bmw e46 bent conrod

[e46fanatic]

Hey,

My Bmw 323ci is sick! I recently drove through a considerably large flood with the result of a suspected bent conrod. The car is mis-firing on valve 6 after 3 minutes when i start it. Im suspecting the ecu is isolating the valve and plug after 3 minutes. Has anyone here encountered this problem before? im currently undecided as to whether i replace the engine or just fix my own! whatever is most price effective is my preferance!!

Help!! :-/

[phelix]

It's worth checking the ECU codes to see what it thinks. Then swap the number six plug and coil with a different cylinder and see what happens. Or do a compression check. I would have thought a bent rod would make for a noisy engine.

[e46fanatic]

I have done a compression test, cylinder six is only at 100. I put a new set of coils in and new plugs but no result! It's not really noisy just vibrates alot. But only after 3 minutes. Otherwise it runs perfect which I find strange. I think a bent conrod is looking more and more likely!!! Ahh

[sniff diesel]

May I ask why you drove through the flood?

[e46fanatic]

It was very decieving, and very dark!

[Dave Dax builder]

The ECU cannot isolate a valve as it is a permanently connected mechanical part.
HTH.

[john_p]

e46fanatic said:

I have done a compression test, cylinder six is only at 100. I put a new set of coils in and new plugs but no result! It's not really noisy just vibrates alot. But only after 3 minutes. Otherwise it runs perfect which I find strange. I think a bent conrod is looking more and more likely!!! Ahh

Surely if it had a bent conrod it would vibrate like hell from the start? Is the three minutes an absolute value (after starting, hot or cold), or do you mean once the engine has finished warming up ?

Edited by john_p on Saturday 19th December 11:00

[e46fanatic]

It's not exactly 3 minutes everytime but in that time range. It seems to me like it takes the ecu the 3 minutes to register the fault and then it cuts of the cylinder. If only it was an older car with points, no ecu to mess things up!! Haha
the oddest thing is before the ecu kicks in it runs just fine!!!

[phelix]

I saw this on a car with a bad coil - the ECU detects the misfire and shuts off fuel to the cylinder to avoid killing the catalyst. All very clever stuff - don't knock it.

What was compression on the other cylinders? Any oil in the coolant and/or coolant loss?

[e46fanatic]

the compression on the other cylinders was nearly 200 ! Quite a differance!! ive put a full set of coils on but to no effect!! Im now beginning to price up replacement engines, its not looking good! I think the moral of the story is Water+Engines=Disaster!!

[john_p]

Have you had the codes read? I still suspect water has got in somewhere between the ECU and the coil packs or perhaps one of the sensors and is causing strange behaviour. The low compression may not be related?

[e46fanatic]

I've had it on the diagnostic machine. It reads a fault on valve 6 and a few other things like camshaft sensor and oxegen sensor. But the fact that the compression is low and valve 1 and 6 are an eight of an inch out suggests to me the conrod is bent. I'm hoping I'm wrong tho!!

[Mroad]

Unfortunately, from my limited experience, it does sound like a bent rod or valve issue due to water intake and the compression diagnosis.
People think a bent rod will sound like the god of thunder banging on your bonnet lid but in my experience (not a BMW though) all I got was what sounded like a really bad tappet rattle and loss of power (that's all honest). The fact I hadn't even driven through any water was even more puzzling when the final diagnosis strip down came.

Just thinking off the top of my head to help diagnose a bent rod with out a strip down you might be able to do the following (depending on plug hole layout):
Whip the plugs out and stick a stiff rod down the plug hole to rest on top of the piston ( e.g. a wooden dowl only slightly smaller than plug hole). Turn the engine over by hand and note the maximum and minimum heights the rod travels to. Compare the heights with the other cylinders, the cylinder with the bent rod obvious won't travel so far up the bore. It might not be much difference (5 to 10mm) but obviously any difference is wrong.

Hope this helps and hope everything works out OK.

[e46fanatic]

I tried marking the pistons and cylinder 1 and cylinder 6 are 1/8 of an inch out! Not Good!!! Thanks for your advice MROAD!!

[rsstman]

harsh news, blame it on bmw`s myself.