So i was having an odd boost problem, and after doing a few searches i narrowed the possibilities down to the double throttle control solenoid, turbo control solenoid, or the turbo control actuator. I decided to check the solenoids in the rack first. So I finally got the rack out and tested all 8 solenoids according to dgeesamans writeup here. I did the cold test first and havent tested any of them hot, but i got some strange results. I'll list them here, with the solenoids labeled as they are in this diagram. Also i haven't gotten to test them with a multimeter yet.

• G. Double Throttle Control: Passed the "basic leak test", but when i tried to connect it to the battery to do the energized leak test, the plunger did not move at all. nothing happend, i suppose the coil didn't work.
• F. Charge Control: Passed the basic leak test, but when energized it leaked under pressure and vacuum. The coil did work though.
• E. Turbo Control:Passed the basic leak test, however the plunger did not move when connected to power for this solenoid either. Dead coil?
• D. EGR: Passes basic leak test for vacuum, fails for pressure; Holds 12 psi energized and releases to 10 psi when disconnected from power; Slowly leaks vacuum when energized.
• C. Switching: Passes basic leak test; Holds 15 psi energized and releases to 10 psi when disconnected from power; holds 25 vacuum energized and stays at 25 vacuum when disconnected from power.
• B. Releif 1: Passes basic leak test; leaks pressure and vacuum when energized.
• A. Pressure Regulator Control: This solenoid was interesting to me when i found it because it had no vacuum lines running to it. but i still tested it, and it doesn't pass any of the tests, but the coil works.
• H. Charge Releif: Passes basic leak test; Holds 12 psi energized and releases to 10 psi when disconnected from power; Holds 25 vacuum energized and continues to hold 25 when disconnected from power.

The problem that I was having didn't even seem like it would be that severe. Intermittently, normally after a nice 2nd gear pull, i would only get about 5-7 psi throughout all the next gear followed by a strange loud noise that has been referred to on the forums as an owl "hoo" when shifting. Sometimes it would stay for a while and do it no matter what gear i was in for a little bit, but it would always go away for a little while (5 minutes of driving or so) before it came back.

So here is what i'm wondering, since apparently the solenoids in our cars are so crucial to them performing properly. How could only 2 out of 8 in my car be working properly when energized and me not have noticed anything else wrong sooner? i mean that seems like a lot. But anyway, I guess i'm going to have to replace 6 of them

Other questions:
Is it ok that the two solenoids that do work hold the vacuum at 25 even when not energized? it says in davids write up that it should all vent out the dump port when not energized.

Same question about those two solenoids with pressure, is it ok that they hold 10 psi even when not energized?

The pressure regulator control solenoid. I've read that this is commonly deleted. However i would like to check and make sure it was done right, does anyone know what changes (vacuum line wise) are needed to be made so everything could be taken off the solenoid but the electric clip?

And lastly, I ordered those Viton check valves daleclark has for sale. I was wondering if it is ok to change out the purge control check valve with one of these. Since it's the only one that's metal, maybe theres something special about it.

Thanks a lot for any advice you guys have to offer me.

-TJ

 

What power source are you using to energize the solenoids? Make sure you're getting a solid 12v to the solenoid. I've used fresh 9v batteries before and they usually work. Perhaps the best is an auto battery charger set to low current - but be careful you don't short it.

If the plunger doesn't unstick after tapping it on the table pitch it.

You can leave the metal check valve in on the purge control system. The viton check valves are more important where they feed the pressure tank and vacuum tank.

Regarding the pressure release test, the number on the Mityvac gauge will only drop a few psi. It's the number of the big gauge that you need to watch. If you just have an empty container instead of an extra gauge, go by the sound that the solenoid makes, you want to hear that big whoosh.

Not all of these solenoids affect boost, and most of them operate only in vacuum, which is why you may not notice major driveability symptoms. And if your tests aren't perfectly done it will show bad results. Be thorough and take your time.

Dave

 

I was using a fresh 9v battery for the power source. But i dont have an old connector or anything so i was just using speaker wire. I also dont have a boost gauge when testing them energized, i just block off that line with a bolt.

i'm going to re-test them one more time tomorrow morning before i call ray and order what I need. Thanks dave.

-TJ

 

Only the turbo control and charge control operate under pressure. The rest are vacuum. Follow the path from the manifold to each solenoid, you'll see most of them have a check valve that permits vacuum only.

dave

 

i too have been suffering from the "owl under the hood" problem.
basically, if i start in, lets say second gear, wot at 3k rpm, i will pull 10lbs, then transition through 8, and back to 10. but if i start at 4k and above, i might get 4lbs of boost if im lucky; as soon as i let off the throttle, i hear the owl (letting me know i fail)
a pull in a higher gear (4th, for example) will pull 10 lbs, then drop off at some point to 3 or less lbs, and ill hear the owl as soon as im off throttle.
i have ordered a mittyvac, but havent gotten it yet, and im trying to figure out what to test first, hoping it is something simple.

 

Yep. I hate that damn owl noise. It still happens to me sometimes.

I ended up replacing 5 of the solenoids with new ones in the rack. It didnt fix it but it did make it a little better somehow.

After all this time a research I'm almost positive its the TCA, but i havent gotten around to checking it yet. There is also a chance it could be the CCA. Those might be good things for you to check before you go ripping into the rats nest like i did. I donno if youve heard of the KOKO test yet, but thats a good basic test for those. Anyway, goodluck. Dont forget to post if you figure out what was causing your problem .

-TJ

 

I believe the owl noise is caused from the lever on the TCA not being connected to the flapper panel thing it is supposed to move. at least that is what it was for me, mine wasnt even on the post. Now the noise has stopped completely, however i do still have a boost problem.

 

The turbo control solenoid "E" (pressure side) is prone to stick and prevent the release of the TCA & valve. The result will be the moo sound and low boost. The real problem seems to be that the solenoid is designed for a vacuum application and is being used in a pressure application. There is not quite enough spring pressure to overcome boost line pressure and vent properly when the its de-energized. It will eventually release when enough line pressure bleeds off; in the mean time, it sucks.