2003 S8 4.2 Wits and wallet's end! Misfires, all on one bank P0305, 306, 307 and 308
10-18-2014, 12:19 PM
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2003 S8 4.2 Wits and wallet's end! Misfires, all on one bank P0305, 306, 307 and 308
Hey guys, longtime troll, first time poster. I'm at my end with my 2003 S8 and can't figure this out! Car has been at a friends shop for 4 months, then moved to independent Audi mechanic for diagnosis. Still no joy.
CEL is on, blinks on deceleration over 2000rpm, random misfire P0300. Further investigation reveals codes P0305, 6, 7 and 8 meaning misfires on cylinders 5,6,7, and 8.
I have replaced camshaft adjusters, timing belt, camshaft timing chains, water pump, spark plugs, intake manifold gaskets, variable intake runner flap connection arm, vacuum lines, valve cover gaskets, and pcv valve. Compression tests and leakdown tests reveal all cylinders within spec and nothing below 185psi. Coils have been swapped side-to-side and misfires don't move.
Both mechanics suggest head removal, may have bent valves but that doesn't make a lot of sense. Leakdown test was perfect. Borescope inspection shows no signs of piston impact with valves. Head removal and rebuild starts at $2500 with no guarantee.
Admission: I ran it on 87, please whip me immediately! I have since ran her very low and put 3 tanks of 93 through her with one bottle of Lucas injector cleaner. CEL stopped blinking for about 200 miles but has since resumed. I'm hoping, fingers crossed that a few more tankfuls of 93 will clear it up, but that's my last resort.
What strikes me as strange is that it's all on one cylinder bank.
I have no idea what to do next! Any insight is greatly appreciated!
CEL is on, blinks on deceleration over 2000rpm, random misfire P0300. Further investigation reveals codes P0305, 6, 7 and 8 meaning misfires on cylinders 5,6,7, and 8.
I have replaced camshaft adjusters, timing belt, camshaft timing chains, water pump, spark plugs, intake manifold gaskets, variable intake runner flap connection arm, vacuum lines, valve cover gaskets, and pcv valve. Compression tests and leakdown tests reveal all cylinders within spec and nothing below 185psi. Coils have been swapped side-to-side and misfires don't move.
Both mechanics suggest head removal, may have bent valves but that doesn't make a lot of sense. Leakdown test was perfect. Borescope inspection shows no signs of piston impact with valves. Head removal and rebuild starts at $2500 with no guarantee.
Admission: I ran it on 87, please whip me immediately! I have since ran her very low and put 3 tanks of 93 through her with one bottle of Lucas injector cleaner. CEL stopped blinking for about 200 miles but has since resumed. I'm hoping, fingers crossed that a few more tankfuls of 93 will clear it up, but that's my last resort.
What strikes me as strange is that it's all on one cylinder bank.
I have no idea what to do next! Any insight is greatly appreciated!
10-20-2014, 04:19 PM
#3
AudiWorld Senior Member
First, I would check to see if there is a common ground or block plug for the wiring to the injectors or coils on that bank, or an intermittent wiring connection on the cam timing adjuster.
Is there a knock sensor on either side of the engine? Do these sensors tell the ecu when misfires occur? How does the ecu generate these codes? Does the problem really exist or is it a false report?
Also, The ECU or PCM or whatever is it called usually controls the injectors with two sets of switches, each handling 4 cylinders. I don't think it is divided up by bank though. Usually it relates to firing order. Anyway, take a look at the wiring diagram and see if it gives you an ecu breakdown. You might just see one group of wires clustered next to each other as a clue for the internal ECU switching. Where is the ECU located on the D3? Is is getting wet?
My D2 ecu went for a swim and the result was not good.
I'm thinking electrical issue common to the bank...what else?....dunno
Is there a knock sensor on either side of the engine? Do these sensors tell the ecu when misfires occur? How does the ecu generate these codes? Does the problem really exist or is it a false report?
Also, The ECU or PCM or whatever is it called usually controls the injectors with two sets of switches, each handling 4 cylinders. I don't think it is divided up by bank though. Usually it relates to firing order. Anyway, take a look at the wiring diagram and see if it gives you an ecu breakdown. You might just see one group of wires clustered next to each other as a clue for the internal ECU switching. Where is the ECU located on the D3? Is is getting wet?
My D2 ecu went for a swim and the result was not good.
I'm thinking electrical issue common to the bank...what else?....dunno
10-20-2014, 04:46 PM
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First, I would check to see if there is a common ground or block plug for the wiring to the injectors or coils on that bank, or an intermittent wiring connection on the cam timing adjuster.
Is there a knock sensor on either side of the engine? Do these sensors tell the ecu when misfires occur? How does the ecu generate these codes? Does the problem really exist or is it a false report?
Also, The ECU or PCM or whatever is it called usually controls the injectors with two sets of switches, each handling 4 cylinders. I don't think it is divided up by bank though. Usually it relates to firing order. Anyway, take a look at the wiring diagram and see if it gives you an ecu breakdown. You might just see one group of wires clustered next to each other as a clue for the internal ECU switching. Where is the ECU located on the D3? Is is getting wet?
My D2 ecu went for a swim and the result was not good.
I'm thinking electrical issue common to the bank...what else?....dunno
Is there a knock sensor on either side of the engine? Do these sensors tell the ecu when misfires occur? How does the ecu generate these codes? Does the problem really exist or is it a false report?
Also, The ECU or PCM or whatever is it called usually controls the injectors with two sets of switches, each handling 4 cylinders. I don't think it is divided up by bank though. Usually it relates to firing order. Anyway, take a look at the wiring diagram and see if it gives you an ecu breakdown. You might just see one group of wires clustered next to each other as a clue for the internal ECU switching. Where is the ECU located on the D3? Is is getting wet?
My D2 ecu went for a swim and the result was not good.
I'm thinking electrical issue common to the bank...what else?....dunno
As a D2 owner I'm sure you're familiar with the water retention of these things once the drains clog (which happens all the time)! I'm not sure where the ECU is located but maybe it's soaked? I can say my feet have gotten literally poured on when cornering and the drains are clogged. Plus water in the rear footwells, maybe 1.5 inches. Can you tell me where the ECU is on the D2 and maybe that will help?
Thanks again for the help and I'll keep you informed.
10-20-2014, 06:17 PM
#7
AudiWorld Senior Member
D2 same as me, ok good.
Sure, PCM and TCM are in the cowl area under the hood...big black box passenger's side on U.S. cars. Not water tight....unsecured hole where all the wires enter underneath it. TCM and PCM are also not weatherproofed in any way...Awesome. Yes, mine went for a swim which proved fatal...Persistent internal error...Altitude Correction...apparently an internal altitude sensor for air density died You will have to remove the perforated debris covers first...mine are in a garage cabinet somewhere for the last 10 years where they will do the most good. There are 4 drains in the cowl area: 1 over each wheel well exiting through little rubber nipples at the top back of each wheel well...they are clogged. There are also 2 larger drains under the central air inlet at the center of the cowl. They have an end cap that looks like a closed 4 leaf venus flytrap...they are clogged... think mine are in a tool box somewhere...also safer there. You can take some flexible 1/4 copper tubing and fish around for the two center drains...feed it in and knock off the end caps and let the flood pour out. When if over flowes in enters the central air inlet and flows through your ductwork...which is not watertight, so it pretty much gets all over the effing place. Mmmmmmmmm smell the mold...
When standing in front of the car, front to back, left side 4321..right (driver's side)5678. 1 & 8 are closest to the firewall of their respective banks. The injectors are controlled by the PCM in two groups, but they are not controlled by bank....both sides are mixed in to each group of 4.
If you lift the front carpets out - they can be removed separately, you will find a trench below them...shop vac out the water. Pop out rear central vent outlet...neck down a shop vac...suck the water out of there as well.
+1 on Tozo's read...search for a common bank specific bad ground.
Sure, PCM and TCM are in the cowl area under the hood...big black box passenger's side on U.S. cars. Not water tight....unsecured hole where all the wires enter underneath it. TCM and PCM are also not weatherproofed in any way...Awesome. Yes, mine went for a swim which proved fatal...Persistent internal error...Altitude Correction...apparently an internal altitude sensor for air density died You will have to remove the perforated debris covers first...mine are in a garage cabinet somewhere for the last 10 years where they will do the most good. There are 4 drains in the cowl area: 1 over each wheel well exiting through little rubber nipples at the top back of each wheel well...they are clogged. There are also 2 larger drains under the central air inlet at the center of the cowl. They have an end cap that looks like a closed 4 leaf venus flytrap...they are clogged... think mine are in a tool box somewhere...also safer there. You can take some flexible 1/4 copper tubing and fish around for the two center drains...feed it in and knock off the end caps and let the flood pour out. When if over flowes in enters the central air inlet and flows through your ductwork...which is not watertight, so it pretty much gets all over the effing place. Mmmmmmmmm smell the mold...
When standing in front of the car, front to back, left side 4321..right (driver's side)5678. 1 & 8 are closest to the firewall of their respective banks. The injectors are controlled by the PCM in two groups, but they are not controlled by bank....both sides are mixed in to each group of 4.
If you lift the front carpets out - they can be removed separately, you will find a trench below them...shop vac out the water. Pop out rear central vent outlet...neck down a shop vac...suck the water out of there as well.
+1 on Tozo's read...search for a common bank specific bad ground.
Last edited by BrianC72gt; 10-20-2014 at 06:20 PM.
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10-21-2014, 06:45 AM
#9
AudiWorld Super User
Did the OP do all the work (post #1) after the misfire detection or did it start after this work?
If the belt or chain is off a tooth on that side, it would likely cause misfires on that bank only...maybe not detectable in feel...seems I've read of this more than once (?)
10-21-2014, 04:14 PM
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Yes, but the next part of detection is done with the camshaft position sensors.
Did the OP do all the work (post #1) after the misfire detection or did it start after this work?
If the belt or chain is off a tooth on that side, it would likely cause misfires on that bank only...maybe not detectable in feel...seems I've read of this more than once (?)
Did the OP do all the work (post #1) after the misfire detection or did it start after this work?
If the belt or chain is off a tooth on that side, it would likely cause misfires on that bank only...maybe not detectable in feel...seems I've read of this more than once (?)
After my local mechanic threw up his hands, a certified Audi mechanic (his buddy, maybe I should find my own?) checked his work and confirmed timing is all set. I may be doubting this confirmation, but I'm low on funds at this point! All signs point to this being something that was overlooked and is simple, but what?!!! Everything has been done, I'm stuck!