Rough idle and no power

Appleby3 · 10-30-2008, 09:33 PM

I have an 04 A4 1.8T-92,000Miles Suddenly Engine Light came on and starting running rough with Engine light flashing sometimes. Just got it home. afraid to move it.

ScratchRob13 · 10-31-2008, 12:04 PM

solair · 11-02-2008, 06:17 AM

When i first got the car, it idled very rough and the check engine light came on. Took it to an Autozone and multiple fault tests were received. I replaced the plugs, mass air flow and one air hose/valve which had a leak near the back of the engine. This fixed the rough idle problem and i got Autozone to clear the codes but the Engine light came back on. Now there is only 1 fault code, P0171. I've seen some forums saying to check for any leak or possibly the O2 sensors?

ScratchRob13 · 11-04-2008, 04:25 AM

That code is for:Fuel Trim; Bank 1: System Too Lean

Possible Causes
Mass Air Flow Sensor (G70) defective

Possible Solutions
Check Mass Air Flow Sensor (G70)

Check Fuel Pressure Regulation

Check Fuel Pump

Check Injectors

Check Intake System for Leaks

Check Exhaust System for Leaks

Check Secondary Air System for Leaks

Check Vacuum Pipes for Leaks

einsgruber · 11-05-2008, 12:18 PM

Most first guesses are the 02 sensor... Mine turned out to be either a dirty MAF sensor, or a loose vacuum hose. I cleaned the MAF really well with sensor clean, and tightened up a vacuum hose (seemed tight in the first place) and it was finally fixed after about a year of fiddling with things.

Before that I'd changed a cracked vacuum hose, replaced the fuel filter, and spark plugs, and changed the front position o2 sensor in an attempt to get rid of the all too familiar p0171 code.

Oh, and also, I remember reading something about a gate in the airbox that can get stuck open and cause the car to go into "limp mode" from what I can recall... may explain your loss of power etc.?

Flashing light means something wrong with your catalytic converter - could cause limp mode I'd imagine.

Someone with VAG-Com can probably narrow it down to something alot more specific.

ScratchRob13 · 11-05-2008, 02:53 PM

aka shut me down, meow!

einsgruber · 11-06-2008, 09:46 AM

einsgruber · 11-06-2008, 11:28 AM

Another poster was having ignition issues and this turned out to be the problem... easy to do, so would be worth a look.

Check plugs for fouling - that can also tell you alot.

10-31-2008, 12:04 PM	#2
ScratchRob13 AudiWorld Super User Garage is empty, add now Join Date: Sep 2005 Posts: 6,524	coilpack, search about it. __________________ -Rob Tow/Work Vehicle: 2007 Chevy 2500 HD DMax 411whp 855wtq AIM: ScratchRob13

11-02-2008, 06:17 AM	#3
solair New Member Garage is empty, add now Join Date: Sep 2008 Posts: 1	2003 A4, Multiple Problems, P0171 When i first got the car, it idled very rough and the check engine light came on. Took it to an Autozone and multiple fault tests were received. I replaced the plugs, mass air flow and one air hose/valve which had a leak near the back of the engine. This fixed the rough idle problem and i got Autozone to clear the codes but the Engine light came back on. Now there is only 1 fault code, P0171. I've seen some forums saying to check for any leak or possibly the O2 sensors?

11-04-2008, 04:25 AM	#4
ScratchRob13 AudiWorld Super User Garage is empty, add now Join Date: Sep 2005 Posts: 6,524	Response... That code is for:Fuel Trim; Bank 1: System Too Lean Possible Causes Mass Air Flow Sensor (G70) defective Possible Solutions Check Mass Air Flow Sensor (G70) Check Fuel Pressure Regulation Check Fuel Pump Check Injectors Check Intake System for Leaks Check Exhaust System for Leaks Check Secondary Air System for Leaks Check Vacuum Pipes for Leaks __________________ -Rob Tow/Work Vehicle: 2007 Chevy 2500 HD DMax 411whp 855wtq AIM: ScratchRob13

11-05-2008, 12:18 PM	#5
einsgruber Member Garage is empty, add now Join Date: Nov 2005 Posts: 698	I had the same code for a looooong time. Most first guesses are the 02 sensor... Mine turned out to be either a dirty MAF sensor, or a loose vacuum hose. I cleaned the MAF really well with sensor clean, and tightened up a vacuum hose (seemed tight in the first place) and it was finally fixed after about a year of fiddling with things. Before that I'd changed a cracked vacuum hose, replaced the fuel filter, and spark plugs, and changed the front position o2 sensor in an attempt to get rid of the all too familiar p0171 code. Oh, and also, I remember reading something about a gate in the airbox that can get stuck open and cause the car to go into "limp mode" from what I can recall... may explain your loss of power etc.? Flashing light means something wrong with your catalytic converter - could cause limp mode I'd imagine. Someone with VAG-Com can probably narrow it down to something alot more specific.

11-05-2008, 02:53 PM	#6
ScratchRob13 AudiWorld Super User Garage is empty, add now Join Date: Sep 2005 Posts: 6,524	flashing CEL also comes on during misfires, it basically signifies very bad codes... aka shut me down, meow! __________________ -Rob Tow/Work Vehicle: 2007 Chevy 2500 HD DMax 411whp 855wtq AIM: ScratchRob13

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11-06-2008, 09:46 AM	#7
einsgruber Member Garage is empty, add now Join Date: Nov 2005 Posts: 698	Yup - I remember reading not to run it when it's flashing

11-06-2008, 11:28 AM	#8
einsgruber Member Garage is empty, add now Join Date: Nov 2005 Posts: 698	Pull out coilpacks and check if there's oil from a leaky headgasket... Another poster was having ignition issues and this turned out to be the problem... easy to do, so would be worth a look. Check plugs for fouling - that can also tell you alot.

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11-06-2008, 11:28 AM
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