[V6-12v] Q: 3700 - 3800 RPM Check-engine light

[Jamescarstuff at aol.com]

Yeah, the Intake Manifold Changeover Valve kicks in at those kinds of revs. 
It just changes over from the long intake manifold path to the short one (or 
vice versa) to even out the power delivery over the rev band. There are two 
things with that, well, three. Fortunately it's really easy to check whether it's 
working. Remove the plastic noise insulation on top of the engine, start the 
engine and get it up to temp. Now get someone else to sit in the car and 
operate the throttle while   you watch the little linkage that operates the valve 
(it's a complex looking little affair that sits above the throttle body). If 
it's working correctly, as the engine gets to around 4000 rpm, or above, it 
should clearly move, operating the valve. If it doesn't, there's a problem 
somewhere. You either have a vaccuum leak, or the solenoid valve that operates the 
vaccuum unit (which is over on the other side of the engine bay) has had it, or 
the valve is quite simply sticking. If it's stuck closed, you'll lose power 
above 4000 rpm, if it's stuck open you'll lose torque up to 4000 rpm.

Good luck!
James

In a message dated 2/8/04 5:49:24 pm, tomchr at ee.washington.edu writes:


> At 09:15 AM 8/2/2004, The CyberPoet wrote:
> >I haven't popped by my mechanic's to pull the computer codes yet
> 
> Why don't you just pull them yourself?
> 
> >  but swapped some vacuum hoses last week and now I'm getting a check
> > engine light specifically somewhere between 3700 and 3800 RPM, irrelevant
> > of gear or other circumstances (engine cold, engine hot, after a mile or
> > after 20 miles of driving, etc). Anyone have a clue?
> 
> Maybe the vacuum operated servo gizmo for the second butterfly valve? Did
> you remember to plug it in?
> 
> Tom