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Audi Q5 Rough Idling

Ant

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Hi All, I am new to site, I found it while looking for diagnostic procedures to help with my Audi. I have enjoyed the informative videos and incorporated the tests where I can.
I would greatly appreciate some guidance if anyone is willing to help.

My issue is with my Audi Q5 2.0 Tdi 2009. Bosch dual control injection system.
For about 3 weeks the engine has been rough idling no issues after 2000rpm. (No recent work done to cause fault and running fine for 18mths) I have Delphi DS150E software and a multimeter,

Findings so far; There are no error codes, the fuel pressure is very erratic, ranging from 16080kPa upwards (it changes so quickly that I can't read a top limit) the fuel consumption is 1.04 l/hr, inlet metering valve running at around 23% and fuel control valve at 22% both changing constantly.

I f I unplug the fuel pressure switch the motor runs smooth, (fuel pressure 200000kPa, consumption 0.44 l/hr), if I unlpug the imv nothing changes and with the fuel control valve unplugged the engine stops.

My multimeter tests results are as follows; pressure switch showing 4.95 v (red/grey wire) 0.5v (yellow/red) and a good earth (brown/green)(tested with test light) with ignition on engine not running, engine running 4.95v (red/grey) and 0.95 to 1.03v (yellow/red) and at 2000rpm the yellow/red is at 1.54v.

The pressure regulator (at back of rail) shows 13-13v (grey/white) and 11.70v (grey/brown) with engine running.

The imv shows 13.10v and 10.34v on each of the terminals.

The car runs fine over 2000rpm but is getting worse at idle particularly when cold (slight knocking this morning).

I have changed the fuel filter, very clean fuel came out of it, tried a used pressure switch and regulator valve and today fitted a new imv (no swarf visible in high pressure pump).

None of these changes had any effect. I think I have covered everything done/tested so far.

Any help with this "challenging" issue would be greatly appreciated. Thanks in anticipation Ant.
 
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Steve SDN

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Hi Ant, do you have Reg & VIN please, it helps our members help you with vehicle specific information.

Ps, welcome.
 

Steve SDN

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J519 fixed it 👍vehicle went out so no Pt3 possible 🥺
 
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Steve SDN

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Rough idle, cold engine -
What is MAF value with EGR open then closed?
Relative compression, starter current and battery voltage - are the compression peaks all even and starter current approx 3 to 3.5 X battery rating? You will have to borrow a scope and amp clamp for this test.
Smooth running and injector correction values?
Hope this helps.
 

Ant

Member
Public Member
Thanks for replies, Steve and John. I will check maf and injector correction values tomorrow. As for compressions, the motor runs sweet over 2000rpm and no noise from intake or exhaust when rough idling, but always a possibility. Thanks.
 
A

Ant.

Membership in process
Here are the results from today;
Injection quantity deviation, cold engine idling.
Cylinder 1) 0.07 to 0.36 mg/str.
Cylinder 2) 0.23 to 0.28 mg/str.
Cylinder 3) - 0.17 to 0.20 mg/str.
Cylinder 4) 0.04 to 0.56 mg/str.
Hot engine,
Cyl 1) -0.58 to -0.8 mg/str.
Cyl 2) -0.32 to 0.52 mg/str.
Cyl 3) -0.32 to 0.19 mg/str.
Cyl 4) 0.24 to 1.43 mg/str.
With my software I can't see egr position, so I checked Maf reading when cold;
Air mass 9.44 to 10.83 Grams/second
Air mass 7.97 to 8.74 Grams/second when hot.
The symptoms are rough idling, cold and hot, worse when cold.
Stuttering and surging when pulling away when cold.
Engine runs smooth when fuel pressure switch is disconnected so hopefully no mechanical issues suspected.
Does this info' shed any light or muddy the waters?
 

LOEdiagnostic

Member
Public Member
Thanks for replies, Steve and John. I will check maf and injector correction values tomorrow. As for compressions, the motor runs sweet over 2000rpm and no noise from intake or exhaust when rough idling, but always a possibility. Thanks.
Its possibel to misjudge a comp. problem by raising rpm. Been there done that :rolleyes:
 

Danny.Baugh

<18Vauxhall Specialist/Now JLR Brand
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Brand Specific help - tag me please
There are so many variables that can lead to differing compression and cylinder pressures.
 
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Ant

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Thanks for messages, I'm not sure if I have reset options with my software I will check. I have tried a DRV but didn't reset.
I will have to try compression test if other options don't give results.
I have some results from earlier;
Injection deviation with cold engine at idle;
Cyl 1} 0.07 to 0.36 mg/str.
Cyl 2) 0.23 to 0.28 mg/str.
Cyl 3) -0.17 to 0.20 mg/str.
Cyl 4) 0.04 to 0.56 mg/str.

Injection deviation with hot engine at idle;
Cyl 1) -0.58 to -0.8 mg/str.
Cyl 2) -0.32 to 0.52 mg/str.
Cyl 3) -0.32 to 0.19 mg/str.
Cyl 4) 0.24 to 1.43 mg/str.

My software doesn't give me EGR position so I checked MAF readings cold and hot;
Air mass 9.44 to 10.83 Grams/second (cold)
Air mass 7.97 to 8.74 Grams/second (hot)
Are these values any help?
 

LOEdiagnostic

Member
Public Member
Thanks for messages, I'm not sure if I have reset options with my software I will check. I have tried a DRV but didn't reset.
I will have to try compression test if other options don't give results.
I have some results from earlier;
Injection deviation with cold engine at idle;
Cyl 1} 0.07 to 0.36 mg/str.
Cyl 2) 0.23 to 0.28 mg/str.
Cyl 3) -0.17 to 0.20 mg/str.
Cyl 4) 0.04 to 0.56 mg/str.

Injection deviation with hot engine at idle;
Cyl 1) -0.58 to -0.8 mg/str.
Cyl 2) -0.32 to 0.52 mg/str.
Cyl 3) -0.32 to 0.19 mg/str.
Cyl 4) 0.24 to 1.43 mg/str.

My software doesn't give me EGR position so I checked MAF readings cold and hot;
Air mass 9.44 to 10.83 Grams/second (cold)
Air mass 7.97 to 8.74 Grams/second (hot)
Are these values any help?
Your airmass readings dosnt look to bad using the ATG VE calculator.
Incase you havent seen the IVS channel on Youtube. They hace a specific VAG commonrail "diag" video.
 
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Steve SDN

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You don't need EGR position mate, start engine, let it idle, let's say the MAF reading is 8g/s then the engine note changes and MAF rises to 12g/s that would indicate your EGR isn't closing fully.
 
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Ant

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Okay I will do that at weekend when I can get back on it.
If I unplug the fuel pressure switch it runs smooth, I assume it reverts to stored parameters. If I have compression or egr issues would you expect that?
 

Steve SDN

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With a significant component disconnected the ECU will run in default settings, it's not a valid test mate.
 

Rgmobile

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hi Ant, its best to use oscilloscope for this test but can be done with a multimeter, connect black lead to earth and red to yellow and red wire
of fuel pressure sensor,disconnect fuel metering valve and get someone to hold revs at 2000rpm,next get a jumper wire or incadescent test light
and ground out the grey and brown wire ( the control wire ) on the drv....... not the 12v supply .the engine will stall but the voltage on the multimeter will go to about 4volts,if the drv is good and holding pressure the voltage should remain at that voltage .if it is faulty the voltage will drop gradually .ps it will set a code but cause no damage ok .
you can buy bosch drv on ebay around £85, as they are mormally about £2oo from motor factors ...
hop[e this helps
rob rgmobile mechanic
 
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