Running a little rough in lower rpm range. PLEASE HELP

[Widebody325]

As most of you knoq I just swapped a M50 into my e30. And in the lower rpms the motor dosent feel like it should. The exhaust is kinda poppy and almost subaru sounding. Tonight I went to the gas station (light was on) and filled it up. (First time I put gas into it since October) That definately made a difference and felt much smoother, but it still feels a little sluggish. I am also throwing a air intake temp code. If im not mistaken that sensor is under the manifold towards the firewall correct? Could that be causing my problem? I also want to mention my tachs not wired up yet, but when I get into the higher rpms the car sounds like it should, and it feels like its making good, smooth power. Could it be that the vanos is stuck on? Any help is greatly appreciated.

[PeaveyBassist]

Car at work today... miss under load, under 2k rpm. Coil(s) going bad. Changed to known good used coils and problem is gone. Dunno bout the air temp code though.

Will

[Jason89i]

I am also throwing a air intake temp code. If im not mistaken that sensor is under the manifold towards the firewall correct? Could that be causing my problem?.

yes, the air intake temp is on the underside of the manifold (80% of the time). does your car lack throttle response in low rpm's? does have a slight hesitation at low rpms with a slight squeeze of the throttle??

i have seen a couple m50 engines that do not run correctly due to stretched wires.....one of mine had the exact same problem. no grounding on tps and iat sensor.

the intake air temp (iat) sensor and throttle position sensor (tps) share a common ground. pull the iat or tps and check for grounding. any good wiring diagram (or the bentley) will tell you which pins in the connectors. if there is no grounding continuity, add a ground.

jason

[Widebody325]

Also, what line goes inthe the bottom of the throttle body?

[SchnellerVert]

Sounds like a possible bad coil. Quick check also on the HFM, disconnect and see if it will rev smoothly. It won't snap back to idle and will hunt but This has been known to cause issues. HFM gets dirty or broken cause limp mode to engage.

[Jason89i]

Also, what line goes inthe the bottom of the throttle body?

two water lines and one vacuume line. do you have the vac line open? if so, that would be another reason for rough idle. jason

[Widebody325]

i think I may have that disconnected. Where does that vac line go to from the throttle body?

[asubimmer]

what year is your car?

[1990m3]

the vacuum line goes to the fuel evaporator, which then goes to the charcaol canister. If you bypass the charcoal canister then you should just get a vacuum cap at Napa for the vacuum port on the throttle body. The vacuum port is the one on the bottom side of the TB closest to the firewall.

Dave