Murilli

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Hey guys, alright so I have a 1986 rx7 NA that's recently been giving me problems. Basically, when I start her up she will rev to about 3k, then slowly decrease to about 1.2k then hover there for about a minute, then bounce from 1.2k to about 1.6k every two seconds. Weird. Then after a few minutes of that, it will decrease to about 800rpms and slowly die. I can keep her alive if I give her gas, but if I rev her over 3k, it will backfire and shoot out some intense flames about a foot long out of the exhaust. So, driving isn't really possible right now, though she starts up like a champ.

I was driving her for about 8 months just fine until this happened. When I first got her she would idle at roughly 750rpms and would bounce around 50rpms. Then, few months later I noticed the idle was at around 500rpms, raised the idle back to 750rpms. 2 months later, the idle was low again, and just turning the steering wheel, pressing the brakes or turning the head lights on would stall it. This became very annoying driving to work haha, the next day I noticed the car sounded completely different and even had a different vibration to it, as I drove her to work, the car stalled several times, and I even had to keep my foot on the gas almost the entire ride to work, where she still is to this day.

Now, I will start her up every few days to keep her battery alive. But when I do, she wants to die and will backfire shooting some intense flames out of the rear exhaust. Like I mentioned previously, there's a noticeable difference in the noise and vibration she makes. I had replaced the spark plugs, alternator, both coil packs, BEFORE it got to this. When I first started experiance the idle issue, I took her to a mech, and he told me my car was running just fine. Right now, I have a friend, who is a diesel mechanic of 20 years and has experiance with rotaries helping me figure this one out... with no luck yet.

With spring just around the corner, and moving back to Michigan soon, I have to get my baby back and running again. So, I'm wondering if any of you guys have heard anything similiar to this, or have experianced the sort. I have looked online and can't seem to find anything, so hopefully you guys will be able to direct me the right way. 1986, Naturally aspirated, 5 speed, for the most part it's stock, minus the radiator, air filter, brand new alternator, and MAF. I appreciate any time given, and if you live in Springfield, MA area and would like to look at her, let me know, thanks!

satch

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Set the Green/Red wire of the TPS to 1 volt w/key to on and engine as hot as it can get.

Murilli

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Thanks! Bear with me, i'm not the most technical.

Okay, so turn her on and let her heat up for a bit, locate the TPS (near the throttle body right?) and then how do i set the TPS?

Murilli

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Found my answer on that, sorry. I'll try it tomorrow morning, i'll let you guys know. I hope that's it, but could the TPS be causing it to backfire that excessively?

satch

iTrader: (1)

Backfiring can come from a number of things. Incorrect timing, improperly set TPS are but two of them. And you need to investigate the BAC as it should prevent the idle from dropping below 750, especially when the car is under load.

Murilli

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So, today I decided i'd go ahead and adjust the TPS. Well, she started up fine, revved to about 3k, slowly went down to 1.2k then started to die, so i gave her some gas, she fired up to 2k, and actually stayed there for a few minutes. When ever I gave her gas, the RPMs would go from 2k to about 1k, very weird! It was the opposite intended effect. After some time, the RPMs went back down to about 800, when I had to keep my foot on the pedal with out it stalling. Due to it being way too cold out, and having to go to work, I decided i'd come back to it later on.

Well, when these problems first started happening I had picked up a brand new TPS never used, for a pretty good price. Though, originally I had eliminated any thoughts of this being the TPS, so i kind of forgot about it. Well me being, well not so smart when it comes to automotive repair, I decided i'd go ahead and replace the TPS. (I may have just been lazy, with high hopes)

So, I replaced it no problem, jumped in the drivers seat, and cranked her up. She wouldn't start at all, so I kept my foot on the gas while I cranked. She finally started, revved up to about 3.5k very rough mind you, and immediately died. Tried again, few minutes later she started back up, revved to about 3.5k very rough again, and gave the loudest backfire i'd ever heard, about the sound of a 12 gauge going off 20 feet away. After the backfire, she immediately died, and I decided i'd call it quits for the day.

So now, without any adjustments being done to the TPS, but a brand new one installed, there is a heck of a noticeable difference. Do you guys think it still might be the TPS? Anyways I'll dress appropriately next time, hopefully it gets warmer anyways. Anyways I appreciate the feedback!

Murilli

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Update! So, I decided I'd try to unplug the TPS and try to start her today, didn't start. So I plugged the TPS back in, and tried to start again. This time, she wanted to start, after cranking her for about 6 seconds she started, almost died, gave her gas real quick and feathered the gas for about 10 seconds, then I noticed she was idling at about 1500RPMs! So i let her do that, expecting her to die soon, I backed off.

The idle was very smooth at first, the new TPS made a world of difference, and for a second I thought she was fixed! As the idle speed gradually decreased to about 1k, the car started shaking really violently, eventually she found her position on the tachometer at 750RPMs. Though, she was still shaking violently, the idle was very steady!! I was very suprised and bet I even had a smile on my face at the time. No backfiring either yet! Which was completely new!

So, she was idling at 750RPMs very steadily, however she was shaking like a leaf on a tree during a windy day! Then, after about 15 minutes of the car being on, and idling on it's own, she started to die. So I gave her gas and kept her alive, I also noticed when I reved her to about 3k, she would backfire, but no fireballs anymore and it wasn't as loud. Though, keeping the RPMs steady with my foot, she was pretty smooth, and there were no vibrations above 1.2k RPMs. Soon after keeping her alive, I killed her as it was work time!

Anyways, I definitely still have a problem, replacing the TPS did a world of difference, however there still seems to be some major issues going on. So, I'm being told by some mechanics ( not familiar with rotaries or anything before 2000) that it may be the O2 sensor, I doubt this would cause it to stall, but what do I know? Is there something that controls and regulates the hot idle?

satch

iTrader: (1)

Replacing a TPS requires setting the new one. There's a screw on top of the engine which helps to adjust the idle speed. To do this though you have to jumper the Initial Set Coupler, located near the leading coil before making any adjustments to the idle adjust screw.

Murilli

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Thanks for the feedback! Alright, now, the screw on top of the engine you're talking about, that's the one on the throttle body yes? Because I had to raise that before, to 1k, so it wouldn't stall when braking or turning the wheel. So this isn't the screw that's next to the TPS correct? I know where the jumper intial set coupler is, not exactly sure I understand what has to be done though. Could this be the cause of it dieing, and shaking violently? (bear with me, this is my first vehicle that I've had problems with, so pretend I don't know anything haha)

satch

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Jumpering the coupler means taking a wire and bending it in the shape of the letter U and placing each end of the wire to one of the wires in the coupler plug. This bridges the two wires in the plug.

Murilli

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Got it, seems simple, so just connecting two wires pretty much, does it have to be a piece of metal, as I have plenty of extra wires laying around here. Once I do that, am I starting the car or just turning it on? Also, what does this accomplish?

satch

iTrader: (1)

Well, the wire has to be metal or the jumpering won't allow the voltage on one wire from passing on to the other wire. So jumper first, then start car, then adjust idle. Jumpering basically turns off the BAC which is part of the idling system. If it's not deactivated then adjusting the adjust screw is made more difficult.

Murilli

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Alright, sorry it's been a while. Anyways, it's nice outside and I can't wait to drive my baby once again! It's time to retire the truck anyways.

So, I replaced both coil packs and all 4 spark plug wires, got a new battery as well. I was looking more into the symptoms I have, and thought it's time to fix her up as soon as possible, and actually have hope it's not a blown rotor or something.

It actually idled for about 30 whole minutes today without any assistance, so maybe the coils and wires did help? It backfires constantly, a very rough vibration, unless I'm holding the RPMs around 1100-1700 then it smooths out. It did idle today, how-ever once the car warmed up, the RPMs dropped from about 1.05k to about 700, then it would struggle to stay alive, even a few times it would drop down to about the 0 RPM and bounce back up to 500RPMs, I'm suprised it even did this, this is new.

Anyways, I went to adjust the TPS, how-ever I'm unsure what the screw I'm adjusting even looks like... Also, where exactly am I jumpering the car so I can play with the idle control screw? I had someone look at my car today, and they told me, well they're totally unsure what it could be, how-ever they did mention timing could be an issue, especially after reading that adjusting the idle control screw without jumpering it can affect timing... maybe that's what caused this? Anyways, advice, guidance, input, suggestions, positive or negative feedback is appreciated, thanks!

satch

iTrader: (1)

Do a search on how to check the timing of the car as it is rather easy.


Pic of TPS, 2nd post in thread.

https://www.rx7club.com/new-member-r...tment-1033944/

Murilli

iTrader: (1)

Thank you, okay so I've been adjusting the right screw then! I'm going to replace my O2 sensor Monday, so I can eliminate that being an issue. How-ever, is there a way I can tell for sure if it's the timing?

satch

iTrader: (1)

Yeah, by checking it.

Murilli

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Is it still possible to check the timing accurately without it idling at 750? I have to keep my foot on the gas to keep it from dieing, should I just use a brick, or would it even be worth it? I've been gone for a week, so all intentions to have it running this week! I appreciate the assistance, and patience!

JimmyJackson

Simply just place and set up the Green/ Red cable of the TPS to 1 voltage w/ key to on and motor and see how much hot it can get . . .

satch

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Idle speed needs to be under 1100 rpm or the timing advances so you just can't set the timing when the idle speed is in excess of 1100.

jtalbury

Could also be 5th and 6th ports

Murilli

iTrader: (1)

Alright, so I replaced the O2 sensor today, that was a pain! That thing was on there good. Not too much of a noticeable difference, oh well. Adjusted the TPS as close as I could to 1 volt with an analog multimeter (I wasn't able to adjust it correctly before due to my colorblindness haha!) I drove it about a quarter mile from the parking lot to the shop where I work on it, it has like no power, 1st gear at 4k RPMs for example, no power at all.

How-ever I'm starting to think it's the timing now, because I adjusted the Idle control screw several times (on top of the throttle body) without jumping it ever.

Anyways, I finally got a video of what it does in action. Mind you, it normally doesn't idle this good, it usually instantly dies once it's warmed up. So maybe the TPS and O2 made a difference?

Murilli

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Also, the beeping noise in the beginning while it's running is new as well.

satch

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There's a sensor in the ignition switch that senses if you leave the key in the car w/the door open. Over time this sensor becomes overly sensitive and can beep when it isn't supposed to. This usually occurs if the key chain has too many keys or weight to it. Try placing just the ignition key in and see if it does the same thing. If it does jiggle it a bit and see if the sound stops.

Might want to check the voltage on pin 2I of the ECU (Water Thermosensor). Should read w/key to on, 2 to 3 volts cold engine and it drops to .4 volts fully warmed.

Does the car freely rev while in neutral? If it does then try unplugging the TPS, pull the vacuum hose off of the Pressure Sensor (doing these two things places the engine under load and will allow you to rev the car over 3800 rpm and this will cause the secondary injectors to turn on) and rev the engine while idling and see if there is any change.

Murilli

iTrader: (1)

Thank you Satch, I do have a ton of keys haha, that would make sense! Also, does the video help identify anything? You said before maybe I should check the BAC, I think i'll do that next, as check the timing, I have the timing light and know how to do it now, how-ever I couldn't seem to find the markings on the pulley.

satch

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Easy timing check: https://www.rx7club.com/2nd-generati...estion-978911/