I'd like to begin by saying that I have researched the forums for many hours trying to figure this one out without any luck. So far I've changed the plugs, oil and fuel filter with no improvement. So here is a detailed description.

When the car is first started it idles rough. The exhaust smells extremely rich and I get a grey/white smoke out of it for about a minute. There is slight popping in the exhaust indicating to me that fuel is burning in the cat. My RPMS are steady at 1500 whether in gear/not in gear, etc. For a brief period about 15 seconds after start up the RPM's will rise to about 2000 RPM then back down to 1500.

When the coolant temp hits about 140 degrees F, the idle will flutter a bit and then it switches to warm idle at about 750 RPM. All is well after that. The car runs perfect in every aspect.

The FSM says to check the fast idle cam, the IAC valve and coolant tempurature sensor. The fast idle cam appears to be adjusted correct from what I can see, however access to the other two items are extremely limited. I'm not sure how I can test either without ripping a ton of stuff apart. If anyone has suggestions they are more than welcome.

On a side note it seems like the warmer it is outside the less rough the idle is. Earlier this week it was 65 degrees outside and when I started it, there was little drama. There was still slight roughness, but not like when it's a bit cooler.

Thanks to anyone in advance that may be able to offer advice.

 

I also forgot to mention that my car is a 1994, 47k miles, and is completely bone stock.

 

By rough do you mean it's loppy? (rpms going up and down Eratically or sounds like a cam'd out v8). Or are you just saying the idle starts high and drops? Because that is normal behavior. It's part of the accelerated warmup system.

As long a it idles smooth (at least while it is not dropping from 2k to 1.5k or 1.5k to 800) then I don't think there a problem.

And like you said, popping is normal, just unburned fuel igniting in the exhaust

 

The gentle popping sound is completely normal as far as I know.

The stock ECU does run really rich on a cold start. Again, normal.

I notice that on my car the popping thing happens more when it's cold and the engine is cold. I don't think it happens much when the car is warm.

 

The RPM's stay steady around 1500 with the exception of jumping to 2000 for about 15 seconds about 30 seconds after the car is started. When I say it's rough it sounds like it's missing. It even shakes. The other odd thing is how the RPM's will fluctuate about 200 RPM for about a minute just before it switches to the warm idle. I also thought that the AWS is supposed to bring your RPM's up to 3000 unless you're in gear or blip the throttle. Thanks for your input.

 

I've also read on some other threads about the water temp switch and/or the thermowax pellet possibly being a cause of bad idle. I'm not sure where to find either or how they interact with the system. Would anyone be able to clarify on that.

 

Anyone have any insight on this? I see a lot of views, but I've only got two posts on this. Bueller?

 

I don't really know what it can be.
You would be more lucky if you search in the forum for someone who might have had a similar problem.

Good luck with that.

 

I have searched the forums for many many hours and I found one person that had similar symptoms, but their problem appeared to stem from some type of tuning problem with their PFC. I don't have a PFC, so the solution wouldn't be applicable to my problem.

 

What car is it?
Is it stock?
Is it modified?

 

I had this same problem for a while. Also if i tried to drive it cold, it would die. What I did was... live with it... because I had no Idea what to do. But one day I decided to replace the o rings on my fuel injector, primary and secondary, so i removed my entire top end. I replaced all the fuel lines, and I completely cleaned the throttle body inside and out to a perfect shine. (it had some carbon). After I did this I put everything back together and I notice a significantly smoother cold start. So... Either the new fuel filter and lines, clean injectors, or spik and span throttle body did the job for me.

 

Mine doesn't die when I drive it cold. In fact there doesn't seem to be any noticable power loss or anything. It just sounds like **** if I stop at a light or stop sign. I'm thinking that next winter I will be doing all my reliability mods, which will include the vacuum lines, so that might be a good time to clean the throttle body.

 

Eduardo - The car is a '94 touring with 47k miles and bone stock

 

Did you ever figure out what was going on? I'm having the exact same problem. Happens only when cold, and hits about 140deg then idles perfectly!

 

I haven't figured anything out on this yet. Since summer is in full swing now, it hasn't been an issue. I have to wonder which one of the sensors is the cause, because the AWS works as it should also.

 

Thanks for the reply! Sorry to hear you haven't gotten it figured out yet.

I'm guessing you're right that it's a sensor problem, I've just cleaned/recalibrated the throttle body/tps etc and am going to re-install it and see if that helps. If not, I'm guessing a coolant temp sensor, or something.

Justin

 

Coolant temp sensor is more the direction I'm leaning with it too. I'll be doing a lot of work to it over the winter and I plan to check into it.

 

Having this issue with the cold weather, any updates?

 

Nothing real definitive. Someone on the main forum suggested checking the purge control, but since it was summer it ran just fine. I haven't really had time to mess around with it. It's parked for the winter now....

 

Hi guys, first time here. I just bought an RX-7 FC S5 with the exact same issue! Some weird iddling in the beginning over 1500 rpm, then after warming up it goes back down to 750 rpm, stable. I had a specialist checking it, in the diagnostic connector and he said it is probably the thermostat that keeps the cooling system "running" even when the car just started. In addition, he also mentioned the throttle sensor should be adjusted. By any chance, did you guys found this solution effective? Or was the problem some other thing?