Suddenly car is shaking and blinking check engine light

[cparke]

1998 Audi A4 Quattro V6 30V (AHA engine)

I am told after shutting off the engine, smoke was seen coming out from under the hood, but I wasn't there and my wife of course refused to open the hood so I could get a clue as to where it was coming from. The car did not overheat, oil and coolant levels are fine, all instrument cluster dials were reading normal. Car had been on highway but was being driving locally immediately prior to the incident.

When I got to the car, no smoke (though a faint smell of unburned fuel in exhaust smoke), here is the VAG-COM fault codes I got:

Address 01: Engine
Control Module Part Number: 4D0 907 551 AH
Component and/or Version: 2.8L V6/5V MOTR AT D01
Software Coding: 06251
Work Shop Code: WSC 06335
9 Faults Found:

17549 - Load Calculation Cross Check: Implausible Value
P1141 - 35-10 - - - Intermittent
17746 - Camshaft Position Sensor (G40): Open or Short to Plus
P1338 - 35-10 - - - Intermittent
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 - -
16685 - Cylinder 1: Misfire Detected
P0301 - 35-00 - -
16690 - Cylinder 6: Misfire Detected
P0306 - 35-00 - -
18014 - Rough Road/Engine Torque Signal from ABS: Electrical Malfunction
P1606 - 35-00 - -
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 - -
16685 - Cylinder 1: Misfire Detected
P0301 - 35-00 - -
16690 - Cylinder 6: Misfire Detected
P0306 - 35-00 - -

Readiness: 0000 0000


Clear the codes, restart the engine, car runs fine, drove it home (including with highway and local driving) without incident, no codes present when I pulled into the garage.

Background: This car has been running with a rich (but not too rich) multiplicative fuel trim problem on Bank 1. I have been suspecting that the fuel injector for cylinder 1 is bad and the cause that problem, but haven't had a pressing need to possibly change it without a CEL until this incident just suddenly happened. Car recently had new coils, wires, and spark plugs installed, so that shouldn't be the cause here. The cause of my engine problems has been very elusive.

The first 2 intermittent fault codes have been sitting in the ECU without causing the check engine light to go on at all for 3 weeks prior to this incident. Those codes were in there when I took the car back from a repair shop which didn't know what it was doing and wanted to change my MAF after I already had changed it myself.

Fuel trims in measuring block 32 were last logged 6 days ago as follows (unfortunately, I didnt re-log them after this incident before resetting the ECU):

Group 032: O2S control learning values (before Cat. Conv.) [B=Bank S=Sensor]
-0.8 % @idle B1S1 +/-10%
-10.2 % @part B1S1 +/-10%
-3.1 % @idle B2S1 +/-10%
-0.8 % @part B2S1 +/-10%


Now, the part that most puzzles me most about this incident is how/why the misfire also happened on Cylinder 6. Cylinder 1 didn't surprise me, I've seen misfires on that one and elsewhere on bank 1, but this is the first time I saw both cylinder 1 and cylinder 6 misfire together, and this happened completely out of the blue without any warning or clue (car was running great just prior to the incident, as well as immediately after, there was no CEL on prior to the incident). Any thought on how a bad cylinder 1 fuel injector could somehow cause cylinder 1 and cylinder 6 to simultaneously begin misfiring together? Is there something else that could explain this bizarre incident.

Finally, is my car wired correctly? On the right (passenger side), cylinders 1,2,3 are plugged in from front to back (cylinder 1 towards front of the car, cylinder 3 towards the firewall). On the left (driver's side), cylinders 4,5,6 are also plugged in from front to back (cylinder 4 towards the front of the car, cylinder 6 towards the firewall). On the coils, cylinders 1 and 6 are connected on opposite ends of the same coil paired section (I can check the other two sections if you think it is important).

Much appreciation for your thoughts. I sure would like to nail this engine problem once and for all.


P.S. We drove the car some more now, and the misfires happened again on the local travel section! This time, the car started shaking and the CEL started blinking for 20 seconds, then it stopped shaking and CEL is steady. Whatever is wrong is at least happening more regularly now, but it still goes away too! I will VAG it when they get back home, but I'm pretty sure cylinder 1/6 misfiring are the main problem again.

[t1demont1]

whens the last time you changed your spark plugs?

[cparke]

whens the last time you changed your spark plugs?

4 months ago---spark plugs, coil pack, wires were all changed.

The bank 1 running rich problem has been occurring all this time; I want to think the two problems are related (fuel injector on cyl 1), but the misfire on cyl 6 also stuns me. Isn't cyl 6 the next in timing sequence after cyl 1? (i.e. could one misfire, if severe enough, cascade to next cyl.?)

BTW - on the second misfiring incident today, 10 seconds of misfiring on cyls. 1/6 (marked intermittent this time), then the rough road again, then just cyl 1 misfire intermittent. Car has CEL but is running okay, though fuel trim is also rich since it stopped learning with the CEL came on and isn't cutting enough fuel.

[Dave@IE]

yup coil would be my guess. Atleast you have v6 not a 4 like me... driving on 3 really sucks...

[cparke]

yup coil would be my guess. Atleast you have v6 not a 4 like me... driving on 3 really sucks...

You think the coil installed this past April is defective? That would be just my luck!

[hiwords1]

i also had the bank one fuel trim too rich but it somehow went away after a few times of clearing it and some seafoam in the crankcase and gas tank. do you always get that cam sensor code?

[cparke]

i also had the bank one fuel trim too rich but it somehow went away after a few times of clearing it and some seafoam in the crankcase and gas tank. do you always get that cam sensor code?

I've been battling the fuel trim problem over 3 months now with many resets. Seafoam scares me because I had tried using regular fuel injector cleaner and that consistently made the fuel trim (on both banks) get worse (up to -25%)! Eventually, I had a repair shop do a computer diagnostic and then give me the car back unrepaired (3 weeks ago), and after that the fuel trims at least returned to somewhat normal values with bank 1 at -10.2%.

The camshaft position sensor code comes up occassionally (maybe once every 4-6 weeks?), not regularly at all. I am seriously considering changing the G40 with the cyl. 1 fuel injector, but I don't understand how the bank 2 cam sensor can somehow regulate fuel trim/ignition timing on bank 1. (the manuals seem to say that the G40 cam sensor is on bank 2 and the cam sensor 2 is on bank 1).

Oh how I pray for my engine problems to finally get fixed on this car!

[Bluejuiced]

the cam shaft sensor is responsble for finding and firing cly #1 if cam sensor fails alot of the times the car wont start but sometimes it goes into a batch fire mode which can cause excessive HC emissions out the tail pipe. now if your car thinks its running rich because its firing in batch and fuel isnt getting burnt in some cyclinders it can cause the LTFT to remove fuel thus your -25% which can cause lean mixtures. now i dont know how this applies in your problem because ive neglected to read the whole post haha but this is a response to the last post

[cparke]

the cam shaft sensor is responsble for finding and firing cly #1 if cam sensor fails alot of the times the car wont start but sometimes it goes into a batch fire mode which can cause excessive HC emissions out the tail pipe. now if your car thinks its running rich because its firing in batch and fuel isnt getting burnt in some cyclinders it can cause the LTFT to remove fuel thus your -25% which can cause lean mixtures. now i dont know how this applies in your problem because ive neglected to read the whole post haha but this is a response to the last post

Batch fire mode could be what's really bugging my car. Even though I don't see the Cam shaft G40 error code often because it is an intermittent failure.

How does the camshaft position sensor G40, which is mounted onto Bank 2's cylinder head, somehow control the firing of Cyl. 1 on the opposite Bank 1 cylinder head? Also, how can I tell with VCDS if the ECU is running in batch fire mode?

[maxspeed]

Batch fire mode could be what's really bugging my car. Even though I don't see the Cam shaft G40 error code often because it is an intermittent failure.

How does the camshaft position sensor G40, which is mounted onto Bank 2's cylinder head, somehow control the firing of Cyl. 1 on the opposite Bank 1 cylinder head? Also, how can I tell with VCDS if the ECU is running in batch fire mode?

well, im no master on cams or v6's, but if the cam position was erroneous on cyl 2, wouldnt it be erroneous across the board for all cyl banks it was controlling?

[cparke]

well, im no master on cams or v6's, but if the cam position was erroneous on cyl 2, wouldnt it be erroneous across the board for all cyl banks it was controlling?

There are two camshaft position sensors on this car.

Camshaft Position (CMP) Sensor (G40) mounted on the rear of Bank 2
and
Camshaft Position (CMP) Sensor 2 (G163) mounted on the front of Bank 1

Do they somehow control the firing on the opposite bank?

[maxspeed]

There are two camshaft position sensors on this car.

Camshaft Position (CMP) Sensor (G40) mounted on the rear of Bank 2
and
Camshaft Position (CMP) Sensor 2 (G163) mounted on the front of Bank 1

Do they somehow control the firing on the opposite bank?

cams dont control spark, just the valves opening and closing, so if your valve timings all fucked it would cause some seriously rough driving.

[cparke]

cams dont control spark, just the valves opening and closing, so if your valve timings all fucked it would cause some seriously rough driving.

Camshaft Position sensor, not camshaft itself!

[maxspeed]

i just noticed your in white plains, if you want, give chris @ last chance garage a call (845 621 7155)

there a really good audi/vw garage about 25 - 30 min north of you

[cparke]

i just noticed your in white plains, if you want, give chris @ last chance garage a call (845 621 7155)

there a really good audi/vw garage about 25 - 30 min north of you

My problem with using repair shops at this point is they all want to ignore everything that I tell them I've done and found already and start doing the same things all over again. I'm not changing the MAF again, or the ECT, I know my O2 sensors are good, and I know which cylinder is misfiring and it isn't the fuel injector, and I know more about my fuel trim problem than they will find by redoing diagnostics themself. I don't know if the two problems are related. Shops also seem to frown heavily on any non-Audi part installed in the car, but I can't help the fact there is a GIAC chip installed in the ECU, and also, when I ordered a new Audi MAF from the discount Audi parts dealer www.germanautoparts.com, I got a non-Audi rebuilt one which is giving absolutely correct readings that are better than the original one (although I still think the original one was okay).

I need a shop that will accept the fact that those possibilities have already been eliminated and instead dig deeper to find the actual problem. With that in mind, I may very well give this place a call later this week to see if they are different and can do just the remaining checks that need to be done.

Thanks for the reference.
CP

[maxspeed]

trust me, these guys respect intellegence and tell it how it is, there not gonna start blindly throwing parts etc...

theyre true enthusiests(sp?) and are a very tuner friendly shop :)

[Bluejuiced]

cams dont control spark, just the valves opening and closing, so if your valve timings all fucked it would cause some seriously rough driving.

haha if your cam timing was messed up you WOULDNT be driving it hahah youd need all new valves and a head. but yes im talking about the positioning sensor. and id have to see a graph of the current from both to take a stab at what it could be

[cparke]

haha if your cam timing was messed up you WOULDNT be driving it hahah youd need all new valves and a head. but yes im talking about the positioning sensor. and id have to see a graph of the current from both to take a stab at what it could be

I changed the Cam Position Sensor G40 (bank 2), no change in fuel trims and CYL 1 still misfires. I am pulling the plug on CYL-1 tonight to check for oil. That would explain a lot if I strike at oil!

[maxspeed]

remember when you check that a LITTLE oil is ok, and dont freak out if theres a drop or two, only get concerned if theres a bunch.

[cparke]

remember when you check that a LITTLE oil is ok, and dont freak out if theres a drop or two, only get concerned if theres a bunch.

Even if there isn't oil on the plugs, the exterior leak of oil through the valve cover gasket is also a boost leak, perhaps if big enough will also cause the running rich condition?

[Bluejuiced]

no quite because the boost it put into the intake manifold and the valvecover would only receiver that boost if you had bad compression in a cylinder because it would be going up through the oil galleys then

[cparke]

Ok, I must have had a defective spark plug causing the misfiring on CYL-1 when revving at idle (probably at other times too but not recognized). I swapped CYL-1 and CYL-2 spark plugs and the misfiring moved to CYL-2! Okay, bug a new plug from Audi and I expect that nonsense is over. Who knows, maybe the bad spark plug weakened the coil over the 4 months they were installed.

I removed my O2 sensors today. They are snow white! (there is some grey on the back end of them). This could be why my ECU thinks it is running rich and pulling back fuel?

[Bluejuiced]

hahaha oh man dont you just hate it when you look so indepth into things and its a spark plug haha

[cparke]

hahaha oh man dont you just hate it when you look so indepth into things and its a spark plug haha

What pisses me off even more is the new Audi spark plug is doing almost the same thing (though somewhat less severe). These plugs have two electrodes, how the hell do you check the gap on them?

[Poopie]

check your maf? i only ask this since there is an implausible signal for load calculation.

[Bluejuiced]

2 electrodes are poooooinnnnnnnttttttlessssssss the only reason they have 2 electrods is incase one burns out it has anouther one to go to. as for checking it would prob be easy to use a feeler gauge on it

[cparke]

check your maf? i only ask this since there is an implausible signal for load calculation.

MAF is and was new., The Load Calculation error hasn't come back again yet even after the reset took away the repair shop's learned values.

[AudiEqualsPain]

I'm having the same problem eith my A4 Quattro it shakes and stalls out I have oil in my turbo I've messed with lines. Also took info from this but still is acting up. Finally took it to the shop they said cylinder 3 isn't firing and afraid it's washed out but I have no leaks and i used blue devil gasket sealer and it seemed go stop the shaking but still is acting up when I try and step on it