Hello everyone, Me and my friends purchased a 1987 rx7 fc a few days ago. We checked the compression and got around 90 on both rotors so it seems that it's in good condition. We drove it for a few hours and we had two issues we came across. The first issue has to do with the temperature gauge. Showing full cold, so we checked the sender and connection to the gauge, cleaned it off and plugged it back in. My guess is that the gauge itself is cooked but we were wondering if there's some way to maybe test it just so we can try everything. The second main issue revolves around tuning the idle. Initially when we got this car it idled at around 2000-2200 rpm. The Snapchat attached video attached to show this. To fix it we figured we'd have to adjust a screw somewhere on the throttle. Looking around the forums and experimenting ourselves we adjusted two screws. The first screw was one that we read had to do with the amount of air, that's the one I circled in blue in the image. It did absolutely nothing.

The second screw was the one circled in red. Us moving it all the way to one end lowered the rpm to around 1500 on the idle, but now it started surging back and forth a few hundred rpm. The other attached video shows that.

Additionally when pulling the throttle control all the way back it does go to around 700 rpm. Also there is no BAC - it's deleted. I assume the previous owner deleted it and it never warmed up properly, so he raised the idle, we just can't find the proper way to lower it back down. I think we'll order a BAC since it's only a $40 part. Thank you for all your input and help.

 

Welcome to the forum. I am not trying to be rude but it is pretty obvious that you are new and didn't read up first before posting. These questions have been asked here a thousand times. This is why the post sat with no response. Check the Factory Service Manual and the below related posts.

You will want to warm you car until it reaches normal running temperature. The screw on top to the intake can not be adjusted until the connector in the engine bay is jumpered, most likely. I am not sure with missing parts. The other screw needs adjusted to 1VDC at the connector or so when the key is turned and the engine not running. Also, you can build test lights too. I forget the order of these things... 1vdc... then intake screw and back again. There are many threads here describing the processes. Report back after you take the time to help yourself. This can be a bit confusing for newbs sometimes.

 

Thank you very much - I admit I did not read super hard and missed some parts, like needed to jumper the connector. Will try that!

 

Hey, worked on this all day and took the time to read things. Really trying to do my homework, we adjusted the TPS properly as per the manual, got one light. Then jumpered and adjusted the idle screw. It changed something for sure, it now seemingly idles around 1000 rpm at the lowest possible setting. Which is absolutely progress, no doubt about it. However this not being 750 ish makes me want to perform a vacuum leak test which I'll do in the coming days. The concern is now shown in the attached video - it will idle smoothly initially, then when it gets up to 1500 or so it will start surging. If you rev it high enough for it to come back with inertia and undershoot to 1000, it will go back there and idle normally.

Looking through the forum, people mainly said bad TPS setting (don't think so as we definitely warmed it up and properly set it to one light), and some people said bad clutch switch (but engaging and disengaging the clutch made no difference so I can't imagine it being that.) This makes me possibly think that it might be an ECU problem - one thing i forgot to mention in my original post is that with the way the radiator fan is temporarily wired by the old owner - it's straight into the battery. So you disconnect the battery every time you don't drive and reconnect it again when you're about to start. A few posts said that it makes the ECU "forget" the idle (as far as I understand) so I was wondering if it's that.

Again, thank you for the input and help, as you can tell I'm very new to this and I appreciate every bit of advice I get here.

 

Good work looking this stuff up. With your electric fan. There is plenty of great information on how to wire a fan on here. You will need a relay, a fuse, some wiring and a sensor. Maybe I am missing something. Just be very careful and don't forget to turn on the fan.

I did read somewhere that the voltage for some works better below 1VDC by just a bit. The TPS should sweep very evenly from start to finish. In the ohms setting, maybe a needle type would be easier to see the sweep? The ohms rating is on here somewhere. If that is good the TPS is good.

That is so cool that you made the lights too. Those are pretty handy to have. As far as the ECU memory goes, I don't know. I don't think the ECU has a write and remember function. I think ECU's like these are logic circuits.... possibly.

 

Well to be fully honest with you we didn't run the lights but used a multimeter and checked the voltage on each connector until one side showed it. A little ghetto but we figured it works. And we did jumper the green connector and we did adjust the idle screw to the lowest setting - it absolutely helped, went down to 1000 there.

But it looks like that's not a main issue for now... Big big coolant leak now behind engine towards the transmission and it looks like I'll be heading out very soon with no time to work on it until August... No oil in coolant and no smoke from the exhaust, I hope it's just some plug, but it's going to be a pain finding the exact source - possibly will need to remove the engine, but it'll have to wait until August. Wack how previous owner dailies it for 3 years and it does this immediately after we buy it

 

I edited my post while you were writing. 😆
The surging issue has been discussed here. The search might find it. I had somewhat similar issues with mine that were never fixed before I parked mine. There are quite a a few great posts here to search for vacuum leaks. I would start there after double checking the lights and idle screw. Some use propane gas and a hose and others....smoke.
Good luck finding the leaky coolant. That can be a bit tricky. Sometimes a thorough cleaning in the area will help make is more visible.
I really like how quiet your exhaust sounds. This is my third 7 and all of them were kinda loud. I will fix mine finally when it is ready to drive. The original owner told me, after long drives, the car was so quiet it was had to tell it was even running.

 

Don't know if this helps.. . It's basically the process I went through to get the car running well enough to pass smog in CA

Down low in the thread is resistance measurement of the water temp gauge.

https://www.rx7club.com/2nd-gen-general-discussion-323/86-n-s4-story-redemption-1154012/

 

It's 99.9% the coolant hose on the back side of the intake running between the thermowax and engine iron, this can cause idle seeking because the the thermowax doesn't like getting air and contributes to the idle. You need to deal with this right now because the engine coolant may be pooling on top of the lower intake manifold(LIM). There are pockets where it can just sit there and it will eat the LIM gasket till you will have to pull the entire LIM to fix the unmetered air entering the engine if you let it sit. Pulling the lower intake is not a pleasant experience.

Also you are missing vacuum hoses on your intake, unless you did a rats nest delete you should have those hoses, they are there for a reason will run you about 5 bucks.

BAC delete probably contributes, but all that would do is make it to where the engine had a low idle or died if you turned on the AC and/or used the power steering.

Also yes, the air idle adjust screw does jack all, in my experience I could only adjust the idle by about 50 RPM with that, and the ECU will straight up gaslight you because it will revert your changes even with the initial set connector jumpered. Hope this helps.

 

I believe there’s one on the rear iron. You’ll need to remove upper intake manifold after draining the BLOCK

 

My air adjust screw also does jack all even w initial set coupler jumped. I’ve just been using my tps and tightening my throttle cable bracket. However my TPS adjusting screw is maxed out to the tightest it can be w the tps barely at 1.0k ohms. Is there something else that effects the tps button being pressed in beside the adjusting screw?

 

It ended up being a blown freeze plug. We took it to Banzai Racing and Chris did a wonderful job rebuilding it. It was also a blown coolant retaining wall in the intermediate iron, so had to get a new one.

I found what the issue ACTUALLY was. It was extremely extremely simple. The throttle I could pull back with my hand previously until it went to idle. So when we got the rebuilt engine, we loosened it all the way so the throttle would be at the lowest possible position. That always died, even when warm. Just a small adjustment then made it idle perfectly at 700 rpm. I'm not sure if this is a bit of a "ghetto" way to fix that issue but it worked well for me.