Folks, ever since the weather has turned colder here in TN, I am having an unusual problem that I have not had at all since I bought this car several years ago. Will start off by saying I have no mods that have been done to this vehicle other than a tailpipe several years ago.

Lately, when it is really cold, my idle is running around 2000 RPM. Used to be that the car being on the road for just 5 minutes or so would make the idle RPMs drop to normal. Even when I drive the car to work which is a half hour drive, when I pull into the parking lot of my work, my car is still idling at around 1800 RPM. Now. Get this. If I let the car sit in my driveway and warm it up, idle will drop to around 800 RPMs. If I drive the car somewhere and then shut the motor off and not drive the car for 15 or 20 minutes, the idle will drop to about normal, almost like something is heat soaking under the hood. I have noticed that the more the car is driven after something heat soaks in the engine compartment & the outside air temps are cold, the idle RPMs begin to go back up again.

I am at a loss for what may be causing this. Anyone else had the same experience as me? I will say that the vacuum lines have probably never been replaced on the car. Again, didn`t have a problem until the weather got colder. Now the mornings and some of the afternoon temps are getting down into the 30`s or less.

BTW, the engine temp gage is showing what it should after about 5~10 minutes of driving. Even though the engine is warmed up as what one would think, the problem still persists. If it is warm outside, I have no problem at all.

Ideas?

 

I'd be having a look at your thermostat. If it's letting too much water through the radiator on reasonable speed, cold weather driving, your temps will stay low, which will keep the idle high. When the car isn't moving you will get up to temp because there isn't any cold air passing through the rad, and so the idle will drop.

 

The strange thing is, the water temp gage shows what it always did when the engine was warmed up and everything was working fine even in cold weather.

 

the engine temp gauge/sensor have nothing to do with activation of your thermostat. it's a $20 fix that takes about 30 minutes to check, it won't hurt anything.

 

the thermowax, which is the thing that pushes the throttle open when the car is cold might be clogged/stuck or just plain bad.

its mounted on the rear of the throttle body, with the 2 coolant hoses going to it

 

Just for giggles, tonight on the way home, I picked up another thermostat. I will put it in over the next couple of days and see what happens. I don`t know when the last one was put in the engine. It has around 160K on it.

j9fd3s,
I will check the thermowax device in a day or 2 also.

For any of you guys out there that drive a GSL-SE, where does your water temp gage needle sit at when your car is warm? Mine seems to always have been about a quarter way up from cold to the middle of the gage.

 

That's perfect i would say and that goes for all 7'ns.

My 12A 85 FB's temperature always sits between a quarter to just before half. When it gets hotter (which it luckely doesn't) i get nervous
So you should be fine. When it gets above half you have a problem.

 

Mine was definitely bad. Wouldn`t check out good with the blow test via the shop manual. Was clogged I guess. Replaced it.

Still on start up.....idle for engine is around 1200 RPMs. Go down the road while cold..........if I reach 4K RPM`s to change gears, idle RPM stays at the highest level of where I changed gears. I look in the rear view mirror and see oil smoke billowing out the back end of the tailpipe. Eek! This morning, had that happen. Car hadn`t warmed up yet. I trounced the accelerator pedal and the RPMs still wouldn`t drop. I ended up turning the ignition off while coasting and restarting the car. RPMs dropped to about 1800.

The only time I can get the car to idle to normal is after everything seems to be warmed up and the outside air temp is around 60 or so.

I do have a new thermostat that I haven`t put in yet. The water temp gage is showing 1/4 way up from cold when warm.

I am thinking that either a check valve of some sort is bad or my throttle body is sticking. I did try a couple weeks ago of spraying out the throttle body with some carb cleaner. Had a lot a nastiness in it. Sprayed off the linkages and anything else I saw that was crudded up. When this high idle condition is cropping up, after the engine is warmed up, I can usually get the car to idle around 1000 or lower in warm weather. In cold weather, it hovers around 1500 RPMs or lower, depending on whether I am driving on the highway or driving around town. Driving around town, the RPMs will drop to around normal in cold weather. Sometimes I can get the car to drop RPMs by stomping the accelerator pedal ( this is only after the car is warmed up ) after driving for around 10 to 15 minutes or so. If you try this before that time frame, car will go to whatever RPM it reached when you did this and stay there. I have to turn the motor off and then back on to get it to drop below 2K or so.

I am really getting confused on this one.

 

Cold weather, high idle and usually results in 'surging' at some point. There's more to the throttle body than just spraying carb cleaner, as you also need to lube the steel shafts where they enter the aluminum throttle body. Your case sounds like a stuck butterfly value due to the shaft sticking in the TB.

Search on "SE Surge" and "SE Throttle Body Sticking", and you'll find a bunch of threads I've written over the years that cover this. Short version, remove TB completely, clean thoroughly, then oil all of the steel shafts, allowing the lube to run toward the TB body, let sit. Turn 180deg and lube the other side, let sit. Reinstall and perform the full "SE Idle Tune", as documented on this site and elsewhere. Good luck,

 

Thanks for the suggestions and info! I will do some reading and see what I can come up with.

I knew I should have kept the TB off of the other motor I had. Nice to have extra parts laying around when you need them.

 

Would like to read what you had written on this subject. What section of the forums should I be searching in Longduck?

 

N/M. Found it! LOL!

 

Well, finally got around to replacing the thermostat today.

Not impressed.

I am seeing engine temps even less than what I had before I replaced the thermostat. Temps on gauge are showing right at the 2nd line above cold. Was higher than that before I replaced the old unit.
The one I took out had completely come apart!
The one I replaced it with was from Autozone and is a Duralast model. Part number is 15048.

I am really lost on this one. Now. Get this. The back end of the new unit touches the water pump housing assembly by about.....I am guessing here.....maybe an eighth inch. Never had that happen before. Something doesn`t seem right. While driving it today in 60 degree weather, sometimes the engine temp gauge would start to go below the 2nd line on the display.

Called Autozone & they verified to me that the part number I had was what their database recommended.

OK. What gives? Should I just call Mazda and have them order me a new factory replacement or get a new thermostat from somewhere else? Where do you folks get your replacement thermostats at?

Next subject.........

I bought a used TB from a fellow I get my used parts from. He is a good guy. Lives nearby too. The TB has been sprayed out to get rid of the excess carbon it had in it and seems to work good. The only thing is, it looks like the throttle position sensor bracket has been bent. The sensor is still there but wasn`t seated on the linkage it is supposed to come in contact with. I bent the thing back into place carefully so as not to destroy the TPS. Now....I don`t know how hard it is to reset the TPS to the correct position. I do have a FSM and know how to read. My only question on that subject is, for you guys that have done a TPS adjustment, is it a tricky subject to deal with or am I making this out to be more than it really is?

I appreciate everyones help in this matter. Good to know that all of us RX7 folks have a wonderful resource as this site to help us in our needs!!

Oh and BTW, got the two "barrel shaped" control solenoids that sit near the oil filler pipe also while I was in the process of getting the TB. I checked my old ones but they check out good. Well, at least I have 2 extra solenoids if I should ever need them.

 

"Setting the TPS - SE" - search on that, as I've written a few things on building the test rig, too.

You're making it out to be harder than it really is. Once you have the 2-light test rig built and know where to plug it in, it takes all of 30 seconds to tune the TPS. You can also use 2 multimeters, but that's overcomplicating an otherwise simple test and check procedure.

On the Thermostat - there are 2 Mazda Factory Tstats that you can get, and both are based on temperature range at which they open. You probably want to go with the HIGHER temp range Tstat, if you live in a cold weather region. I live in the Sonoran desert, so I get the LOWER temp Tstat, for obvious reasons!

 

Thanks LongDuck! I have been doing some reading lately and it doesn`t seem to be that hard to get the TPS adjusted correctly. Think I was making it out to be harder than it is to adjust that sucker the right way!

Oh...something else. After doing some reading in the FSM.....there is a jiggle pin comment that I should have known about when I did the T-stat replacement.

Not sure where it resides direction wise right now. Guess I need to get back in there and find out. Will try this weekend. The manual says straight up. Also a comment in the manual about how the opening temperature will change if it isn`t where it should be.

When all else fails, read the manual. You know us guys though. We don`t need no stinking manual!!