Mechanics

540I, ROUGH IDLE, NO ACCELERATION, 12

1994 BMW 540

Engine Mechanical problem
1994 BMW 540 V8 Two Wheel Drive Automatic 150000 miles

So the 540i has 150,000 miles on it. Has a rebuilt transmission (at 110,000), rebuilt engine at 65,000 for some recall on the M60's (previous owner), new cooling system.

So the problem is one day I turned it on and the engine was super rough and check engine light was on. Checked the codes and it gave me a
1222 Lambda Control 1, here what it says about it:


T" his code is stored when the DME detects excessive
deviations in the air-fuel mixture (too rich or too lean) for longer
than 10 seconds. Possible causes: Fuel tank ran empty,
Incorrect Fuel Pressure, Injector valve defective or coked,
Engine Temperature Sensor defective, Secondary air leak,
Fuel evaporation control system defective, Air Flow Meter
defective and/or the combustion is being disturbed by
mechanical failure (Spark plugs, compression,
intake/exhaust valves ect"

Problem went away after driving down the road about a mile, took it into the shop and they told me it was going to be $1300 fix and they had to replace my motor mounts because they were colapsed (smelled BS). Mabe so but I don't think the motor mounts have anything to do with my problem. Had them replace the spark plugs and thats it. Problem started again and will go away periodically.

SYMPTOMS: rough idle (gets better after you drive it for the day), pressing gas pedal in the morning yeilds little no acceleration until after you drive it for 15 min then it gets better, when I release the gas pedal and its not accelerating and I lift off it the car will " jump, " engine shakes pretty bad. You can see it move about half inch when its having the problem, exhaust pipe- you can feel the exhaust pop randomly with the engine shake, feels like a couple of the pistons are not firing when you idle, (then again I don't know what that would feel like)

Here is what the mechanic said:

" the codes we got could be set if 1 oil has not been changed enough and has fuel in it 2 you ran out of gas 3 the oxygen sensor on bank 2 is bad. Mechanic tested for any vacuum leaks that could effect mixture and found none. It is still possible to have a vacuum leak at the maniold when the engine is cold and first started. Check of spark plugs show they are worn and there is oil leaking from the valve covers. Replaced spark plugs.&Quot;

If you help me it would be great.

One more thing. When I park after driving it you can smell something that sort of smells like burnt plastic.
Avatar
Swineninety9
September 16, 2008.



" the codes we got could be set if 1 oil has not been changed enough and has fuel in it 2 you ran out of gas 3 the oxygen sensor on bank 2 is bad. Mechanic tested for any vacuum leaks that could effect mixture and found none. It is still possible to have a vacuum leak at the manifold when the engine is cold and first started. Check of spark plugs show they are worn and there is oil leaking from the valve covers. Replaced spark plugs.&Quot; What has been done to remedy the situation beyond changing the plugs? If oil is leaking from the valve covers and is filling the spark plug wells, then the possibility exists the coils are at risk and/or are faulty. If there is a faulty PCV plate and/or profile gasket, intake manifold gaskets then they need to be addressed. If the oxygen sensors are old and are lean biased they need to be replaced. If the mass air flow element is bad it will require replacement. Has a smooth running test been performed? The aroma is something I cant comment on from cyberspace, have you inspected for the cause? (Plastic bag stuck to the exhaust or?)

Dr. Hagerty
Sep 16, 2008.
Thanks for the reply!

After you and two other people on the bimmer forums sugested I unplugg the MAF and start the car I did and that fixed the problem. Plugged it back in and the problem returns. So I think thats it unless you have some other considerations.

One other question, how do I know its the sensor and not the cable? Is there a multi meter test I can run to figure it out?

One other thing. With the sensor unplugged the RPM needle will jump up from 500rpm to 1000-1500 rpm and then drop back down when in park sitting idle. Do you think that is just because I have the MAF unplugged?

Tiny
Swineninety9
Sep 17, 2008.
It is unlikely the wiring is the cause, you can however run continuity tests on the individual conductors and inspect the connectors. Unplugging the MAF will tend to throw the idle, do you have another MAF to try?

Dr. Hagerty
Sep 17, 2008.
Thanks again.

I figured it was just because the MAF was unplugged but then again some people on the forums were having issues with the RPM jumping and air intake leaks so I wanted to make sure.

I don't have another MAF to test but there is a garage that I can take it too that probably does.

Do you have any recommendations on manufactures for BMW MAF sensors?

Tiny
Swineninety9
Sep 17, 2008.
Call (619)444-2290 and talk to John or Sean. This is Autobahn dismantling in southern Ca.

Dr. Hagerty
Sep 18, 2008.