K04 missing low end torque

Previously, I had a driveability issue caused by a loose ignition coil ground point, giving the car intermittent power, almost like the turbo didn't spool up (but it did).

The ground issue is now fixed, but I could no longer spin my tires even with modest throttle off the line like I could before on this K04. Now it simply won't do that at all. The traction control light still comes on if I floor it and the car hits around 40 MPH, but not at lower speeds or RPM, and without much wheel slip.

The car has zero codes and otherwise drives fine at highway speeds. The only thing I noticed is that the engine surges a little if I depress the clutch pedal with the shifter in neutral.

If I floor it, the revs build as usual but the torque comes in after a 1 second delay.

Do I have an engine harness issue? Is there a vacuum leak?

Also, I can only manage 280 miles per tank while driving normally.

Any ideas?

Well revs go up but car doesn't go forward with normal torque could very well be a clutch starting to go (slip).

GIACUser said:

Well revs go up but car doesn't go forward with normal torque could very well be a clutch starting to go (slip).

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The car goes forward while revs build, but there's not much torque until higher RPMs. Certainly not enough torque to spin any tires down low.

For the 1 second delay, that's the dead zone that almost feels like turbo lag. I have never experienced this before on this K04.

Clutch is new, and spark plugs and coil packs are all new too. My ground issue fried a coil pack but it didn't throw any codes. I believe the camshaft position sensor is close to the ignition coil ground too.

Leak? Did you check the intake pressure?

Perpetuus said:

The car goes forward while revs build, but there's not much torque until higher RPMs. Certainly not enough torque to spin any tires down low.

For the 1 second delay, that's the dead zone that almost feels like turbo lag. I have never experienced this before on this K04.

Clutch is new, and spark plugs and coil packs are all new too. My ground issue fried a coil pack but it didn't throw any codes. I believe the camshaft position sensor is close to the ignition coil ground too.

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Knowing the above...
Do you have Vag-Com cable. You need to log boost to see what is happening.
Boost requested vs Boost Actual.

If you don't have a cable I would encourage you to get one, they are super handy in situations like this.

You can also look for a leak between turbo and throttle body. There are a number of connections between the two that may have come loose, the hoses can tear especially at the edge of a hose clamps. Connectors at the intercooler can come loose etc.

vwengineer said:

Leak? Did you check the intake pressure?

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You mean if the air intake connections are tight?

GIACUser said:

Knowing the above...
Do you have Vag-Com cable. You need to log boost to see what is happening.
Boost requested vs Boost Actual.

If you don't have a cable I would encourage you to get one, they are super handy in situations like this.

You can also look for a leak between turbo and throttle body. There are a number of connections between the two that may have come loose, the hoses can tear especially at the edge of a hose clamps. Connectors at the intercooler can come loose etc.

Click to expand...

I have VAGCOM and definitely will log boost again this week.

Also have a VWR intake system and the sleeve fix to fix the fuel trims. I did not have the sleeve installed before when the car is running fine with the K04, so I removed it last night. Well, looks like it drives even worse without it, giving me +16% long term fuel trim! (instead of +6% when I had it installed)

Went ahead to reinstall it tonight but at least I know it's not a fuel trim issue.

The hose clamps are good I think. The only one I am not too sure about it the elbow coupler that connects between the throttle body pipe and the throttle body itself. Since I have the BSH pipe AND a water meth spacer, I had to buy a custom elbow and trimmed it down to size to fit it. The clamp fits tight but the elbow isn't at the perfect angle. Any leak at this elbow would not be detected by the MAP sensor since it's after it.

Also, I cannot hear the wastegate open at all under hard accelearation. I used to be able to-

It got late tonight, but this is what my engine bay looks like:


This is the water meth spacer that I installed at the throttle body. I am not running water meth so it's capped off at the nozzle inlet. I had this since day 1 of the K04 install when it was running well:


This is the custom elbow fitting between the throttle body pipe and the throttle body:


Because I have a large intercooler, there was literally 2mm of space between the fatter than stock BSH throttle body pipe and the coolant fans. The BSH pipe originally was secured only with clamps and no bracket to hold it. Essentially, it was not very secure and was free to move around as the engine torqued under acceleration. In the beginning after I just installed my K04, this throttle body pipe kept popping loose under moderate acceleration. It popped loose 4 times.

I have since made a custom bracket to better secure the BSH pipe and now have 3mm of space between BSH pipe and the coolant fans. Not sure if there is still any interference under boost when the engine torques, but by the time I made the bracket, I started to notice the intermittent driveability/loss of torque already becoming more frequent-sometimes even during the same drive. I have a suspicion about the fitment of this pipe still, but I can't be sure.

Perpetuus said:

You mean if the air intake connections are tight?

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I meant boost pressure in fact. Also is the size of the intercooler good for this turbo? Because bigger=the more lag

"Any leak at this elbow would not be detected by the MAP sensor since it's after it."

No, it would be detected as there would be a drop in pressure even if the leak occurred after the MAP.

GIACUser said:

"Any leak at this elbow would not be detected by the MAP sensor since it's after it."

No, it would be detected as there would be a drop in pressure even if the leak occurred after the MAP.

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Logically, I know you are right. I'm just not sure if it's leaking some boost when the engine torques under high acceleration.

Well, I think it's best for me to get those boost curves to see.

vwengineer said:

I meant boost pressure in fact. Also is the size of the intercooler good for this turbo? Because bigger=the more lag

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Oh, I know what you mean now.

I am running the Wagner tuning intercooler (similar size to APR's).

I did have noticeable boost lag when I ran this with my K03, but it worked fine with my K04 from the start.

However, the car now feels similar to when I was running this intercooler with my K03 with the lack of power and delayed power.

Perpetuus said:

Logically, I know you are right. I'm just not sure if it's leaking some boost when the engine torques under high acceleration.

Well, I think it's best for me to get those boost curves to see.

Click to expand...

The logs should tell you if you have a leak, also interested to hear if you have any codes.

GIACUser said:

The logs should tell you if you have a leak, also interested to hear if you have any codes.

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Pulled some logs today for boost. The plot looks fine I think as boost hits requested. Fueling was also good. Only suspicion is the N75 never hitting close to 100% even with WOT in my pulls. Not sure if this is be design from Unitronic.



Also noticed the power to be intermittent again tonight. Some pulls produced torque and some pulls produced far less torque, as if the turbo isn't spooling (but logs show otherwise).

As for codes, there are zero both before and after my runs tonight. Long term fuel trim is at 7% with my VWR intake, which seems reasonable.

00-Steering Angle Sensor -- Status: OK 0000
01-Engine -- Status: OK 0000
03-ABS Brakes -- Status: OK 0000
08-Auto HVAC -- Status: OK 0000
09-Cent. Elect. -- Status: OK 0000
15-Airbags -- Status: OK 0000
16-Steering wheel -- Status: OK 0000
17-Instruments -- Status: OK 0000
19-CAN Gateway -- Status: OK 0000
1C-Position Sensing -- Status: OK 0000
25-Immobilizer -- Status: OK 0000
42-Door Elect, Driver -- Status: OK 0000
44-Steering Assist -- Status: OK 0000
46-Central Conv. -- Status: OK 0000
52-Door Elect, Pass. -- Status: OK 0000
55-Headlight Range -- Status: OK 0000
56-Radio -- Status: OK 0000

It certainly looks like you should be producing power.

How does timing look per cyl during these runs?

GIACUser said:

It certainly looks like you should be producing power.

How does timing look per cyl during these runs?

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Got those plots now too. Something wonky is going on as the ignition angle is being massively delayed after hitting target boost. Some other runs show it to be +20 degrees BTDC after target boost is achieved, which is even worse than what is shown here.

Note that this is a different run than the previous plot*

No idea why it would be running so many degrees BTDC here. Coil packs and spark plugs are brand new since 200 miles ago so it shouldn't be misfiring and causing timing issues (misfire count read 0). These timing issues have to come from another source.

In fact, it's driving worse now than last week. When I cleaned the ignition coil ground point and retightened it, the car drove reasonably more predictably and with lots more torque. Now it's back to its previous behaviour for some reason.

P.S.: Running 94 octane gas for this Unitronic 93 octane tune. Not expecting knock.