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Discussion Starter · #1 · (Edited)
There was a lot of discussion in this thread about fuel consumption while coasting in gear versus neutral. That discussion aside, I decided to use the secret menu today and see for myself. I currently have a faulty injector on cyl #1 so I figured this test may also be evident of that fact.

This lead me to wonder if the L/H test could be used to judge the healthiness of fuel injectors and the entire fuel system or possibly any idle issues. For example, my idle fluctuates within a .04 L/H range constantly. I would assume a healthy fuel system car would see a fairly constant reading.

So if everyone agrees, how about we post up some information and see if we can draw any conclusions from the data??

Mileage: 97k
Software: Evolve Alpha-N tune
Fuel System Health: Poor, cyl #1 injector faulty, fuel pump original with no problems <-- please be as descriptive as possible for this information
Idle L/H reading: 1.7-2.0 when cool, 1.9-2.2 when warm, 2.0-2.6 when misfiring, rapid fluctuation within the ranges

Please contribute! ;)

I will update after my fuel injectors are cleaned and replaced this weekend.
 

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Discussion Starter · #2 · (Edited)
Come on guys, this test takes less than a minute. Help add knowledge to the board! For all mankind! :)

Mileage:
Software:
Fuel System Health:
Idle L/H reading:

Sal, in your Evolve software, what is the correct idle value for this??
 

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I will happily add a data point, but I can't until tomorrow because my car's having a service & MOT. From what I can remember, my idle fuel flow varies by around 0.3L/H, which I believe is normal, but I shall check as soon as I get the car back. Unless it fails its MOT.:eek:h:

I agree with your thinking though, if there was a problem with the injectors or any other part of the fuel system, it would surely be reflected in unusual fuel flow readings. I expect a misfire would result in a higher idle flow and knackered injectors would lower the flow at WOT...
 

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idle synchronisation

There is a service function on some diagnostics that allow you to correct injector deviation in a smooth running test.It won't tell you what goes on at WOT though but will indicate a bad injector and correct any slight imbalances at idle.

I did a post on it a while back.
 

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I don't have my car on the roads but this is a very interesting thread and could be used as a reference for injector healthiness.
I was trying to find a DIY for injector servicing out of curiosity but with no luck. Can someone please post something regarding it?
 

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I don't have my car on the roads but this is a very interesting thread and could be used as a reference for injector healthiness.
I was trying to find a DIY for injector servicing out of curiosity but with no luck. Can someone please post something regarding it?
You remove them and give them to a show who cleans them and checks the flow rate and corrects them.

Equipment is quite expensive,hence you did not find a DIY...
 

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Discussion Starter · #9 · (Edited)
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This test won't show anything conclusive WRT fuel injector idle duty cycle, as it's reading fuel pump flow. This changes based off of load...not so much on how well your injectors flow at any given rpm. As Raikku mentioned, send them off to get cleaned/flow tested. That's your best bet.

Drew: if you have INPA, you can use it to determine if you've got injector/plug issues
 

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Mileage: 29,100
Software: Stock (01/2001 production)
Fuel System Health: 126 L/H at WOT in 3rd, otherwise normal
Idle L/H reading: 1.6 +- .2
 

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( 05 / 2003 )
Miles: 65K
136 L/H max
stock software, X-pipe, ss cans
1.9-2.0 idle
 

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( 02 / 2000 )
Miles: 142K
142 L/H max
stock software
1.5 +/- 0.1 idle (when properly hot - obviously higher when warming up)

BTW - agree not too relevant for injectors, but it's an intersting bunch of data none the less.
 

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Discussion Starter · #14 ·
This test won't show anything conclusive WRT fuel injector idle duty cycle, as it's reading fuel pump flow. This changes based off of load...not so much on how well your injectors flow at any given rpm. As Raikku mentioned, send them off to get cleaned/flow tested. That's your best bet.

Drew: if you have INPA, you can use it to determine if you've got injector/plug issues
Thanks. My injectors arrived at the shop 8AM this morning. Will be back in the car tomorrow.

Would it be accurate then to say the idle L/H reading is more appropriate for judging fuel pump health?
 

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Discussion Starter · #16 ·
Flow test results:
 

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Damnit now I have L/H at WOT envy!! My 126 is pitiful compared to 142. Sigh.

Russ, I'm looking forward to your L/H numbers after the cleaning.
 

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Thanks. My injectors arrived at the shop 8AM this morning. Will be back in the car tomorrow.

Would it be accurate then to say the idle L/H reading is more appropriate for judging fuel pump health?
I dont think it's an accurate measure of any kind of health really. There are so many variables that affect the number generated that it's kind of useless to use for anything meaningful. Im pretty sure the engineers used it for something during R&D, but it's sorta useless for us.
 
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