2000 540iT very rough idle

[rapence]

The M62TU engine in my 2000 540iT has a very rough idle, with engine shaking and check engine light blinking. The engine smooths out above 1000 rpms, stops shaking and the check engine light goes out. Other than the idle problem the engine seems to runs well and has good power when accelerating and the check engine light mostly stays off. OBD code reader shows misfire codes on cylinders 1,2,3,4. I've used the spray test to check for vacuum leaks on all vacuum hoses, intake manifold, and PCV/CVV and there is no changes in the idle. Cleaning the MAF shows no improvement. Unplugging the MAF stalls the engine. Unplugging the electronic idle control (PN# 11741742711) results in no change in the idle. I unplugged the hoses from the PCV/CVV at the rear of the intake manifold and there was a slight drop in rpms and there was a noticeable vacuum present. I checked the sparkplug holes for oil contamination and there was no oil present. The sparkplug electrodes from cylinders 1,2,3,4 were black with carbon while the sparkplug electrodes from cylinders 5,6,7,8 were a tan color. I replaced plugs (NGKs) in cylinders 1,2,3,4 but there was no improvement. Are cylinders 1,2,3,4 are running too rich? The car presently has 212k miles. New timing chain guides, tensioner, PCV, OSV, and profile manifold gaskets were installed at about 185K miles. Also both cats on the exhaust from bank A (1,2,3,4) have been deleted. Any advice would be much appreciated!
Richard

[scottieducati]

Did you try a light clean of your TB? The butterfly could be sticky and not allowing correct air intake.


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[mateo8]

The M62TU engine in my 2000 540iT has a very rough idle, with engine shaking and check engine light blinking. The engine smooths out above 1000 rpms, stops shaking and the check engine light goes out. Other than the idle problem the engine seems to runs well and has good power when accelerating and the check engine light mostly stays off. OBD code reader shows misfire codes on cylinders 1,2,3,4. I've used the spray test to check for vacuum leaks on all vacuum hoses, intake manifold, and PCV/CVV and there is no changes in the idle. Cleaning the MAF shows no improvement. Unplugging the MAF stalls the engine. Unplugging the electronic idle control (PN# 11741742711) results in no change in the idle. I unplugged the hoses from the PCV/CVV at the rear of the intake manifold and there was a slight drop in rpms and there was a noticeable vacuum present. I checked the sparkplug holes for oil contamination and there was no oil present. The sparkplug electrodes from cylinders 1,2,3,4 were black with carbon while the sparkplug electrodes from cylinders 5,6,7,8 were a tan color. I replaced plugs (NGKs) in cylinders 1,2,3,4 but there was no improvement. Are cylinders 1,2,3,4 are running too rich? The car presently has 212k miles. New timing chain guides, tensioner, PCV, OSV, and profile manifold gaskets were installed at about 185K miles. Also both cats on the exhaust from bank A (1,2,3,4) have been deleted. Any advice would be much appreciated!
Richard

When the timing chain guides job was done were cam chain guides or tensioners replaced? I would start with a leak down test to determine if everything is good with the head on bank 1-4

[rapence]

When the timing chain guides job was done were cam chain guides or tensioners replaced? I would start with a leak down test to determine if everything is good with the head on bank 1-4

The cam chains, guides and tensioners were replaced at 185k. I may try the leak down test. Thanks!

- - - Updated - - -

I'll clean the TB with some carb cleaner and see if that helps. Thanks!

[jclausen]

What are the fault codes

[JimLev]

FYI, that part # you call the idle control is the secondary air injection which runs for 2 min or less when you start up a cold engine to help burn off the rich mixture and warm up the CATs quicker.
It has nothing to do with idle, the DME and throttle body control the idle.
A blinking CEL isn't good.
You removed both CAT's on Bank 1, you did leave the bank 1 O2 sensor closest to the engine connected, right? That controls the fuel mixture for bank 1.