pianoprodigy

I can't believe this. I finally get a cool car and now
I'm probably screwed. Last weekend I bought a 90 vert with 103K from a private seller for $3900. Car has all options and is in perfect cosmetic shape and seemed to be in great mechanical shape; however, the car keeps stalling when I'm idling at the light (5 speed) I took it to a local dealer and they said that it is a compression problem, and that I have to get a new engine for like $3500 installed. Don't get me wrong...it runs great when you get going, but I can't drive it because it will just stall out if you don't keep giving it some gas. Will someone please help me out. My dad says that I have to trade it in, but I won't be able to get **** for the trade in, that is IF they're dumb enough to trade it. Remember the car is absolutely sweet. Factory headrest speakers are great and has MB Quart midbass drivers. Sounds so good. Leather everything. I don't want to sell this car. Can anyone give me some advice here! By the way I believe the mechanic said the compression was like mid 6's instead of 8's like it is supposed to be. I'm in a pinch for time because I'm supposed to drive this car back to college in 2 days! I can leave it here with my dad and he can get it fixed if I don't have to freaking spend $3 grand to fix it. Please help. (Is there such a thing as like a partial rebuild? The mechanic said everything is perfect except for the compression...) Also, It will run fine for like 5 minutes but when it heats up, RPMs just drop.

SonicRaT

iTrader: (6)

Does it idle on it's own (with NO electrical/AC/etc turned on at 750?) It could be that your bypass air control valve is stuck open (which causes stalling with AC turned on) Mid 6's? Compression? The hell is he talking about? He should've gave you a PSI reading. Chances are it's the BAC (usually is when it stalls at stoplights) and if it's running good/starting easy then I can't imagine bad compression being the cause.

cool3865

are you running tha car with tha A/C on full blast if so dont use tha A/C mine dose that sometimes and i have learn to live without tha A/C

SonicRaT

iTrader: (6)

Oh, you also might want to check for engine error codes, check out http://www.1300cc.com/ (click the enter button, goto howto's and then goto error codes on 89+) and try to see if your car is spitting out error codes, could also help track the cause down.

Edit: whoops, posted the wrong webaddress, fixed now

SonicRaT

iTrader: (6)

cool3865: head over to the website I mentioned above, and goto the howto/tech area and read the BAC valve cleaning page, that should fix your issue with your AC, and you'll be able to run with it again

pianoprodigy

Don't you think the dealer would have noticed this valve that you're talking about though? The compression he says is good when you first start the car 8:1 i guess but as it gets hot it goes down to like 6.5:1. I'm in no way a mechanic. The AC will make it stall faster but it still stalls without AC too.

SonicRaT

iTrader: (6)

98% of the time mechanics have no idea what they are doing on a rotary, so ignore that for now. It sounds like your bypass air control valve is stuck open or closed, go through the process of cleaning it like I mentioned above for the other guy and see if that fixes anything (make sure you have a gasket or some RTV for when you put it back on)

SonicRaT

iTrader: (6)

Oh, and IIRC, the compression should be 9.7:1 on a 90NA, so if the mechanic thinks 8:1 is good, I think he's got a problem, check the BAC.

Aaron Cake

iTrader: (1)

First check compression. If that checks out (even if it doesn't) test the BAC valve. Most likely, it's the BAC causing your problem.

If you aren't experiencing hard starting problems, lack of power and flooding, I doubt it's your engine.

SonicRaT

iTrader: (6)

Thanks for the second opinion Aaron, it's just hard to imagine the low compression causing it, as to all the issues I went through with low compression, and his only problem is stalling, which is commonly the BAC. Sorry about the screwed up website, I corrected it now, should be http://www.1300cc.com and not .org

eViLRotor

iTrader: (2)

LOL!
That's all the dealer ever says. That's all they know...

SonicRaT

iTrader: (6)

That and they want your money

pianoprodigy

Guys,
I know very little about cars. My dad has rebuilt corvettes but knows nothing about rotary. Where can I find this valve and what do I do when I find it? Should I try to go to a local shop to have it checked out?

Aaron Cake

iTrader: (1)

The BAC valve is the roundish cylinder thing on the upper intake manifold (passenger side on 89+ cars, drivers side on '86-'88 cars). There are testing procedures in the Haynes and factory Shop manuals.

SonicRaT

iTrader: (6)

No no no, local shops are idiots when it comes to rotaries, better to learn Since this is an NA It'll be on the drivers side of the car, see where it says Mazda 13B? Right below that on the side there should be a round canister looking thing (metal) with a square connector running to it and two coolant lines running to it. You can also download the FSM from http://www.fc3s.org and http://www.1300cc.com and check out the sections on the BAC


that's what it looks like on a turbo, the NA one looks just like it, but is on the other side of the engine. Just take the two phillips screws out and move the coolant line out of the way, then remove the two 10MM bolts that hold it on, take the connector off, and then follow the cleaning procedure listed here: http://www.1300cc.com/howto/how2/bac.htm

junior-coyote

A dealer told that to the previous owner of my car and I got the car for $500. That was 20K miles and several autocrosses ago. Problem: There was a mouse nest on top of the air filter.

I'm a real fan of rx-7s because people give up on them so easily.

jimmyv13

Did you go to the afore mentioned site and read about it?

This is the page you need to read.

BAC

The pictures are the BAC from a turbo, but the BAC looks the same on an NA.

I searched this site and came up with a bunch of threads about idle related problems with the BAC. You will find what you need in here

Good luck!!!!!!!


Jim

rx_7_driver

"Since this is an NA It'll be on the drivers side of the car"

edit: its on the passengerside for an s5


shawn
90 n/a vert

SonicRaT

iTrader: (6)

Damn, didn't know they moved it on series 5 NA's, never seen a series 5 na under the hood so I guess that's why Thanks for the correction, oh yeah, if the BAC is the problem, I request a $20 knowledge fee (just kidding!)

pianoprodigy

If I can fix my car on my own in the next 2 days with you guys' help, I'll send all of you $20.

SonicRaT

iTrader: (6)

Hahaha, don't make me have to register different screen names now! Anyway, back to being serious, you should be able to do it yourself fairly easily, just 10mm socket/extentions/rachet some RTV gasket maker, razor blade to scrape the old gasket off with and some carb cleaner/brake parts cleaner and have at it. Let us know how it goes

jimmyv13

After you clean your BAC with the WD-40 or similar, apply 12V to one pin and ground the other pin. If it clicks then it's good, if not you can try more lubricant and keep trying the voltage check. I just went through this same situation and I could not get my BAC to click, so I had to get another one.

If it clicks, then OHM the resistance between each pin and the casing of the BAC. There should be a ZERO reading here meaning that the BAC is not grounding out with the case. If this checks out, then it's time to move on to the connector and the ECU.

pianoprodigy

Yeah, my dad has the car at his office. Earlier today I had given up hope on the RX7 and was looking at other cars. I saw a 91 MR2 Turbo with 104K for $6K. Price is steep but it was really clean. Has anyone ever raced or ridden in a MR2 Turbo? I definitely want to keep the RX7 if I can fix it.

SonicRaT

iTrader: (6)

Keep the rx7 or we'll hunt you down and kill you, er, yeah Definatly keep the rx7, for your own sake It's probably just a simple fix, don't worry too much and go work on it damnit!

deadRX7Conv

You can download the '89 FSM(90 will be similar) from these two websites:
www.iluvmyrx7.com
www.fc3s.org
Definitely read the fuel/emissions/engineelectrical chapters.
Haynes has a descent book for basic backyard preventive maintenance and repairs.

Dealers suck and will replace the engine if the paint is faded Never go to the dealer other than for parts. The links up above and mazdatrix are another source for parts and info.

$3900 is a great deal for a good vert. Give it a good tuneup. Check oil frequently because they are oil injected. Change oil frequently because it is oil cooled and beats the snot out of the oil. Do not use synthetic engine oil. And, stick with quality oils filters(mazda/mobil1/amsoil/kn). Also, always use standard green antifreeze not the extended life orange stuff.

Go here to scan ecu.
http://www.1300cc.com/howto/how2/codes.html
http://home.rmci.net/panther/89_91ecu.htm

And, it would be good to replace all fluids/filters/plugs.... and give the car a good tuneup if you are unsure of the maintenance history.

Rotaries need a special engine compression tool to check the compression. There are 3 readings on each rotor. 6 total. If you did not get 6 numbers from the dealer mech, I would ask for a refund for their BS low compression diagnosis.

The BAC valve will prevent stalling when you flip things on like headlights/ac/top movement...... When my TPS was poorly adjusted, it caused erratic idle and stalling. I also replaced the o2 sensor and got a good jump in fuel economy(from 10 to almost 15mpg). And, make sure that there are no vacuum leaks which can cause all sorts of problems. And, run a few tanks of gas with FI cleaner. Some rotaries tend to have carbon problems. Rotaries like to be driven hard.

Don't bother sending me $20. Donate it to charity or keep it for future mods.