Problems after Mess Under Intake...

[jbgood51]

This past weekend I completed the "Mess under the intake" delete, but have ended up with worse idle and a "Check Engine" warning. Car is a 91 318i convertible with 142K miles. Very well maintained and ran perfectly, until the port on the top of the plastic coolant pipe snapped off. In an effort to make things simpler, I followed the many threads available here and on several other forums. I capped off the top port on a new coolant pipe, and the water outlet from the head. Deleted vacuum and water hoses under intake, leaving a vacuum line from the valve cover to the throttle body, and another from the ICV to the air inlet boot. The pictures in the following thread are exactly what I see (minus the clean engine):

http://www.m42club.com/forums/showthread.php?t=3621

I did leave the throttle body heater plate in place, simply because I did not have any cutting wheels for my dremel to shorten the studs: there are no water lines running to the heater plate. The plate's ports are not capped off, since it appeared to be a closed system into itself.

During the tear-down I cleaned out with intake manifolds and sprayed down the fuel injectors; I did not remove the injectors. I used two new gaskets for the lower and upper manifolds, along with a new throttle body gasket.

The vacuum hoses from valve cover and ICV do not appear to be collapsing and I've found no coolant leaks.

The problems are a rough coughing idle, an intermittent "Check Engine" light, and a high pitched whining sound from the top of the engine. The sound isn't quite a whistle, but is related to RPMs and very noticeable from inside the car. The idle smooths when revved high, and on a quick trip around the neighborhood the car ran decent. Pulling back into the driveway was loud and painful.

My concerns are that I:

• mucked up a fuel injector by just spraying it off externally
• seated something incorrectly and created a leak somewhere on one of the manifolds
• angered the Gods by working on the car on SuperBowl Sunday

Any suggestions on correcting the issues? Anything jump out that I may have forgotten? Thanks for the help!


John

[DesktopDave]

Try the stomp test.  It doesn't sound like you missed anything, maybe a bit of wiring went awry?

[Nelson_40]

When I ended up with a whistle/shriek from the top of the engine above the TB it turned out to be bad seating of the lower manifold to the head due to a screw up with the locating dowels.  This caused my idle to bounce between ~400 & 1100rpm.  My bet would be a bent/distorted locating dowel on either one of the intake manifolds.  Can you get a video of the sound?

[Geoff]

+1, sounds like a vacuum leak.  its pretty easy to get the intake manifold on there so it looks right, but still has a gap, either the aforementioned dowels, or a mis-alignment somewhere else could be the cause
                                                              Geoff

[victor.askew]

Your lower intake manifold may not be seated aginst the head. Use an inspection mirror and look along the interface between this manifold and the head to see if you have gasket showing, also look for carbon burns from leaking exh gases due to back firing taking place at the point of the leak along this manifold/ head interface. Good luck.