Hi,

Car: E61, 2006, 535D. 130,000 miles.

I got my water pump, both thermostats and belts changed at an indi garage recently, water pump was becoming very noisy and at least one of the thermostats had failed.

Since the work was done, my eml light has come on and there are engine start and power delivery issues if the maf is plugged in.

Cold engine (MAF plugged in);

Severe starting issues, engine will start for 2-4 seconds and then die. it will eventually start after multiple attempts (10+). Once started, it will idle very rough for 1-2 minutes, rev counter is very low and there is zero response from throttle press. After this short period , throttle response goes back to normal, If I restart the engine, it will start first time but has severe power delivery issues, see below. If I don’t restart the engine after the rough idle, power delivery is normal.

Hot engine, or engine restarted after rough start. (MAF plugged in);

Car starts first time but very little response from throttle press, moving off is painfully slow. Delayed response to throttle press with little power when it does start to respond, then sudden surge of power and then back to previous mode...

Maf unplugged (Hot or cold engine).

Car starts and drives normally, both turbos kick in on power demand, pickup is smooth with no sudden power surges.

I have replaced the maf, first unit was a Bosch from eBay which I returned thinking it was faulty or counterfeit, current maf is Hella branded from Amazon but still the same symptoms. EGR was checked and cleaned but not much in there anyway.

Only 1 relevant error code is MAF fault, no error codes for crankshaft or camshaft sensors, I'm using Ista-d for diagnostics.

Some of the symptoms (hard to start, rough idle) point to crankshaft sensor but the car does not stall and no related fault codes. I never have problems starting the car when the engine is hot but then car has severe loss of power, delayed response to throttle press.
Is there any way to test the MAF, camshaft and crankshaft sensors without buying replacements first? Anything else around the water pump / belt area that could get disturbed to cause these symptoms?

I have been driving the car with maf disconnected and except for the Engine Management Light and high emissions warning, not had any issues starting the car or felt any hesitance in power delivery.

Any thoughts on what could be causing these issues?

Thanks.