Bcdd

[rcb280z]

Update,

Capt., yes I agree after thinking about everything for awhile. It is an intermittent electrical issue I believe.

I performed the test in the FSM (EC-5) and got good results. Put rear end up on jack stands, ran the car up to 15 mph, and had voltage between A and B at the test connector. And no voltage at idle. So it must have been working at the time of the test. I waited to hear the click so I could test again and it wouldn't, of course! Now that I'm looking at it it's not going to act up! Figures. 

So, what's the worse that could happen if it continues to do this intermittently? Leaner at idle? I'm trying NOT to have to remove and replace the speedo that I just put in about a year and a half ago. I have a full dash cap and remember trying to remove the tach once and gave up because I couldn't get it out. 

My next test should be of the amplifier and speed switch though if I read it right. I have another speedo in a box (used) so hopefully its good.

I wonder if this has happened to more people like specifically the ones that believe the ecu is "floating lean" I think they called it. That's what it feels and looks like...a lean condition when the solenoid activates. The bullet connector is corrosion free also, made sure to add that info.

[Captain Obvious]

Duh. Well of course if didn't do it when you were looking for it! You didn't realty expect it to do what you were hoping, did you??  It's going to wait for the most inopportune time to start acting up again! About the EC-5 test... Don't forget that just because you have a good signal at the test connector doesn't mean that you've got the same good signal in the coil of the solenoid valve. You could still have an intermittent at that connector or in the wire leading to the solenoid. In fact, the solenoid itself may be intermittent. But unfortunately you'll never figure that stuff out unless you can get it to act funny while you have some diagnostic equipment hanging on it.

 

So what's the worst that can happen? Your BCDD can become activated when it's not supposed to (like when sitting still at idle) which can result in engine speed fluctuations and (at worst) maybe not returning to idle at all, but instead hanging up a little instead.

 

Forget about it going lean. The BCDD has no effect on mixture, just engine speed. Speed only, not mixture.

 

Think of it as a secondary device that pushes the gas pedal down a little when you lift your foot abruptly. Even though you lifted your foot, the BCDD holds the throttle open a little until the vehicle speed coasts down below 10mph. (Doesn't really pull on the throttle linkage, but does the same thing a different way).

 

Is your car an auto or manual? If it's an auto, there is one additional complication in addition to the speedo amp.

[rcb280z]

Duh. Well of course it didn't do it when you were looking for it!

Ha! don't I know it.

 

Well it definitely isn't that bad then....idle is just a little rough when it energizes, nothing too serious. 

 

It's a 5 speed.

 

I thought the idea of the BCDD was to introduce extra air into the intake. Thought that was what it took to keep the rpms up high enough while the BCDD is activated. 

 

So I should remove the solenoid and test it?

[Captain Obvious]

I was thinking about this a little more and wanted to talk some about the BCDD's impact on mixture and bring up one other additional thought. If the rubber diaphragms inside the BCDD are in good shape then the BCDD won't have any impact on mixture. However, I can imagine a scenario where there could be holes in one or more of those diaphragms which COULD affect mixture ratio. So to modify what I said up above a little...

 

The BCDD doesn't normally have any impact on mixture ratio, but I can imagine a scenario where there could be holes in diaphragms whereby the BCDD draw outside unmetered air into the intake manifold which CAN affect mixture.

 

What you said above about the BCDD's job to introduce extra air into the intake is correct. But an important detail is that extra air is supposed to have gone through the AFM first. If it goes around the AFM and leaks in past one of the diaphragms, then it's a problem.

 

Mine was leaking internally (which doesn't affect mixture), If yours is leaking EXTERNALLY, then you WILL mess with the mixture.

 

And you don't have to remove the solenoid to test it. You can do this:

 

Disconnect the BCDD at the bullet connector.

Turn the ignition key to RUN but don't start the car.

Walk around to the engine compartment and connect the BCDD bullet.

You should hear a distinct "CLICK" from the BCDD when you connect it.

Connect and disconnect the BCDD a couple times and verify that it clicks immediately and there's no delay caused by sticky buildup inside.

 

Or if you'd really rather... it's very easy to pull the solenoid off the BCDD and test it on a bench. Just don't lose the plunger or the little spring.

[rcb280z]

Yep, solenoid is good. I did that test first. Thought we were looking for something in particular, other than the click.

 

Maybe one day when I have the whole day to spend on the Z I will remove the throttle body and open up the BCDD to check the diaphragms for holes. I can disassemble the throttle body and clean it up as well. Unless its not a good idea to open up the BCDD. I see where people have done it but the FSM doesn't recommend it.

 

As far as an external leak I don't think its the case because my intake vacuum stays between 18-19in's. If I had a leak it would probably show up on my vac gauge right?

But, when the solenoid actuates (when its not supposed to) it does seem as if there is a vacuum leak and I don't recall a change on the vacuum gauge. Something to pay attention to next time I look at it.

 

I hate walking away from something until it is fixed so I will continue until I figure it out. Pretty sure it is speedo related though. Next will be to try and remove the speedo with the dash cap still installed. I think this will be a bigger issue than the BCDD.

 

Thanks to you, Capt and Zed Head, for your time in this.

[Captain Obvious]

But, when the solenoid actuates (when its not supposed to) it does seem as if there is a vacuum leak and I don't recall a change on the vacuum gauge.

 

Yeah, and that's why I added the thoughts about the fact that it COULD cause a vacuum leak if the holes are in the right (wrong?) spot. I don't think it would take much of a leak to have a significant impact on idle mixture. Wouldn't make nearly as much difference once your foot was on the pedal, but at idle you really need every air molecule going through the AFM.

 

Good luck and here's hoping for the best!

 

PS - I had a dash cap and I took it off. I'd rather look at the cracks than deal with the cap. I know others feel the opposite, but that's just me.

[rcb280z]

Thanks Capt. It only seems like a vacuum leak when the BCDD solenoid activates at idle when it shouldn't activate. Otherwise it runs good. Might just leave things alone for now unless things worsen.

 

Yeah the dash cap thing is an issue for me too but if you could have seen my dash you would say "oh I understand", ! 

Some of the cracks are so wide that you set a Taco Bell taco in it  . Even have a crack starting in one of the gauge pods . I would remove the dash and fix it but I don't have that kind of time. So the dash cap will have to do for now. 

[Zed Head]

The old trick of spraying starter fluid around potential vacuum leaks works very well on the BCDD.  Of course, it has to happen on the "right" side of the click.  If you're sucking in unmetered air, the starter fluid will find it.

[rcb280z]

Yep, have that on my list of things to get from Autozone today.

[rcb280z]

UPDATE

 

So no vacuum leak at the BCDD, That I can tell. Sprayed some starter fluid around it and there was no change in idle.

I was told by a mechanic that I could just remove the plunger and spring from inside the solenoid and that would temporarily fix the problem. I did that but after driving it around I decided to re install the plunger and spring. The reason: It drove fine, just decelerated differently and sounded different. Decelerated faster to a stop (in gear) and the exhaust had a deeper tone to it. But the worst part was the smell of burning oil. I remember Blue mentioning in a post that without the BCDD it would cause oil to be sucked up past the rings. At least I believe thats what he said. It has an oil burning smell anyway but it is very noticeable without the BCDD solenoid functioning. So I'm not a candidate for the BCDD removal. And from what I have experienced they should not be removed. But that opens up another problem for those who's BCDD's are no longer functioning at all.

The next step for me would be to remove the speedo and replace it. FSM shows an amplifier and speed sensor test. That has to be where my issue is. But because I have a dash cap installed I'm in no hurry! Beside's, it's an intermittent issue and will be difficult to find. So for now I'm just going to drive it and not worry about it.

[EuroDat]

Yer, The BCDD should reduce the high vacuum in the high rev range during decel when working properly. The high vacuum will suck oil past the valve guides and rings.

If you give it full throttle after that you will probably see a puff of blue smoke out the back.

Goodluck hunting down your problem.

Chas