06 BRM Engine Misfire

Hey guys,

My '06 TDI sounds like it has a misfire, puffs more than usual black smoke when under acceleration, and has a loss of power. Compression test checked out good and cam doesn't look to be worn. If the car is under heavy acceleration, the misfire or knock gets extremely loud.

The only code it threw was P161D - cylinder 4 glow plug (which was full of soot unlike the other 3).

Here's some log info regarding injectors.

19:56:33 Group 013: Idle Stabilization (Injection Quantity Deviation)
0.07 mg/str Injection Quantity Deviation Cyl. 1
0.14 mg/str Injection Quantity Deviation Cyl. 2
-0.42 mg/str Injection Quantity Deviation Cyl. 3
0.19 mg/str Injection Quantity Deviation Cyl. 4

19:56:33 Group 001: Injection Quantity
0.07 mg/str Engine Speed (G28)
0.14 mg/str Injection Quantity
-0.42 mg/str Injection Duration (specified)
0.19 mg/str Coolant Temperature (G62)

19:56:33 Group 041
95.5 % Duty Cycle Is this indicating cylinder 1 injector is stuck open?
12.0 % Duty Cycle
13.1 % Duty Cycle
5.6 % Duty Cycle

Any and all help is greatly appreciated!

How many miles on the car?

Tony

275k.

What was your compression test results? Meaning, we need numbers for each cylinder. Just 'Good' is not enough. These engines can be VERY sensitive to seemingly small changes in compression.

Also, what were the test conditions? Engine cold? At operating temp?

Tony

Engine was cold on both tests mentioned below.

1st test was cranking engine till compression stopped rising which was about 6 cranks and each cylinder was 480.

2nd test was 4 cranks and resulted in 3 cylinders with 400 and 1 at 380. I'll have to see if I still have my paper I wrote the results on because I don't remember what cylinder was 380 but I figured 20psi difference wasn't material relatively speaking.

A buddy suggested a do a running compression test next.

Your group 1 numbers must be a typo. They are the same as the group 13.
Group 13 readings would be way different if the injector was stuck open.

If your engine has 275K and the camshaft has never been addressed I would still suspect there is something wrong there. Hand crank your engine around to see if there are grooves in the cam's injector lobes. It is hard to see the lifters with the cam in the way. There could be a perforation in the lifter surface there that you are not seeing.

A compression test should be on a warm engine. The 2nd test was not done correctly and is invalid. I would call the first test valid even though the engine was cold.

Per Bentley's on a warm engine the new engine limit is 363 to 450 with a max difference of 73 PSI.

What is a "running compression test"? Is that is that were you have someone tow the car and do a compression test while you are running down the street? If he means a "leak down test" it's probably not indicated here because your compression appears to be good.

In any case, I would trust the first test numbers, but for accuracy you could do the test on a warm engine.

I would check for a boost leak. Have a helper firmly hold the brake, put it in 1rst and gently feather the clutch until the engine starts to lug and then listen under the hood for a hissing sound.

Only do this for a few seconds at a time so you don't fry the clutch. What you are doing is putting a load on the engine which causes the turbo to come up on boost.

Thanks for the help/replies.

I figured I'd do the compression test cold because I didn't want to run the engine any longer than I needed to and figured it would still be a good indicator. Had I seen a large variance in pressure between cylinders, I would then consider retesting on a warm engine.

As for the running compression test - I have never heard of it either until it was mentioned to me. Here's a link to where the test is described if you're curious to learn about it https://support.alldata.com/article/tech-tip/running-compression-tests.

I dropped it off at car doc where oilhammer works yesterday to see what he can find. I need to get this thing sorted out so I can stop driving my 3/4 ton Sierra 100 miles a day and gets 14.5mpg on the highway.

Thanks for the suggestions and I post back what oilhammer discovers.

Thanks for the clarification. It does look like the running test would be a great tool to have in your diagnostic bag of tricks. Less complicated than a static leak down test and you don't need a special calibrated orifice or a compressor to do it like you would need for a static leak down test.

98midnight said:

Thanks for the help/replies.
I figured I'd do the compression test cold because I didn't want to run the engine any longer than I needed to and figured it would still be a good indicator. Had I seen a large variance in pressure between cylinders, I would then consider retesting on a warm engine.
As for the running compression test - I have never heard of it either until it was mentioned to me. Here's a link to where the test is described if you're curious to learn about it https://support.alldata.com/article/tech-tip/running-compression-tests.
I dropped it off at car doc where oilhammer works yesterday to see what he can find. I need to get this thing sorted out so I can stop driving my 3/4 ton Sierra 100 miles a day and gets 14.5mpg on the highway.
Thanks for the suggestions and I post back what oilhammer discovers.

Click to expand...

That test is written for a gasser, so I wonder if it would actually work on a higher compression diesel engine. I've never heard of it, but that doesn't count for much.