Guackman

I just wanted to chime in with my 2 cents.

I recently bough a 1985 GSL-SE with 228K kilometers on it.

I seem to have the same problem you guys have. Hunting idle from 1500 to 2000 sometimes. Usually after cruising on the highway for a while.

At first I gave the secondary throttle valve lever a turn counter clockwise to see if the valves were sticking. It seemed to fix it that time. It started doing it again though and now turning the throttle lever doesn't fix it.

My second solution seemed to be removing the vaccum line from the vent solenoid valve and blocking the whole on the valve with my finger. I have to try this again to see if it really fixes the problem.

I found these 2 fixes in a .pdf file of a Mitchell manual. I think on http://www.iluvmyrx7.com/

It says that if you remove the vacuum line from the vent solenoid valve and plug the valve with your finger and this solves the problem, to replace the vacuum switch valve (part # N304 13 240) which includes the vent solenoid valve.

Let me know if any of you try this and it solves your problem.

BTW, what does the vent solenoid valve do? Could I not just unplug the tube from it and plug the valve with a cap? Voila no more problem.

Thanks.

Greg

FJ

If yours is simply bouncing at idle after driving on the highway, and not sounding odd while cruising at a steady speed as the others were, I would start by checking the basics if you have not already. Such as: have you adjusted the TPS (with a hot engine), cleaned and lubricated the throttle linkage, checked for vacuum leaks, sprayed carb cleaner around the BAC gasket to check for leaks, and cleaned around the throttle plates? The fact that it used to get better when you opened the secondaries suggests the linkage may be sticking, but of course that may have just have compensated for the actual problem. When it happens, try what I've mentioned to "gump" below in this thread, it may give you a clue...

The link Zulu provided is good, if you have not already seen it.

"BTW, what does the vent solenoid valve do? Could I not just unplug the tube from it and plug the valve with a cap? Voila no more problem. "

No more problem to an extent, but the BAC controls the idle speed, depending upon the load.(Headlights, amplifiers, fog lights, heater fan, A/C, etc.) The Vent and Vacuum solenoids control the BAC together. As their name implies, one applies vacuum to the BAC diaphragm and the other vents to atmosphere. Push, pull. Together they compensate for loads on the engine at idle. I've attached a scan of the diagram of the BAC and it's V&V solenoids for clarity. Disconnecting one or the other of the V&V vacuum lines and blocking it would simply disable the BAC, not solve the problem; same effect as unplugging both lines, or disconnecting the V&V connector, or blocking the air supply hose as gump has done.
The V&V solenoids are going to be hard to check, as their operation may vary with heat. But as a basic check I measured mine and both were 36 ohms +/- one ohm when cold. I know they are relatively old, but I haven't heard they are a problem. You have replaced the vacuum lines, haven't you?

Here's the BAC diagram:


I had downloaded the PDF you mentioned but didn't look at all of the pages: do you recall the page number where the BAC (vent solenoid) check was mentioned?

Good luck with the idle.



gump Did you put the hose back to the BAC and try what I suggested earlier? That is:
"Two things:
-I also would have checked the voltages when it was idling normally. If they are the similar to when it acts up, it would point to the BAC itself.

-Did you try unplugging the V&V connector while it was idling badly? If not, might be worth the time to try it. If the idle returns to normal it would point to a bad signal from the ECU. "

It may not prove anything but I'm curious, and others (billions upon billions) are waiting for your solution...(well, O.K., maybe just thousands).

Guackman

Thanks for the input. I'll have to spend an afternoon testing and checking and cleaning a few things to make sure everything is working properly.

I suspect something might be a little gummed up in the intake manifold, i.e. the throttle plates. The reason I say this is I noticed that I had the pressure line to my auxiliary ports (5th and 6th) disconnected, so the ports were not opening up at 3800 RPM. I remove the actuator valve and tried turning them by hand. They were very hard to turn and I had to work them back and forth to free them up. I think because they haven;t been used in a while, they were gummed up in some way. I finally have them all the way open and have them wired open. My idle seems fine, low end power hasn;t been affected in any noticeable way and the top end is must better. I notice more power about 4000 RPM now with them open.

As soon as I get some new gaskets for everything, I'll remove the whole intake manifold and make sure everything is clean, lubed and working properly. Should help a lot.

BTW, the page in the full Mitchell manual in the .pdf document is 240. It is tech bulletin 008/84

Thanks again.

Greg Bowie

FJ

You're welcome.

"I suspect something might be a little gummed up in the intake manifold, i.e. the throttle plates. The reason I say this is I noticed that I had the pressure line to my auxiliary ports (5th and 6th) disconnected, so the ports were not opening up at 3800 RPM."
It might be a good idea to start your own thread (don't be shy ), as it doesn't appear that your symptoms are similar to the others.

But, while we're here: the throttle plates and the aux valves are two different things. Dirty throttle plates will cause a rough idle, but once you get on the gas, it doesn't affect anything. The plates are open and the volume of air is not affected by the restriction. It only shows at idle.

I removed the actuator valve and tried turning them by hand. They were very hard to turn and I had to work them back and forth to free them up. I think because they haven;t been used in a while, they were gummed up in some way.
That's normal, unfortunately. Over time they build up with carbon and do not rotate. But it's worth the effort to free them up.
The aux valves do make a difference when operating normally. Your idle will be fine whether they are open or closed, but you are going to miss power somewhere,as they help power at the low end when closed and allow more air at higher RPM. I'm surprised you're low end power has not been affected when you wired them open, but I suspect it's a lack of comparison.

I would not wire them open as a fix. It isn't that hard to remove the lower intake manifold and clean them, but if it's your first time, it's a bit of a chore.
It's worth it, though. And while you have the dynamic chamber and manifolds off, it's a good time to replace the vacuum hoses with silicon hoses. At this point, you are glad you don't own an FD.

If the hoses are original, they will cause other problems. If you want to keep the car, you're wise to get it done now.

"BTW, the page in the full Mitchell manual in the .pdf document is 240. It is tech bulletin 008/84"
Thanks. I appreciate it. I'll check that tomorrow.

gump

That is a good lead, thanks. I'm all for trying it, but I'm guessing that part would cost a fortune from Mazda. It would be worth it if it works though, anyone thing if I went to the Parts counter at Mazda they would be able get this part being that it's so old?

Ok, I'm pretty sure this is what I did to temporarily stop the problem, but I plugged the larger tube that runs from the dynamic chamber to the BAC which should do the same thing? I haven't done anything new. It runs just fine with it blocked up I just have to be careful using the A/C because the idle drops to near stalling when I have it on. Yes I'd like to finally fix it but I not knowing whether it's the ECU or either the Vent or Vacuum solenoid or something completely different hinders that from happening. I'm on dial-up so I'm in the middle of downloading that Mitchell manual right now, I'll take a look.
FJ, I have not reconnected the tube at all, but I may do it today or tomorrow, and see what happens. I'm pretty sure I've disconnected the V&V solenoid connector while it was happening and there was no change, but I will reconfirm and get back to you. One thing I'm noticing is that this seems to occur on high mileage cars only. It was happening to mine when I got it at 139k and got progressively worse (more frequent) over time. What I'm getting to, is it possible that low compression could be a factor here as Manttis mentioned early in the thread? I have nothing to test compression with. Well thats my update for now. I was hoping the next time I saw this thread pop up someone would post a magical easy fix, lol.
Take care.

Zulu

My engine has 20,xxx kilometers on it since it was rebuilt, however other electronics and such weren't, so, I'd suggest it isn't a compression thing. Esp based on how erratic it is.

I'm pleased with how mine runs with that plugged. It doesn't run as well before it's warm as it did before, meaning the idle sometimes drops dangerously low, but, it's never died and it goes fine, and once it's warm it's awesome.

gump

Well. I reconnected my BAC today. I could not get the wacky idle to happen for more then a second or two for about 20 miles of driving, then tonight on the way home, it happened, and it didn't stop. I got out and tried to disconnect the V&V solenoid connector, no change. I pulled the vacuum line off the top of the Vent solenoid but I forgot to try and plug the inlet on the solenoid like the article mentioned, there was no change when I pulled it. I think the vent solenoid has two vacuum hoses attached to it, one on the back and one on top, and from the picture I'm having a hard time figuring out which one to pull. I can take the top one off no problem but if it's the back one I need to pull and plug to see if the problem stops, I'm going to be burning up my hands trying. I reread the article when I got inside and saw that I needed to plug the inlet. Oh well. Theres always tomorrow. The car starts much differently with the BAC connected. Before when I had it blocked and I started the car, I had to hold the gas down partially to get it to fire up, but with things connected normally it fires right up to about 2k rpm and then drops down to idle speed, like most normal cars. So thats todays findings.

Zulu

Yeah that's what I meant when I referred to the changed startup.

Guackman

I'm glad I brought this thread back to life. Some very intesting symptoms being discussed.

As for me, I'm just waiting for by gaskets to come in for the intake manifold and I'll take everything apart, check the BAC functioning and lube everything up with WD-40.

I also have to clean up and get my auxiliary ports to work properly instead of having them wired open all the time.

We'll see if all this work pays off.

Thanks again to everyone for their input. This is great!

Greg
85 GSL-SE with 228K kilometers

gump

I was able to do things the way the Mitchell said today. I pulled the inlet vacuum hose off the vent solenoid valve and put my finger over it while the tach was bouncing and the idle returned to normal!!!! Thanks for posting that information about those fixes Greg! Now I'm on the quest for new V&V solenoid valves.

One more thing, I kept the larger vacuum line that runs from the dynamic chamber to the BAC connected and just plugged the inlet to the Vent solenoid valve. This worked better then plugging the larger vacuum line for me becase now the car starts normally without help from my foot.
Getting closer.

Zulu

Time for more pictures!!!

Guackman

Just wanted to let you know I checked at the dealer up here in Montreal and the V&V solenoids are $268 !!!!!

I guess I won't be getting any new ones if this turns out to be the problem.

BTW, I haven't had the strange idle for a few days, not since I gave the vacuum solenoid a little whack with a small hammer. I thought maybe something was stuck in there.

Anyway, we'll see if this all purpose fix works!

Greg

Manntis

enough info here to make my eyes cross...

gump

Finally! Everything is hooked up under the hood the way it should be, and I have no problems. I replaced the Vent & Vacuum solenoids (see pic) and everything is fine now. I didn't by new ones, I found used ones which work fine. I'm attaching the picture below of the solenoids. Apparently the one on the left is the Vent Solenoid and if you are having the problem discussed in this thread,when you remove the vacuum hose from the port that sticks up and cover the port with your finger and the idle returns to normal, then you need this solenoid. I'm so so glad this is finally resolved. Please let me know if any of you try this and get the same result.
Matt

a-cups847

does anyone know about a sticky throttle?? everytime i hit the gas hard, it gets stuck. tried turning it off but as soon as i started it the rpms jumped up to redline. turned off again. cant figure it out.