Bypass Air control problems

wantafastsvx · #1 05-01-2008, 04:23 PM

I have swapped a new engine into the suby and am still battleing the same code for the bypass air control solenoid. It just threw this the other day when i went to move the car. Can anyone think of anything that would have stayed on the vehicle while swapping engines that would still be causing problems with the b.a.c.s.? I know of the very in depth write up as i have used it with the old engine and never found a cause. Tried multiple solenoids and cleaning to no avail. The only mods to the car are as follows:

ecutune stage 1: Possible problems here maybe?

exhaust that has been englarged from directly behind the o2's to 2.25in to the center cat and 2.5 from the cat back. It does have a slight leak where the shoddy exhaust shop didnt seal the weld all the way around. Would an exhaust leak cause this problem perhaps?

And a wrx 5spd.

all other mods are suspension and rims thats it.

I will be going through the in depth article on testing and cleaning which i still remember pretty well but have a fear that i will find the same problem. Which is everything checking out ok, and the armature moving freely and not sticking while returning to center.

I appreciate all the help.

Trevor · #2 05-01-2008, 08:03 PM

Have you checked that an electrical signal is available/present, and that the rotary solenoid is moving in response to this signal?

TomsSVX · #3 05-01-2008, 09:03 PM

I am having the same troubles in my Converted Legacy... Trouble is, I have full continuity to the solenoid w/ a good power supply... I have run through the service manuals time after time... Replaced the solenoid, but not the valve... Only thing off is low voltage on the open and close pin on the ECU... If I make any progress if I ever have time to get back at it, I will let you know

Tom

YourConfused · #4 05-01-2008, 09:19 PM

I wouldd assume it is either bad luck, or an issue with your vehicles wiring to be the culpret. It is possible to have gotten a different motor with x amount of miles on its components that just may have the same problem, but what are the oddds?
More likely wwould be an issue of your connectors, harness, ecu. Maybe someeone with wiring diagrams coold point you in the direction of how to test your carw wiring. I assuume you are experiencing the ssymptoms associated with the code you are getting.

Trevor · #5 05-01-2008, 09:42 PM

[U]

Quote:

Originally Posted by YourConfused

I wouldd assume it is either bad luck, or an issue with your vehicles wiring to be the culpret. It is possible to have gotten a different motor with x amount of miles on its components that just may have the same problem, but what are the oddds?
More likely wwould be an issue of your connectors, harness, ecu. Maybe someeone with wiring diagrams coold point you in the direction of how to test your carw wiring. I assuume you are experiencing the ssymptoms associated with the code you are getting.

Test the assembly on the bench if possible. The operation of the valve is quite straight forward and confirming that the required signal is present at the solenoid should not present a problem.

Refer last paragraph below:-

By-Pass Air Control Solenoid Valve
Cleaning, setting and Testing.

Description.

The By-Pass Air Control Solenoid Valve, or Idle Air Control Valve, allows the Engine Control Unit/Computer, to control an adjustable inlet of air in order to control idle speed when the throttles are shut. One obvious function is to increase the airflow when the air conditioning system imposes an extra load on the engine. The SVX has a second valve, The Bypass Air Control Valve, to supply extra air during cold starting.

The unit comprises a rotary solenoid valve, biased towards a central rest position by means of a permanent magnet. A double wound coil provides reversing open closed operation from a mean rest position, at which point the valve is half open. This arrangement provides two way variable control, dependent on the applied voltage.

Adjustment of the mean position is provide for by incorporating slotted screw holes in the housing, probably to allow the position to be set during manufacture in order to allow for anticipated tolerances.

Three electrical connections are involved. The centre pin on the connector is common to both windings and is energised positive. The remaining two connections provide for open and close operation of the valve via negative circuits.

Cleaning and Adjusting.

Cleaning is best achieved by removing the solenoid coil by undoing the two attachment screws, which pass through slotted holes so as to provide a degree of adjustment. Make a scratch mark, so that the original position can be retained after reassembly. Magnetic force will be apparent as the solenoid coil is separated from main body.

The armature which rotates in ball races, when moved by hand should rotate open closed, with virtually no resistance. The valve should be cleaned of foreign matter using a suitable solvent/lubricant so that is completely free to move.

After reassembly the valve should rest in a position, half open and half shut when set to the original mark. If there is a large discrepancy, this may indicate that the setting has been tampered with at some time and it should be reset.

Testing.

The solenoid resistance should measure 9 ohms, each side of the common connection, i.e. 18 ohms overall, a small tolerance being acceptable.

With positive to the common connection, 8 volts DC applied alternatively to the two remaining connections, should fully open and close the valve from rest. Return to the rest position should occur reliably without hesitation. In the event that 12 volts must be used, this will suffice for intermittent testing, but the extra torque available must be appreciated,

If a variable voltage source is available, continuous opening closing according to the applied voltage can be reproduced. However this more critical test and should not be a necessity.

JLHollowX13 · #6 05-01-2008, 10:19 PM

i have had the same problem with mine since i bought the car, i got a new-used valve and threw it in with no luck in it changing anything. my car runs good though, for awhile it idled like crap but after a cleaning it fixed it. im still trying to figure this out myself, so i will definitely find help on this thread when you figure out what is wrong.

so to anyone that has any advice: your advice will be taken thankfully by me also.

wantafastsvx · #7 05-02-2008, 10:27 AM

thanks for posting that trevor as that saves me the search and to answer your question. With the previous motor i did bench test the assembly with power to it and the armature did move. However i have not even tested anything on the present motor. I plan on pulling the valve and cleaning, ohm'ing it out and then applying power to see if the armature on the present solenoid works. I just figured i would throw out those possible issues with the vehicle to see if maybe they could be the culprit. I will test solenoid and get back to you all. Thanks again for the quick replies and hopefully its just luck of the draw and a dirty solenoid