Heeelp! We are trying to figure out a strange problem on my NA '87 Rx. The problem started gradually but has recently become bad enugh that the car is pretty much un-drivable. The idle is smooth and happy but when we step on the gas the car will rev up and down by 500 rpms or so. This causes the car to buck wildly when trying to drive at a steady speed.

Our first guess was TPS. We cleaned the sensor and messed with it and it doesn't seem to have any effect on the rev'ing problem.

Second guess was the Idle Air Control thingy. We took it off and cleaned the heck out of it but that hasn't helped eathier. When we disconnected the IAC motor we noticed that there was coolent on one end but the other end was dry, a vacum problem maybe?

third guess, throtle plate adjustment? Is it ok to clean these with carb cleaner or will this cause damage to the engine? We are going to try it but its too freekin cold outside right now. Lets hope that some clever RX7 owner on the internet has some information that could help us.


We want to aviod thowing parts at this problem if at all possible. Any suggestions are greatly appriciated.

THANKS!
Toast n Tharkin in NC

 

can someone please explain how the Idle Air Controler works. We are trying to determine if it is working and exactlly what it is suppose to do.

 

Have you tried putting a different TPS in there? Like one out of another 7?


Carb cleaner won't hurt anything. Spray the hell out of it. But be warned that your exhaust will briefly be even more nasty afterwards.

You'd probably be able to do a better job with the CC if you pulled the upper intake manifold off and not only sprayed the throttle plates, but scrubbed at them where you could with an old toothbrush or similar item. Simply wetting carbon with cc will neither loosen nor remove it - scrub it or hit it with a continuous blast.

Btw, I doubt that goo on the throttle plates is your problem, but it doesn't hurt to clean them anyway, if only in the name of good maintainance.


Doesn't surge at idle? You may have the only 7 on earth with that problem.

 

Hahaha ya i agree...but instead he's got an even WEIRDER problem.

Now i'm no expert on rx7's (yet)...but maybe this is caused by a vacuum leak or the BAC? Probably wouldn't hurt to check that stuff anyway.

 

Things you might want to check, timing, air filter, vac leaks, and sparkplugs.

 

arent we suposed to check those for EVERY other problem the car has. just goes to remind you how important regular maintenance is on your 7.

 

And I'm about 90% sure his car is acting this way do too poor mataince.

 

Can we use a TPS off an 85 gsl-SE to swap with my 87? Its the only other car I have available to mess with right now.

Tharkin has been messing with it today while I am at work, he says it was surging at idle when it was cold. He messed with the upper throtle body and it quit but still does it when we step on the gas. Just put in new plugs, new wires. Checked the timing, checked for vacum leaks, checked the airfilter and all were ok. He was testing the tps with a circuit tester to see if there was power to the TPS and when he connected it the light was very dim and the car stalled out.

Is this possibly a logican or grounding problem?

Thanks for all your suggestions

 

NO.

I mistakenly put one on my car this past fall and almost blew the motor - the throttle maxxed out in moments. Don't do it.





What did you use to check for vacuum leaks? A garden hose is my #1 fav method.

I don't know what to tell you about checking volts to the TPS - hopefully someone else can tell you what to do.



Logicon - I don't see how.

Grounding - possible. Have you added any ground wires to the engine bay?

 

could this be cause by bad injectors?

 

Surging? Doubt it.

#1 explanation for surging (AFAIC) is a vacuum leak. The extra air getting in ultimately befuddles the ECU, which then chases its own gauges (to borrow an aviation term) trying to compensate.

 

WhooHooo! We got it!
A new TPS was all it took, go figure!


Thank you all for your suggestions!

-Toast out