Help a fellow BT B5 A4 1.8T owner fix a P0300

[2001BTA4]

So ill try to include all info without rambling to much. One day Ill make a build thread. For now Ill get to the build facts. This by no means is a complete list.

2001 A4 Quattro 1.8T AWM code ( daily driver )

stock bore stroke
034 1 point compression reduction head gasket after 10 thousands combined off head and deck. So about 8.5:1 compression
IE street cams
IE Intake
complete built head to support IE cams and 8500rpm
IE rods
apr R1 diverter
tial 38mm WG
SPA top mount exhaust manifold
Precision 5558 .63 a/r
2.0 coil conversion
United Motorsports stage 5 tune with 870cc injectors
870cc Dekas flow matched
Pro maf ( the bigger one )
OEM replacement coil wires
bosch F6DTC plugs
engine re freshened rings files to spec, bearings, gaskets, oil pump, etc
compression: 150, 150, 150, 145 1234
E fan conversion
stock pistons
drop in 040 pump
3 bar FPR
stock TB
and supporting modds

So what im trying to figure out is what is causing this P0300: with 2 or 3 cylinders miss firing. Is this tuning related or mechanical, ecm?

short version of story:

2nd engine rebuild for the car. First time rebuilding I dropped #4 piston during install and put a gash between the 1st and 2nd ring. I asked 034 ( complete other story ) and a local machine shop about using the piston. Both said yes. Well another long story short should of gone with my gut feeling. Well had a huge oil leak too because of misinformation and lack of catch can. As well as 20+ psi lower psi in #4. This was on Uni BT 630cc tune, stock intake man and stock cams. After 10K miles on the build I decided to rebuild again. I had 10K miles of CEL free running. So I bought cams, Intake, head upgrades, and UM stage 5 tune with 870s ( Uni told me they stopped their BT tunes and would take a unknown time to get to my ECM. another story in itself ) oh and a extra ecm to save my Uni tune.

So I start the car after rebuild and it was trouble from day one. First time out with it after warm up and changed oil cars running better then ever, broke it in hard, ran great... Till 65mi...BOOM CEL! So some where along the ride my rebuilt Alternator shit the bed and by the time the CEL came on at 65mi I barely made it home. Open circuit on all injectors, 0300 with every cylinder. UM said I have a break in the injector harness somewhere but I found nothing. There is a, should i call it hiccup at idle that you can hear in the vid. So i replace alt ( another complete BS story LOL ) Reset codes and drive again. Every 120mi CEL for 0300 with 2 or 3 cylinders miss firing, never all 4. Reset and drove like 5 times. Then one day car doesnt start. Bad crank position sensor, LOL. So buy new one and 2 new knock sensors because local vw buddy said they could be bad. 120mi later CEL. So I bought oem coil wire replacement. Drive it... 120mi...................NO CEL! 200mi.... NO CEL. Did 275mi in 3 days, joyriding around. Day four I go to start the car.... And it wont start got these codes:

15 Faults Found:
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-10 - - Intermittent
16685 - Cylinder 1
P0301 - 35-10 - Misfire Detected - Intermittent
16686 - Cylinder 2
P0302 - 35-10 - Misfire Detected - Intermittent
17968 - Maximum Engine Speed Exceeded: Engine Warranty VOID!
P1560 - 35-10 - -) - Intermittent
17633 - Fuel Injector for Cylinder 1 (N30)
P1225 - 35-10 - Short to Ground - Intermittent
17635 - Fuel Injector for Cylinder 3 (N32)
P1227 - 35-10 - Short to Ground - Intermittent
17636 - Fuel Injector for Cylinder 4 (N33)
P1228 - 35-10 - Short to Ground - Intermittent
17634 - Fuel Injector for Cylinder 2 (N31)
P1226 - 35-10 - Short to Ground - Intermittent
17949 - Fuel Pump Relay (J17)
P1541 - 35-10 - Open Circuit - Intermittent
17772 - Cylinder 4 Ignition Circuit
P1364 - 35-10 - Open Circuit - Intermittent
17766 - Cylinder 2 Ignition Circuit
P1358 - 35-10 - Open Circuit - Intermittent
17763 - Cylinder 1 Ignition Circuit
P1355 - 35-10 - Open Circuit - Intermittent
16891 - Idle Control System RPM
P0507 - 35-10 - Higher than Expected. - Intermittent
17953 - Throttle Valve Controller
P1545 - 35-10 - Malfunction - Intermittent
17072 - ECM Power Relay Load Circuit
P0688 - 35-10 - Open Circuit - Intermittent


So I replaced relay 30 under hood and it fired right up, still had no CEL. So after 1049mi of joy riding I cant figure out where my problem is. I am super lost and im hoping someone hear can point me in the right direction. I can build it but my advanced problem solving isnt as good as my build skills.

Ill try to list everything I have tried/facts:

pushing it off a cliff J/K

compression test. results at top
boost leak test
all vac/boost hoses new and are double zip tied
replaced ecm relay, fuel pump relay, coil wires,
checked all fuses
new 034 silicone pcv system
new billet pcv 034
new jet suction pump
sprayed starter fluid at vac/boost hoses, injectors, and intake manifold to head gasket while engine was running with no idle change
cars does 8500rpm cleanly no break up
random rough idle
T belt rechecked dead on
did not recheck cams but I know it would throw a code for that. Did one off on sisters B6 1.8t and code comes up like 2min later


so what do you guys think? tuning issue, bad cam file or bad maf file? or air leak or ignition?

I have vagcom but dont know how to use it to narrow my problem down.

idle vid first start of day cold :

https://youtu.be/uLpLCmdHomw

idle issue hot start:

https://youtu.be/C8cVFy2K-os

[ruiz]

I was having similar issues and checked literally everything I could and threw parts at my car before finally inspecting my wiring harness a little more in depth following it from the ECU. It ended up being my harness was rubbing against a bolt in the firewall which caused the wire to strip away and occasionally blowing fuses and throwing 15 codes if the bare wire was touching the metal. So UM might be right, I would trace the harness back a little more and use a mirror to get a peek behind parts of the harness that you cannot see without moving it. I was literally going inch by inch down my harness twisting and turning before coming up on the frayed wires that I would have missed if I hadn't done it that way.

The short to ground code means exactly that, they're shorting to ground; something metal or to a ground wire. Also, according to your codes you are missing on 4 cylinders, not 2 or 3 like you stated. If your harness is fine I would check what other components are on the same line as your injectors that could be shorting out. I don't think any of your suspicions regarding your issue could cause a short to ground, but don't quote me on that. I know on the 2.7t I saw a thread about a guy having similar issues and it was a bad cam chain tensioner that was causing shorts.

[2001BTA4]

So right now after about 42mi since last clear I have p0300, cyl 1. 2. 3 pending no cel yet. A full scan shows this:

7 Faults Found:
17968 - Maximum Engine Speed Exceeded: Engine Warranty VOID!
P1560 - 35-10 - -) - Intermittent
16891 - Idle Control System RPM
P0507 - 35-10 - Higher than Expected. - Intermittent
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 -
16688 - Cylinder 4
P0304 - 35-10 - Misfire Detected - Intermittent
16686 - Cylinder 2
P0302 - 35-00 - Misfire Detected
16685 - Cylinder 1
P0301 - 35-00 - Misfire Detected
16687 - Cylinder 3
P0303 - 35-00 - Misfire Detected


so #4 is Intermittent. In previous scans it was usually 2 or 3 cylinders random. So far I have not blown a single fuse yet. It puzzles me that the injectors came up open circuit once at 65mi but the Alt went at the same time too. After that no open circuit injector issues till the time the 30 relay under hood was bad/stuck. I removed it took the cover off and moved it by hand. put it back in and the car fired right up. Changed it anyway though. Or is it I have checked the wires from the injectors and they werent rubbing anything. The p0507 is new ( still pending ). I think the injectors have 5 wires going to ecm: 1 power from the 4 injectors and then a ground wire from each injector that is used as the trigger? I could try to run 5 new wires from the injectors to the ecm. Is there any log I could run to see if the injectors are going crazy from bad wires? I would do that first?

[Dan[FN]6262]

How much boost are you running?

What's your AFR at WOT on the top end?

[2001BTA4]

well this is the part where Im not sure how to check. I can find out how to log it but I dont know what module and code to use. Can you tell me. Started out at 15psi now Im at 20psi.

[Dan[FN]6262]

There should be a sticky on how to log with vagcom, as well as which blocks to log. I cannot remember which blocks are what anymore, I've been using maestro for the past 4 or 5 years.

[2001BTA4]

I have not yet been able to log WOT a/f. But im trying to brain storm here. So the open circuit code on the injectors means there is a definite short somewhere? Its not software related at all? If there is a short some where why doesnt it come up on scan like the 0300? Is it that it needs more miles to figure that open circuit out? Im trying to eliminate things. Could this be a ground issue? I have upgraded both neg snd positive wire to 1/0 or is it 0/1 wire for stereo reasons. I did check with multi meter for breaks in injector wires, they were all good. With the pro maf you dont use one of the 4 wires, according to the instructions. Just trying to think of everything here

[2001BTA4]

after 280mi i finally get a CEL

7 Faults Found:
17968 - Maximum Engine Speed Exceeded: Engine Warranty VOID!
P1560 - 35-10 - -) - Intermittent
16891 - Idle Control System RPM
P0507 - 35-10 - Higher than Expected. - Intermittent
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 -
16688 - Cylinder 4
P0304 - 35-10 - Misfire Detected - Intermittent
16686 - Cylinder 2
P0302 - 35-00 - Misfire Detected
16685 - Cylinder 1
P0301 - 35-00 - Misfire Detected
16687 - Cylinder 3
P0303 - 35-00 - Misfire Detected


if the injector harness was at fault why isnt it throwing the open injector code every time?

i would try to run some new wires myself. could i crimp it though instead of soldering it?

[Dan[FN]6262]

Run it at 13 psi until it pops a CEL again and report back.

[Aragorn]

unstable crank signal?

[Mattr567]

Electrical portion of ignition switch?

[ray4624]

Did you talk to um after the build? When I called them about my stroker build they told me the tune is for stock cr/cams/valves. Any change to those things would need a custom tune. They could do the compression ratio changes easily by were unsure on the cam or valve tuning. May be a decent place to start.


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