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View Full Version : My first cylinder misfire. Awesome. (HELP!)



sixfiveoh
02-21-2008, 08:32 PM
So after thinking the MAF CEL had gone away for good, I'm driving home today and all of a sudden my car starts boosting only to 5psi. I take it home, scan it, and here's what I get.


6 Faults Found:
16486 - Mass Air Flow Sensor (G70): Signal too Low
P0102 - 35-10 - - - Intermittent
18010 - Power Supply Terminal 30: Voltage too Low
P1602 - 35-10 - - - Intermittent
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-10 - - - Intermittent
16685 - Cylinder 1 Misfire Detected
P0301 - 35-10 - - - Intermittent
16687 - Cylinder 3 Misfire Detected
P0303 - 35-10 - - - Intermittent
17536 - Fuel Trim: Bank 1 (Mult): System too Lean
P1128 - 35-00 - -

A few days ago, I was having problems with the MAF connector, and thought I had solved it, but the same code is being thrown now that I thought I had taken care of. No CEL though. Here's the thread from a few days ago

http://www.audizine.com/forum/showthread.php?t=191091

Where do I even begin?! I just checked all the codes on Ross-Tech, but I'm a little overwhelmed... could all of this be caused by the MAF?

seatown88
02-21-2008, 08:53 PM
sounds like you are still having problems with your MAF....

17536 - Fuel Trim: Bank 1 (Mult): System too Lean
P1128 - 35-00 - -
http://wiki.ross-tech.com/index.php/17536/P1128/004392

16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-10 - - - Intermittent
http://wiki.ross-tech.com/index.php/16684/P0300/000768

16486 - Mass Air Flow Sensor (G70): Signal too Low
P0102 - 35-10 - - - Intermittent
http://wiki.ross-tech.com/index.php/16486/P0102/000258

sixfiveoh
02-21-2008, 08:57 PM
That's what it looked like to me. But wtf could be wrong with it? What should I do? Take it out, clean it, examine it? How can I tell if it's shot?

seatown88
02-21-2008, 09:09 PM
You can try cleaning it and what not, but i doubt that will help, my guess is during the removal the MAF got messed up too much. Your probably going to need a new MAF to fix this.

If you have a buudy around you with a MAF for a 2001, try it out and see if it fixes your problem.

sixfiveoh
02-21-2008, 09:12 PM
Damn. Is it the actual plug itself that would have been screwed up, or the honeycomb area that the air passes thru? Because I know the plug got knocked around quite alot, shit was breaking off of it and everything, but that honeycomb tube thing wasn't manhandled at all...

seatown88
02-21-2008, 09:34 PM
My guess would be that the plug and connectors are whats broken here.

sixfiveoh
02-21-2008, 09:34 PM
So I just reset the ECU and took it for a drive and it's boosting 10psi fine now. What gives? Should I be expecting the problems to come back? Going out to scan the car right now...

Poopie
02-21-2008, 09:37 PM
The problems might come back. Sounds like the maf and connector need to be replaced.

Ewok_Fetus
02-21-2008, 09:38 PM
They will be back... Log your MAF with VAG... See what values it is pulling...

chris164935
02-21-2008, 09:38 PM
If the codes come back, clear them and run the car with the MAF unplugged. If the misfires stop, then you know it's something wrong with your MAF sensor and/or MAF sensor harness.

EDIT: Just read your previous thread, definitely need to get that connector fixed.

sixfiveoh
02-21-2008, 09:41 PM
And it looks like the codes are still there. I can't clear them though. Either the older software doesn't let you clear them, or I just can't figure it out.

From the VagCom website:


While the scan is running, VAG-COM will cycle through the Open Controller and Fault Code screens for each controller before returning to the Auto-Scan screen. On newer control modules which have different Hardware and Software part numbers, Auto-Scan includes the Hardware Part Number as shown in the screenshots..

Double-clicking on any of the Control Modules highlighted in RED will open the Fault Codes screen for that controller and allow you to clear the codes.

Nothing ever comes up in red when I scan the car, maybe this is only on the newer versions? I tried double clicking the fault codes but can't find a menu to clear the codes...

sixfiveoh
02-21-2008, 09:41 PM
They will be back... Log your MAF with VAG... See what values it is pulling...

What block?

Poopie
02-21-2008, 09:42 PM
log block 003

sixfiveoh
02-21-2008, 10:08 PM
Ok, here's the log:

http://spreadsheets.google.com/pub?key=pwZSQlG13OQG6Vxdiy0bfBA

Hopefully someone can tell me what's going on.

Poopie
02-21-2008, 10:12 PM
hhmmmm you're not chipped right? Those maf readings look ok to me. You didn't clear the codes after you fixed the maf connector right? It could just be a lingering code. See what happens in a couple days.

sixfiveoh
02-21-2008, 10:19 PM
not chipped... those codes weren't there before I fixed the connector... only "16486 - Mass Air Flow Sensor (G70): Signal too Low" and it was causing a CEL, after I fixed that wire and reset the ecu, the CEL went away and I didn't bother scanning it again. Today when I was driving I randomly went into limp mode, boosting only 5psi, but no CEL... that's when I scanned the car again and all these codes came up. I unhooked the battery for 30min, and when I drove the car again I was boosting fine, but the codes are still there? Wish I had a way to clear them, I don't think this version of vagcom can do that...

sixfiveoh
02-21-2008, 10:26 PM
Is there any possible way that this was just a fluke?

Bic-Ball
02-21-2008, 10:28 PM
heres the log i did of my car just yesterday:

http://spreadsheets.google.com/pub?key=pyGEz9QLXTVuRKcM9g2gVIA

at 5360 rpm my air flow was exactly 120, for you, at 5400 rpm your airflow was 97.56. ross tech calculated that our airflow should be at around 120 g/s at redline so im thinking yours is a bit low. maybe someone else could be more specific.

sixfiveoh
02-21-2008, 10:34 PM
My redline is around 6400, I logged 102.67 g/s at 6400. What does this mean?

Poopie
02-21-2008, 10:37 PM
you are running different mafs..one is for DBC and one is for DBW. I'm not sure if they are scaled the same. Best bet is to find another stock 2001 log to compare.

Bic-Ball
02-21-2008, 10:39 PM
i was going according to the last paragraph on this page:
http://www.ross-tech.com/vag-com/cars/fuel-trim.html

Here's a good sanity check for the status of your MAF. Do a full-throttle run all the way to redline in a single gear (second works fine). Group 002 usually shows air mass in g/s. Your peak airflow should be roughly 0.80 times your horsepower. So, if you have a stock 150 hp 1.8T, expect around 120 g/s. If you see significantly less than that, you MAF may be on the way out. This still works if you are chipped, but "race" programs may make more power through timing, rather than airflow. Therefore, take all readings with a grain of salt.

sixfiveoh
02-21-2008, 10:41 PM
Well if I go by that paragraph, my peak airflow should by 136 g/s. In which case I'm even lower, I peaked at like 105 g/s... Is that paragraph directed specifically towards your car? Or all A4s in general?

Poopie
02-21-2008, 10:44 PM
just buy a new maf. Its gonna go sooner or later.

sixfiveoh
02-21-2008, 10:48 PM
Bah, I knew it'd come to that. For the time being, would it be better to just run with it disconnected? Any chance that it's the actual connector plug itself that is faulty? Because that's the part that was kinda damaged and whatnot...

Poopie
02-21-2008, 10:51 PM
you can buy the connector from the dealer. You can definanly just leave it unplugged.

sixfiveoh
02-21-2008, 10:58 PM
If the car goes into limp mode again, unplugging the MAF will make it run normal for the time being until I can replace it, right? If that's the case, why don't we all just run with our MAFs unplugged?

Poopie
02-21-2008, 11:02 PM
it is said mafs are more reliable and acurate then maps to meter air.

Ewok_Fetus
02-22-2008, 05:08 AM
Also while in VAGCOM to clear codes... Are you doing the auto scan? Or do you open the engine controller and scan for codes that way?

If you try to clear codes in the autoscan, for some reason it won't clear them.
Open the engine controller through VAG and clear them from there...

sixfiveoh
02-22-2008, 08:39 AM
Yeah, I was doing autoscan, I'll try it the other way...

If I clear them, and the problem persists, they'll pop back up again, right?

sixfiveoh
02-22-2008, 08:45 AM
Well, that worked. Thanks. So now it's just a matter of waiting to see if they come back?

Ewok_Fetus
02-22-2008, 09:22 AM
Yep! Glad I could help with the code clearing at least! Also, it did look like your MAF values were a little low...

sixfiveoh
02-22-2008, 11:16 AM
Bah. Is there any chance this is being caused by a boost leak? I've noticed that all of a sudden I don't hold 10-11psi anymore, it's more like 8-9...

Poopie
02-22-2008, 11:23 AM
no because you would have a rich code. not a lean code

sixfiveoh
02-22-2008, 11:28 AM
That what I was thinking. Weird that it'll only hold 8-9 all of a sudden though. Maybe I'm imagining things.

sixfiveoh
02-22-2008, 03:35 PM
So I went into limp mode again today, so I just pulled the MAF connector and everything works fine again. Looks like it's time for a new one. While the MAF is unplugged, I'll continue to throw the "16486 - Mass Air Flow Sensor (G70): Signal too Low" code, right?

Poopie
02-22-2008, 03:46 PM
yes you will get a code for the maf. I think instead of signal too low it will be for an implausible signal.