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Very random 2.7t misfire

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Old 02-21-2014, 06:09 PM   #1
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Default Very random 2.7t misfire

Car: 2000 A6 2.7t auto Quattro
Mileage: <180,000

So, I've been dealing with this misfire since purchasing the car in Sept. 2012. I purchased the car knowing it needed some work but it never misfired when on test drives. It started 2 days after purchasing and driving it home. The misfire comes and goes, usually after driving awhile(full warm up) and then sitting for about a half hour. The misfire is so bad the car shakes at idle, as if more then 1 cylinder is missing. I looked it up and google mentioned coil packs. I knew there was an oil leak and a coolant leak on the motor when I purchased the vehicle.



Understanding most peoples lack of maintenance, I purchased a timing belt kit, spark plugs and coil packs, valve cover gasket kit, oil and air service kits. While replacing these items I also replaced the oil cooler coolant hose that had ruptured. All was good for a week or so, then came back the misfire. Now sometimes the missing begins at start up and goes away a few miles down the road or it starts up fine and then starts missing after driving most of the way. Understand this car only misfires 10-5% of the time. Most of the time it drives great. My daily drive requires lots of stop and go. When it's missing I can tell the catalytic converter (passenger side) is getting very hot. While missing and I give minimal throttle, it misses but chugs along, if I get on it, it stops misfiring in higher RPM's but then the CEL starts flashing, BAD, I know.



This whole time I've been scanning the CEL's(see below) everything pointed to the EGT sensor on bank 1. So I finally replaced it! Now, not getting a CEL for the EGT but still getting the misfire. Still getting CEL's now different codes. This weekend I checked for vacuum leaks again, this time checked at the BOV's. The bank 1 is not holding vacuum. I still have a coolant leak at the aux H2O pump under the intake that needs to be sorted. When I replace that I will be using new intake gaskets, new injector o-rings, install the bank 2 EGT, all O2 sensors(only have done B1S1), the spider hoses(PCV) and BOV's(710N's)..Oh I've also replaced the fuel pressure regulator and the temp sender(old one black/new one green). After replacing the temp sensor I noticed the temp gauge didn't go to 12 o'clock anymore, now more between 11 and 12. All parts used are either Audi/VW, Bosch, Karlyn, NGK, MANN, gaskets and belt kit purchased from Bl*up*rts. Most parts are from Rock*uto, ECS, Bl*up*rts, or Adv*nced Autom*tion.

Any help is super appreciated!

CEL:
8/29/13
P1454 INTER
P1131 INTER
P0421
P1423
P1355 INTER
P0300
P0301
P0303 INTER
P1411 INTER
P0306 INTER
P1361 INTER
P1624 INTER

8/29/13 cleared and reset
P0300
P0301
P1355
P1131 INTER
P0305

9/17/13
P1454 INTER
P0300 INTER
P0301 INTER
P1355 INTER
P0304 INTER
P0303 INTER
P1361 INTER
P0305 INTER
P0306 INTER
P1423 INTER
P1411 INTER
P0421

9/17/13 cleared and reset
P0421
P1131 INTER

1/26/14
P0421
P1361 INTER
P0300 INTER
P0301 INTER
P1355 INTER
P0303 INTER
P0304 INTER
P0130 INTER
P0306 INTER
P1131 INTER
P1453

1/26/14 cleared and reset
P1131 INTER
P1361 INTER
P0421
P1355 INTER

2/16/14
P0421
P1624 INTER
P1361 INTER
P1411 INTER
P0300
P0303
P0306
P1355
P0301
P0304 INTER
P0305 INTER
P1131 INTER

2/21/14
P1364 INTER
P0300 INTER
P0304 INTER
P1131 INTER
P0421
P0303 INTER
P1370 INTER
P0306 INTER

2/21/14 cleared and reset
P0300
P0306
P1370
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Old 02-22-2014, 04:26 AM   #2
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Get yourself VCDS and a laptop. Clear all the codes and diagnose the misfire as soon as it occurs (even pull over to the side of the road if you have to.) At that point, only the most recent event will be the one you have logged. Fix that problem and move on to the next one. Do it often enough and you will eventually fix them all.

That said, here's what Ross Tech says about P1370:

http://wiki.ross-tech.com/wiki/index...8/P1370/004976
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Old 02-22-2014, 06:51 AM   #3
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Quote:
Originally Posted by georgeb944 View Post
Get yourself VCDS and a laptop. Clear all the codes and diagnose the misfire as soon as it occurs (even pull over to the side of the road if you have to.) At that point, only the most recent event will be the one you have logged. Fix that problem and move on to the next one. Do it often enough and you will eventually fix them all.

That said, here's what Ross Tech says about P1370:

http://wiki.ross-tech.com/wiki/index...8/P1370/004976
Thanks for the link and the info. I do have the laptop, cable and VAG adapter. The software I currently have is a non-registered light version. If you see on the CEL list I have days when I copied and then cleared, drove a while and then rechecked the codes. The software I have doesn't give me full access to all the metering block either. Not that I know what all that info is anyway. I do have the Bently manual for this platform. I guess I should bite the bullet and get the full VAG-COM software and learn how to use it.
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Old 02-22-2014, 07:26 AM   #4
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When this misfire occurs:

Cold start(early morning): 5%
Cold start(late afternoon): <20%
Full tank fuel: 10%
1/4 tank: >50%
Low ambient temp(winter): 20%
high ambient temp(summer): 40%
Warm start <30 min restart: 10%
Warm start >30 min restart: >50%
Starts fine then misfires while driving: 10%
Starts misfiring then clears up: 25%
Misfiring before refuel, then clears up after fill-up: 50%
When I tell people my car is running like ****: doesn't misfire for a week
When I tell people my car is running better: starts misfiring within 2 days
After replacing a part or pair of parts: 2-5 days w/o misfire

I've been wrenching on motors for 20+ years and have always done my own work. I've been a rental/heavy equip mechanic for 10 years. I am not a parts changer, I am a problem solver....Until this twin turbo, vacuum/ elect. sensor nightmare. This car has me and all the mechanics at my work stumped. Yes we work mostly on industrial diesels and large hydraulic systems but problems usually can be tracked down.
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Old 02-22-2014, 07:55 AM   #5
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Well, the ross tech wiki does mention the fuel pump relay. I would swap the #6 ignition coil with one of the others and see if the symptom changes. If the symptom doesn't change it might be the wiring or it might be the relay.

(I understand your frustration. I work on Porsche 944 turbos, and I used to think that they were complicated until I started to understand this 2.7t engine.)
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Old 02-22-2014, 08:30 AM   #6
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Quote:
Originally Posted by georgeb944 View Post
Well, the ross tech wiki does mention the fuel pump relay. I would swap the #6 ignition coil with one of the others and see if the symptom changes. If the symptom doesn't change it might be the wiring or it might be the relay.

(I understand your frustration. I work on Porsche 944 turbos, and I used to think that they were complicated until I started to understand this 2.7t engine.)
Weird thing is most of my problems have always been at cyl 1 and gassy exhaust from bank1... Last weekend when doing some vacuum leak tests, I switched ICMs to see if the misfire moves. I noticed the thermal paste had hardened and they were not stuck to the sink any more.

Yesterday, after work, started fine, remembered needs water(leaky aux pump), open hood and here this high pitched noise from the back of bank2. Sounded a bit like an electric motor, spinning high RPM's that's fan blades were slightly touching / grinding on it's mount. That stopped within 30 seconds and the drive home fairly smooth, just approx 2 mins of misfiring during drive. I'm wondering secondary air injection pump? Also there is always a noise from under the passenger side, not vacuum leak more like high pressure thru a venturi. When doing the passenger side suspension, I see something has struck one of the fuel hard lines under the car. Right as they turn up at the inner fender well. I've also replaced the fuel cap and fuel filter.
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Old 02-22-2014, 09:31 AM   #7
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Quote:
Originally Posted by CRSmith78 View Post
Weird thing is most of my problems have always been at cyl 1 and gassy exhaust from bank1... Last weekend when doing some vacuum leak tests, I switched ICMs to see if the misfire moves. I noticed the thermal paste had hardened and they were not stuck to the sink any more.

Yesterday, after work, started fine, remembered needs water(leaky aux pump), open hood and here this high pitched noise from the back of bank2. Sounded a bit like an electric motor, spinning high RPM's that's fan blades were slightly touching / grinding on it's mount. That stopped within 30 seconds and the drive home fairly smooth, just approx 2 mins of misfiring during drive. I'm wondering secondary air injection pump? Also there is always a noise from under the passenger side, not vacuum leak more like high pressure thru a venturi. When doing the passenger side suspension, I see something has struck one of the fuel hard lines under the car. Right as they turn up at the inner fender well. I've also replaced the fuel cap and fuel filter.

Two things, based on what you said, if you just tell everyone you know once a week that your car runs like crap, problem solved. Lol

Sounds like you may have a boost leak which is bad news. You need to pull the spark plugs and read them. If you see a lean condition on 1 or more plug, (mixed with the airy sounds you hear) a boost leak is likely
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Old 02-22-2014, 11:52 AM   #8
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That high pitched dentist drill sound when you start the car cold is indeed the secondary air injection pump. Normal if it dies down after about 30 seconds. Not normal if it sets a CEL. VCDS has an output test for SAI that turns the pump on.
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Old 03-15-2014, 08:45 AM   #9
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This last weekend I spent it's entirety working on my 2000 A6 2.7t. These repairs were to hopefully find and fix the misfire culprit and also fix the coolant leak.
My replacement checklist:
Aux. water pump w/ hoses
PCV spider valve
Bank 2 EGT
Bank 2 sensor 1 O2 sensor

During the tear down to get to the aux. water pump, I found one bad vacuum check valve and the lower line of the spider valve all but clogged up. There were a couple vacuum lines that were fairly spongy too. I also realized the coolant leak wasn't from the pump, but coming from the return heater hose connection. After checking the AWP it was not spinning like the new one, so in the new one went. Had to order the coolant hose and check valve so spent the rest of the weekend replacing vacuum lines and installing the B2S1 O2 sensor and B2 EGT. After replacing all found issues and reinstalling all parts in their perfectly routed spots. It started with no issues, idled very smooth and had power. I could now feel the turbos down in lower RPMs help the motor accelerate. I think to myself, it's fixed, finally! WRONG!

After driving approx. 25 miles that evening, w/o issue, I take the car home. That morning I start up and drive the car to work(12 miles) w/o issue. After work, drive to Dr's appt(25+ miles) no issues, lots of power. After Dr's appt, restarts no issues, drive in stop and go for about 5 minutes...then it starts misfiring. Misfiring so bad the CEL starts flashing and at idle the motor drops to around 500rpm almost stalling. I get on the freeway, still misfiring, after a mile or so it stops, back to full power. Then exit freeway, misfires a bit, smooths out, then starts misfiring the rest of the way home.

So the only items I haven't replaced are the downstream O2 sensors and the ICMs. I have switched the ICMs, so I will check the misfiring cylinders. I am at a loss, I can't replace every part on this motor, but I really can't give up on this car either. I've put to much into it.

Does anyone know how to test the ICM's or ever have a misfire issue like this?
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Old 03-15-2014, 02:50 PM   #10
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To diagnose the ICMs, start carrying your laptop, software and cable with you. As soon as you experience a miss, pull over and pull the codes. Save them to the log, clear them, and continue to drive. If you still have a miss, pull the codes again, then swap the ICMs (the one closer to the firewall is for Bank 1) and see if the codes move with the ICM.

You will also need to carry a 7 mm socket to remove the ICMs from the intake.
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Old 03-15-2014, 03:11 PM   #11
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You might also carry a can of refrigerant/freeze used to test electronic parts. When you get a misfire, spray/freeze the ICM(s) and see if the misfire goes away.

But chances are you've already identified the problem if you have no or hardened dielectric grease under your ICM (well, between the power transistor and the heat sink). If you have some dielectric grease suitable for automotive heat sink use, try replacing the grease.

I cooked an ICM (power transistor) on a saab 900T by failing to cover the ICM with a plastic bag or tin foil wrap when cleaning the engine with gunk. Once burnt, twice shy.
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Old 03-15-2014, 04:04 PM   #12
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I should have mentioned that in the midst of all the other repairs... Yes, I took the ICM's off the airbox cover. Thouroghly cleaned and reinstalled them with heat sink compound. I also dielectric greased all electric connections upon reinstall. Great idea on the refridgerant!! I was gonna take it to my shop/garage tomorrow and try a different approch. I was thinking of heating each ICM seperately with a blow dryer/heat gun to try to reproduce the misfire. Any ideas on that??

I've done the copy codes when misfiring, clear and recheck. Weird thing is after clearing the codes, the misfire doesn't go away... and the CEL doesn't come back immediately, and no new codes appear. I have to drive it for a while before any codes show up. I think I really need to invest in a full VAGcom software and learn how and what blocks I need to read. This is getting tiring. It seems as if the more parts I find bad and replace due to being old / worn the worse the misfire is when it shows up. When this car is not misfiring it is a dream to drive. Especially after replacing the bad parts last weekend, it has sooo much more power. But then it starts this misfire BS...
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Old 03-16-2014, 07:30 AM   #13
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Yes, if you don't have the full VCDS, you are screwing with a condom (with a hole in it.)
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Old 03-16-2014, 10:34 AM   #14
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Looking on the Ross-Tech website now... I have the laptop, serial cable and OBD2 adapter. The adapter has a 2 position switch on it. After searching the Ross-Tech site, I'm thinking the software I have is the free version. What is everyone's opinion on which software I should get? I will continue owning Audis and my wife-to-be drives a 2008 VW. I can make good use of the code reader as I do my own repairs. I'm thinking the lite version @ $99.
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Old 03-16-2014, 10:55 AM   #15
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After reading the chart showing the functions of VCDS and VCDS-Lite, I would think that you could get away with the Lite version, as long as you don't change laptops. That said, the $350 that I spent on the HEX-CAN cable has paid for itself many times over in diagnostics. As a matter of fact, the first time I used it, I was able to diagnose a weird problem that had stumped several shops (a bad circuit in the ECU was flipping a bit on an O2 sensor heater circuit, showing it open when in fact it was in spec.)
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Old 03-16-2014, 10:59 AM   #16
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Okay, looking at my DTC from when I cleared it after performing the last set of repairs. I looks as if the missfires have moved from bank 1 to bank 2. Bingo, ICM!! Here's the kicker, I didn't mark them before removing, cleaning and resetting them on heat paste... Which one is which? Looking at the airbox from the passenger fender, there is one closer to the front of car and one towards the firewall.
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Old 03-16-2014, 11:06 AM   #17
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Default VCDS

Georgeb944, thanks for the reply. What is the difference with your HEX-CAN? Is it software access or is it the cable/adapter? There were a couple options, some very expensive down to $99(Lite). I'm wondering what the upgrades above the Lite version would do for me as a weekend warrior.
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Old 03-16-2014, 11:31 AM   #18
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Basically, the HEX-CAN is a cable that will work on any VAG car with OBD2 from 1996 to current and will provide diagnostic interpretation of error codes and Service Reset (SRI) for all years. VCDS-Lite will only provide interpretation to around 2006 and no SRI. If you can live with those limitations, then save a couple hundred bucks.

First, before you make any $$ decision, check to see if VCDS-Lite will work with your wife-to-be's VW. If it doesn't work without registration, it probably won't work after registration.
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Old 03-16-2014, 11:52 AM   #19
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Black connector is cyl 1,2,3. Brown connector is cyl 4,5,6.

Last edited by georgeb944; 03-16-2014 at 11:55 AM.
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Old 03-16-2014, 12:50 PM   #20
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Thanks for the reply again, just drove car w/ VCDS on, metering blocks 014, 015 & 016. Took about 5 mins driving and then 5 mins idling, #3 on 016(cyl6) started counting. I sprayed with compressed air, spraying upside down on brown connector(4,5,6) ICM. Guess what missfire went away for approx 30 seconds. then came back. I can notice the temp. difference between (4,5,6) ICM and (1,2,3) ICM. I also noticed that when sprayed the (1,2,3) ICM stayed colder/wetter longer. Probably running cooler. Now, I'm gonna switch ICM positions and give another go. Laptop needed to get charged back up.

On the VCDS use with 2008 VW , I used it do the DSG trans drain and refill on her car. I wasn't able to read all the blocks but at least it read the trans temp so I could correctly fill and get to correct level.
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Old 03-16-2014, 12:50 PM
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