Should fuel vapor valve draw a steady vacuum????

[Robert K]

I've still got a slight jerking feeling at either light throttle cruise conditioners, or when the throttle gets closed such as coasting down on the highway. Both of these are high manifold vacuum conditions. I've replaced a couple of original vacuum hoses that had cracks but still have this problem. The other day, I disconnected the fuel vapor vacuum line at the cannister located by the power steering reservoir (on my 1991 535i). With the engine running and warm, I did not have a steady vacuum from the open line, but a on/off type vacuum, say like a single cylinder engine might produce. I thought this odd but didn't know if that was something that the little inline electrically operated valve was supposed to do. Does anyone know if that's the effect a properly operating valve has?

Grace and peace,

Robert K
1991 535i

[Bill R.]

that its going to the idle position... if this isn't working it will jerk some when coasting down... There's actually 3 settings on the tps for the m30... There's idle, and full throttle, then the other setting that the computer uses is the position that covers everything in between those 2... IF you suspect the tank ventilation valve is giving you problems then plug up the manifol hose and leave the tank unvented long enough to drive it and see if the problem is eliminated.

I've still got a slight jerking feeling at either light throttle cruise conditioners, or when the throttle gets closed such as coasting down on the highway. Both of these are high manifold vacuum conditions. I've replaced a couple of original vacuum hoses that had cracks but still have this problem. The other day, I disconnected the fuel vapor vacuum line at the cannister located by the power steering reservoir (on my 1991 535i). With the engine running and warm, I did not have a steady vacuum from the open line, but a on/off type vacuum, say like a single cylinder engine might produce. I thought this odd but didn't know if that was something that the little inline electrically operated valve was supposed to do. Does anyone know if that's the effect a properly operating valve has?

Grace and peace,

Robert K
1991 535i

[Robert K]

I actually ordered a new throttle position switch and plug wires from BMA yesterday. As I had mentioned before, I know for a fact that the WOT switch in the TPS is not working now. I'll make certain the idle switch is being tripped when the throttle goes back to idle when I install the new one. The plug wires are 13 years old, so I ordered a new set of those too. One thing's for certain, once I get this problem tracked down, my car should be running perfectly! And...it won't leak on my nice, clean floor either.

Grace and peace,

Robert K
1991 535i