M42 Guys: HELP!

[e30jake]

I finished getting the replacement engine in and hooking up all the wiring (correctly as far as I can tell.) It is kinda hard to tell in the video, but there is just vibration everywhere. It starts and idles at around 750 rpm, but is unbelievably rough. The whole car shakes. Has only died once or twice, and it was while I was messing with stuff on the engine. If I unplug the AFM, idle goes to around 3000ish rpm. If I unplug the TPS, idle goes up a tiny bit then goes back to what it has been doing. If i unplug the ICV, idle goes to around 1500-2000 rpm.

When I first start it up the check engine light is not on. If I let it idle for a bit without touching the gas it comes on. As soon as I poke the throttle though it goes back off again. It also comes on if I hold the throttle steady (at 2000 rpm FWIW) and goes off once I let off. Tried stomp test for like 10 minutes and couldn't get it to throw any codes.

I tried a different AFM from an e36, a different TPS and throttle body, different ICV, and different ECU. Started between each switch. None of them changed anything. I searched and found that mystery plug by the firewall can cause idle problems if it is plugged in, so I unplugged it. Didn't help. I'm at a loss. I spent 4 hours today trying to figure it out and I'm no closer than when I started. It does seem to rev fine. Any other suggestions?

[absolutdog]

If you don't get help here, cross post on m42club, though the helpful guys are on in the AM over there

[e30jake]

If you don't get help here, cross post on m42club, though the helpful guys are on in the AM over there

Thanks. I wasn't sure there was even that much activity there. I'll make sure to bump it in the morning though

[bmwman91]

In what sort of condition is the motor that you swapped in? Was it known to be running when you bought it?

Is it just running really rough, or does it make loud/bad/abnormal mechanical noises too? Could you have mixed up two spark plug wires or something (if you unplugged the coils for some reason)?

[Ian Bowers]

Are the two plugs under the intake mani (Coolant/intake air temp I believe) plugged in correctly? That can cause some bullshit stuff.

Also: Have you checked the timing on the engine?

[e30jake]

The background on the engine was I went and bought the full car with the engine not running. The PO didn't know the first thing about cars. He drove it to his parents house, stayed there overnight, and it wouldn't start the next morning. It sat long enough for the battery to die. When I got there, the intake boot was cracked to the point it was almost completely separated from the AFM, so I figured that was the problem. After looking over the car some more at home, I realized it had more rust than I thought, body wasn't great, interior sucked, so I pulled the engine and turned it into a parts car. I put the engine in this one just assuming it was fine internally. Everything rubber is new and I did the mess under the intake.

It doesn't seem to make any noises it shouldn't. I am 99% sure the spark plug wires are right, but I will double check in the morning. I'll also try switching the coolant and air temp plugs. They are the ones under the manifold toward the front of the car, correct? I have not checked the timing either. Noob question I know, but how do I check it and how do I adjust it? The only other car I've gotten this in depth into engine related stuff was my m10 318i which basically just involved turning the dizzy. I think I read somewhere to pull the valve cover and there should be timing marks?

The other thing I just thought of, was the PO of the car the engine is from had a mechanic look at it who replaced the fuel pump. This obviously didn't fix it, but if he thought it was fuel related could it be the injectors? I can't remember which engine I pulled the rail I'm using from, but would that even cause something like this?

[bmwman91]

Aaah...so you put a new intake boot on? Did you buy a new plug for the second hole in the bottom of it? There's the place that the ICV plugs in, and then another opening beyond that. New intake boots don't come with the little plastic plug that needs to be in there, allowing a good amount of un-metered air in. Check that.

[e30jake]

Aaah...so you put a new intake boot on? Did you buy a new plug for the second hole in the bottom of it? There's the place that the ICV plugs in, and then another opening beyond that. New intake boots don't come with the little plastic plug that needs to be in there, allowing a good amount of un-metered air in. Check that.

It is plugged. I wish it was that simple

[///digitalme]

did you check all the hoses? it seems like an air leak.. have you checked your fuel pump?

[e30jake]

did you check all the hoses? it seems like an air leak.. have you checked your fuel pump?

Hoses are good. Did mess under the intake and only reused 2 or 3 hoses, all of which had zero cracks anywhere. Haven't checked fuel pump. Besides the engine, everything in the car was good and driven daily by PO (r3v member) which seems like it pretty much narrows it down to something related to the engine. Also I have covered the hole in the airbox with my hand while it is running to suffocate it, and there doesn't seem to be air getting sucked in from anywhere else.

[///digitalme]

Maybe you have a bad motor with bent valves if everything checks out a ok

[e30jake]

Maybe you have a bad motor with bent valves if everything checks out a ok

I'm hoping that isn't the case, but it was one of the first things I thought of. The fact that the PO was driving it and then it just wouldn't start one day makes me think it's something else though. Hopefully tonight I will test the rest of this stuff, and start testing stuff with an ohmmeter.

[e30jake]

So i tried switching the temp plugs. Car would start and die immediately so I'm pretty sure I had it right the first time. Also did a compression test and got 200-205 across the board. Pulled all the spark plugs and they all looked normal. There was a change when I switched the temp plugs back to normal. Instead of staying steady at 750 rpm it would die down to 400 or 500 then try to correct itself back up to normal then die back down again so I'm thinking I bumped a wire or something. Will start checking current at the ecu plug tomorrow. I have a pinout of what wach one is, but I don't have what each one is supposed to read. Anyone have a link that can point me in the right direction?

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[vpilarrt]

What code is the "check engine" throwing?

[e30jake]

What code is the "check engine" throwing?

I tried the stomp test multiple times and couldn't get it to work. I don't have any kind of diagnostics reader either.