Rough Idle sometimes... (e32/m30)

How old are your rotor arm and distribuotr cap?

Maybe 3 weeks.

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this is a cheap fix that works probably 90% of the time. Get some "sea-foam" spray deep penetrating lubricant and some intake cleaner. Working one line at a time, take off the vacuum hoses that you can find, spray with the intake cleaner until it appears clean inside. Then repeat right at the intake, remove the hose, make sure the car is off, and thoroghly douche it out. Take seafoam and saturate the inside of the intake as well, careful to blast into any nooks and crannies. Replace intake hose. Take off vacuum line that feeds into the valve cover. Spray seafoam liberally into the head. Start car, (it will be rough for a min till all the intake cleaner is burned out). Then, once the car is running, remove the vacuum line that feeds into the intake, spray seafoam into this line, taking care not to stall the car, little bit at a time. I would advise you empty the can into the system, it will start to "smoke" out of the exhaust, fear not, this is the excess carbon and sludge in your motor. As soon as your can is empty, turn the car off, allow it to sit for about 10 minutes, no longer than 15. (the seafoam will be disolving deposits in the motor but you dont want to risk any damage by letting it sit too long.) Then fire it up and go for a joy ride, the car will be smoking like a bastard. Drive it at high RPMs (3500-5500) until all smoke is gone. (the high RPMs help to burn the deposits and remove all the crap). I do this about once every 6 months with the bimmers and Rovers to keep the motors in good shape, if this doenst fix the problem I would consider cleaning out your cold start valve(does that 3.5 have a CSV?) or stepper motor.(electical cleaner)

Thanks - will look for this sea-foam spray & give it a whirl.

Not sure if it has a cold-start valve; but do believe it has a stepper motor, as it used to "hunt" when started and they said the stepper motor might be having problems.... It hasn't done the "hunt" for a while and just recently started the "rough/miss" starts. The past 3 starts have been fine - no roughness.

I'm wondering if there's an electrical problem -- usually when it does this rough start (like it's missing) steering is also harder, like I'm low on power-assist. There's an electronic valve, if I'm not mistaken, to give the car variable assist. Could the electronics be screwy with the ignition & the power steering? 90% of the time it starts fine, that 10% is almost embarassing as the car puttter-spit-put-fitz-putter-pud-pud out of the driveway.

Thanks!

-josh

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I would not do the sea-foam deal except as a last resort on a very old and tired motor. The idea is it will loosen the carbon deposits and they will then be blown out the exhaust. This doesn't sound like such a spiffy idea to me.

motor has 160K on it -- burns no oil, doesnt' smoke, has even compression & plenty of power... if it's more for old tired motors, I'll pass.

Thanks

-josh

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Josh, I get similar symptoms myself and am coming around to the view that it's not solely temperature related but more aligned to how damp the engine is. I'm not totally convinced yet but this in the summer it was fine - this autumn and winter the problem started and has remained.

HTH

Interesting. I wonder if the pressure or mass airflow are getting moisture on them.

Now that I think about it -- the problem started (around) the time I cracked the boot from the airfilterbox to the MAF..... I keep the car garaged, but it is moist in there becuase of the rain (dripping off the car).

Maybe I'll try sparking up the heater.

thanks

-j

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I wouldnt say seafoam is for tired old motors by any means, granted, its not the most well known product yet, it is highly regarded by many auto groups, Land Rover, Mercedes AMG, Porsche and it was recommended to me by a mechanic here in SLC who has been doing work for the local chapter of the BMWCCA here for years. More to the point, I would say to use seafoam if the motor is in good condition only, a motor that has bad seals etc.. will see a definate degradation of performace as all the crap in the motor will be removed and if you motor is relying on sludge and build up for sealant it will perform more poorly. Seafoam will more restore the motor to like new spec, its a little more aggressive than other products like BG44k, but it does work alot better. Sorry if I sound like a commercial but I live and die by this stuff, and if your motor is pretty tight I would bet you will be amazed at the difference in power after a good "seafoaming". Ive run it in Series 1 Discoveries, 04 Freelanders, e30 M3s, e36 M3s and 318, 88 and 91 E32 735s, and a few e28 535s. Only one that ever gave me problems after the seafoaming was a 535 with 410,000 miles on the clock still running the orig. motor, it cleaned it a little too well and I ended up doing a motor swap as it was cheaper than a rebuild.

How long since you had new plug wires??

about 45 days now...

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