Help with Compression Numbers

[Bm3875]

Hi All,

Have a E46 2004 325XI (Auto) with a P0305 Cylinder 5 misfire (and goes into limp mode).

A little background:
- Checked out the coils, plugs and injectors (swapped cylinder 5's with cylinder 2; misfire didn't follow; stayed with cylinder 5).
- I did change the starter out about 4 months back (required removal of the intake). CCV redo at the same time.
- Was also having fuel pump issues recently (running out of gas/stalling at 1/8 tank left, etc.).
- Has burned oil like a mother since I've owned it (3 years; at least a quart every 500 miles); CCV redo didn't help that.

I'm having issues interpreting the compression test numbers. The numbers a very low across the board, but for some reason, they are even lower when testing the engine warm vs. when cold. Cranked 10 times, pedal to the floor for each test. Did a west test that didn't affect the numbers.

Here at the numbers:
C1 Cold: 59 Warm: 20
C2 Cold: 60 Warm: 20
C3 Cold: 60 Warm: 20
C4 Cold: 50 Warm: 20
C5 Cold: 65 Warm: 20
C6 Cold: 60 Warm: 20

Not sure if it's worth mentioning but when testing warm, the number will hit 20 while cranking, and then slowly dip before I take a gauge out.

Here's what I've been thinking as possibilities:

• Newly formed intake vacuum leak from the starter job (ran fine for 4 months)?
• Fuel pump issue causing a lean misfire?
• Of course, head gasket (what are the odds all cylinders would be affected?)

Thanks all!

[dworthy]

I hope you disabled the fuel pump, as those number reflect rings getting washed out by fuel.

Leave the spark plugs out for a bit, like 30 minutes, and drop a tad of oil into the cylinders. Turn the car over to make sure the oil gets back into the rings and try again.

[MIKYZZ4]

+1
Fuel wash
Do like dworthy suggested, remove plugs and allow fuel to dissipate.
You can remove fuel pump relay to disable fuel pump.
A small capful of oil will help with readings.

[Bm3875]

Hi Dworthy,

Thanks for the reply. I did remove the DME relay before each test - anything else you'd suggest to disable (I'm hoping that was all I needed to do to disable the fuel pump)?

I first suspected the washout, so I dumped a cap of oil in each cylinder before the cold test and got the numbers above. Put the coils and plugs back in, started her up to get her warm for the warm test. Then after getting the lower warm numbers above, I put another cap of oil into each cylinder to try a warm wet test, but the numbers didn't change.

Thanks much!

[MIKYZZ4]

Checked out the coils, plugs and injectors (swapped cylinder 5's with cylinder 2; misfire didn't follow).

Did you clear all codes after last scan?
Did you perform a drive cycle long enough for new codes to be recorded?

[Bm3875]

Yeah, reset the codes each time. Drove for a bit and the P0305 came back within minutes. Good point of clarification, edited the OP.

[MIKYZZ4]

This won't be the first time a faulty gauge was suspect on this forum.

[Bm3875]

I did get a loaner from Autozone... Looks like I'll give another shop a try. Try another gauge.

[MIKYZZ4]

I would also compare #5spark plug(condition,color,tip gap,wear)against others for any differences that stand out.

[Bm3875]

Oh yeah, they ALL are pretty worn. ALL are black and have build up on the tips. The only thing that stood out between the six of them was that #3 came out with oil on the tip.

[Bm3875]

Alright, got a new gauge from a different shop. Looking better now. Prelim numbers from a cold test:

C1: 210
C2: 225
C3: 230
C4: 230
C5: 230
C6: 230

Going to put coils and plugs back in, get her warmed up and see how a warm test goes with the new gauge.

[MIKYZZ4]

Due to the condition of the plugs,
I would replace the set(https://www.fcpeuro.com/products/aud...PD_BwE#fitment)

I believe in preventive maintenance,
just because platinum,iridium,whatever are rated at 100k miles,
I change spark plugs on all my vehicles between 30k~50k miles(dependent on condition) or 5yrs,whichever comes first.
If one coil fails between 100k~200k miles, I replace the set,as the others can't be far behind.

[Bm3875]

Yeah, now after testing with a GOOD gauge, definitely plugs are going to be my first route.

For what it's worth, warm test numbers are:

C1: 210
C2: 210
C3: 200
C4: 200
C5: 200
C6: 210

I guess the only last question I have re: the compression test is that there's wasn't a noticeable spike in PSI from a cold to a warm test (it even dropped a bit). From what I've read, numbers should be higher on warm tests. Anything to be of concern there? At least there's no great difference from cylinder to cylinder either way. :-)

Thanks much for the help!

[MIKYZZ4]

You Have good #'s cold vs warm, should be no concern.
follow my recommendations on previous post (#12),
and you should be fine. Update on outcome.

[dworthy]

+1

Plugs can cause misfires, so be sure to inspect and replace them. You can run some ATF thru the oil, as this can clean some of the crap out of the motor, just google "ATF motor Flush". I do this on all my cars right before it is due an Inspection, or about every 30k miles and it keeps the motor nice and clean.

Check out the Wagons motor from 2 years ago when I did the valve cover gasket:

[Bm3875]

Wow, that is sexy clean! :-)))) That's one thing about this one - it's a dirty 'ol oil burner. Smells like burning oil, burns through so much. Wish I could clean all that up.

So an update on the misfire: Swapped out the plugs with new, misfire still came back (still good that I swapped out, they were terrible). Swapped out cylinder 5 with a new coil, all is good now. No more misfires.

Thanks for all the help!

[dworthy]

Good to hear.

Now on to your other problem: Oil Burning.

How much oil are you using? BMW says that it is acceptable to use about 1 quart every 1k miles, but I do find that a tad excessive. My wagon goes thru a quart about every 4k miles and is pretty stable. I had thought it was the CCV, but it was still in good working order. I am thinking about installing a catch can, but I change my oil about every 12k miles, or when it wants that 3rd quart.

As a side note, when I had the 5W-30 in the winter car, it too would drink about a quart every 2.5k-3k. I switched to the Mobil 1 0W-40 and now it goes about 3.5k-4k a quart. I am thinking about doing the same for the wagon and see if that will help on the oil burning as well.

[Bm3875]

Yeah, I'm burning about a quart very 500 miles or so. Seems REALLY excessive. No leaks, just stinky, burning oil smell and dirty exhaust.

I replaced the CCV when I had the intake removed when I swapped out the starter in December. Was hoping that would address the oil burning but no dice. The only thing I didn't address at the time was pulling the oil dipstick and cleaning/replacing. Kicking myself for that now. Thinking that might be the final 'clog' in the CCV cycle. :-((((((

[dworthy]

I upgraded my dipstick tube, and the old one wasn't very dirty.

So if your motor is rather dirty, than I would suspect that the tube would be dirty as well or completely clogged.

I think that a quick ATF flush might help as well, for freeing up dirty oil scrubber rings.

[MIKYZZ4]

Use this pro product:https://www.walmart.com/ip/Parts-Cle...-Carb/17491945

[MIKYZZ4]

Sorry,
to clarify, only to be used to soak, and unclog dipstick tube,
in this particular situation.