Phoenix Jones

iTrader: (1)

Well i bought this car from a buddy of mine; he didnt have time to fool with it and i did .

Anyways, a little info, It is a 91 Vert 123k on the orginal motor. Hs new plugs and plug wires, New TPS calibrated by Mazda( Local dealers around here arent that great) Fresh oil change, etc. Just some basic tune up items.

Well my problem is as follow. WHen i start it up it will idle at 3k(normal) and after a few seconds it will drop to around 1k-1.5k and will start to surge until it warms up. After it warms up the idle will drop down to the last bar before 0RPMS. The check engine light will come on and if i try to drive it it will bog/hesitate if I give it anything past 1/4th throttle.

Mazda printed out the codes for me, TPS and O2. They also said my cats were clogged. They calibrated the TPS for me and said if replaced the 02 and the cats my problems should be fixed.

The O2 is a cheap universal replacement and i am waiting until tomorrow to get a standard replace from the Part Shop. I just purchaced the Mangaflow 2-in1 replacement and it should arrive shortly. IM hoping that my problems will be fixed after that but im not sure. IM going to pull out my multimeter and check the voltage on the TPS when i get a chace to validate the accuracy of the calibration that Mazda did.

Also, I noticed at night my after a short/ average drive, that it does run a tad rich and i believe i have a slight charging issue. When I arrived at my destination, I rolled up the windows and noticed that my lights would dim slightly. The volt meter on the dash was reading between the 12-14, im going to guess 13.something volts. I didnt have my multimeter on my at the time to confim the volts but will once i get back home.

SoOo in conclusion( sorry for the WALL of text; IM just trying to accuratly describe my symptoms ) I figued i would post as much as i could and was hoping that you Gurus could point me in the right direction as to what i should focus on to make my car drivable!

Thanks in advance!

Aaron Cake

iTrader: (1)

It could very well be clogged cats but the only way to verify is via an exhaust backpressure test or visual inspection. If they didn't do one or both of those, they are guessing.

Calibrating the TPS won't help if it is bad. It should be checked for smooth sweep via either an analog meter or a scope.

O2 sensor won't prevent the car from running but will prevent it from going into closed loop.

I'd suspect that your stalling is due to a big vacuum leak or a bad/disconnected AFM. Also check to make sure the BAC is working.

Phoenix Jones

iTrader: (1)

It could very well be clogged cats but the only way to verify is via an exhaust backpressure test or visual inspection. If they didn't do one or both of those, they are guessing. I wasnt there when they checked it, my buddy took it up there so im not sure. He told me he took off the cats and One was gutted and the other wasnt. So he went ahead and gutted it. O well Im not a fan of doing anything half-assed, so i bought a replacement set. We will see once they arrive.

Calibrating the TPS won't help if it is bad. It should be checked for smooth sweep via either an analog meter or a scope. It is a replacement from Rock Auto, it was the cheapest the PO could find. Im going to check it via the FSM, My other friend advised me to that as well. He said it could have a dead spot.

O2 sensor won't prevent the car from running but will prevent it from going into closed loop. I figured that, i know that it doesnt have very much adjustability. But better safe than sorry.

I'd suspect that your stalling is due to a big vacuum leak or a bad/disconnected AFM. Also check to make sure the BAC is working. It doesnt stall ( well it does only because i havent learned the clutch yet) it just seems to idle low. I havent had the time to adjust the the IAC( IF RX7s even come with them) to see if changes. Also i havent looked at either of the BAC or the AFM for problems.


ALSO. My friend was running 87 octane. IM sure that has an effect on it as well. I know my sisters RX8 runs 93 so im assuming that RX7 also take 93.

Cheers; Thanks for the ADvice

Snowburn

iTrader: (2)

I do know that in any engine you want to run the lowest octane possible without having pre-ignition.

Phoenix Jones

iTrader: (1)

Well after finally driving it around today, I think I found some of the problems. I noticed that if I sit for a mintue or so at a light, my volts will steadly drop. I went from 14.00 to 12.00 waiting at the drivethru. I'm goin to swap in my new battery from my other car and go to the parts house and get a new alternator.

Also, I'm pretty sure my check engine light is coming on because of my TPS. I was messing with the throttle noticed that it would come on as I would hit the throttle reguardless of what the operating temp was.

I'll mess with that stuff and see what happens.

Red_Rotor

iTrader: (3)

check all ur grounds. clean em up and run new ones if u have to. if it surges at idle its the tps. take a voltmeter and hook it up. should be set at 1kohm at idle and then do a clean sweep up to 5k to find dead spots.

Aaron Cake

iTrader: (1)

The BAC/IAC may be disconnected to jammed, leading to the low idle. Don't adjust it until you have made sure that it indeed works and that there aren't any vacuum leaks. These cars are very sensitive to vacuum leaks which cause all manor of issue.

The low idle could also be attributed to the alternator issue you describe. If the thing is loading the engine past what the BAC is compensated for.

87 octane.

Phoenix Jones

iTrader: (1)

I changed out my battery and it does great doing the day, but at night I'm still having a charging issue I checked the volts at idle with my lights in, and it was reading 13.4 volts. I'm thinking my alternator is going bad.

I changed out my O2 and that helped my gas mileage. I replaced my cats too. They were gutted already.

I'm going to check my TPS and all the vacuum hoses and go from there.

Thanks for the advice!

littlebit421

my 90 vert is doin the same thing with the check engine light, when I tap the throttle at idle it will blink on and off, and if im crusin around 3000 3500 rpm's and roll into it, at about half throttle the check engine light will blink on and off rappidly a couple of times then go out. It only does this when its really cool outside, like below 50 degrees. I pulled the codes and they were Tps Throttle Sensor (TPS) Narrow Range - Fixed at full-open and Pressure Sensor (intake manifold pressure) - Fixed at 29.9 inHg, I replaced both tPS and pressure sensor and it still does it, my advice would be check parts before you replace and when in doubt check vacume lines. Also not to impose on your thread if anyone had any advice on this check engine light think that would be nice.

StevenL5975

Never heard of a replacement other than the Mazda OEM one.

It could be a bad unit since you are saying it was a cheap one. Afaik the TPS is an expensive part on the 7.

You can check it with the resistance method which is more accurate than the voltage method.
Did mine few weeks before, very easy. Here is the howto http://fc3spro.com/TECH/HOWTO/TPS/tps.html

Steven

satch

iTrader: (1)

"Always" set the TPS after the car is fully warmed up, which a good 20 minute drive ought to do the job. The factory alternators fall short of what they should output so either upgrading to an FD alternator or having the amperage increased on the current one would help greatly. Additionally, redoing the charging system wiring as far as cleaning up the ground side of things should help too. Aaron Cake has a good article explaining this.

Aaron Cake

iTrader: (1)

2nd gen alternators do have a high failure rate. They are all getting old and are overstressed from the factory. If you are replacing it, I'd suggest using one from the FD RX-7. Instructions on the simple bolt-on upgrade are in the FAQ.

Phoenix Jones

iTrader: (1)

I have a S5, so I'm not sure f this will work on a s5 or not since my TPS is 6 wires and the S4 is only 3 wires. I do have a copy of the S5 FSM which shows me the about the same procedure.