[V6-12v] Hesitation

[Tom Christiansen]

James,

>I cleaned the MAF sensor very carefully with some isopropyl alcohol (I had 
>some left over from the days when I had cassette deck heads to clean!) and 
>a very fine, soft inter-dental brush (even a q-tip was too large and heavy 
>handed for those very delicate wires.

Maybe I'll try that.

>Yeah, the fuel pump was replaced a year ago, with no change in this 
>particular problem. However, I never thought of the relay. I kind of 
>assumed that the relay was closed continuously as soon as the ignition is 
>switched on, but it kind of makes sense that if the contacts are dirty you 
>could get a voltage drop. I guess the easiest way would be to replace it 
>and see if there's a difference.

Sometimes when the contacts arc, you get a carbon buildup on the contact 
points. The points also wear over time.

>I'm familiar with the second valve you mention (the Intake Manifold 
>Changeover Valve - which swaps between the 'long' and 'short' air intake 
>routes above 4000 rpm to even out the torque curve) and have checked the 
>function of that valve visually (you can clearly see it operate when you 
>rev the car past 4000). However, I was not aware of the smaller valve 
>which opens the bigger one. Whereabouts is that, exactly? Or are we 
>talking about the same valve?

We're talking about the same one. There are two butterflies in the throttle 
body. One is directly linked to the throttle cable, the other is controlled 
by a vacuum slave cylinder/rubber thing. If the second butterfly opens as 
rpm is increased above 4k, you're fine in that regard.

>I had considered a sticky throttle valve, but I think the valve is 
>directly connected to the throttle cable (is that correct?) so if that 
>were true, I should feel the throttle peddle jam, which it doesn't...

Correct.

Tom