OK, I have been chasing down a fuel mileage problem and think I have it nailed (fuel filter was GARBAGE! Very sludgy and dark and I ONLY use 93 Mobil) but still need a tank or 2 more to be "for sure". I have replaced the plugs, fuel filter, air filter and PCV valve all with Nissan OEM and cleaned the throttle body by hand.

On to the problem. Now (might have always been there) when "getting on it" above 4K...like around 5.K I feel a slight hesitation and then it pulls again. So it kinda goes puuuuuuuuuuuul, brief second of hesitation which causes a slight jerk, puuuuuuuuuuuuuul.

Question: Is this how VIAS it SUPPOSED to act? Or could I be experiencing problems? I have a 5spd, 28K, 2001........

 

check the vacuum lines going into the VIAS solenoid control valve... make sure they are not kinked.

 

Is the transition supposed to be smooth as it feels like it takes a second to engage. I am going to look at lunch at the VIAS vacuum lines.

 

It's smooth on mine. I can only really tell b/c of my POP charger. With it, I can hear it engage, otherwise I couldn't tell. Hope this helps. Peace_

 

If it takes too long to engage, maybe the vacuum hose is kinked (or a small vacuum leak exists somewhere)... the normal action of the VIAS system should be instantaneous--the VIAS control solenoid switches the Power Valve to vacuum, vacuum pulls the valve quickly, which opens the VIAS valves immediately.

 

Which directly relates to what UMD_MaxSE said. Didnt get to check at lunch...will do it tonight. I hope its a kink and not a subtle "split" somewhere in the line where it might have flexed to much.

Anybody know a "good" way to test vacuum? I am assuming there is a meter (hopefully cheap). Also...anybody know what the "reading" should be during engagement. This could be a HUGE pain to test for.

Still hoping its a kink [crosses fingers]

 

easy check: have a friend rev up the car to over 5k rpm in neutral or park and see if the power rod (L-shaped rod) moves smoothly. The rod is located under the black box with the vaccuum lines going in on the driver side of the engine.

 

I did some snooping around the VIAS. Everything looked ok...but I took off the 'Y' tube and looked at it. It has a "hard" outer covering on like a 1.5-2 inch segment. I looked at it closer and it "possibly" rotated around a bit. This "may" have restricted airflow.

I made sure that it lined up correctly and reinstalled. Took it for a test drive and boy, it does act a LOT different.