I had a thread going for a few months because I could not get my 1990 RX7 GXL started. A wonderful rx7 expert helped me tremendously in the area of the electronics and now he feels my problem is beyond his scope right now. FYI, for background, it is mint, one owner, never handled by anyone but a Mazda mechanic the first 10 years, and it has oly 33k on it always garage kept. My issue started when I did not warm it up enough this past winter and I noticed that as I drove the tach started coming down and it wanted to stall fast and the only way to keep it from stalling at a rest was to give it gas then throw it into gear(it is a 5 speed BTW). I changed the oil, oil filter, gas filter, spark plugs, checked the coils and spark plug wires and they are perfectly fine, checked the TPS and it is perfect, did an idle adjustment to get it to 5 volts, checked the fuses and they are all OK, car gives no codes when I ground that green connector, the fuel tank was inspected and is clean and the fuel sock is like new and the fuel pump is operating well! I put in fuel injector cleaner and ran 6 gallons of V power 93 octane gas through it and got the white smoke and then it cleared up and turned transparent but wrecked in smell! In fact it makes the actual rear bumper just around each exhaust BLACK every time I warm it up now. Now, it only seems to start if I pull one leading coil plug and lie it next to the bore and watch the arcing spark....and I have to floor it and the tack slowly goes up!! Then I put something on the accelerator to keep it at 2000 rpms and reconnect the boot to the coil bore get back in the car and warm it up. If I let the rpms go below 1000 rpms, it invariably stalls out! On yesterday's warm up I noticed that there was one tiny drop of black oil just smack in the middle under the car on the garage floor after the warm up and the garage smelled a lot of gas! In fact the gas gauge sure went down rather fast in the warm up! I also noticed when looking under the car an intense orange glow from whatI THINK IS THE CATALYTIC CONVERTER? Do not know cars well enough to know.....but it was almost on fire orange! Today in the morning when I warmed it up the same way as above it was not quite as orange. Seems like I have a few problems here and would take anyone's advice on where to start. Thanks for listening to this BUT you need the whole back ground to diagnose what you as an expert think is going on here. Thank You all!

 

https://www.rx7club.com/2nd-generati...xhaust-929306/

 

Your catalytic converter is clogged and it needs to be replaced.

If you cant afford to replace it you could at least take it off and punch a hole through it somehow so it will flow.

I'm sure all this is explained in the link above.

 

Ok, have you a suggestion on exactly what make CC to use and shall I have a rotary specialist in the NJ area do it? Is the hard start and need to floor it as the tach very slowly goes it probably related to this as well as the fast consumption of gasoline? What else aside from the replacement of the CC do you THINK will be needed to do?

 

I really don't know what size exhaust you have on your car but if its stock you could get a universal CC and it will work, personally magnaflow are decent and not too expensive, main issue is they have to be welded on.

The na does have a pipe coming off its cc that goes to the front of the car.

rotary > pistons

 

You know, today I put 1 gallon of gas in because it was just about empty and it started with that same DIFFICULT START where you have to give it gas as the tach very slowly goes up and it wants to stall. If you give it just enough gas it gets up to 3000 rpms and I hold it there. If i let it go down below 750 it just about stalls! INTERESTINGLY, so much less smell and fumes this time and it was a little easier to keep the rpms at 1000 rpms! No remarkable things happened! That fuel injector cleaner must all be out of the system by now! I put something on the pedal to keep it at 1500 rpms and I observed all around and under the car! No oil leaks, no gas leaks, no flames or incredibly orange glow like last time! I let it eat up the whole gallon for maybe 15 minutes or so and then turned off the ignition. Tried to start it again and it just would not get started. I tested that TPS voltage again and it is at 1 volt. I want to know if anyone has any other suggestions on 1)WHY THE START IS SO HARD if it starts at all! , 2)WHY IT STALLS AND CAN NOT IDLE, AND 3)WHAT OTHER TESTS I CAN DO TO SEE IF MAYBE a)there is a block in returned gas(whatever that means.....someone said gas is "returned" and I am like "returned from where to where??" ) and b)what e acts is the test and what exactly do I use to check for a hose leak under the hood? Thanks for all your help guys!

 

glowing cat/hard starting/slow to rev all point to 3 things

low/no compression on a single rotor
faulty ignition on a single rotor
faulty primary injector on a single rotor

i would lean on it being faulty ignition, spark plug or wires due to the glowing cat but i'm not going to rule out a faulty injector either.

first, redo your compression test and get 3 consecutive compression figures from each rotor(6 in total). if none of thoe figures are below 80PSI then you can move on to the ignition system since it is simpler to get to and maintain. replace your plugs and wires with OEM NGK parts. if there is still no change then move to the injectors, remove the UIM, inspect the injector clips for breaks in the casings, loose connections, pushed in pins inside the connector or corrosion on any of the pins.

if the injectors look ok then follow the test procedures in the FSM. jumper the yellow test connector at the RF strut tower, remove the primary injectors and tie strap them to the fuel rails, disconnect the ignition system and crank the engine and watch the flow patterns, if either injectors fails to respond replace it.

check the timing as well, this will be difficult but try to see if the timing is near the ballpark.

if all that fails to impress the car then you may have the less likely issue, a failed coolant seal pushing coolant into the engine. coolant does not ignite and fouls ignition. most coolant brands will smoke like a train though if this is the case.

 

THANKS SO MUCH FOR YOUR EXPERTISE AND I STARTED TODAY ON MY WAY TO DIAGNOSING WHAT IS GOING ON THANKS TO YOU. Firstly, I did the compression test again like a did around a month ago and got around 80 psi for each roter and I video taped the gauge and it nicely repeated patterns of triplets like it should for the 3 areas of combustion around the roter. I assume since each behaved identically and gave the same triplet results around 80 psi each time that my roters are undamaged and the apex seals are intact...do you agree so far? Secondly, I moved on to do just the ignition system today. I mentioned I did in fact install new OEM NGK plugs around a month ago and they were the first plug change for this car....remember it only has 33k on it. The old plugs did not look too bad. It should be noted that the factory installed BUR9EQ T PLUGS ON THE BOTTOM POSITION FOR EACH ROTER AND BUR7EQ L PLUGS ON THE TOP, SO I REPLACED THEM JUST THE WAY THE FACTORY HAD THEM even tough I have read everywhere that L means Lower and T means top! Why change what was good for 33k? Correct? I found on checking the plugs that the one in the upper front roter chamber was NOT firing(a BUR7EQ L) even when I placed it in a different spark plug wire it would not fire! I guess one of the 4 plugs I bought was bad! So I used one of the original ones and it fires and is just fine. So now all plugs are firing! Lastly, for today, I started the car and it gave a tough start again even tough now all plugs are firing and the roters are ok. Once I watched the rpms go up slowly I have it gas and just got it up! Kept it at like 2000-3000 rpms for 10 minutes and brought it down to 1000 rpms. It was rocking and shaking and lightly back firing as I gve it more gas and let the tach come down! Difference this time from last is that I was able to keep the rpms as low as 500 without a stall BUT had to have my foot on the gas. After maybe 15 total minutes I lightly let go of the gas at like 300 rpms and it stalled! Damn! Does not want to idle and instead wants to rock and shake like the timing is way way off. Is there a way to set timing? My TPS is set perfectly to 1 volt. Here are some observations that may give you some more insight: after the car stopped running 1)under the hood the parts that were HOT we're the alternator, the big hose from the anti freeze to the engine, the oil filter. But, the metal top of the engine where it says "13B" was not hot and got hot after sitting for maybe another 20 minutes! Also, the antifreeze cap was not hot...I always thought that gets hot fast?? 2)I put the air cond. on and it smelled just like pure gas was hitting me in the nose! 3)the orange glow when I looked under the car was much less, BUT there was that orange glow in that hole that I guess you can see into the carburetor? So, what is your assessment so far? Next is fuel injectors, but I am going to have to ask you how to remove the UIM because I have to idea how. Awaiting your reply and think so much!

 

an easier step to checking the injectors before ripping the intake apart is to backprobe the injector wires at the ECU, turn the ignition on and check to see if all 4 register nearly 12 volts.

 

Sounds great. Now where exactly are the injector wires at the ECU on my car? I know how RO back probe to check voltage and see if it is 12 colts, but I do not know the location of the injector wires at the ECU. Waiting your reply. Thanks!

 

Smallest ECU plug. They are Light Green with a stripe except one is plain Light Green. And the car has no carburetor. And doesn't the link I provided show how to set the timing? I believe it does and that's why it was provided.

 

Hi Satch! Thanks, BUT I meant WHERE in the car is this plug?
Which link shows how to set timing?

 

you have to remove the passenger side floor mat, door trim base plate and kick panel on the right side. once you get those 3 things out pull up on the carpet and push it towards the center console to expose the ECU kick shield. unbolt the 4 bolts holding the cover on and work out out of the car from under the carpet. the ECU will be right there.

it's a little bit of a pain to get to but with these cars it's good to get accustomed to getting at it. takes about 2-3 minutes once you get the hang of it.

 

Thanks so much. I will do this Thursday or Friday and revert back to you with details. I appreciate that very much.

 

Second post in this thread.

 

Guess I was completely wrong about the clogged cat then eh? I hope you get the problem fixed. Parts are pretty easy to find if you need something replaced.

I love rx7s, so easy to work on. Na's are a lot easier though than turbo.

rotary > pistons

 

Yeah, who knew except these experts above that the RX7 does not even have a CC! These guys are amazing! They know everything! Especially RotaryEvolution and Satch. Two remarkably helpful caring wonderful people!

 

Mission accomplished. Took me like an hour since it was my first time doing this! What a pain! Anyway, I am assuming you mean the 4 wires that are the furthest to the left on the N351 Denso EGI. Top left was lime green/black stipe down the length of the wire and to its right was a lime green/yellow stripes around it. Under those was a lime green/red stripe down the length of the wire and to its right an identical lime green/yellow strip around around it like the one just above it. ALL GAVE EXACTLY 12.53 volts and my battery gives me like 12.83 volts measured directly. So, did I use the correct wires? And, now that the car is opened there, are there any other voltages you would want me to measure to rule out anything else before I attempt to close it up? Love to hear from RotaryEvolution and Satch. Thanks so much you guys!

 

And the readings you took on the injector wires should be done w/the ECU plug removed.

And I forgot you had an S5 so all of these injector wires would be located towards the end of the plug in a boxed formation, two on top and two right below them.

You might want to measure pin 2E, Green/White wire located in the smallest ECU plug on the top row. 2E is situated between a Black wire and a Black/Green wire. W/key to on and the engine cold (not running) as it should read close to 2 to 3 volts. W/the engine completely warmed up it should read close to .5 volts.

And I still believe your primary injectors if not all of them are in need of cleaning.

 

So I should take the readings of the first 4 green wires on the connector plug side NOT IN THE ECU? Just curious as to why?
Also, what is the pin 2I do? What is that for on the car and why the difference hot and cold and if it did NIT give these values what could that indicate? And should it also be tested with the plug out at the plug side?

 

The green/white wire gives me 2.5 volts cold. Will is what it gives when I try starting it next probably tomorrow. But, what is that wire for? How is it related to my possible problem wit my symptoms? Also, tried the 4 green for fuel injectors both ways and I still get the 12.53 volts.

 

Pin 2I is connected to a sensor which helps determine how much fuel is used, dependent upon the engine temp, colder the engine the more fuel is used

 

Thanks. I will try it hot and see what I get if it starts of course! I assume there is nothing else to test in the ECU that can be related to this problem. Is that about correct so that after I try that wire hot I can put the car back together.

 

try checking codes before going much further. all you need to do is find the single wire green connector near the leading coil pack at the front and ground it to the battery with a jumper, turn the key on and read the flashes on the check engine light. as well before jumping into the injectors you may want to rent/borrow a fuel pressure test gauge from an auto parts store and check your fuel pressure between the fuel filter and the hard line to the engine. it should read about 32psi with the engine running idle and about 40 psi without the engine running, clamp the return hose and it should read about 90psi.

if that all checks out then i would start pulling the upper intake off and send the injectors out to be checked and cleaned.

 

Thanks so so much for that! I tried the codes a month ago, but Saturday I will try again and let you know if I get any codes. Early next week I will rent or borrow a fuel pressure gauge and check pressures. I need a little help on that however. I know the line that goes from the fuel filter to the engine that is hard lined. When I remove the hose from the engine, don't I have to clamp it to make sure gas does not leak out before I connect it to the gauge? And, do I also need another piece of hose to hook from the other side of the gauge to the engine and then measure the pressure with engine not running and then with engine running? I need to know where the return hose is? And when you say "clamp the return hose" do you mean leave the gauge where it was previously and in addition clamp the return hose so that it is in effect clamped closed and read the gauge?