fuel trims means the car is adding or pulling a certain percentage of fuel. With a vacuum leak, air is entering the engine but not passing thru the MAF sensor.....so air entering the engine is greater than air measured entering the engine, so the computer is adding extra fuel vs what is measured to meet target air fuel ratio.