I have a 1990 13b non turbo.....When I start it up ..it revs to 2800 for 10 seconds then drops to 1200 and revs up and down for as long as I leave the car running????????What do I look for ??I am really new to the Rotary scene.............

 

check your TPS.....go to www.teamfc3s.org and look at the factory service manuals for how too....

thats just the 1st thing I'd check..could be a billion other things..

also search a bit...lots of ****

 

hmm... does it eventually even out (ie. as the car comes up to temperature) or will it stay fluctuating?

 

You may want to, In order, readjust your Throttle Position Sensor, your Idle Speed and than your Idle mixture.
The manual can be found at www.fc3s.org or/and www.iluvmy7.com
For the sake of simplicity, you may want to additionally want to do a major tune up first. Doing this, will rule out alot of potential culprits.

 

Did this happen all of a sudden, or did you mess with anything? It could be the TPS, or a vacuum leak somewhere. Those are the 2 most probably causes..

 

Sorry guys I was outside kicking the rx7........Yes it will do it constantly til I run out of gas........

 

It wouldn't hold an idle at all til I replaced the orings on all the injectors.......tit still a little hard to start ,,,,,.but it will if you hold down the pedal

 

I say you have a pretty sizable vacuum leak somewhere. While the car is idleing, go around the engine bay and spray some carb cleaner around areas where you think you might have a leak. Do this VERY carefully as carb cleaner is very flammable. When you spray where there is a leak, the idle will jump up and steady out. This will tell you the area the leak is.

 

I have already sprayed a whole can.....also when I bring the idle up ....to 2000 still pulsates ...2400 pulsates.....when I hit 3000 it is perfect

 

Have you tried adjusting your TPS?

 

not yet.....trying to figure out how........doesn't look at all like any tps on american cars I have seen

 

My first gen 13b did some thing that sounds like this. I could not figure it out, I ended up swapping throttle body from another junk se and the problem went away. I got lucky in the shoot gun trouble shooting methode. Now the idle ust sticks a little high and all I have to do is tape the gas and it drops back to 900, still tring to fix that though. I would look into you TPS settings, vaccum lines and others. No real help here. Sorry.

 

Trying to figure out how to adjust that tps black prong...I don't see any adjustments??????????

 

http://fc3s-pro.com/TECH/HOWTO/TPS/tps.html

or

http://home.rmci.net/panther/tps.htm

 

RXMFN7............That is really appreciated!!!!!!!!!!

 

Sounds like a vacuum leak to me...

 

My s4 n/a has that fluctuating idle After i did the vaccumhoses, this thread might solve that

 

I have something like this on my TII, once the car is at normal temp the car idle really rough and the engine move alot (engine mount is ok) I'm still trying to find out whats wrong with it.

 

Just was looking at a 90 with the same problems. This was a manual car (obviously clutch was pushed in..) - wonder if this is seen in automatics as well?

 

my car just starting doing this not too long ago. It only does it when it is not completely warmed up though. I removed the bac valve thinking that it was the cause but it didn't help much. My TPS is already adjusted to where it needs to be so I don't think that its the problem. Any help would be awesome.

Thanks,
Aaron

 

My TII does exactly the same thing as the original poster. Only it only started doing after a TPS adjustment(ohm and lamp method). Before the tps adjustment the idle would just stay at 2k rpm. So I adjusted the tps and now the idle starts out at 3k for ten seconds, then bounces between 1.4k and 2k. Two things i plan on testing as soon as this april snow is gone is vac leak and BAC. Other than these two things, is there anything else we should be looking at?

 

1) make sure the cars warm when you do it
2) make sure your fast idle cam isn't jamming and holding the throttle open more
3) make sure the dashpot isn't stuck as well
4) see if you can't pull the throttle closed while the cars running and see if it changes, if it does chances are somethings holding it open somewhere
5) adjust the tps after the cars warmed up completely
6) check for error codes

 

bring the idle DOWN. My S5 TurboII did that when I had it idling at around 1400-1500 RPM. Now that it idles around 800 it doesn't bounce.

 

OK guys. I already adjusted the tps to where it should be, but maybe I should do it again just to be sure. It seems that when the car is first started, it idles fine, but after a few minutes it just starts bouncing b/w 1200-1500 or so. I checked for vacuum leaks and couldn't find anything. I also have an exhaust leak, but I don't think that it would cause that kind of problem. I've had the leak for a while now, but the pulsing idle seems to have happened pretty recently. I will check the throttle and make sure that it isn't being hindered anywhere. Thanks for all the help so far, and any more info would be greatly appreciated.

Thanks,
Aaron

 

I am not that experienced, so what exactly is the dashpot??? The only warnings that I'm getting is the "cooling fan" but I haven't been able to figure that out yet and don't know if it has anything to do with the idle problem.