K04 missing low end torque

Can you just log Engine Speed and 020-1,2,3,4. Just want to see a run under load from 2500 to near redline. Just spreadsheet, no graph.

Some new thoughts:

GIACUser said:

Can you just log Engine Speed and 020-1,2,3,4. Just want to see a run under load from 2500 to near redline. Just spreadsheet, no graph.

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The CFs are relatively low.

But so far we know that boost is good and fueling is good. So this leads me to think something is wrong with ignition (or some sensors are telling the ECU to adjust the timing like this).

Is this ignition timing normal for a K04 meeting specified boost?

I went back to basics again tonight and noted that:
1) Ignition is commanded sooner BTDC when engine runs at higher RPMs. This is because the air-fuel mixture takes longer to burn at higher engine speeds.
2) A lean air-fuel mixture requires a longer burn time in the cylinder. Because of this, the cylinder pressure achieved occurs too late (after top dead center) and creates a loss of power.
3) Ignition timing is determined by input from the crank shaft position sensor, cam position sensor, and MAP sensor, primarily speaking. The IAT sensor, knock sensors, throttle position sensor, and engine coolant temp. sensors should also play a role.

Since the air flow into the engine is dependent on the throttle body opening (99% in these plots) and engine speed, the air flow amount is not being influenced by the ECU. On the other hand, the fueling amount (injector duty cycle) can be controlled by the ECU.

Basically, since the rail pressure is meeting target- unless all 4 injectors are broken or all identically clogged, then the engine should be getting the right air-fuel mixture for the most part.

Now comes ignition -
My spark plugs and coil packs are new, so there shouldn't be an issue with producing a proper spark to ignite the fuel. However, if the spark is weak (maybe wiring harness issue or ground issue again), then the weak spark cannot burn the air-fuel mixture properly -> leading to a long burn time, and maybe that explains the very high BTDC ignition timing angles.

Meanwhile, if the spark is so weak that it is unable to burn the optimal air-fuel mixture within these specifications, then perhaps the ECU might adjust the injector opening time to reduce fuel into each cylinder to match the weak spark (My speculation)? - leading to further reduced power

On the other hand, it's still possible that the crank position sensor, cam position sensor, and/or MAP sensor are faulty. Strangely enough, I have zero fault codes, which means those sensors might be ok or still within spec. somehow.

With this, I am curious if my fuel injector timing looks correct for a K04 under these RPM and boost conditions.

Also curious if there is some way to test the actual power output of these ignition coils as-installed on the vehicle.



And spreadsheet attached-


Actually, looking at the 0.8 Lambda values, the air-fuel mixture seems correct. I still believe that it is not being burned properly though.

Well you aren't pulling any significant amount of timing but I have to ask what gear these were done in.

Though you have new plugs, what plugs and gap?
I had best luck with NGK PFR7B .026

Also after you do another run, pull your plugs and have a look at them. Ideally right after a good 4th gear pull and look for a tan finish. White too lean (not likely in your case) and of course black would indicate too rich or incomplete burn.

GIACUser said:

Well you aren't pulling any significant amount of timing but I have to ask what gear these were done in.

Though you have new plugs, what plugs and gap?
I had best luck with NGK PFR7B .026

Also after you do another run, pull your plugs and have a look at them. Ideally right after a good 4th gear pull and look for a tan finish. White too lean (not likely in your case) and of course black would indicate too rich or incomplete burn.

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All runs were done in 3rd gear starting from 20-30mph.

I have used PFR7S8EG (original plugs at time of K04 install) and also PFR8S8EG (currently). Just checked the specs on NGK's website now. Both show up as .031 spark plug gap. Should I regap them?

The plugs are definitely black. Same as the last set of PFR8 I had used. The PFR7 I used were also black.

Gap current plugs down to .026 and give it a few runs. That change alone may make a significant difference. I am assuming air filter is new or clean, fuel filters in good shape etc.

I would also stay in the 7 vs the 8 heat range unless you find you are getting timing pulled. You want to go with as hot as the motor will tolerate to avoid fouling and unburnt fuel.

Also if possible do runs in 4th gear so the engine is really under load and you get a better picture of what is going on at the extreme. In 3rd gear the car is so quick it rips through the rpm range too quickly and easily. Or if you can't do 4th do the run uphill if possible.

This is a pic of one of my plugs pulled directly after a 4th gear run. Tan is the color you want to see. It means cyl temp good and burn is complete.

Closing the gap and going with a 7 heat range plug should help you.

GIACUser said:

Gap current plugs down to .026 and give it a few runs. That change alone may make a significant difference. I am assuming air filter is new or clean, fuel filters in good shape etc.

I would also stay in the 7 vs the 8 heat range unless you find you are getting timing pulled. You want to go with as hot as the motor will tolerate to avoid fouling and unburnt fuel.

Also if possible do runs in 4th gear so the engine is really under load and you get a better picture of what is going on at the extreme. In 3rd gear the car is so quick it rips through the rpm range too quickly and easily. Or if you can't do 4th do the run uphill if possible.

This is a pic of one of my plugs pulled directly after a 4th gear run. Tan is the color you want to see. It means cyl temp good and burn is complete.

Closing the gap and going with a 7 heat range plug should help you.

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Thanks, will try that out. I have a spare set of PFR7S8EG (but not PFR7B).

Specs on NGK's website show the PFR7B to have a 5K ohm resistance and the PFR7S8EG to have 1K ohm resistance. Not sure what that means yet, but that is the only difference I see between them.

Is there a spark plug that is correctly gapped at 0.026" in heat range 7 for our cars?

No plugs don't come gapped for custom stuff like you have. You should always gap your plugs before installing. And as you have already seen the plug point wears down with use increasing your gap so you need to check them and re gap from time to time.

The 5K vs 1K resistance has to do with RFI (radio frequency interference). 5K means RFI will be suppressed much more than 1K. 5K is what you should be running with cars that have a lot of electronics.

Would encourage you to order a set of the PFR7B plugs and gap to .026.

In the interim try your PFR7S8EG gapped at .026

GIACUser said:

No plugs don't come gapped for custom stuff like you have. You should always gap your plugs before installing. And as you have already seen the plug point wears down with use increasing your gap so you need to check them and re gap from time to time.

The 5K vs 1K resistance has to do with RFI (radio frequency interference). 5K means RFI will be suppressed much more than 1K. 5K is what you should be running with cars that have a lot of electronics.

Would encourage you to order a set of the PFR7B plugs and gap to .026.

In the interim try your PFR7S8EG gapped at .026

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Thanks, I just ordered the PFR7B's.

Also going to swap out my engine harness because I am 100% convinced that it's still acting up with some intermittent issue that's causing all these random driveability concerns.

Some photos and my motivation for changing the engine harness:

One of the PFR8S8EG plugs from the car yesterday (after sitting for 2 days) and it looks like this. This plug has 300 miles on it.


This was the previous PFR8S8EG with 7,000 miles on it. Looks terrible.


The corroded ignition coil common ground point. It's very close to the CKP sensor on the battery-side of the block.


Honestly, I am not sure how this occurred because the nut seemed tight. I've throughly sanded and cleaned this point and the car drove alot better (since 3 weeks ago), but it's still not what it should be.


The engine harness when I removed it out of the car and tested some areas pin-by-pin. Problem, is, I still had no idea what the intermediate sections inside the heat tape looked like.

Before you rip out harness because of suspect bad ground why not check out your grounds with a multimeter. Your voltage reading (car running) across battery terminal should be X.

Put positive on battery and use the negative cable to touch and test grounds and even touch block if you can. Each time you touch the voltage should be equal to X with no or very little drop. If you drop a volt, you have a problem. The ground in the pic.... I would unbolt, wire brush the contact areas and the bolt and put everything back just because.

Clean with baking soda and water first. Wire brush and sand. Get some anti corrosion washers from the autoparts store (they are felt embedded with anti-corrosive stuff. Or you can coat with dielectric grease.

GIACUser said:

Before you rip out harness because of suspect bad ground why not check out your grounds with a multimeter. Your voltage reading (car running) across battery terminal should be X.

Put positive on battery and use the negative cable to touch and test grounds and even touch block if you can. Each time you touch the voltage should be equal to X with no or very little drop. If you drop a volt, you have a problem. The ground in the pic.... I would unbolt, wire brush the contact areas and the bolt and put everything back just because.

Clean with baking soda and water first. Wire brush and sand. Get some anti corrosion washers from the autoparts store (they are felt embedded with anti-corrosive stuff. Or you can coat with dielectric grease.

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The test with the negative cable to the different grounds is a good idea. I might try that this week.

I had a chance to clean the ignition coil ground point already and admittedly the car drives alot better (did this 3 weeks back). However, the intermittent power issue came back this week for some reason. The only thing I changed on the car was unscrew that ground point and tried to make it more robust with dielectric grease and a nylock washer good for up to 150C. Of course, this wire was moved around a bit while I tried to line it back up to the stud to bolt it down. It's very unusual.

My other observation was that when my charge hoses popped loose under boost, the ECU immediately cut power to the engine and put it into safe mode. The shock to the engine was quite violent and easily felt. The charge hoses popped loose 5x or so and with each successive time, the car drove worse (with intermittent power). This is why I suspect the ground point got pulled loose.

I followed the Bentley manual and tested continuity from this ground and got under 1.5 ohms (spec) after cleaning the corrosion off. But - unsure about its behaviour under dynamic conditions plus with the heat in the engine bay. It passed the wiggle test though. There may be other wires in the loom that are no good.

Also worth noting - the top of this wire loom was touching a pointed part of the engine block and burned a large hole through (on the left part of the photo). I discarded the old loom here and put on a new one in this area and inspected the wires inside and couldn't find any shorts though.



Will try to clean all the other ground points in the engine bay too. It's surely worthwhile on a 12 year old car.

Good luck and always consider you may have multiple issues. Hope you find it/them.
Look forward to how plugs and gap affect things for you.

Can hardly wait to drive my car and hope I don't have any gremlins given how much work was done.

GIACUser said:

Good luck and always consider you may have multiple issues. Hope you find it/them.
Look forward to how plugs and gap affect things for you.

Can hardly wait to drive my car and hope I don't have any gremlins given how much work was done.

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I thought you had your car all sorted out. What else does it need right now? Wish I was on the west coast and could enjoy my car year round too.

I cleaned the battery, engine and power steering ground straps today. All sparkling clean now but the copper beneath the outer plating is now somewhat bare due to wire-brushing and sanding. Coated all with dielectric grease so should be fine. Will check again later since it's easy to access anyway.

P.S.: I put in a 9lb lithium battery before. Cranked fine and held charge fine but the casing started to bubble last year. The manufacturer would not even take a look at it even with the safety implications. The battery still works but I am wary of a bloated lithium battery. Let's just say it's $700 gone. Would not buy again.

Temporarily put in a new battery from another car today and not totally happy with the weight, but the car drove smoother (I think).

Since this is my summer-only car I can get away with a smaller battery. Looking at Odyssey and Deka Powersports AGM. Any recommendations?

Perpetuus said:

I thought you had your car all sorted out. What else does it need right now? Wish I was on the west coast and could enjoy my car year round too.

I cleaned the battery, engine and power steering ground straps today. All sparkling clean now but the copper beneath the outer plating is now somewhat bare due to wire-brushing and sanding. Coated all with dielectric grease so should be fine. Will check again later since it's easy to access anyway.

P.S.: I put in a 9lb lithium battery before. Cranked fine and held charge fine but the casing started to bubble last year. The manufacturer would not even take a look at it even with the safety implications. The battery still works but I am wary of a bloated lithium battery. Let's just say it's $700 gone. Would not buy again.

Temporarily put in a new battery from another car today and not totally happy with the weight, but the car drove smoother (I think).

Since this is my summer-only car I can get away with a smaller battery. Looking at Odyssey and Deka Powersports AGM. Any recommendations?

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My car is sorted and tuned. AU Tuning has done the work over a period of a year and he just wanted to back over the work to insure they have not missed anything.

Yes, living in CA does have the benefit of year round track days.

I have had nothing but consistently good experiences with traditional lead acid batteries. I tried lighter sealed battery once and it ended up much like yours.

As for weight savings .. meh... not really interested in isolated weight savings, makes no diff all by itself.

GIACUser said:

My car is sorted and tuned. AU Tuning has done the work over a period of a year and he just wanted to back over the work to insure they have not missed anything.

Yes, living in CA does have the benefit of year round track days.

I have had nothing but consistently good experiences with traditional lead acid batteries. I tried lighter sealed battery once and it ended up much like yours.

As for weight savings .. meh... not really interested in isolated weight savings, makes no diff all by itself.

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So, I finally put in a new harness, new battery, and new PFR7B spark plugs yesterday.

When I went to start the car, it now cranks but engine won't fire up.

Troubleshooting time...

I found the knock sensor connector on the driver's side (brown connector) was not completely set. Just fixed that now but will keep looking before I put it all back together again.

GIACUser said:

My car is sorted and tuned. AU Tuning has done the work over a period of a year and he just wanted to back over the work to insure they have not missed anything.

Yes, living in CA does have the benefit of year round track days.

I have had nothing but consistently good experiences with traditional lead acid batteries. I tried lighter sealed battery once and it ended up much like yours.

As for weight savings .. meh... not really interested in isolated weight savings, makes no diff all by itself.

Click to expand...

Tried reconnecting all connectors again. Engine cranks but still no start.

I am starting to suspect that this good wiring harness making proper connection has made a fuse finally go bad. Perhaps a fuse/relay was previously damaged from arcing due to intermittent connection (speculation), and now a proper connection is enough to blow it.

Problem is, I can't find my ignition coil fuse.

Found this photo online of the engine room fuse box, but mine doesn't look like this at all:


Also referenced the Bentley manual for this fuse box, but my fuses don't seem to be arranged this way either... (See fuse F14 for ignition coil fuse)


What am I missing, and where is the ignition coil fuse?