Don't flame Ive used search and the answers i got made me even more confused. Well I've got an 87' TII, had the car a few days and i hate the idle already, SOMETIMES after the car has warmed up it wont do it but when it does it will idle high around 1000-1500 and when its there it jumps up about 300-400 rpms constantly. And other times when im driving and going slow enough it bogs like I dont know how to drive stick WTF? I dont really wnat to regret buying it, i love it! Yeah, I've been told its a vacuume leak and then I've been told its the TPS sensor but i figured I'd come I'd search and get my own answers. If somone needs any more info let me know I have no idea what else to mention. Thanks!

 

Dude, I guarantee it's in the search...use the words "idle" and "adjust". TONS of info

 

bogging... hunting idle ~500 rpm... most likely TPS misadjustment

search for "adjust TPS"

 

Thanks

 

Here is the deal. The rotary engine has so little torque at idle that half of the stuff on top of the motor is for idle speed control.
The BAC is the main controller of idle speed but it needs help with suddenly switching loads like headlights or AC or heater fan on high. These accessories have signals to the ECU to open a vacuum bleed solenoid to help out.
That is why the idle tune up is so complex.

I had a similar gremlin.
Sometimes it would idle perfect, then for no apparent reason, start surging up to 1500, stumble , fall to 400, and surge again, sometimes stalling.
When I went to get tools & meter to start checking, it would idle perfect.
I had a big improvement show when I replaced the firewall to bell housing ground and added an alternator to body ground. If those grounds are not perfect, the ECU's sensor grounds try to carry some of the spark & alternator load. The ECU tries to recalibrate & goes nuts.

The short range TPS:
Its job is to tell the ECU you're at closed throttle.
If it is out of adjustment, the ECU may not activate the BAC to handle idle speed.
If it is worn out, the ECU may see random closed throttle signals while you are driving, giving you a bad misfire.

 

I had the same problem as you are describing....
turned out to be a combination of two things, that if I,d done better checking, probably would have been one. I first too looked at the TPS. It was out of range, but no mater how many times I adjusted it, it would not fix the high idle, only the surging, then I looked at everything....except what it was. I finaly found the dash pot to be sticking a lttle. It wouldn't seet all the way back like it was supposed to. I found out by reaching back and pulling it by hand back and the idle dropped. I then used the idle air flow adjuster on the intake to raise the idle a bit as I had used it to lower it screwing it all the way tight, now it was mostly centered. Then I loosned the dash pot lock nut and turned it till the idle got to exactly 900. Then I readjusted the tps, and then the idle using the adjuster on the intake, and finaly readjusted the tps again at the right idle of 850. It now idles pefect, no surging, and pulls great off idle. All this may be different for as turbo tho, but may not be.

Hope this can help a little.

PS. The dash pot is the round vacume cylinoid looking thing on the back side of the intake. If you are standing on the pass side looking into the engine compartment, you will see the lock nut on what looks like more throttle linkage..and actually is for the back side of the intake.

Leslie

 

Dude, I had the same "symptoms about three years ago on one of my 88 REX's....in my case it turned out to be the Pulsation Damper located at the end of the fuel rail just under the intake tubes on the top front part of the engine...if it needs replaced you have to remove the Dynamic Chamber and intake cluster....so you will need new gaskets for all that....do you smell fuel too? If it is the "Pulsation Damper" it will probably start leaking if it doesn't already....Mazda dealer charged me $239 for the the whole deal...part and installation....good deal I thought so I did it....been fine since.....Good luck !

 

well its starting doing something different today. Everytime i started it when it was cold it went down to normall idle. But after i drove 4 feet and left it idle it started it all over again. I havnt had the time to start checking things out but i'm gathering as much info as possible for this weekend when i get on it. I was told today by a fellow rx-7 enthusiest that if it was the TPS it would also bog on WOT. Any thing on that? These might be stupid questions but this is my first TII and i want it to last a long time.

 

test your BAC definately and i agree with the TPS

 

Could also be the Sub Zero start system. Is the little resovior full in the back left of your engine bay? Do you have the right thermostat? Both those things caused my idle to wack out. I replaced the whole subzero start system with a good working one and my idel is pristine again. Now I just need to adjust the TPS again to get it perfect.

 

your questions definately arent stupid man but most of this stuff is in the FAQ or found by using the search option. here is a link that comes from the "OTHER" forum


this is a great link
http://www.teamfc3s.org/info/articles/idle.html

 

This maybe car specific, because i ripped that piece of crap out of my car and it didn't change anything for the better or worse.

 

Screwed over my car. You have an S4 or S5? Anyway, make sure you have the proper thermostat.

 

i have a 88 TII, hes got an 87 TII

 

Thats the best explanation of the TPS ranges i've read so far. Thanks a lot!

 

Hey, GeTCrAzYKiD, Just wondering, does this USUALLY happen after you were cruzing on the highway for a little while, or just after your car has warmed up, then not after that?

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Hrm, SureShot, you claim a worn TPS will send random closed throttle signals? Perhaps that is what causes my related problem:

My car will run perfectly, rock solid idle, pulls hard and strong, totally predictable power band and good (for a 7) fuel economy. However, sometimes I'll be sitting at a light just idling fine and then BLAM my idle drops wayyyyyyyyy down for a fraction of a second and the car shakes, and then it goes right back up, just like a misfire.

Do you think that caused it?

 

Well in the mornign when i start it it does the 3000 rpm warm up cycle and then it goes to normal idle but as soon as i start to drive liek backing out of my driveway or even pull forward a few feet it starts the funky idle. But if hadnt moved it would stay normal. This is why im so confused.

 

Yup - could be.

The golden test:
Pull the TPS plug.
Clip a cheap analog (needle type) VOM (set to the 1K ohms scale) on to the green & orange wires.
Hold the throttle open.
Slowly push the TPS plunger in & out.
The VOM needle must sweep smoothly from ~0 to ~5K.
If the needle jumps around, goes high or drops during the plunger stroke, the ECU will get confused.

I have had good luck using spray contact cleaner if there were some minor drops, but once the TPS is worn out, it must be replaced.

 

couldn't you trick the ecu by placing a 1k ohm resistor in the green and orange wires thus bypassing the tps completely and never having the problems again? just wondering.....

 

No then it would only think you are idling and would drive horribly and get even worse gas millage

 

the TPS uses a variable resistance device. depending on much that plunger thing is depressed, it will increase resistance. i believe that it is a proportional resistance change though...for example, for every 1 cm movement, the resistance changes "x" many ohms...

 

Now if only someone could make a OEM TPS replacement. This part seems to fail on most FCs(maybe just old). $150 brand new is a pain. I wish it came with warranty. It seems like such a simple piece of equipment.

 

yeah, even if i adjust my TPS, it seems that it goes out of whack a bit again after a while, and then i need to readjust it. i guess this is the TPS, but it really only affects my idle, so i'm not too quick on dishing out the cash for it...

 

It affects mileage also, and with gas prices being the way they are using a good tps can pay for itself fast.

 

crap, that's what i was afraid of...what do you guys consider a TPS that is "bad" (needs to be replaced)? like i said, mine starts going out a bit after awhile, but it is not incredibly severe.