E46 2001, M43B19 - Diagnosing Vacuum leak and removing intake manifold

[Jawn46]

I bought this car only a month ago and it has some serious power loss when accelerating, especially 1st gear and second gear and i checked the fault codes because it has the check engine light on and got these fault codes. It also has a rough idle from time to time.
I was suspecting a vacuum leak and decided to remove the intake manifold, replace the gasket and check all vacuum hoses.



After removing the lower intake manifold, i noticed that only 1 knock sensor was actually connected and the other one was just laying around in the engine bay(the one closer to the front of the car was connected).

The air intake boot was cracking, could see both on the outside and inside (i am not sure if this is enough to cause such a power loss).

The engine wire harness seems to be in bad shape , i was wondering about replacing this but without replacing the whole wiring harness. (photo below)





So my questions:

While i have removed the intake manifold, what should i inspect and what should i be replacing before putting all back together?
Can i order just the engine wire harness, so i can replace it?
I will replace the intake manifold gasket(the one with the 4 rings), should i also replace the one at the other end where the oil separator is? (the 2 rings one, it actually looks good).

[MarcoZandrini]

What codes are you getting? Replace every vacuum hose you can get to. Also, you might want to replace the fuel filter.

Two websites you need to know about:
www.realoem.com
www.newtis.info

realoem gets you part numbers, rudimentary drawings and parts interchangeability.
newtis is BMW’s official technical information system. It’s free.
To either site, enter the last 7 characters of the car’s vehicle identification number. Hit enter and bookmark the page.

What are you using to scan the engine computer (DME in BMWspeak) for codes? I recommend the OBDFusion app for your smartphone or tablet. It comes in both iOS and Android flavors. Go to E46Fanatics and search for recent threads on OBDFusion in which jfoj has commented. He’s the guru. You’ll need a communications adapter that plugs into the obd2 port under the dash. jfoj’s post will tell you which one to buy.

[Jawn46]

What codes are you getting? Replace every vacuum hose you can get to. Also, you might want to replace the fuel filter.

Two websites you need to know about:
www.realoem.com
www.newtis.info

realoem gets you part numbers, rudimentary drawings and parts interchangeability.
newtis is BMW’s official technical information system. It’s free.
To either site, enter the last 7 characters of the car’s vehicle identification number. Hit enter and bookmark the page.

What are you using to scan the engine computer (DME in BMWspeak) for codes? I recommend the OBDFusion app for your smartphone or tablet. It comes in both iOS and Android flavors. Go to E46Fanatics and search for recent threads on OBDFusion in which jfoj has commented. He’s the guru. You’ll need a communications adapter that plugs into the obd2 port under the dash. jfoj’s post will tell you which one to buy.

Thank you for the links, i didnt know and the first one is really nice.

The codes i am getting are shown in the first picture(P0135 - P0170 - P0325 - P0130 - P0304), i used an OBD2 scanner and the Torque Pro app.

[MarcoZandrini]

The bank 1 (cylinders 1-3) pre-catalytic converter oxygen sensor is bad or it’s wiring is messed up. The P0304 code sez cylinder 4 is misfiring. How m any miles on the pre-cat sensors. They need to be changed every 100k miles with genuine Bosch sensors. The cylinder 4 misfire could be a bad coil. Mark the coils with their respective cylinder number. Then swap the coil in cylinder 4 with the coil in cylinder 5. Clear the codes and see what pops up.

[Uku]

Air intake boot is before or after MAF?
If after MAF, maybe that causes it.

[Jawn46]

@MarcoZandrini Its a 4 cylinder engine, i will try the tip with swapping the coils, i can just swap 3 and 4 right? Thanks

@Uku I think its after the MAF, im hoping the code will go away after replacing the boot

[vilkas88]

There are 2 coolant hoses/pipes under intake manifold, which should be changed now, since you opened it all.

P/N: 11537502525 Water pipe
P/N: 11531705210 Heater pipe

and your 2 knock sensor wires are usually attached to each pipe with cable ties.

[MarcoZandrini]

Yes, label the coils so there’s no mix up and then swap them. How many miles on the car and the pre-cat oxygen sensor?

[Jawn46]

Thank you for the part numbers

the knocksensors were not attached to anything

[Jawn46]

I bought the car with 315k kilometers on it here in Russia, i got it inspected before buying and there are somethings to be done. How long the oxygen sensor has been on it, i dont really know.

[vilkas88]

Given a high mileage - you should replace the knock sensor too. Part # 13627568422.

I suspect that your current knock sensor is dead. Probably it was causing misfire codes - thus prior owner unplugged them - to avoid or worsen the misfires. Your other rough idle issues need to be resolved by finding vacuum leaks and cleaning idle control valve.
Also, check if your fuel purge / breather valve is stuck open - it should be closed normally, but they wear out and become permanently open (part # 13901433603).

[Jawn46]

Thank you everyone.
I changed a lot of hoses, camshaft sensor (i broke it, didnt come off), knock sensor, rubber boot, intake manifold gaskets, ccv valve and hoses etc.

@vilkas88 i did replace the knock sensor and the fault code doesnt appear anymore.

So out of 5 fault codes i still have one showing and its the P1305 (Oxygen sensor bank 1 sensor 1), i just cannot locate it and i cannot find a diagram of it on the internet either.

Can somebody show me where i find it?

[harrier]

Here is a guide to “what to refresh” under the intake

https://www.e46fanatics.com/threads/...fresh.1267259/

[harrier]

In addition, you can repair a tatty harness with high-temp split wire loom.