1997 328i Rough Idle on Cold Start - BMW Forum

Larry Horne · 01-22-2006, 09:21 AM

Ok, need a little help.

I have a 1997 328i with 145,000 miles. Just replaced both pre-cat O2 sensors due to code that has been on since 80,000.

I did a basic tune up on it recently, plugs, coil boots, T-Stat gasket, belts. I also replaced the secondary air pump valve due to code.

Now I get a rough idle on cold start, in garage or outside parking. It had been doing this prior to O2 sensor replacement so I doubt its linked to it.

No codes.

What's next?

Lar

nukeduster · 01-22-2006, 11:08 AM

Erradic idle speed or rough/alot of vibration?

What speed is it idling at when it is doing this? Idle could be set too low. Do a compression check on it, make sure all of the cylinders are within 5-10psi of each other.

Larry Horne · 01-22-2006, 09:31 PM

just rough, running rich actually......................not erratic........its certainly a fuel mixture type of issue. once temp gets off of cold its fine.

BMWJNKY · 01-22-2006, 10:24 PM

What plugs did you use?

Linds · 01-22-2006, 11:56 PM

Just say no to Autolite and Bosch +4.

tomctx · 01-23-2006, 07:27 AM

You say you replaced the secondary air pump valve. I wonder if the secondary air pump is not working correctly? A bad valve can cause collateral damage. And the air pump is set up to work for only a few minutes after the car is cranked.

Larry Horne · 01-23-2006, 08:36 AM

Plugs: Bought from local BMW Dealer, OEM items
Pump and Control Valve: Pump currently runs for approximately 2-3 minutes on inital start then cuts off.

I can disconnect the vacuum line to the control valve and see if any change on cold start. The only thing I am aware of wrong with the 2nd air system is that the pump bearings are making some noise but it is moving air.

Lar

BMWJNKY · 01-23-2006, 01:48 PM

Quote:

Originally Posted by Larry Horne

Plugs: Bought from local BMW Dealer, OEM items
Pump and Control Valve: Pump currently runs for approximately 2-3 minutes on inital start then cuts off.

I can disconnect the vacuum line to the control valve and see if any change on cold start. The only thing I am aware of wrong with the 2nd air system is that the pump bearings are making some noise but it is moving air.

Lar

The reason the air pump is making noise is because moisture got in there because of the bad valve. The pump will eventually fail in the near future.

Larry Horne · 01-23-2006, 09:11 PM

AJ's320i,

I agree. I have posted on the Classifeds a WTB for a new or junk yard pump...........I hate to pay $250 for new internet pump.............I've taken the pump apart and cannot get it separated enough to lub the bearings.

I'll replace it once it goes belly up but I've bench tested it and it is working ok, just noisy.

Lar

polaris448 · 01-24-2006, 09:42 PM

I have had rough idle problems due to two things. One being the due to extreme cold temps and two being that I was using 15w-40 when it was cold. The book and my local parts guy at the stealership said to switch to 10w-30 for the winter. After that, problem solved.

BMWJNKY · 01-24-2006, 09:47 PM

Your rough running could also be caused by a VANOS unit that is sticking. Before you do your next oil change try running a can of BG Quick Clean for engines. Add the can to your oil when the engine is at about 1/4 temp, then go drive arround town for about 20 min, stop and go driving is the best because it will make the VANOS unit work the most, then drain the oil and change the filter and refill with your standard 10-30 oil.

polaris448 · 01-24-2006, 10:02 PM

Quote:

Originally Posted by AJ's320i

Your rough running could also be caused by a VANOS unit that is sticking. Before you do your next oil change try running a can of BG Quick Clean for engines. Add the can to your oil when the engine is at about 1/4 temp, then go drive arround town for about 20 min, stop and go driving is the best because it will make the VANOS unit work the most, then drain the oil and change the filter and refill with your standard 10-30 oil.

are you referring to me? And i have the m44 so no VANOS for me.

Larry Horne · 01-24-2006, 10:30 PM

please help my ignorance. what is the vanos? i've been trying to figure this out for a while............how do i determine if my car is equiped? What is BG?

I use 15W40 so a change may be in order.

HELP!

polaris448 · 01-24-2006, 11:44 PM

from what i know it is an air intake system that uses the variable valve lift to regulate how much air is let into each cylinder rather than a throttle body. so these cars do not have throttle bodies. i think it is another way the bmw can make more hp by not having the turbulant air from the throttle body. fyi a throttle body is a round metal housing that has a metal flap hinged in the middle the reg. air as i mentioned earlier. does this sound about right guys?

tomctx · 01-25-2006, 12:09 AM

VANOS is a system that advances the intake cam at lower rpm's to give you more torque at that setting. After you pass a cetain rpm level, it retards the cam back for more high rpm power. If you have a 325 after 1992 or any 323 or 328, you have the VANOS system. If you look at the front of your engine, you will see a bump-out on the intake side. That houses the VANOS components. There is no variable valve lift, just changes the duration at certain rpm levels.

The rough idling could also be your ICV, Idle control valve. This valve allows air in at idle since your throttle body is closed. Try cleaning it and see if it helps. Not sure where in the intake system it's located, maybe someone else can help.