Hi guys im after your help. Maybe the community could shed some light on something im otherwise over looking.

 

I bought my vrs was back in 2012. Its never ran right, with hesitation under boost (no misfires). Ive chased the solution to this ever since then.

 

My car has the following mods:

 

1) N112, N249, SAI, EVAP deletes (these are not coded out via software, rather replaced with resisitors.

2) Long ram air intake with K&N filter

3) Forge turbo intake pipe

4) Forge 008 diverter valve

5) PCV deleted with oil catch can sysyem

6) Syvecs/Walbro fuel pump

7) 2.75" Turbo back exhaust system (decat)

8) BAM injectors

9) ECS 2.0ltr Red top coilpack conversion

10) N75J

11) Stage 1 remap

 

The car has been running happily (albeit with slight hesitation on wot)I for the past couple of year before my current situation. So getting to the point - over the past month my car has been deteriorating. I noticed things like the wot hestitaion become worse and my car would occasionally not respond to the throttle for seconds at a time. Oddly my ecu would not through any codes other than that for the sai, and primary and secondary lambdas. Now this is where it get expensive. 

 

Biting the bullet i book the car in at a local vag specialist with rolling road to see whats happening while the car drives. We discovered that the car had a nasty misfire at roughly 4k everytime it ran wot. What was causing this? The garage wasnt sure so we did some logging.

 

With misfires registered i bought some more second hand coilpacks, injectors and a fuel pump, fitting them but to no avail. So we decided to have another look and possibly write another software file.

 

All seems ok on dyno; she opens and holds 1.5 bar boost until the 4k point when she misfires. Shes overfuelling (obviously due to injectors) but we cant fathom the issue. We tried remapping and changing the fuelling for the injectors but to no avail. We tried revo software, no joy and viezu software with no joy. Viezu suggested a hardware fault so to return software back to standard and resolve the issue.

We did a pressure leak test and all is fine.

 

Ive found that since the cars time on the dyno, it has become so much worse than before. The hesitation is horrendous and the car now sounds like a rally stage monster thanks to its humongous misfires. Im no further forward after this and im left with a car thats not running propperly.

 

So what have i done now. Well since the dyno ive changed the following:

Maf sensor

N75 valve

Oil and filter change 

Spark plugs (denso gapped to 0.7mm)

Pulled and checked boost pipes and intercooler.

Drained oil from intercooler.

Cleaned all associated engine management sensors.

Cleaned out oil catch tank system, cleaning out all breather pipes.

Replaced injector O ring seals.

Replaced brake light switch.

Double/tripple checked everything ive recently done.

Reset the throttle body via vag com.

Brand new Bosch primary lambda sensor.

 

Vagcom showed bank one sensor one lambda issue. Heating circuit open; same with secondary but not much of a concern. This is where things get interesting as adter fitting the new lambda, we used vagcom to delete codes however they stay! I cannot get rid of the primary lambda fault. So i had no choice but to check all wiring. I managed to find an ecu pin layout and wiring diagram and set upon the mamoth task of testing continuity throughout. So from the sensor, through the harness, branching off to the fuse box and relay 409 and to the ecu itself. I found i had full continuity all the way through!. Which led me to exchange the lambda for another under warranty. This has since been replaced but it hasnt solved the issue. What do you guys think??? Ecu fried? Fuse 43 is in one piece, my car primes the fuel pump and always starts first time - does that mean the relay is fine too?

 

Funny thing is, my car hasnt been using the primary lambda for the past few year. I know this as to my dismay, i found the primary lambda wiring hangging on the ground. After a quick investigation i found the numpty who fitted my new steering rack (some 2 year ago) had jammed the wiring between the underbody and front subframe, totally destroying the lambda side loom.

 

While i was on the case of wiring, i also found my coilpack loom was destroyed. The external sheething was crumbling away and an alarming amount of copper was on show. So PSi tuning helpped me out big style by having a replacement loom in stock ( you can only buy wires and pins from the dealers now). So another mamoth wiring session later saw a new coilpack loom fitted all the way to the ECU connector including all pins. If anything this has resulted in an amplified issue with the car! It obviously needed doing but my god i cant get this car running for love nor money.

 

So my latest upgrade ( as of 2 hours ago) was to fit an ECS 2.0ltr coilpack conversion kit. Just incase my second hand items were rubbish. These havent helped in the slightest. 

 

What am i doing wrong? Anyone know whats the next port of call? Im sorry i dont have a laptop and VAGCOM to use at home.

 

Thanks if youve managed to read this far. Any help is greatly appreciated 

 

Adam

 

 

 

Edited 4 June, 20188 yr by Adz_VRS

Have you checked the engine has a solid earth?

Sorry i should have mentioned this. 

Under the battery tray are 3 earthing points that feed the wiring harness. While i was there i did indeed clean these up, taking their points of connection back to bare metal. Up at the ecu (under scuttle panel) are another 3 branched earths... all of which recieved the same treatment. 

 

However there was one of which concerned me. Directly under the battery resides a hefty gauge black earth. Said earth is ground to car but leaves main core open to elements and this had obviouse signs of corrosion. Due to its overall hefty size i deamed it must be ok as it feeds the starter motor and alternator (both of which are working ok). Should i have another look at this?

have you checked the map sensor. i have broken a few just with running high boost. and that will cause a huge misfire and stutter. try running with it unplugged. 

then check compression. as it could be a vvt issue