Insava

I have a 1985 GSL-SE that I recently purchased, 100% stock that I know of. When I bought the car it had starting issues but I have fixed the problem by replacing most of my ignition components. It seems the issue was down to the center carbon plug in the distributor cap being completly worn down so it was only firing on the trailing plugs.... now it starts right away hot or cold.

My new issue is that the idle is getting stuck at 3000 rpm. I can manually adjust the idle to about 1000 by rotating the throttle assembly to close the throttle plate but once I hit the gas peddle it will get stuck back at 3000. I just opened the front of the throttle body by removing the intake runner and sprayed the inside with some carb cleaner and wd-40. It definitely cleaned some carbon deposits but still won't idle at anything less than 3000. Before I take my whole EGI system apart I want to check if there is anything else that could cause this high idle condition. I have been through the idle trouble shooting page and now I'm getting to the dynamic chamber tear down which I would like to avoid.

I've also closed off the BAC valve to see if that was effecting my idle but I couldn't hear or see any changes.

Thanks for the help.

j9fd3s

iTrader: (3)

the throttle bodies in a GSL-SE like to get stuck. there are no bushings for the throttle shaft, so the bores wear out.

there are a couple things to check before you pull it apart though.
1. the throttle cable adjustment, it should be fairly loose, there is a spec in the FSM, if its too tight it can pull the throttle open, or keep it from closing all the way
2. the Thermo-wax. this is the thing that pushes the throttle open when the engine is cold, the hoses clog up, and sometimes the pellet goes bad too

derSchwamm

iTrader: (1)

Don't be afraid of tearing it down. I had intermittent problems with mine for a year before I finally pulled it off and took it apart on my coffee table with a beer in hand. It didn't take too long, and I carefully laid everything out in order so assembly wasn't bad. I cleaned everything thoroughly and oiled the throttle body shafts on each side for ~24 hours before I put it back in. It worked great after that, and I pulled it every 6 months or so to re-oil it for the next few years

If you need random parts off the throttle body I have two basically complete spares I bought while trying to fix mine

mazdaverx713b

iTrader: (91)

Great suggestions above! Have you checked for any major vacuum leaks? It the throttle arm on the throttle body resting against the throttle stop screw? These are the two places I would check before attempting to mess with any throttle adjustments.

Insava

So, I'm pretty sure vacuum leaks are not a problem. I've gone over and manually checked all my lines and they are still rubbery and I see no cracking or splits in them. I've gotten the dynamic chamber off now and inspected my throttle plates... everything in there seems to be working fine and not sticking. So now I'm down to my thermowax.... I've tried to push it down with no avail and when I rotate the screw it pushes on to I can see the throttle plates close ever so slightly. This might be it....

I have a few questions regarding the thermowax....

Does it extend when hot or reced? (From my diagnostics im expecting it to extend when the car is all warmed up... which would help close my throttle plate)

Can it be cleaned in anyway? or will I have to try and find another gsl-se dynamic chamber / new thermo wax pellet.

Can the system be deleted in anyway... I have read in a few places of people deleting the system but I dont want to be tredding in uncharted territory?

And final question... there is a rod connected to the right side of the main throttle rotating assembly near the TPS that goes down into the engine behind the water pump. What does the rod connect to??? Is this another idle system?? I cant see that deep into my engine bay.

LongDuck

Run a search on my username and "thermowax pellet". Read to your hearts content. I recommend you leave it alone, and also believe thats not the problem.

Insava

I think I might have found your thread and I definitely understand exactly how it all works now. I was about to post an edit to my previous post... I even figured out what that bar connects too, the OMP.

If its not sticky throttle plates and its not my thermowax I'm really not sure where to look next. It idles really well at 3000 and when I close the main throttle plates manually my idle will drop right down to 1000-1200 but will hold that idle really nice too, untill I pump the gas peddle then.... right back to 3000.

I'm really at a loss right now

derSchwamm

iTrader: (1)

This sounds like a classic case of throttle body shaft binding. Most likely you need to rebuild your throttle body and oil it or else find another one to try

j9fd3s

iTrader: (3)

i think it extends when hot (or the other way around?), you do want to make sure the water hoses are not plugged and have water in them, if the car has been sitting both are possible. its not hard to get air bubbles out, its just possible to have some

the wax pellet is pretty reliable, but they do go bad occasionally. the linkage is also adjustable, so once you've verified that the valve is actually getting coolant, you can adjust it. the specs are in the FSM, but i've had better luck adjusting it on the car.

FSM is here Foxed.ca - Mazda RX-7 Manuals

Insava

So I just tested the thermowax with boiling water and it appears to be extending. This is good!! another thing ruled out.

Now that I have my dynamic chamber and throttle bodies separated I saw a decent amount of carbon built up behind the main throttle assembly. Thats now been cleaned with a good carb cleaner and now I have them soaking in some wd40 with the assumption that it will leach down my shafts and lube/clean the rotational points. Since there are no bushings in this rotational assembly, i figured this would be the best way without completely tearing down the throttle assembly.

Should I completely tear it down to ensure a well oiled and clean rotational shaft? Or would the soak in wd40 be sufficient enough to stop the sticking?

j9fd3s

iTrader: (3)

try the soak first, see what it does.

Insava

Ive got it back together now... just need to find some gaskets and ill throw it back on my car. If this doesn't work im gonna take the whole assembly apart. Hopefully it doesn't get that far... i have clutch issues to deal with next. I cant actually tell a difference through manual inspection so hopefully it works

LongDuck

I sat up all night long thinking about your problem (*kidding), and offer the following advice, in order;

1) with the Throttle Body apart, it's important to lube the Butterfly Valve rods with something that will stay. WD40 dissipates quickly and isn't suitable for this area. Use something heavier with a higher viscosity so it will remain in place in spite of motion, heat, and vacuum. Even light 3-in-1 Oil is better. ATF might work well, too. Apply the lubricant to the rods on the inside and outside, then rotate the TB 90deg up so they point at the sky, then flip it upside down so it seeps into the other side. Leave the TB in the flipped condition for an hour or so on each side to let the oil flow. Note that there are Secondary Throttle plates (choke) in front of the main butterflies that also need lube, and these move with your Thermowax pellet.

2) the 'bar' as you called it, is the Oil Metering Pump rod that moves with the TB rods to open up more intake oil flow under higher throttle settings. It needs to move smoothly and without binding. You can test this on the car by lifting the top of the rod up, and then releasing it. It should flop back fully down where it started. When you do this, it's moving an actuator arm on the valve of the OMP. If it gets stuck or binds, then your oil consumption will be higher than normal and it could be preventing your TB rods from returning to normal idle (900rpm). Sometimes the rod gets hung up on the wiring harness behind the Water Pump, so give it some clearance and bend it slightly so it doesn't bind on anything. It should move VERY smoothly and easily.

3) your high idle all the time may be due to the Fast Idle Cam setting when it shouldn't. What happens on startup of an -SE is, you push the accelerator pedal down fully ONCE, release it, and then crank until start. This sets the TB on a Fast Idle Cam position that increases idle to about 3k RPM. It does this to keep the engine running when choked and to heat up the catalytic converter quickly (*with side benefit of getting more heater effect in cold climates). When the Thermowax Pellet melts from hot coolant flowing through the TB, it opens the Secondary Throttle Plates (choke) by vacuum, and rotates the Fast Idle Cam out from under the Throttle stop. This drops engine idle from 3k RPM to normal 900rpm. If your Fast Idle Cam spring isn't resetting, it will prevent the cam from moving out from under the Throttle stop, and the car will idle at 3k RPM all the time. Even if you lower the idle by hand, as soon as you push the gas pedal, the Fast Idle Cam rotates under it, and you're back to 3k RPM idle.

4) your accelerator pedal cable is sticking.

Does that sound about like your symptoms? Post back after you've had a look, and if you can post a picture facing the throats of your TB in position (*showing the Thermowax Pellet and Fast Idle Cam mechanism which is to the firewall side), I may be able to eyeball it for you and confirm whether it's spring is set properly.

Insava

So #1 I'm gonna take my TB apart again as I just put it back together but I absolutely understand what you mean about the WD40 not being sufficent for lubeing. I was thinking the binding might be due to carbon build up so I was hoping that the WD40 would penatrate enough to combat this... I'll be lubing it up properly now.

#2 I just check the omp and it seems to be move freely with no binding at all.

#3 this is where i think my problem was occurring. You described my situation perfectIy just need to find this cam... its the one that connects to the thermo wax assembly right.


I've also included multiple pictures of my tb for diagnostic help.






I stupidly adjusted alot of screws in the quest to find a solution to my problem... some being while it wasn't on the car. So some will definitely be out alignment.

Insava

Also you help has been a god send!! I love working through problems but it was hard to have a clear starting point as I've never worked on a rotary or older car like this one. A community like this is another reason i love this car so much...probably even more once I get to drive it.

LongDuck

Your first picture tells the story; the Fast Idle Cam adjustment screw has been cranked all the way down.

Try backing it out to about 1/2 way and go from there. The FSM (*You read the FSM on this, right?) state's that you set this when the engine is cold and adjust the screw so that the Fast Idle Cam is roughly centered on the hash mark on the Throttle Body rod. This gives the cam enough movement so that when the Thermowax Pellet melts, the metal piston rises against that adjustment screw, and moves the Fast Idle Cam out of the way of the Throttle stop.

Word to the wise, most of the adjustment screws on an -SE intake system don't do what the FSM calls them... You probably want to avoid adjusting things haphazardly until you learn their true function, and that takes an inquisitive mind, a gentle touch, and being able to ****** the pebble from my hand...

Only then will you be a Shao Lin monk of the FB EFI order.

Insava

So that was something I had done after the fact since I finally figured out how the whole thermowax system works... it was gonna be the first thing I tried once i got it back on the car. And if I'm being honest its what I believe was my problem... I had a mechanic friend adjust **** when we couldn't get it to start and I'd bet he turned it all the way down. And once it was finally stated I was at a loss for what to do. Another great lesson tho, before tearing into something make sure you understand the very basics of it. Still my fault for not researching enough about the system tho.



It appears this rear screw has been adjusted as well, which from looking at the TB would effect that cam position as well.

LongDuck

Whatever mechanic friend you took it to is neither a mechanic, nor a friend.

I'll bet everything would have worked just fine if you had focused on just getting it started, but live and learn. Very few mechanics are ROTARY ENGINE mechanics, and only the basics of ICE engines translate. There are very specific differences in the intake and exhaust paths of rotaries that most mechanics will not be attuned to understand, so they default to tinkering - which always makes things worse.

On this intake, and the various positions of the tuning screws, you're going to want to spend some time reading the FSM for the -SE specifically to set them back where they belong. You might get lucky and look closely at the screws to see if you can make out tarnish lines to try and get them back to where they started. Each engine will need different settings to run well in YOUR locale and altitude, which is why Mazda saw fit to provide tuning screws for the various components. I can tell you that cranked down completely and flopping around loosely are not the factory settings, so go for middle-of-the-road, and then tune as you go.

I went out in the garage just now to give you some starting points. It's 116F today, and my garage is about 105F, so sorry for the picture quality. Briefly, the Fast Idle Cam adjust screw acted upon by the steel piston of the Thermowax Pellet is about 1/3 of the way inserted. The Throttle Body Rod adjuster is about 2-3 turns out. I also took a pic of the FRONT side of the TB so you can see how the TPS, OMP Actuator Rod and Throttle Stop are configured.




Just a heads up, but don't expect the car to run well when you get it all back together. It will run, but you're going to be tuning it for awhile, trying different tweaks one at a time, until you reach that ideal setup. Just be patient, (*and read the FSM)

Insava

So it was basically the carbon plug on the distrubutor cap that was preventing me from running. And once I got it started and noticed the new issues I told him unless he come backs with researched information I wont let him do anything to the car anymore. I knew it was a mistake but he just stopped by and wanted to help so I let him go for it.... I'd like to think I've grown from that mistake. I've been going through the Haynes religiously but have found it hard to pin down exact sections that have the information i want to review. I'll start on the FSM asap as I've always had better luck with fatroy manuals anyway. Thanks for all the help hopefully I can get some good rides in before it get parked for the winter.

Insava

Just an update before I'll be done with this specific thread.... its idling beautifully now at a solid 800. Took us untill 4 am yesterday but hey, It now runs!!!

It appears that it was the throttle plates sticking and a good cleaning and lubing fixed that problem right up. It was stalling out at first but after following the idle adjustment procedure and methodically adjusting the various idle adjustment screws. We have finally found the optimal setting.

Thanks you all your help Longduck, I'm sure ill have more than enough questions for you soon enough.