M42 engine help!

[That_E30]

Just finished the mess under intake mod on my 1991 318i. Fired her up the first time. It idles like it wants to die for a few seconds then revs up like a raped ape. Vaccuum leak I take it?

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[kylelauffer]

Check the idle control valve and rubber hoses on right side of intake manifold. There no way of saying what you all changed. But ya vaccume line for sure

[bmwm42]

You have a huge leak im guessing you might have not seated the intake right if you removed it

[That_E30]

You have a huge leak im guessing you might have not seated the intake right if you removed it

I don't believe that's even possible that I didnt seat it right but ill definitely look :) thanks for the advice guys

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[Martin C.]

...leak sounds to me like...smoke test!

[e30austin]

Another vote for the ICV hose. Just went thru this on my parts car the other day.

[That_E30]

Another vote for the ICV hose. Just went thru this on my parts car the other day.

Just checked it. The icv has arrow pointing up, top hose connects to intake Mani, bottom hose connects to intake boot.


Hose connected from valve cover to bottom of throttle body.

Hose connected from fuel pressure valve to side of throttle body.

I don't see anything obvious. I guess ill just have tear it all apart again and make sure everything's connected.

Are there any sensors that can cause this? I hate when this kinda stuff happens. seems I followed instructions to the tee. That's why I went into the medical field and not mechanics lol

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[bmwm42]

Did you remove the lower intake...if you did I'm sure your vac leak is from not seating the injectors

[That_E30]

I did. And I did indeed have a hard time trying to push the injectors into the holes. I put alot of force onto the fuel rail and it seemed as though they got in the holes tight but maybe not?

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[bmwm42]

I'm going to say that's your issue....trust me man ive been thru these engines

[That_E30]

I'm going to say that's your issue....trust me man ive been thru these engines

How do you properly seat them?

[Matt-B]

In the past I have used a tiny bit of silicone grease, and use a rubber mallet to tap them in place

[kylelauffer]

vasiline works good

[SoundByte]

You should make sure your intake boot and IACV aren't secretly cracked before you go tearing your intake off again...

[That_E30]

So, took apart the entire intake system again. Cleaned the surfaces of where the gaskets go, put a little grease on the injectores and seated them well, put everything back on with caution. Fired up after a couple cranks, idles well. :) When i give gas, the rpms go up as they should but when they come down, they dip to 3-400 rpm before going back to 7-900. Havent let it warm up completely yet but hopefully that will go away. Next thing is to get the 8 year old gas out of the tank and try to flush out the rust. Dont have the funds to buy a new tank yet so will have to work with what i have. Thanks for the help guys :)