1985 Rx-7 (stock)

Basically, when I take the "foot off the gas" the RPM will increase at intervals until it reaches a solid 2500 RPMS. Rather than dropping to its normal 1K - 1.5K idle. What could be causing this?

If I open and close the choke, the RPM will drop to 1 to 1.5K

Thanks ppl.

 

have you messed with the dashpot settings?http://pittdp.homestead.com/underhood.html
check out the link above, should help......good luck

 

Just for reference. 1-1.5k RPM is not a normal idle.

 

well... i have a stock tach in my 85 and it's growing grey hairs... hehe
sometimes my old tach will become "stuck" at a higher RPM reading--i have an engine analyzer and i use that to adjust my idle speed so that it's around 750. but sometimes when i am pushin my 7 the tach jerks a little (cuz i'm speeeeeeeeeeed shifting) and it starts to read about 500 higher than what its supposed to... not a real problem though, i just let it sit for a little bit and it goes down by itself

so maybe your tach is not that accurate, i know mine isn't!

 

Mine's fairly accurate, although I don't have a way to really check.

Please check me on the following:
For handheld tachometers that connect to your coils, do you set them on 4 or 6 cylinder?

I usually set mine to 6 as the coil fires three times per revolution, but people have said that you set aftermarket dashboard tachs to 4 cyl.

Do you connect to leading or trailing coil?

I don't think it matters on '81 and newer cars.

 

The coils fire twice per revolution, not three times. The rotors are only spinning at 1/3 of the speed of the eccentric shaft so in one revolution the coils fire once for each rotor. That's why you set aftermarket tachs to 4 cyl. mode as you would with the handheld tachs as well I imagine.

 

The coils fire three times per every one revolution of a rotor, right?

And the rotor turns three times per one revolution of the shaft.

Wait a sec. That's 9 fires per revolution.

And now it dawns on me that in stock config, the leading coil does both rotors, so thats 18 fires per revolution.

Great. Now I'm all confuzzulated.

I would go back to my high school and look at that series 4 with a removed front cover, except they have a DIS and wasted spark setup.

 

You've got that part around backwards. The e-shaft turns three times faster than the rotors. Ahhh, now it makes sense you say.

 

Damnit! (Hopefully the Doh smilie is working by now.)

Okay.. So, The rotor turns once per three e-shaft rotations.

The spark fires thrice per rotor turn or once per shaft rev.

Times 2 per rotor and

2x per rev. 4 cylinder.

Set it for 6 if I had a 20B.

 

New as I am to the rotary and the first gen RX-7's, the problem is fixed. Problem with the throttle body, TPS and the Dashpot settings (thanks Donna) God I love this ride. Im going to have to replace the O rings which, from what I've read in this forum, requires a tear down and rebuild, or engine replacement. Whatever the case, Im going to upgrade the water/oil cooler after the replacement or rebuild.

85 base model 12a stock 240,000 miles (woohoo!)

 

OMG... I did not know all that Pele...

But, I think i set mine to 4 cyl and connect to leading--but either one seems fine, there is little difference between leading or trailing (at least that's what i remember)...

Can ya throw me some info? where is the TPS? and what does it stand for... (i'm too lazy to figure this out)

Thanx!

 

You say you got a Choke in the 1st post, maning you most likely have a 12A.

TPS is only on fuel injected 13B's, I think.

TPS = Throttle Position Sensor. Tells the ECU how heavy your foot, or the brick you have set on the gas pedal is.

 

Actually the nikki has a tps. I know it can go out of adjustment. but I do not know what it controls. It may have some thing to do with the emissions computer these things have. probably opens a solonoid valve for something like the shutter valve.

Just my $.02

 

yea, i discovered a screw below my carb and it adjusts the throttle.... i'm not sure if that's the TPS... but when i adjusted that screw it did change my pops--i adjusted it till it only pops when i rev my car to like 5000 and then take my foot off the pedal...

maybe that's the TPS in a 12A?

*pretty clueless--only knows that it helps* :o

 

Damnit.

My RX-7 has a TPS, my Honda has an o2 sensor. Both are carbureted. Whats the deal.

 

A 12a tps is located on the front of the carb, and is used to activate the decelartion valve. It's a little two or three wire plastic plunger switch that is depresed at idle. If the idle is too high and the emission system is working properly you will hear the decel. valve going open and close, or it will just stay open if the idle is way high.