740il not running properly

[7BMW]

Hi, i'm new here but i've been referring to this forum for various helpful topics so I wanted to ask you guys your thoughts and get some help and feedback on my issue.

Ok, I own a BMW E38 740il of 1995. Recently, the car was vibrating as if one of the pistons weren't working properly.
Brought my car to the mechanic and had them check it up on the computer, but it showed there were no problems or errors.
They told me to put in the STP fuel injector cleaner.

The car hardly made 1 km after minutes of putting the cleaner in!

Managed to get the car back to the mechanic.

At this point, when the car is cold, it starts up, but not with all 8cyl...
When the car is warm, it takes a while before we can get it started up, but still, not all 8 cyl. are working!
After a few min, the car dies.

Now the computer shows there is an increased air intake.
I had them empty the tanks from the STP and cleaned everything before refilling it with 10liters of petrol.

Retried starting it, nothing changed.

The mechanics also changed all spark plugs, MAF, air filter, fuel filter, clean injectors, measured piston pressure, and the fuel pressure was measured.

Retried again, nothing changed.

Since the 4 cyl. on the left side of the block were clean and still run properly, they thought of inverting the oxygen sensor in the exhaust because 3 out of 4 cyl. on the right side of the block were somewhat dirty.
Still, nothing.

Spent my weekend trying to find and answer online before they tow it to the BMW shop tomorrow.

Can anyone give me some advice or thoughts on such?

Thanks.

[brettski]

Welcome to the Werkz.

Was there any work done on this car prior to this issues occuring?

When you start the car will it rev up at all? Can you smell unburnt fuel in the exhaust? Have the spark plug coil packs been changed? Have you confirmed the earth straps on the coil packs are properly connected?

[7BMW]

Thanks!

Was there any work done on this car prior to this issues occuring?
No. I'm the 2nd owner of this car since 1999. The previous owner didn't do any work as he was a wine maker, Zonin.

When you start the car will it rev up at all?
With difficulty, but yes.

Can you smell unburnt fuel in the exhaust?
No unburnt fuel.

Have the spark plug coil packs been changed?
Yes.

Have you confirmed the earth straps on the coil packs are properly connected?
Yes.

[7BMW]

Update

Got the car back from the BMW shop today after it being there for 2 days.
They got it back to the conditions it was in before the STP fluid/cleaner was put it. So it starts now but still has the light knocking/vibrating/soft whistling sound when idle or runs slowly.

Their computers showed there were no errors.
So they said the issue was with the exhaust and changed both catalytic converters.
I clearly told them I changed the spark plugs so they're new, yet, they changed them all anyway..

Again, in the end of it all, it still vibrates and has a soft whistling sound.

I'm afraid to use the car, it's now sitting in my garage.

Any thoughts or advice on what the problem is with the car?

[7BMW]

Also measured the coil pins of the crankshaft position sensor (500 ohms), and camshaft position sensor coil (1,000 ohms), so those are fine as well.

(Adding as much info as I can of all the tests and changes that have been done.)

[brettski]

Can you tell where the whislting noise is coming from? Does the volume or the pitch of the whistle vary at all when you rev the engine?

Is there any smoke on start up?

Is it using any engine oil?

[7BMW]

Can you tell where the whislting noise is coming from?
Seems to be exactly at the center of the middle block. I'm told it could be the crankcase vent valve considering it's coming from that location. But I read that the "check engine" light would be on if such was the problem..and it's not on/lit.


Does the volume or the pitch of the whistle vary at all when you rev the engine?
When I speed up, it disappears.

Is there any smoke on start up?
No.

Is it using any engine oil?
Yes.

[brettski]

If you start the engine and let the idle settle, then pull the engine oil dipstick does the idle drop and then recover and a slurping noise come from the dipstick tube? The idle should change if you place and remove your thumb over the dipstick tube. If this happens its likely to be the rear intake manifold cover (AKA OSV).

Pull the engine acoustic cover off and then check for intake manifold leaks around the throttle body. Also check the vacuum lines that cross the engine. Get a can of carby cleaning spray and a jet nozzle so that you can focus the spray, and work your way around the various suspect lines and manifold gaskets (with then engine running), if you get a change in idle at a particular point you may have found your suspect. Do this with the normal precautions, not on a hot engine, and don't smoke either (general health warning as well as a safety tip).