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[magik123]

Buddy of mine left his car with me (98 BMW 540I).  He has had a severe random cylinder misfire at start-up that cleans up at operating temp, Seems low on power tho and will start missfiring at cruising speeds if you dont shift into neutral.  Scanned it got Cam Pos. Sensor, IAC, and then codes for all 8 cyl missfire.  Well I replaced the CPS pulled the battery to reset codes, took about 2 days for the light to come back CPS code is gone now just IAC, and missfire codes, so my question would be will the IAC cause this tugboat to missfire like crazy...?  He said he cleaned out the IAC but i think he thought the MAF was the IAC, so maybe ill try that first, shit is $400 for this thing which i aint gonna buy for him lol.

Cliffs
98 BMW 540I -- Cam Pos Sensor, IAC, and all 8 cyl missfire codes set
replaced CPS, still missfiring
does the IAC cause some crazy missfire issue on these things???

[HiProfile]

My guess is somehow the cam is off a tooth, but I presume it's chain driven. Reminds me of k-series with failed chain tensioners, tensioner fails, chain slaps around, cam sensors go crazy - but you only get cam sensor codes. If the cam is off, it could be causing low idle vacuum and think the IAC is stuck open.

[random-strike]

ive had several cars run really bad, even misfire with a messed up iac, try and clean it out if possible

[slappynuts]

Oil on the ends of the coil packs by the spark plug. Eventually this will kill the coil packs as well. You need to put in new valve cover gaskets if they are leaking.

[rawr]

lose timing chain or failing tensioner, bad ground for ignition system, faling packs, something in the timing system moved, underware gnomes

[highroller54]

underware gnomes

bingo!

[accordepicenter]

fuel filter or pump? Im betting its a fuel issue

[BoostedSchemes]

Unplug battery + MAF, wait 10 minutes, plug in battery and see how it runs without the MAF. If it runs OK (no missfire) then you know its the MAF. This is second most likely after the earlier suggestion that the plugs are sitting in a pool of oil.