Stuttering acceleration, noise, and engine vibration

06 Jetta BRM 245k - No EGR, gutted cat, turbo replaced 20kish ago with used and zip tie mod, cam and lifters replaced anywhere from 40-60k ago.

Was driving down the highway and engine cut for a quick second a couple times,kind of like a blip in power. When pushing the accelerator it would stutter quite a bit. Making noise. Luckily I was only a mile from my exit.

DTCs that were set when I parked were p2425 EGR gas recirculation, p0401 another EGR code, glow plugs codes, and a code for the EGR valve stuck open/closed.
P2425 and p0401 are usually there due to the EGR delete. Glow plugs there due to engine harness garbage.

Checked my EGR flap (in the metal body behind valve cover on passenger side that connects to the intake) and it was open and moved freely by hand. Didn't see any disconnect vacuum lines at turbo and the 2 vacuum bodies that have 3 vacuum houses connected at them. Mass flow sensor plug connected, no noticeable issues. Checked oil to be safe. No noticeable leaks of any kind under the vehicle. Restarted vehicle let idle. Only DTC is the p2425.

Ideas what to check?

Sent from my moto e5 plus using Tapatalk

Also a decent amount of white smoke occurring. No change with MAF sensor plug on or off. Serpentine belt tensioner is bouncing a bit. No change with AC on to load the belt more.

Sent from my moto e5 plus using Tapatalk

This is the kind of thing I saw when a part of the harness for one of the sensors started shorting. Check your wiring for a short. Try wiggling the any visible harnesses and restart the engine, rinse and repeat. If you finally get a clean start and it's running like normal for a few seconds, then it's likely a wiring issue. Somewhere.

When I had this happen, it did exactly as you described and VCDS didn't show any wild codes. It's likely that when it shorts, it reverts the ECU into a mode that's similar to a limp mode.

You mentioned you do not have an EGR, but you're getting EGR codes. Check your harness for your EGR, maybe a connector that you unplugged is snagged on something. I assume you have a tune to complete the EGR delete, right?

No tune, so that's why I have the EGR codes. I'll check the harness.

Sent from my moto e5 plus using Tapatalk

How about a new harness and a proper tune? All sorts of problems arise when the BRM's engine harness goes bad. There is almost an unlimited possibility of strangeness. If you already know of these things, I'd fix those. Just ignoring them makes diagnosing problems like this just that much more difficult.

I've replaced the harness previously. About two years ago.

Sent from my moto e5 plus using Tapatalk

borjawil said:

I've replaced the harness previously. About two years ago.

Sent from my moto e5 plus using Tapatalk

Click to expand...

So, then why did you say you have glow system faults due to "harness garbage"?

The glow harness was separately fixed, but still get DTCs for it. Likely due to resistance issues.

Sent from my moto e5 plus using Tapatalk

I am not following you. The glow harness is part of the engine harness. If you installed a new engine harness, that would have also been new.

In any event, the fuel filter service interval is every other service (20k miles). The PD engines have little tolerance for neglect with these. Has the element been kept replaced properly? That can cause a no-DTC driveability problem on these.

Glow harness was damaged and needed repair. Any whoooo, fuel filter was replaced with a KN filter about 10k or so miles ago. Supposed to last 15-20 I think. But I'll go ahead and replace it just in case.

Sent from my moto e5 plus using Tapatalk

Fuel filter didn't correct it. And I'm pretty sure it's not a limo mode issue. I've dealt with the wiring chafe issues and limo mode. The engine is shaking pretty well. Like a gas engine runs if it's missing on a cylinder. At idle when giving it gas there's a decent amount of white smoke.


Sent from my moto e5 plus using Tapatalk

It may have had something mechanical fail then.

I would see if you can narrow it down to a cylinder with a scan tool, cylinder balance numbers would show that. Then do a compression check, and see where you are.

Three kinds of "white smoke":

coolant (smells sweet, and is like steam)

motor oil (bluish tint, burnt smell, does not go away quickly)

unburnt diesel, similar to oil, in conjunction with something that is causing no combustion (like no compression).

No vagcom type scan tool unfortunately. Hoping to get it towed home (where all my tools are) this evening. Was hoping for an easy fix since I'm 70mi from home.

I did notice.on the three wire connector in front of the engine (BLK/wht, grn/prpl, grn/br) the black and white wire isnt broken but the insulation is missing in places. Anyone know what that connector is for and/or has a wiring diagram?

Sent from my moto e5 plus using Tapatalk

Possibly map or maf connector?

Sent from my moto e5 plus using Tapatalk

Looks like it's the crank position sensor, and upon closer examination all three wires insulation are broken. Any issues with jumping the wires past the connectors?

Sent from my moto e5 plus using Tapatalk

CKP wire goes directly into the CKP sensor, and that too would have been new when the harness was replaced. So I am not sure I know what you are talking about. Can you post a pic? Because if the engine harness was replaced, literally everything that connects to the engine would be new wiring wise.

Engine harness is no longer new. It's been a couple years since I replaced it. I'm well aware of what the engine harness includes. I've done all the work myself. Here is a picture of the connector. Black side harness, grey side to the CPS

Sent from my moto e5 plus using Tapatalk

That is the CMP (camshaft position sensor) I believe you are talking about. Gray connector that goes to the timing belt end of the engine? The plastic stay is on the front of the block, near the cylinder head mating area?

CKP sensor is down low, in an area between the oil filter housing and the bellhousing.

Two years is not a long time for a harness, it should not have been giving any issues by now. Not sure if I would want to try and wire around the connector, but instead if needed splice in a new connector assembly (the shell has a part number on it, you can use that to get the correct repair wires).

Checked out the cam and it looks fine. Hard to see the lifters but nothing noticeable and no broken bits in there. Guess I'll have to get a connector and go from there. But I'm still wondering why I'm not getting any DTCs regarding it

Sent from my moto e5 plus using Tapatalk

If you are not using a VAG specific scan tool, you are not getting the whole story. There may very well be all kinds of DTCs related to your problem, you just can't get to them. The generic OBD2 stuff is very limited.

The CMP sensor does not care about the condition of the camshaft. And the camshaft itself has no bearing on the CMP sensor's ability to properly report the kurbelwinkel.

Replaced the connector and no change. Unplugged sensor and no change. No new DTCs either way. Looking at picking up a vcds soon. Anything else I can check/do while I wait for it?

Sent from my moto e5 plus using Tapatalk

With the key on, check the voltage of the two outside wires. You should be seeing around 5 volts and around 1.5 ohms of resistance. If not, you've got issues with the wiring harness elsewhere. In case if you have to unhook the connector to the ECU, the pins should be 27,28 and 12(according to my Bentley manual).

If the ECU isn't getting a reliable signal from the cam and crank position sensors, it will run like crap no matter what. It uses the data to determine the timing window to fire the injectors. Unlike some of the Powerstrokes, it won't leave you on the side of the road if one of the sensors fail.

Ok, maybe a DB question but is it ok to drive if one of these sensors or wiring fails? It's currently a $300+ tow or I'm driving an hour one way to get to it.

Sent from my moto e5 plus using Tapatalk

I did it when I lost what appeared to be both sensors, I don't think I have any issues as a result. But your results may vary.

Also, there's still a chance it could be something else since ruling out these sensor issues is just part of the diagnostic stage. Does it have a long crank before starting? Usually that accompanies the sensor being down. If you lose both sensors, your tach won't work. If there's a short in the harness, it usually kills the tach and you'll get a full Christmas(low oil pressure light and coolant light flashing).

I've loss the tach/gotten the crazy Xmas tree lights before due to harness chafe. Not getting this. Starts up like normal. Never check if the tach is working but I'm pretty sure it is.

Sent from my moto e5 plus using Tapatalk

Im getting 5v between the black and grn/brw, and black and grn/prpl. Nothing between the two greens. This is with key on, and connector connected.

Sent from my moto e5 plus using Tapatalk

If you're getting the 5v between the signal wires and ground, you're good for that part. VCDS will definitely help get the rest of the story as Oilhammer said.

If you want, you can test the cam position sensor. The Bently manual doesn't have a listed resistance value for the sensor for our cars. But someone found a Bently procedure for a different VW engine's cam sensor.

https://forums.tdiclub.com/showthread.php?t=464616

In the meantime, it wouldn't hurt to check the voltage on some of the other sensors, especially any that are disconnected for the EGR delete. Deleting the smart actuator with the turbo swap is what got me, I didn't cover the abandoned connector and paid the price.

I don't remember a disconnected connector with the EGR delete. Just the two block off plates, and a vacuum line/maybe 2 that needed to be plugged.

What other sensors would you recommend checking?

Sent from my moto e5 plus using Tapatalk

I have my vcds! So where do I begin? Never used vcds before and not sure what to look for.

Sent from my moto e5 plus using Tapatalk

First thing first, run a full auto scan and save it for future reference. The data will be good to have in case if you need to reset a module in the future. It wouldn't be bad to post the full auto scan. The page view would be annoying since it's long(you can use code tags to fix that), but it'll give a good chunk of usable info.

You'll also be able to use VCDS to go into the engine module and check the measuring blocks. You can check the cam torsion, injector deviation. You can also usually tell if the fuel filter is clogged using VCDS.

https://forums.tdiclub.com/showthread.php?t=480462