I'm getting nowhere diagnosing my car. Lots of details inside.
 

Still fighting.... posted about this a week or so ago. Refresher, plus more info.

Car has been feeling down on power under boost for the last couple months, no obvious problems though. Felt a bit like it was pulling timing, but didn't have my vag cable to check. A month ago I blew my head gasket, was spewing white smoke. Fixed the gasket, did the N249/SAI delete at the same time. Start the car up after getting everything together, and the fun begins....

With the MAF unplugged, it idles and cruises fine, but misfires like its its job under boost. Depending on load, as little as 1-2psi (low load). Handles 5-6psi if i'm moving slow and its in a high gear, but it still has no power.

MAF plugged in, it'll barely even idle.

Mods: foam air filter, forge turbo inlet, manual boost controller, SAI delete, N249 delete, PCV delete (replaced with catch can, does not recirculate air), muffler delete (still have resonator muffler, straight piped from there). NOT chipped, or resistor'd or anything.

Codes:
4 Faults Found:

18057 - Powertrain Data Bus: Missing Message from ABS Controller
P1649 - 35-00 - -
17840 - Secondary Air Injection Solenoid Valve (N112): Open Circuit
P1432 - 35-00 - -
17695 - Boost Pressure Control Valve (N249): Open Circuit
P1287 - 35-00 - -
16486 - Mass Air Flow Sensor (G70): Signal too Low
P0102 - 35-00 - -

ABS fuse is out because I have a cut ABS sensor wire, and the ABS was going wild. Will solder wire and replace fuse when a spot opens up in my buddys garage to do it.

MAF is unplugged, already explained.

N249 is unplugged to see if it'd run any different. Vac lines were replumbed but the N249 was still in place until recently.

O2 sensor was just replaced, so I'll assume its reading correct. 'No boost' conditions put readings at .04, attempting to boost .035 down to the occasional .025, but usually .035 or .03

Coolant temp is always 90-93°C
IAT sensor is reading correct for the seasons cold outside air temps (so I wouldn't expect a fuel adjustment based off a bad reading there)

Group 116 - fuel correction is all 0%
Group 122 - timing retard reads 'no torq required' down the list

Pressure tested the system, no leaks.

Tried running on just the MAF with the MAP unplugged - not much change. (was thinking maybe the MAP was screwed up)

Not sure what I should be seeing between manifold pressure/command pressure/intercooler pressure and/or barometric pressure. I can say its commanding more than its getting, eg; manifold 1000mbar, command 1660mbar. 500-600mbar is the average difference for the entire log.

Timing- with MAF plugged in at idle, I'll get a swing of 10°BTDC to 6°ATDC. MAF unplugged, its stable. Unplugged cruising vs boosting it's somewhere around 28-30° vs 13-18° BTDC, until it starts to misfire hard, then it'll drop to 6-ish°. (Knock sensors not reading any knock at any point)


I know this is a jumble of information, but I'm trying to highlight everything I've checked across multiple logs. Everything looks normal to me, aside from the command-manifold pressure, and apparently my ECU thinks the same by the lack of codes... I'm hoping someone might be able to think of something I haven't checked, or spot something out of the ordinary that I missed.

Only other oddball thing related to my catch can. Breather filter iced up, pressurizing my block, and thats how I end up with coolant in my oil (maybe the head is a tiny bit warped?). Thought I blew the gasket again the other day, removed oil cap, pressure vented, smoke stopped. Left the breather filter off since then, no oil/water issues since.


BTW, I'll log whatever you guys think I should and post the whole thing if it'd be easier... I need to get this resolved.

TIA.

What do your spark plugs look like? Running really lean? How many miles?
 

Is your fuel pump making any noise?

Plugs look really good.
 

Pulled the denso's out after the head gasket thinking plug fouling might be causing the issue. put some autolites in temporarily, didn't change a thing. Put the denso's back in the other day, autolites looked as good as the densos did the first time I pulled them out.

Got the coil wires plugged in right?

VS plugged in wrong, or not at all? ; )
 

Fully secured, all 4 of them.

Oh yeah, fuel pump, light buzz, like it always has.
 

Rear of the car is gutted, so its pretty easy to hear. Doesn't sound any different than it has since I gutted it last spring. Potential that I haven't noticed a slow change though.

Also, fuel filter was changed about a year ago.

Wrong order. I've done it with plug wires. Thought I'd mention it.

I'll double check it- but since it idles/cruises fine... i'd imagine its ok?

O2 replacement before or after the head gasket fiasco?

After. Ruling out coolant contamination as the cause of my woes.

MAF? Usually when the car acts up with the MAF plugged in.
 

I have seen that a 1.8T With that MAF plugged in and its missfiring and sputtering then you unplug it and it fine indicates a bad MAF. Have you tried cleaning it or known good one? I would also clean and adapt the throttle valve. I would start from there... This sounds like you need to be there to see, hear and feel this carry on. I would also loose the MBC and get chipped. All your doing is tricking the ECU and making the stock file run to its limits. Not a big fan of those.

this is all with the maf unplugged. car barely idles with maf plugged in.
 

maf is fairly new anyway, throttle body was cleaned 2 months ago, aligned the other day.

WOW....sounds like a mess. At this point, you have so much going on>>>.
 

that it is hard to tell what is causing what...

I would probably re-plumb the N249 back in, and setup the catch can to vent back into the intake hose. Not sure if the pressure is causing the leak into the crankcase or not..but i am sure it is not helping...

Just my two cents...

Yeah...start unwinding the mods....>
 

until you can get it to run again. IMO You've really farked things up..Turn in your Vortex user ID..

LOL - I agree in this case - mods that make the car run worse FTW!

Isn't this when he gets his Vortex ID and has to turn in this one? ;)

lol

Not necessarily. If you got the right two swapped you could run on two cylinders

Had similar problem with the blue car recently
 

Car started stumbling very badly, not running on all four cylinders, stalling with just the slightest load. I thought it was a coilpack or three but unplugging the MAF fixed it. Turned out that's all it was, new MAF and it's fixed.

I wouldn't call running on 2 cylinders 'idles/cruises fine.' I'm gonna rule out the coilpack theory

c'mon now... AW is my technical 'go-to'. AF is where I normally troll.
 

Un-modding it is for now....

I really feel like plugging that crap back in is only going to mask the issue. If I came on here saying I did a coil pack delete, and now my car won't run smooth, I could see how plugging in that last pack would fix the problem.
But...
These cars shouldn't NEED the N75, N249 or SAI (or muffler) to run right though, and it's not uncommon to remove them, and I've NEVER heard of anyone having such issues.

I'd also like to clarify, the MBC is not on there to try to squeeze out some more power w/o being chipped. Its set at 14psi. N75 failed on me at one point, so I replaced it with a mechanical controller. I HATE all these little electronic gizmos everywhere. All my engine related 'mods' were put in place after the stock stuff started acting up. All my REAL modding is focused on handling/braking. I'm happy with 225hp (that is, when I actually have it)

When it runs fine before the mod, and lousy after....>>
 

Logic would say your mod, or the execution thereof had some causal affect. The fact that a botched Catch can install resulted in a blown head gasket should convince you to back away from the car! Revisit that whole head install. You missed something somewhere..

like i said, i'll de-mod, and see where I am. feeling doubtful though.
 

it's not like i haven't thought over the head gasket thing. not many places to 'miss' something, not that complicated a job.

probably report back this weekend after i've had a chance to replumb some stuff...

Glad to help. Don't check. Whatever.

checked. ruled out. relax!

IF all these parts were unnecessary - Audi would have not installed them in the first place.....
 

why add cost when you don't need it. Sure - you can eliminate some of the parts and the car will still run and i've read enough about the 1.8T over the past 10 years to know which mods work and which don't. The is absolutely nothing to be gaining by removing the parts except aesthetics.

OK, I thought I had troubles...
 

I'd approach in this manner..
1ST: pull valve cover, check cams marks, and cam pulley and crank and tranny for TDC
2nd: Check your vac lines, sounds simple but with the head off and all the mods you've done you may be missing some check valves or have lines hooked up backward.
3rd: as much as I hate to say it you need to de-mod, get to a baseline so that you can find your real problem.

Re: IF all these parts were unnecessary - Audi would have not installed them in the first place.....
 

<center><img src="http://www.42draftdesigns.com/images/dealers/sms.jpg"></center><p>I can agree with Joe... But as far as your stumble issue is concerned, it sounds like your MAF... The MBC IMO is a bandaid and owning a Audi you should be able to spend the 90 bucks to fix that issue. I would Never remove a part and replace it with Bo BO parts just to save 90 bucks... Only for diagnostic purposes only I may install it one if I didnt have a choice.

The best way to tune your car is to get it back to OE standards and go from there. If you replaced the MAF before, it still doesnt mean its not bad... This is why I said to get a known good one to test it out. Or get a multimeter and check your output or even a VAGCOM to check your specs. It is almost impossible to diagnose these cars without knowing your actual values and what the requested or stock spec is. Just my 2 cents.