20B 3 Rotor

iTrader: (7)

Hey guys, just got my FD and I have been having some troubles with it idling, and I was wondering if you could help me.

I bought the car a couple weeks ago, its a '93, automatic (yes I know, but I love my 7 and I wouldnt trade it for anything), 30000 miles on the rebuild, tranny rebuilt last year (previous owner had it done), compression test was done, passed with flying colors, I only use 91 octane gas. When I was driving it, and sitting at a stop light it would idle down to like 100rpm and start to shake, not really struggle to run but shake, so I would slip it into neutral and it would idle up a bit. I took it to a local mazda dealership, had it serviced, $800 bill (no surprise), and they replaced the spark plugs, rear differential flush, oil change and filter, fuel filter, i think that is it. After I picked it up it no longer would idle low at stoplights, and is now currently not idling that low at stoplights or shaking.

The problem I am having now with it is sometimes, well usually when I start it, it will rev high to about 3000 rpm, at close to 110 psi on the oil gauge, then after a little bit idle down to 1500 rpm, at 60 psi on the oil gauge, and after sitting their for a bit longer it would go down to about 1200 rpm, now at around 40 psi on the oil gauge, and would start to shake, but it would be quite a harsh shake, so i would have to start to drive it and then it would be fine, the oil psi would stay around 30 when I am driving it and would idle fine.

I thought of replacing the TPS, but have not done so, I was just looking for a second opinion to see what you guys thought, because it could be something completely different as I have little experience with the rotary engine, or it could be just the way they are and im worrying to much about my new baby, im not too sure, so any help would be greatly appreciated.

Mahjik

iTrader: (1)

When the car begins to rise to 3000 rpms after starting it, tap the gas pedal and see if it goes to it's normal idle.

20B 3 Rotor

iTrader: (7)

alright I wil try that and let you know, thanks.

20B 3 Rotor

iTrader: (7)

Alright, I tried that this morning when it started to rev up to 3000rpm, this time it just went straight to 1500rpm and i didnt have to wait for it to come down from 3000rpm, but it just continued to do that same thing, slowly idle down to like 1300rpm and continue to have harsh shakes.

Mahjik

iTrader: (1)

For starters, depending on what version you have (US spec or JDM spec), the cars are equipped with an Accelerated Warmup System (AWS). This automatically revs the car to around 3000 rpms on start to help quickly warm up the catalytic converter. For guys with manual transmissions, it doesn't do it with the car in gear so that's how they get around it.

For the idle, is the car shaking at idle? I didn't understand from your original message if that was fixed or not by the service you had performed on the car. And about what rpm is the car idling at when it sort of settles down?

revhardallday

iTrader: (1)

im having a similar problem my car will idle with a skip in it and when i drive around and come to a stop sign or a red light the idle drops from 850rpms to like 200rpms and right when its about to die i tap the gas and it goes back up to 850rpms but still has a skip in the motor...other times it wont idle down when i come to a stop...this all happend 4 days ago out of no where the car idled perfectly for two year....... i did a compressino test just to make sure the motor was okay and i got 92 psi from both housings i thinks its still good... also my trow out bearing started to make noise on the same day and time as the idle problem... but i dont think the trow out bearing will cause a problem with the idle...

wb123

I have the similar problem when the car is hot.

I will be replacing the spark plugs wires, O2 sensor , and fuel filter within the next week.

I will see if things have changed

revhardallday

iTrader: (1)

im also suspecting the plug wires......because my car is skipping at idle wich makes me believe its a misfire plus my a/f wide band is reading 11.1:1 at idle thats really rich so im gonna have to say its a rich misfire ... problem with plugs wires or coils im gonna do the plugs and wires....

20B 3 Rotor

iTrader: (7)

Yeah, sorry about not being to clear, I tend to write alot, alright I will try to be as clear as I can.


Problems Solved:

High Rev at Startup:
Rev to 3000 rpm, us spec, due to Accelerated Warmup System ( thanks Mahjik)


Things that are still a Problem

Low Idle at Stoplight:
Bought the car, when stopped it would idle down to 100 rpm and shake, so I slipped it into neutral and it would stop shaking and go up to like 400 rpm. Took the car to get serviced (plugs, fuel filter, rear differential flush, oil change and filter, by the way, I suspected the plug wires too, but they side mine were in mint condition). For a brief period after it was serviced it stopped, but then it started to do it again and is STILL CURRENTLY doing the same thing (stopped, idle to 100 rpm, slip into neutral, idle up to 400rpm)

Rough Idle After Accelerated Warmup System:
After the Accelerated warmup finishes, it will idle to 1500rpm sit their for a bit, then slowly creep to 1400 then 1300 rpm and give me harsh shakes.


Conclusion

Hopefully that clears it up (for those other people with the same problem and still decide to get your wires changed let me know if it fix's the problem, because then I might get mine changed anyways)

Also, not too sure if this is related anyway, at cold startup, it will just have constant white smoke, but once warm it will go away and when their is no smoke there is a slight smell of gas coming from the exhaust, which i thought was normal, so it could be I'm running rich, but i dont think so as my car is completely bone stock.

revhardallday

iTrader: (1)

white smoke could be coolant maybe a weak coolant seal or condensation from the weather...does the white smoke smell sweet? and for the gas smell you should be fine rx7s run rich anyways.

Mahjik

iTrader: (1)

20B 3 Rotor,

I would start with a few things:

1. TPS adjustment. Make sure that is adjusted within spec
2. Clean and re-lubricate the ISC
3. Adjust the idle with the throttle body adjustments

If you are still having a problem after having those done, then we can start suggesting some other things but these are a good start.

20B 3 Rotor

iTrader: (7)

alright, I will try that, thanks alot man.

20B 3 Rotor

iTrader: (7)

one question before I adjust the idle, I read somewhere that the correct idle speed is 850rpm, is that what I should be adjusting it to?

wstrohm

My 1994 factory workshop manual specs the idle speed (when warm) at 720 (+30, -20) rpm with no electrical load, and 775 - 825 rpm with electrical load. If the A/C is on, idle speed should be 875 - 925 rpm. (This info is from page F-82.)

The idle speed should be adjusted with the air bypass screw while the "TEN" terminal in the Diagnostic Connector is jumpered to its "GND" terminal.

One technique for finding the right setting on the air bypass screw is to listen to the engine speed with the TEN-GND jumper in, and then to pull the jumper out and listen for a speed change. When the setting is right, there will be no change in idle speed between jumper in and jumper out.

20B 3 Rotor

iTrader: (7)

Thank you all for your help, I only wish that what you guys said was actually the problem, because it would have been alot cheeper to fix. I took my car in to a mazda dealership ( ive used them before, do a great job ) to fix an oil leak, thought it was from the powersteering when I had it on a lift at work, turns out it was something I would have never expected . Timing chain gasket, labor (pull the motor out, 2 days of work) $1700 , second turbo leaking oil , no price yet, but will be crazy. For now, she will be parked till I find the money, just bought it, drove it for a week, nothing but babied, just filled the tank with gas before i took it in so I will lose all that if they take the motor out, still paying off the loan. For now, she will just be a picture on my computer and memory's of blasting crazy techno through winnipeg.

Mahjik

iTrader: (1)

Well, all I can say is if they told you they need to replace the "Timing Chain Gasket", take it somewhere else.

20B 3 Rotor

iTrader: (7)

exactly

20B 3 Rotor

iTrader: (7)

correction, I just got an estimate from the dealership, it says the engine front cover neads to be resealed, and once I take it to this other rotary shop to determine the state of the 2nd turbo, if it is blown I will probably be going single turbo, looking at the GT35R.

20B 3 Rotor

iTrader: (7)

Ohh yeah, I almost forgot, for those who are having the same idle problem is I was, check your oxygen sensor, mine was malfunctioning and not allowing the right air/fuel mixture.

Mahjik

iTrader: (1)

You do understand that it's more than just buying the turbo kit. You'll also need a fuel fuel system, programmable ECU and other goodies.

20B 3 Rotor

iTrader: (7)

yeah I took that into account, started pricing it, but it's the way I'm gonna have to go, because if I went with the efini twins or the BNR's I would be still running into fitment issues, so I might as well go the whole way with a single, not too mention it simplify's the system a bit, rx7store.net is a about to get alot of money from me.

manveru

if you're completely serious about going single, hold off, research as much more as you can, and then start going through the classifieds on here. you'll end up saving a lot of money, and learning your car a lot more thoroughly throughout. and the smile on your face when you DO finally drive it will be oh, eleventy-gazillion times better.

but i still don't understand the fitment issue you would have with a set efinis or BNRs?

Mahjik

iTrader: (1)

The '99 Spec twins are a straight bolt-up just like the stock turbos. I would suggest getting your motor in running condition then get a good compression test first. No sense spending a bunch of money on a single turbo setup if the engine is not healthy.

You know, you can find good used stock turbos for around $200-300 here on the forum easily.