My car is stock except for a K&N panel filter, RB muffler, Bonez catted pipe. Recently my idle started staying at 500 rpm and bounces a bit. When A/C is turned on, it naturally rises to 1000 rpm and runs smooth. I also notice a rich exhaust smell when idling at 500rpm. Note my air adjust screw is all the way out and I still can't get her to idle at 800 rpm. I ran checks on the BAC valve according to the FSM and the vacuum solenoid valve failed. I have all new (Mazda OE) plugs, wires, cap, rotor, coils, vacuum lines, intake gaskets (all). Any ideas?

 

BTW, I'm nowhere near a rotary mechanic. I would really like to talk with the resident expert here about a few issues with the car. I've been working on this project for two years now and I really need someone to help me dial it in. It's sooo close but I just can't get it.

 

 

sounds like a vacuum leak. Check the vacuum lines that are under the upper intake, they tend to dry out.

 

As I stated above, all vacuum lines have been replaced. Thanks anyway.

 

the variable resistor may be out of adjustment. i would play with that in SMALL increments and then check and adjust the TPS as needed. it couldn't hurt to remove and clean the BACV.

 

Removed and cleaned BACV, tried another one just for grins, same results. I did adjust TPS and it made no difference. Why is my air adjust screw all the way out and I am still at 500 rpm? Why when the A/C is on and the idle is kicked up, the car idles beautifully? Wouldn't a vacuum leak act up all the time? This vacuum solenoid valve that failed the FSM test, I know it adjusts timing on deceleration but could it have an effect on idle since it works with the BACV system? I've also ran through the " Fixing GSL-SE Idle Problems" posted on here but I'm starting with a very low idle so many of the tests can not be applied. I would like to adjust the variable resistor too but I need to get my idle corrected so that I can measure that properly. Keep in mind that this car idled perfectly up until a few weeks ago. I initially changed the plugs thinking it was time but that had no effect as well.

 

Wild guess, but check the flap in the AFM, make sure it isn't sticking.

 

Moves freely.

 

Seriously contemplating putting a Ford 302 HO in it. I just cant find any help with getting this motor tuned right, here or anywhere else and I even work for Mazda. I've got two years and nearly 8k invested in this car. It has really come a long way from the $250 I paid for it. Not to toot my own horn but I've only seen a handful on the web or anywhere that I would consider nicer than mine. Would love to meet up with some of you at a rally someday but I'm just not willing to take this thing on a long journey until I know it's right. Sorry to rant but I'm just fed up.

 

have you checked for a leak at the injectors themselves?

 

Fuel leak? Injectors are new and so are all the seals that go with them as well as the plugs that connect them to the harness. All fuel lines have been replaced front to back.

 

well, I had meant a vacuum leak since it's easy to overlook them as possible cause for a vacuum leak when the seals around them rot. however, you answered my question anyway. sounds like you've been quite thorough.

 

i would try adjusting the variable resistor and see if that yields a change. they can work their way out of adjustment if the filling has been removed. it can't hurt to try. i've solved quite a few SE idle issues and even on my own car couple years ago by adjusting the variable resistor.

 

Even if the car will not idle above 500? FSM says engine has to be at 800 before adjusting the resistor.

Can anyone answer my question about the vacuum solenoid valve failure and what effects that may have?

Today I spilled some water near the lower intake while it was running and it started running rough. It only did it when it was cold. I assume it seals when it gets hot and expands. If that is the case, why does the idle not go up to normal after it warms up and theoretically seals? In fact, after it warms up is when it starts to bounce from 500 rpm to 800 rpm. I could have multiple issues.

I just changed that intake gasket and THOROUGHLY cleaned and sealed it and tightened it per FSM. Despite mixed responses on this forum, I put a thin layer of copper RTV just in case there were any variations in the surfaces. The only other thing I can think of is that the surfaces are warped a tad.

I appreciate all the posts, but, this is so much more than what is on here. This car has thoroughly been gone through and I left nothing to chance. Working for Mazda I was able to get all oe parts (sometimes cheaper than aftermarket at my cost) so nothing is rigged. Anything and everything that basically people should change when restoring one of these has been done. By that I mean ANY/ALL rubber hoses and vacuum lines, cat converter, fuel tank, pick up line/sock, cleaned fuel lines front to back, fuel injectors (cleaned, flow tested and all seals) injector electrical connectors, belts, radiator, all ignition except distributor (of course cap, rotor, checked air gaps), timing, TPS adjustment, replaced BAC valve (used one), and that's just motor related. Motor is untouched because it's compression tested out as follows: Rotor 1: 6.9,6.7,6.8 bar. Rotor 2: 7.5,7.4,7.4 bar. I was told anything over 6.0 bar was good. All the solenoids around the intake, firewall etc are original and so is the intake, minus gasket and a thorough cleaning. I ran through all of section 4B in the FSM and I have the notes and results documented in the manual. My ACV isn't passing but I replaced it with two others and those didn't pass either. Is it bad parts or is some other system affecting the results of the tests I'm running on the ACV...AHHHHH sometimes I feel like I'm chasing my tail.

I guess what I'm trying to say is that I need to talk to a seasoned rotary specialist. I have no problem paying someone but I just cant find anybody. I'm looking to this board for some suggestions. Please don't waste my time with "did you change the fuel filter." As much as I appreciate you all taking the time, like I said above, I did all the common sense stuff already and now I need a real rotary tech to get me all the way home with this project. Again, sorry for the rant, but I'm sure some of you can relate. Can anyone help?

 

you have nothing to lose by attempting to adjust the variable resistor IF it no longer has the factory sealant in place. if the original sealant is in place then it's time to look at some other areas of interest.

the vacuum control solenoid valve is only in effect on deceleration and its job to cut the vacuum supply to the distributor during decel.

if you are seeing a vacuum leak when cold and not when warm, then its time for a lower intake manifold gasket. i would guess the gasket between the dynamic chamber and the upper intake manifold has started to fail and is causing vacuum issues when the engine is cold. when warm the aluminum manifolds expand and will expand, sealing and masking an issue.

have you considered looking into the intake air temp sensor? when it fails it can cause idling issues, though it normally does not fail. but since it has a big effect on the BACV control i would not rule it out. the BACV controls all bypass air and it does this to maintain a constant idle speed.

it sounds to me as if you have an issue with the bypass air control system. a low idle can be more troublesome than a high idle in certain instances. i'm not a rotary specialist but i have owned 34 RX-7's over the last 14 years and have seen all kinds of idling issues. commonly i have seen issues related to the above and also to include one faulty injector, a bad injector ground cable (bolts to the emissions rack bolt and consists of two single black wires with a ring terminal on each wire), faulty fuel pressure regulator, misadjusted variable resistor, faulty idle adjust screw on top of the throttle body, vacuum leaks, faulty vacuum control solenoid valve, which caused a low idle, and the obvious air filter blockage. keep plugging away and asking questions and spending time with the car. if you were closer i would offer for you to bring the car over and i would give you a hand working on the car.

 

Thanks for the offer I appreciate that. I would think owning 34 RX-7s would make you somewhat knowledgeable especially if you worked on them yourself. I'll tinker with the resistor for grins but I may have to start with a new intake gasket. As I stated earlier I just changed it a couple weeks ago so it hasn't failed it just never sealed.

I agree with you in that it seems something with the BACV system.


One other piece of the puzzle is that my air adjust screw is all the way out. That would indicate to me that all the way out means it is closing the butterflies inside to compensate for too much air. Does that make sense to you?

You also mention above that the vacuum solenoid valve could cause low idle. Mine in fact failed the FSM test. Where can I get a good one? Mazdatrix has them for nearly $200 or $300.

 

My SE once acted the same way----really low idle and extremely rich. It turned out that one of the fusible links was loose-----I believe it was EFI link. I took it out and installed a fuse, and the idle smoothed right out. Just a thought :-)

 

maybe replace that?

 

Low idle kinda sounds like the ECU is trying to hit a target idle speed with the butterflies closed, via the IAC (or RE-EGI equivalent). That says to me air is getting beyond those butterflies when closed, as this is the only place you are having problems. Also, the engines condition can be reflected though a poor idle.

Try a vac test. Also my 1984 GSLSE *hated* water. Take this car to a car wash, and wash it while its idling. Notice any differences? Mine turned out to be a bad seal along the distributor, allowing moisture into the cap. Some days, when it was humid, moisture would accumulate in the cap on its own, making it hard to start and a lumpy idle. Not saying this is your issue, but its worth a look.


Ive also had a 1988 GXL that had a AFM that hated rain/car washes. Did what you described, but after a drive would clear up.

Check your spark plugs too, again. Idle is based on a set amount of air/fuel moving through the engine at CTP (closed throttle position) which is set from the air screw (controlled vac leak) and the variable resistor.


Check your fuel pressure.


Drive the car 30 minutes or more, then listen to idle.

Rotaries are picky about conditions, especially the Bosch Jet-Tronic system in place on a GSLSE. Your car is 30 years old, perfect idles are not overly common on any vehicle of this era. My 04 RX8 stumbles at idle occasionally too, and smells rich. Runs great though, and would never condemn a perfectly good rx to a V8 swap because I had a less than perfect idle.


Try getting a vid of the "bouncing idle" you describe after its "warmed up"

 

Remove this screw, inspect the tapered end.