fast50

my 90 gxl is not wanting to idle right and dies when i come to a stop the only thing that looks any diffrent is my volt meter is at 12 instead of 13 could this be the reason.

HAILERS

No, most likely the engine needs a tuneup. A tune up in this case meaning to set the timing, setting the TPS, setting the idle and making sure the BAC's electrical plug is connected and the BAC is working.

The above answer is a bit vague in nature. To do the above you really need to download the FUEL section of the FSM off the internet and follow the instructions in the FUEL section of the FSM.

A tuneup in the nature of replacing the sparkplugs and airfilter/oil and oil filter never hurt.....but most probably won't fix the problems described in your post.

Unless it's been fiddled with, it's likely the timing is ok. There's no sound reason for it to have moved if it was set right the last time it was checked.

Setting the idle is realitively easy. You fully heat the engine, install a jumper in the initial set coupler, adjust the bac's adjust screw on a turbo and if it's a series four non turbo adjust the screw on top of the dynamic chamber. And if its a series four you might have to adjust the variable resistor also.

If you car would only idle around 750 or below you could check the function of the BAC by merely removing the bac's electrical plug and listen for the rpms to drop a touch and when reinstalling it for the bac to raise the rpms a touch and maybe even cause the rpms to go up and down for a couple of cycles til it settles down to around 750 rpm.

Most of this is in the free download of the FUEL SECTION of the FSM that is FREE to download from the World Wide Web (except in China, N. Korea and a few others).

SureShot

Here's a few tips:
The rotary engine has so little torque at idle that half of the stuff on top of the motor is for idle speed control.
The BAC is the main controller of idle speed but it needs help with suddenly switching loads like headlights or AC or heater fan on high. These accessories have signals to the ECU to open a vacuum bleed solenoid to help out.
That is why the idle tune up is so complex.
The short range TPS:
Its job is to tell the ECU you’re at closed throttle.
If it is out of adjustment, the ECU may not activate the BAC to handle idle speed.

Note the link to my copy of the on-line manuals in my sig below..

fast50

also i took out the a/c compressor and dryer/ condenser could this have an effect. i unpluged 3 wires 1 on the compressor and 2 small ones on the dryer i think it was.and its a 90 13b 6 port n/a

ctsupacat

I had a fluctuating idle issue myself when my car was stopped and the clutch was engaged. I called a rotary specialist and he suggested the clutch switch might be bad. Turns out I had a broken spring in my clutch switch which is located behind the clutch pedal. All you have to do is unscrew the clutch switch from the pedal and open the switch using a flat screwdriver. Inspect the switch, clean it with alcohol and make sure the spring is in one piece. If not replace the spring and you should be fine. Or you can just purchase a new clutch switch- shouldn't be that expensive.
Also make sure your idle is @ 850 rpm in neutral after the car is warmed up (drive for 10 minutes). adjust idle screw at top of manifold with black rubber cap. Clockwise to idle down... and counter-clockwise to idle up.

My idle is PERFECT now!

Trinilimer

.

demontwig

^^Is that all you ever have to say? Damn.

SureShot

(Still adds to post count.)

BOFHMike

I tried to adjust my low idle tonight. Warmed up the engine (20 min) She went from about 2100 high, to 1400 mid idle perfectly. When she dropped to low idel and I had to manually give her more gas to keep her running. I can see the Thermomax is operating (plunger extended) I turned the Dynamic chamber adjusting screw (with jumper wire installed) couter clockwise several turns w/o any noticable change.
How many turns from full-clockwise (closed) is a "typical" starting point? Or should I just turn it counter clockwise as far as she'll go w/o falling out and start from there?

BOFHMike

Follow up on my adjustments. Tonight I decided to start my adjustments from scratch. Started her up, she idled for about 20 untill she was warm. Pluged in the diag jumper and turned the screw on the top of the Dynamic Chamber all the way counter clockwise. (should be highest RPM posible) - I still didn't see any change while adjusting the screw. - Disconnected the jumper... Used the LED method to adjust the tps. Restarted and used the voltage method to fine adjust the tps. W/ one lamp lit, the voltage was close to .75, I turned it up to .85 volts and acheaved a good even idel, 1.0 v was spotty and didn't hold very long.

It's still not idleing long, but it is improved. I'm concerned that I had to adjust the screw on the top of the DC all the way open. Is this indicative of any known issue?

Brodie121

iTrader: (8)

Did you set the idle mixture?

BOFHMike

That would be the screw on top of the Dynamic Chamber. I have turned it counter-clockwise as far as it will go, I noticed NO change in idle speed, and full counter clockwise should push it to the highest RPM possible at idle. (and yes, I had the jumper installed)

satch

iTrader: (1)

I think he might be referring to the "variable resistor."

BOFHMike

Ahh, in that case, no. I've left that one alone.
(trying to make as few adjustments as possible to not compound issues.)

ifryrice

Theres a lot of things that'll make troubleshooting the idle an absolute pain. The first, and biggest of those in vacuum leaks. Almost 95% of all idle issues are leak related. If you're absolutely sure it's not vacuum related, and you've checked everything else and unassited the car idles too low (meaning BAC is not working), you can adjust the throttle stop to bump the idle to a reasonable starting place. Generally once i've checked everything (vacuum leaks, TPS, thermo sensors for Air/Water, etc), i'll check the cars mechanical idle (without BAC), and dial it to about 700, reset TPS, reconnect BAC and go from there.

A lot of times the car will be idling at 400-500rpm, and using the BAC to maintain the 750 idle, when load occurs it can't bypass enough air to maintain idle and will drop/stall. Check everything else first though.

Richter12x2

iTrader: (1)

First thing I'd check would be vacuum.

BOFHMike

The prior owner did replace all of the vacume hoses, but I found two last night that popped off w/ very* little effort. I have quit trusting anything he did. I'm going to start over tomorrow night by presurizing the air system and see what I can find.

BOFHMike

Over the weekend I presureized the air intake system and sprayed everyting down with soapy water. Only trouble spot I could find is where the air intake hose connects to the UIM/DC. Since that would be pre-vacume / fuel mixture, I'm guessing it's ok. If not, let me know.

Oherwise... I decided to go on an electical gremlin hunt. I turned to pulling ground points in the engine bay, cleaned the contacts, cleaned the bolts, and used a LOT of dielectric. This brouht my voltage leak from +45mv at some points between battery negative post and various "grounded" locations in the engine bay to 0.00. figured I might as well check out the ECU while I was at it. Found a little mess (see my gallery) and cleaned that up w/ solid grounding. Now I have 0mV at every point I tested. Started up the 7, and idled like a champ for over 40 min. Low idel isn't quite right (800-1000) But left alone, idled great. Very little "hunting".

All that for the following....
Idles GREAT for 40 min. I'm trying to get the rpm at idel down to the 750 range, or at least 800. Per the SM, I turned the screw on top of te Dynamic chamber clockwise, very* little effect (yes I had the jumper wire in place) Then suddenly it would drop idle and run really low (near 500) I give the screw a turn CCW and recover. It was almost as if the ECU was waiting for me to step away before paying attention to the last adjustment....
I get the idle back to aprox 1000. Again, idles great. I jump in, give it a little (1700 RPM) throttle and let off. That's it, she spits in my face and stalls. Isn't the dashpot suposed to keep the throtle from returning too quickly leading to a stall? Or is this indicative of something more sinister?

Amur_

If it's occurring 'behind' the AFM, it's unmetered air entering the system and a problem that needs to be fixed.


A healthy FC will idle below 500. Your engine dying is not related to the dashpot.

Go buy some new neoprene vacuum hose and replace EVERY hose you can find.

My own vacuum leak finding trick is use a garden hose. With the engine idling and a slow, steady stream of water from the hose, move the stream slowly around and over the engine. Let the water run over every hose, joint, etc that you can and let it do that for several seconds before moving on to the next. If the water stream hits a leak, the engine will react and you can start to zero in. The only problem with this is that the water stream may pass over a lot surfaces before finally falling off the engine. Which brings me to technique two...



With the engine running, start blasting in the area where you think the leak is. The butane dissipates fairly rapidly, so it's less likely (imho) to give you a 'false return' away from a leak source, unlike when using water as described above. You might also try spraying Quick Start, although I don't use it for that. I don't trust it.

One last thing: fuel injector o-rings and grommets. Over time these harden and stop sealing. Mazda used to sell all the pieces for one injector in a single kit, but when I tried to order one last summer I was told by a local dealership that they dont carry them anymore. The guy was quite happy to sell me the pieces individually, though, and the price worked out to something ridiculous like triple what the kits used to cost.

BOFHMike

Ah, Didn't think about that. Thanks, I'll need to address that leak.

I can force the idle down below 700 by turning the fuel adjustment on the DC. She'l shake like hell below 700, but she'll do it. It only stalls if the thottle is moved which leads me to belive the problem is physical not electrical or mixture.

Prior owner replaced 90% of the hoses already (see my galery), but then again, nearly every repair he's done, I've had to re-do because it was half assed.

Too bad the hoses are put away for the winter.

Nice! I've read several articles that use starter fluid, butaine, or propaine. I have propaine, easy enough to use.

I have a new set of injectors I can toss in if I pull the UIM. I'm hoping to avoid tearing into the engine this winter.

Thanks for the pointers/ideas.

Amur_

It could still be any of those. At least the car is still functional and driveable. Have a read:

http://howto.globalvicinity.com/gv_w...i=60&co=1&vi=1

Maybe something in there will catch your eye.


Exactly. The hose is cheap so why not replace it all and remove that possible source from your list?


I prefer the butane because it blasts out rapidly in a fog. I can see exactly where it's hitting and I fire it in 1-2 second bursts. I'd be concerned with propane if I just ran it continuously while moving the nozzle around; does it turn into a water-like situation where it's building up and hitting a vac leak that's away from where I think it is? There's also no concern (with butane) about slowly flooding the surrounding air with the gas and possibly harming myself.


yw

BOFHMike

Nice article. Thanks!

I stopped at two stores on Sunday, neither one had vacume hoses. Amazing!

Oddly enough, I could not find a sprayable butane. (I must be going to the wrong places, hardware stores are NOT what they used to be) Only butane I'm finding is designed to fill lighters, nearly impossible to aim.

As an update, I checked ou the dashpot, at idle it wasn't making contact w/ the tab. I removed it, cleaned it, made sure it was working, and re-instaled. Grabed a neighbour to hold the rpm's at 2800 while I made adjustments, and it works! It's great when stuff falls into place. I need to do a lap around the block a few times before I claim victory, but this is a major step forward.
I also pulled the snorkle from the DC. Cleaned the butterflys, brushed the seal face/grove, and added some silicone to the rubber gasket to make a better seal. (only leek I found while presurising the air system.)
My FC is geting closer to returning to the road every day, and I like it. (Now if I could only find all the interior trim parts I need to finish it up.)

BOFHMike

Since there have been no posts since my last post I'll give an update.

Found a major problem. My aftermarket cat was clogged. Thus everything I was doin to increase RPM was in fact causing more back presure and having reverse results.

I've replaced the cat w/ a proper cat set and the car runs like a charm, but now I have to un-adjust a few things that I adjusted. The TPS should be right, but the screw on the Dynamic Chamber has been spun way to many times, so it needs adjustment. I'm going to bet the prior owner may have made tweaks to compensate as well. What other adjustments would co-inside w/ building backpresure?