1.8t BAM misfire problem

[AceD909]

My LCR 1.8T BAM has had a persistent misfire issue for the past six months, and I haven't been able to resolve it.

Misfire only on idle, driving and just reving it or cold start it doesn't misfire

Issue Overview:

The misfire occurs only when the MAF is connected.

When I unplug the MAF, the misfire disappears.

However, the issue affects only one cylinder.

Diagnosis So Far:

Using VCDS, I identified that Cylinder 3 is misfiring. Here’s what I’ve tried:



Swapped the ignition coil – The misfire remained on Cylinder 3.

Installed new spark plugs – No change, Cylinder 3 still misfires.

Swapped injectors (3 ↔ 4) – The misfire moved to Cylinder 4.

I cleaned the injectors, and the problem was resolved for about a week.

After that, the same injector started misfiring again.

Additional Tests:

Unplugged the MAF – Misfire disappeared.

MAF connected, but EGT sensor unplugged – No misfire.

The EGT sensor was reading 1110°C, likely causing the car to run rich.

Both MAF and EGT unplugged – No misfire.

It seems like when the engine runs rich, the misfire does not occur.

Questions:

Given this behavior, what should I check next? Could this be a fueling issue, or is there something else affecting the mixture and causing the misfire?



Any advice would be greatly appreciated!

 

[Alexis27]

Sounds like your cleaning didn't work. Did it have a proper ultrasonic treatment?

 

[AceD909]

Sounds like your cleaning didn't work. Did it have a proper ultrasonic treatment?

Yes, they provide the best service for injectors, so I have no doubts about their quality. I can bring them in for cleaning again.

I'm also looking to buy new injectors, but finding the 06A906031J long-nozzle injectors seems impossible. I did find the 06A906031BC, which has the same 269 g/min flow rate, but it's a short-nozzle version.

Is there a way to check if the injectors are making the mixture lean or rich at idle? Or will the engine not misfire if the mixture is rich? I don’t have a clear understanding of how this works, so any advice would be helpful.

I also have access to VCDS and ME7Logger.

 

[nd-photo.nl]

You can check fuel trims for that (with VCDS). I would also advice to buy new injectors if you are planning to keep the car. They are very old at this point and its a mechanical/electrical component which will wear out in the end.

You can probably also check higher output injectors, but then your mapping needs to be corrected. Hopefully someone with more specific knowledge might help you investigate this path.

Fuel Trim Info - Ross-Tech Wiki

wiki.ross-tech.com

 

[AceD909]

You can check fuel trims for that (with VCDS). I would also advice to buy new injectors if you are planning to keep the car. They are very old at this point and its a mechanical/electrical component which will wear out in the end.

You can probably also check higher output injectors, but then your mapping needs to be corrected. Hopefully someone with more specific knowledge might help you investigate this path.

Fuel Trim Info - Ross-Tech Wiki

wiki.ross-tech.com

I will check later with VCDS, but what are the best replacement injectors? What should I get?

I’ve had the car for almost six years and want to keep it. It’s mostly stock, with some bypasses like the N249. What would be the best way to solve this problem? Would upgrading to aftermarket parts be a better option in terms of longevity?

 

[nd-photo.nl]

Original injectors are from Bosch if I am not mistaken. If I look on Autodoc for the CupraR, I see this. That looks like the correct ones, right?

https://www.autodoc.co.uk/bosch/1150390

 

[AceD909]

Original injectors are from Bosch if I am not mistaken. If I look on Autodoc for the CupraR, I see this. That looks like the correct ones, right?

https://www.autodoc.co.uk/bosch/1150390

Mine are Bosch 62529

https://autodoc.co.uk/bosch/1150367

 

[nd-photo.nl]

Ah this explains the long-nozzle notion, I have never seen this before. My AUQ had the "normal" short injectors. A popular upgrade for the AUQ were the BAM injectors, and I never knew these long-nozzles existed

My old AUQ injectors

 

[ExiledWeegie]

whatever you do dont go for cheap no names or Frankberg that come from Ebay, I did and nearly bore washed one of my cylinders, there was raw fuel pissing through the exhaust. ended up getting a set of recon Bosch injectors and been fine since.

 

[AceD909]

whatever you do dont go for cheap no names or Frankberg that come from Ebay, I did and nearly bore washed one of my cylinders, there was raw fuel pissing through the exhaust. ended up getting a set of recon Bosch injectors and been fine since.

I will get Bosch for sure, but im not sure if there is difference between the long-nozzle and short-nozzle.
Also there are probably good and bad things about them.
I saw there is adapters to make it longer, but i don't have experiance with any of this and it is my first time with bad injectors.

 

[ExiledWeegie]

best thing to do would be remove one and check the part number on them and buy like for like.

 

[AceD909]

best thing to do would be remove one and check the part number on them and buy like for like.

Yeah, but impossible to found.

 

[AceD909]

Guys, what injectors to get? I can only found on ebay but not sure what brand they are, i don't want to risk.
What is best one, even higher cc i will get it mapped.
Anything will be helpful.

 

[Battoussai]

Guys, what injectors to get? I can only found on ebay but not sure what brand they are, i don't want to risk.
What is best one, even higher cc i will get it mapped.
Anything will be helpful.

Hi there.

If you said "Mine are Bosch 62529" why don't you just go with those?

 

[ExiledWeegie]

theres a few sets of second hand Bosch 62529 on ebay, say working and good condition, you could get a set and buy a service kit for them which consists of oring for top and bottom and a new petrol filter for the top.

 

[AceD909]

Hi there.

If you said "Mine are Bosch 62529" why don't you just go with those?

I would buy them if they are not out of stock every where.

 

[AceD909]

theres a few sets of second hand Bosch 62529 on ebay, say working and good condition, you could get a set and buy a service kit for them which consists of oring for top and bottom and a new petrol filter for the top.

I will get mine to service again tomorrow, i don't want to get second hand ones, no for fuel parts or ignition.

 

[Battoussai]

I would buy them if they are not out of stock every where.

Check here:
Injector Planet

 

[AceD909]

Check here:
Injector Planet

Just the rebuild kit is available.

 

[AceD909]

My injectors were cleaned and properly tested, i was told they are fine in ohms test.
1 injector was fueling 2mg more that the others, can this cause misifire problem?
Also they were all rebuiled with new filters new o-rings.
I will check my car for misfires again using vcds and keep you all informed.