when my car is coming to a stop (gear in neutral, foot on brake, car still rolling), the rpm would fluctuates between 1.1k to 1.5k and as soon as the car comes to a complete stop the rpm would stablize at 1.3k which is what my car normally idles at.

From searching this forum, I'm guessing my problem might be related to the TPS being off. I haven't check the voltages on my TPS yet but I would like to get more ideas as to what my problem might be before i mess with any adjustment since my car runs fine as it is right now except this annoying fluctuation and slightly high idle speed.

Also, I have some questions about Damian's post (https://www.rx7club.com/forum/showth...1&page=1&pp=15). He talks about setting the throttle body to ground zero prior to adjusting the TPS, which involves closing the Air Adjusting Screw (the "AAS" as mentioned in FSM) and adjusting the Throttle Adjusting Screw (the "TAS" as mentioned in FSM). However, I dont understand what am I aiming for when adjusting the TAS? Do I screw it in all the way?

Ideas anyone?

 

My car idled sorta like that just recently. Mine would hunt from 1000-1500rpms while clutching in and also while sitting at a light. Usually the rpms would stabilize after a little while. If idle was steady, it sat at 1500rpm. After a few weeks of driving though, the idle rose to 2000-3000!!!

I found my problem to be a LIM gasket. LIM gasket replacement was quoted like 800-1000usd or something like that, so I just did it myself and spent $100 on parts. Changed it, and idles perfectly now.

So you might wanna check for vacuum leaks. Spray some water/dish soap combo around near the connection points while the engines running - TB to UIM, UIM to LIM, and LIM to block. If you notice a change in the engine, then you may have a vacuum leak.

Also, check your TPS. Do you have a PFC and commander? It's easy to check the voltages on the commander if you have it. Otherwise, you can do what Damian did in his post.

Unplug your ISC solenoid and see if your hunting idle stops. This can sometimes stick open or close, causing your idle to change as well.

Waxrod assembly. This helps with startup during cold mornings etc. I disabled mine completely following robrobinette.com.

Dashpot. This just helps to prevent your car from stalling when you're decelerating.

Check all of the things above. I had a bitch of a problem solving my idling problem, so I hope that helps you out at least.

 

Sounds like a vacuum problem. I also had this problem and I adjusted my idle screw and my tps screw. If you mess around with both of them, you should be able to fix the problem if it's not vacuum.

The TPS or TAS basically it controls the butterfly doors inside of the manifold. The more you screw it down, the further it allows the doors to open up inside and allow air to come into the car with no throttle applied. The screw basically pushes against the plate and allows it to open up.

Also, check your sensor for the idle speed control. I believe it's a blue plug under the manifold, mine wasn't plugged in but I don't know if it would cause that cause I couldn't start my car =P

I also removed the double throttle like Quickfini, I followed the robinette guide too.

Good luck =P

 

I have a Power FC and mine does that when my water temps get high (100 Celcius +). I thought that was normal (the engine trying to keep water flow up to cool the engine off). Once it drops down below 100, normal idle.

 

Quickfini:

How hard was it to replace the LIM gasket? How do you unplug the ISC solenoid (where is it located)?

I don't have a PFC but I will following Damian's post to check the TPS. Hopefully that would fix my problem. I really dont think its a vaccuum issues (im hoping) because the fluctuation only occurs when im decelerating (with foot on brake and the car almost coming to a stop) and it goes away as soon as the car comes to a complete stop. If i blip the throttle while its fluctuating it would stablizes at the normal idle speed.

 

agreed. sounds like a vacuum leak. i had the same problem.... with high electircal load the fluctuations were not as apparant, but with low electrical load it was very noticeable. your RPM is high, which is another sign of a vacuum leak. i replaced... the UIM-> LIM gasket, and the LIM-> motor gasket. what year is your car? the LIM->motor gasket was made out of paper for some years... mine was a 94 and it was a paper gasket. these tend to fail over time. while you have everything disassembled (if you havent done it already) now would be a good time to do your vacuum lines as well.

if you would like any help/tips doing these things feel free to ask. good luck, heath

 

The LIM gasket isn't TOOOO bad. You just have to follow the FSM and make sure you label everything as you go so you make assembly easier for yourself. I'm by no means a mechanic, and I'm pretty new to rotaries as well. But if you follow the FSM, you should be ok.

The ISC is a solenoid just connected under the UIM, so all you gotta do is reach back and under and unplug it. It's just clipped onto the solenoid. You can use a small screwdriver to help you if you got big hands.

 

Yeah my idle was bouncing today (first time i got to run the car with the large ported motor) - looked under the hood and the 2 vacuum caps on my UIM were missing, put some new ones on and idles great =P

 

I've got the same problem when I stop at a light! Except, I've isolated the high idle problem(~1500 rpm). It only happen when I put the car in 1st gear w/ the clutch in. When I move the shifter into neutral with clutch in, the idle settles back to normal (under 1000 rpm). I've adjusted the TPS with a meter. Any other suggestions?

 

I'm having the same problems, only if i blip my throttle it only goes away for a minute or so. Just got my motor done by pettit a couple of months ago. dhahlen, what caps are you talking about exactly so that i can check.

 

Before anything else, make sure your throttle and cruise control cables aren't a little too tight and limiting the throttle travel back to "zero".

This problem can get worse after the underhood temps get high and the cable housings expand, so check the cable slack when the car is hot.

 

My idle is still a little weird too. Mine was idling at 1200 with the TAS screwed all the way in. The other idle adjustment would raise it, but not lower it. Then Dave W suggested I adjust the cable which made sense. Now it still idles high unless I'm sitting still for a minute or start to let out the clutch a little. then it will drop down to 800 and stay there. I haven't checked the tps yet. I'd have to be be pretty bored to do that.