Thread: Air by pass ( Stepper ) valve clean

I am working through the possible causes for the erratic idle on the Duel Fuel D1.

It does it on both LPG and Petrol.

We will get there

The first 2 things I am doing is lubing the air valve spindle and changing the ECU temp senso ( One at a time to see what makes a difference , if any .

It rarely does it when cold ( but it does sometimes) and seems to get worse the hotter it gets , say 0.5 hr out in traffic.

I did a search and have seen the discussion around it.

A simple question. Can it hurt to squirt some WD 40 or CRC or puff some graphite down into the shaft and around the spring?

I know it should be a little stiff because its motor driven.

Pete

Some will say otherwise but IMHO it will not help to spray stuff into a stepper.
I have pulled one apart and it has a screw on the plunger and the motor it self turns and drives the plunger in and out. Every time you turn off the ECU commands the stepper to fully retract, so it is always exercised.

The usual problem is sticking of the cone in the housing and a cotton bud with brake cleaner can be inserted and swished around the housing. The cone can also be cleaned. You could also look for leaks , such as the stepper housing being loose which is quite common. Also look at the hose to the fuel pressure regulator which comes off the housing to make sure it is not split. Of course other air leaks are possible such as a split in the T piece on the crankcase vent hose.
Regards Philip A