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Just a FYI, unless the car is full warmed up, the TPS can only be tested to see if it is in range and has a smooth sweep.
I have never seen a thread where MAF cleaner was used. Once again, you will be testing to see that the signal sent to the ECU is in range and the sweep is smooth. There could be other things that I am unaware of.
The forum has a wealth of info on these types of issues if you spend a lot time searching. I have brain fry sometimes reading all of it
The FSM will have a flow chart for stalling issues as well. Just follow the flow chart very methodically.
After being so old, the water temp sensor behind the alternator and air mass flow meter will both go out of spec. Replace these.
They have a big impact on being able to start cold.
Your intake looks like a 86 to 88 S4 version.
Sorry but this is rather horrible advice, the only AFMs available are chinese ones that are made for multiple applications and not the proper ones calibrated for the RX7 or remans of unknown origin and application as well as nonexistent quality control. One that also fits an MPV van won't work for an RX7. replacing it with an old one off a parted out RX7 that's had its hood open to the elements for 20 years also isn't a great alternative and new OEM AFMs don't exist anymore. My experience with aftermarket AFMs has not once been good.
Even remanufactured ones are garbage, usually mismarked applications for other AFM vehicles. back in the 80s and 90s applications lists weren't tracked very well and the aftermarkets didn't give 2 craps about whether a part worked properly or not for a wide range of cars. fast forward 35 years and those application lists are even muddier than they were then. Some low paid worker at a remanufacturer doesn't know an N327 AFM is for a 1988 non turbo Mazda RX7, instead they peel the label off and say it fits 300 vehicles because some chart sais so. Now that no longer properly marked certified N327 AFM is floating in the ether, no one can even tell what the calibration really is for, same goes for some J9 Mazda MPV AFM that you could be getting in a box after it's been sanblasted and resembles every other Nippondenso AFM from the 1980's.
If those AFM remanufacturers list an application from an RX7 to fit a 323 and MPV van they obviously have never been tested or calibrated for the airflow demands of a rotary engine. The truth is they just do simple resistance sweeps and throw it in the box, uncared for who has to deal with the ramifications of the carelessness next.
I'm weary of places like even Mazdatrix and Atkins selling what appears to be non OEM/remanufactured units. I doubt they test them themselves and trust what their suppliers say, there appears to be no official Nippondenso labels on them.
Troubleshoot what you have and save yourself from throwing money needlessly at the car, otherwise it feels like i'm standing next to my coworkers and watching them throw parts at a car with other peoples money.
The listing basically states it would work on any S4 RX7, turbo or non turbo, a J9 AFM that's not even for a rotary engine..... anyone could purchase and think they are doing right by their car when the truth is they just created a new problem AND potentially be out $300, left with an AFM that's not even for their car.
He can jumper the fuel pump test connector on the RF strut tower to see if the AFM fuel pump trigger switch is the issue. Other starting and stalling issue usually point to large leaks in the intake system like a BAC or brake booster line disconnected.
It is true that the AFM can lose calibration over time, good thing the S4 comes with an idle mixture trim pot on the RF strut tower as well, it's covered by a rather easy to chip out epoxy. There is also an aluminum plug on a port on the AFM that can be drilled out, exposing the air bypass screw, to help you re-tune an old AFM(i always suggest turning the screw all the way in while counting turns and note the default setting before messing with this screw). Screwing in the AFM air bypass screw fully and attempting to start the car could also help determine if the intake has a large leak present, although not a fix for leaving leaks in the system.
only adjust this after resolving a start/stall condition, it's only made to help adjust your idle mixture setting not to resolve major fuel system issues.
L<--->R do not mean Left and Right, like it's some sport suspension adjuster for the struts, it means "Lean<---> Rich". This input only works when the engine is in idle mode if memory serves, keep in mind I haven't touched a stock RX7 in over 10 years now even though I probably still retained more knowledge than 99% of FC owners care to know.
Originally Posted by todzilla220
Yes. I need to lookup this FSM flow chart and go down an analytical path.
Kind of a dumb question, but do I need to install the air filter and close the intake box?
New fuel pump and filter. I did confirm it’s hooked up correctly and has great pressure. Surely it should be primed and ready.
Like said. Gotta be patient and go through things. I need to also make one of those diodes to get the error codes.
You don't need the airbox or filter installed but the AFM and everything downstream of it needs to be plugged in or sealed up so that there is 0 air leaks in the intake, otherwise as soon as the immediate rush of air past the AFM is past the flapper door from the engine starting will allow it to close again to the point the fuel pump switch will open and the fuel pump will shut down and stall the engine. Hopefully it makes sense, air leaks in the intake mean the AFM is not pulling air past the flapper and it is closing too much, instead the engine pulls air from whatever leaks or open ports in the intake stream that it can.
As well, did you replace the fuel filter? it is located on the framerail in the engine bay just in front of the driver. Fuel shooting out of the line when disconnecting them doesn't mean you verified proper fuel pressuring during crank and starting because fuel pressure can bleed off very rapidly if there is a major restriction in the fuel supply. A fuel pressure test gauge is really the only way to verify fuel pressure both cranking and after starting. The location to hook it up is near the oil filter, not at the rails. Hooking up the fuel lines at the ports near the oil filter can also cause a start/stall condition, as only a trickle of fuel is allowed to backfeed through the FPR.
Though this is a turbo diagram the lines off the fuel filter and return to firewall hardline connections are the same:
High fuel pressure could point to your lines being backwards at the engine, low pressure could point to a plugged fuel filter or issue with the pump still or voltage powering the pump. pressure should be in the 36-40psi range while cranking and initial start.
Last edited by notanymore; Mar 31, 2025 at 02:29 PM.
I came home and thought about putting the air filter and lid back on the box. Maybe TOO much air is the problem.
Lo and behold, now I’m able to start and rev between 4-5K rpm for up to 15 seconds!!! See video.
Then we start to sputter and die.
But I got all the marvel mystery oil out of the system.
Now just get the girl to idle. Inching closer.
How do I make one of those things that flashes the LED since I don’t have a flashing check engine light? I’ll look for it.
But after sucking fumes, I’m seeing colors and counting letters!
Nice progress, I can hear a squeak or something, your belts or? It seems that it doesn't rev cleanly to your highest point on the video. It has some hesitation or something, it's hard to tell.
Like the post above you mentioned, stalling is almost always a leak somewhere. me personally, what I would do is, if you think that you can keep it running without damaging the engine. Verify the fast idle is working, then say with the car until it warms up completely. If that means feathering the gas pedal, do it. Then set the TPS, and then check vacuum if the car stays running afterwards. The pressure tester kits are cheap. Do the idle set procedure, too. Alternatively, if you have the cash, a smoke tester will do you some good even before you start the car again, most likely.
As what was mentioned above, this is important to know. I have a rough idea how to do most of the adjustments that are locked out for the average person. Those things are kind of advanced as it isn't in the FSM.
Edit: I forgot that there is a way to bypass the quick start if it is working properly. Then you can set the TPS without a full warm up. I am not sure if the two light method will work that way by bypassing the quickstart?
Babysitting the idle is the only way that I drove my car for the 30,000 or so miles that I drove it. Not a good way to take care of a vehicle.This was 20 years ago and I new little about these cars and went to the library to look up fixes on this site.
I had the same thoughts about the squeaking. Brand new belts. Perhaps not tight enough? Perhaps it’s not the belts? Perhaps it’s a leak?
I need a volunteer to stick their head in there while we do these starts, rev like mad, then die.
I’ve had more success with “blipping” the throttle. If I hold steady she dies immediately.
Can I rent a smoker machine at autozone? And next dumb question— where do you plug it in at? Specific hose? Also I’d still like to get some cleaner on that MAF sensor.
Appreciate the feedback. Can’t thank everyone enough for helping me. Can’t believe just putting the airbox back on made such a difference!
I had the same thoughts about the squeaking. Brand new belts. Perhaps not tight enough? Perhaps it’s not the belts? Perhaps it’s a leak?
I need a volunteer to stick their head in there while we do these starts, rev like mad, then die.
I’ve had more success with “blipping” the throttle. If I hold steady she dies immediately.
Can I rent a smoker machine at autozone? And next dumb question— where do you plug it in at? Specific hose? Also I’d still like to get some cleaner on that MAF sensor.
Appreciate the feedback. Can’t thank everyone enough for helping me. Can’t believe just putting the airbox back on made such a difference!
It's not a MAF, it's an AFM. airflow meters(AFM) is a flapper door air density sensor versus a resistor wire that measures air density, airflow meters aren't really bothered by dirt, however internally they have a swept brush on resistor very similar to how a fuel level sensor works and that resistor plate can get dirty/worn and have dead spots or the resistance can be off due to the wear.
I don't believe that you can rent/borrow smoke testers. I can not vouch for the effectiveness of the pump included cheapy Amazon ones. although I am about to find out. I had a thought about an EGR leak. Would it be caught if the leak is the diaphragm? I don't think so.... There is one more, I just can't remember now. These smokers come with cones for the intake and spliters for hoses. I would split it near pressure sensor but don't know for sure.
You most likely have one or more issue. After some thought, if putting the air filter in, things got better. Take apart the entire intake up to the throttle body. Check your rubber gasket and verify that the pieces are not sucking air where they shouldn't be. Also take off the air box and inspect for leaks and check the seals/screws. I have an air box that was sitting in my garage for 20 years that came off the old car that I owned. Wouldn't you know that when I finally inspected it 20 years later, all four 10mm bolts were loose, letting air get by that shouldn't. It was like this for some time based on the dirt trail that it left. Also, the soft rubber piece of the intake was folded in on itself on my current car, letting air in there where it shouldn't be.
If you didn't clean the plastic bits below the fuel injectors, those could be dirty. Hopefully you read the intake removal write-up.
You might have air leaks at the throttle body too, I can't help you there. Plus many other things I am not knowledgeable about to advise you on.
Just a side note: If you have old cats underneath, and the pipes are super rusty, I would be extremely careful starting the car. Those old guts can crumble and bad things happen, it it hasn't happened already.
Edit: You can buy the test lights for the ECU. It is expensive for what it is but is way nicer than my home-brew one. I can't seem to find it online now though, perhaps the wrong search term?
the fact the car starts and runs but then stalls tells me it's not an exhaust issue, however i can't hear how it sounds during those few seconds it is running to tell if it's something much deeper or not.
like i said, it's usually best to tackle issues with proper diagnostics, when you start getting lazy and just throwing parts at the car folks are going to be less willing to help.
if you can't smoke test the intake, you're gonna have to be very thorough and check it for leaks visually and with other leak detection tools which require the engine to be running, so you're not to the latter point yet.
one less intrusive method is to have someone crank the engine while you push the flapper door of the AFM, trying to see if you can prevent it from stalling by manipulating the signal.
Last edited by notanymore; Apr 2, 2025 at 10:04 AM.
Just for grins and giggles. Did the whole routine of taking out plugs. Adding some marvel mystery oil, doing some cycles.
Then while a friend cranked, I did some shots of starter fluid.
Got about 10 seconds of running, but that was all entirely off the ether. There’s no fuel getting through.
So again, my guts are telling me it’s time to take off the intake manifold, and get the primary and secondary injectors replaced.
The timing and everything sounded good for that brief moment.
Then we had to get out of the garage because of all the white smoke. lol.
I have a theory about the "White Smoke" thingy.
My first experiance was starting my ":Flooded" engine at about 75k miles.
Filled the street with smoke!!
Happened at the Mazda dealership a couple of years later, filled their whole repair area!
My theory is that when trying to start a car that isn't starting, everyone has the tendency to pump the accelerator.
With a rotary we have a "Sub Zero" assist that injects a 90/10% mixture of anti-freeze when it is minus 0 degrees below freezing.
But when you depress the pedal trying to get the engine to catch you inject that 90/10% anti-freeze mix into the intake manifold.
This anti-freeze injection is what causes the white smoke.
I have blocked off the injector system now, unless you live in Alaska where you really need it.
I would look into the heated dipstick thingy.
My first experiance was starting my ":Flooded" engine at about 75k miles.
Filled the street with smoke!!
Happened at the Mazda dealership a couple of years later, filled their whole repair area!
My theory is that when trying to start a car that isn't starting, everyone has the tendency to pump the accelerator.
With a rotary we have a "Sub Zero" assist that injects a 90/10% mixture of anti-freeze when it is minus 0 degrees below freezing.
But when you depress the pedal trying to get the engine to catch you inject that 90/10% anti-freeze mix into the intake manifold.
This anti-freeze injection is what causes the white smoke.
I have blocked off the injector system now, unless you live in Alaska where you really need it.
I would look into the heated dipstick thingy.
What do you think??
The white smoke is the oil/marvel mystery oil he put in it prior to starting as well as just unburnt fuel.
The sub zero systems never even operated, even though the systems were installed. Fuel cut is activated on series 5 cars by pushing the throttle 90%+ and cranking the engine which keeps the ECU from pumping more fuel into the engine, though no fuel cut on the S4 1988 and earlier models.
The white smoke is the oil/marvel mystery oil he put in it prior to starting as well as just unburnt fuel.
The sub zero systems never even operated, even though the systems were installed. Fuel cut is activated on series 5 cars by pushing the throttle 90%+ and cranking the engine which keeps the ECU from pumping more fuel into the engine, though no fuel cut on the S4 1988 and earlier models.
Since around 1970 I have seen a few cars that were burning oil. The smoke that they emitted was always grey in color. It did not linger around like the white smoke does.
Nothing was added to help start my engine, no ATF, mystery oil, or anything else.
The only things in the combustion chamber when it finally caught was gas & oil, which will never cause lingering white smoke! Gray smoke, but never white smoke.
So, the only other fluid that can enter the combustion chamber is anti-freeze from the cooling system from a cooling seal leak 50%/50%, or from the sub-zero system when you depress the accelerator pedal when starting.
If you smell the white smoke as it drifts out of your garage and down the street it does not resemble any oil smoke I ever encountered.
Here is my fix for starting a rotary engine that has low compression and floods easily.
Since it does not start because there is too much fuel being injected on startup, you have to reduce the amount of fuel.
At first, I had success with pulling the main fuse for the EGI system, then cranking the engine over to get rid of the excess fuel in the engine and the fuel line feeding the injectors.
After replacing the fuse, the engine would catch and down the road I went. No cloud of white smoke or any other smoke.
This got old fast, so I discovered a way to prevent the extra fuel from flooding the engine that resulted in a no start state.
I installed a lighted toggle switch into the steering column cover which I put inline with the fuel pump relay to the right side of the column under the dash.
I just cut the power line and spliced the toggle switch leads into this wire. When the switch lighted up, power went to the fuel pump.
Here is the important part, before you turn the ignition key off, turn the toggle switch off and let the engine stall due to lack of fuel. Takes a few seconds.
This purges the fuel line of any pressure so that when you go to restart the engine it does not get the full amount of fuel that the ECU sends.
After using the switch for a couple of years, it did what I needed to restart my low compression engine.
I would turn the ignition key to the start position with the toggle switch off and let it crank for a couple of seconds.
Then I would flick the switch on then off very quickly to introduce some fuel into the engine, sometimes this was enough for the engine to catch. Then I flicked to switch on and away I went.
Sometimes I had to flick the switch on and off a few times for the engine to catch, but it always finally did.
When I bring it in for service, I need to explain to the mechanics what I did, and they always understand!
I do not remember if I read about the switch or thought of it myself. (probably read it somewhere).
What do you think of my fix?
I don't worry about some smoke from an old car that's been sitting a while. there is stale fuel in the injectors, humidity and oxidization inside the engine, critters living in the exhaust, dry carboned up seals letting all the above pass by until the seals feel like working again. I've seen those sub zero bottles on many cars, I've also never seen a drop of coolant in the lines to the intake.
I'm a firm believer in premixing these engines with 2 stroke lubrication(unless you still need to keep that catalytic converters for emissions), a little MMO on an engine that has sat for a year or more also is never a bad thing. The worst thing is assuming the seals will eventually move freely without a little help after sitting, I've seen plenty of original engines carbon wedge the apex seals and crunch them up like crackers in a sandwich.
Unburnt fuel can in fact come out white, I know that from tuning plenty of rotaries, it very closely resembles burning coolant clouds. Granted my experience was by disabling decel fuel cut which also net resulted in some pretty impressive fireballs.
Last edited by notanymore; Apr 6, 2025 at 10:15 PM.
Hey Guys.
Sorry it’s been awhile. Been unable to post and update with my latest troubleshooting.
So where’d I leave off and what have I been up too.
I replaced my fuel pressure regulator. It was easily reachable and not too expensive to replace. And still have the same results.
Start car.
Revs slowly and then will rev on its own to about 3K, but on the way down when it’s looking for a landing spot to idle, it’ll burble and die.
Then doing more reading, started to wonder if after it does it’s own startup, the MAF sensor isn’t right.
So for grins and giggles I disconnected it and didn’t seem to notice much change or difference.
I also found what part is squeaking/whistling. Should or shouldn’t it be? Is that a leak?
Dont know what it is?
I’m kinda at a loss. I still haven’t found anyone with a smoker.
Thanks everybody.
the pressure sensor (map sensor) on the right strut tower doesn't do much, the airflow meter(AFM) attached to the airbox is the single most important fuel related sensor on the engine.
raising up to 3k isn't alarming, as the car has a fast idle warmup function, it should drop down if you stab the throttle after a few seconds. but if it still wont hold an idle then you obviously still have something going on.
It seems like you would rather run you car through the parts cannon than follow test procedures or buy test equipment. It will be very difficult to find problems that way and most here will not start guessing at parts to replace.
The three things that leaked vacuum and were not detectable with a smoke test were the EGR, The piece that you took a picture of above and the BAC. Even with just those leaks my idle was a bit low still. Check those three things with a vacuum pressure gauge like the kind with a pump that you find in a one man bleeder kit. You can also put the pressure gun thing and connect it to the pressure sensor hose. Pull a vacuum and see if it drops.
We should have recommend the EGR delete or test when the Intake was out. If it needs blocked off, the intake needs removed. \
The hose on the part you pictured can be reversed if it holds pressure and it will block that part off if it doesn't hold pressure the normal way. The BAC most like needs removed, too. I applied 12vdc to the BAC and blew through it with a closed mouth, quick and very dirty. Do it with a tightly fitted hose on the intake if you want, it is either closed or open, as far as I know.
Some of the test procedure for the AFM is in the FSM. The other part will be to measure the voltage to the ECU. I am not sure how to do it but it would be easier to see the sweep with an analog meter. You can buy a new AFM but those sometimes are bad out of the box. I would swap in a known good one for a test. Best wishes with this.....
Edit: BTW, you would have much better served to take out your injectors and send them to be cleaned and have gaskets replaced. Those ones you bought could be part of the problem. Those are so cheap, most places won't even test, clean and ad seals because they are so problematic. If I am remembering correctly.
Was there a compression test done, I assumed it was done by now.
Hey all.
Yeah, I’m just throwing money at parts, but everything that had fuel just was clogged and smelled awful of bad ethanol gas. So I figure it wouldn’t hurt to replace these parts.
I need to rent the tool to do a compression test. I don’t have that or a smoker machine readily available.
I did have a question about back pressure. The exhaust system from the manifold back is rust and just a mess. Needing to get looking at an exhaust system replacement. But with the car starting and wanting to run for 25 seconds then die, in my mind I can’t figure out why it just won’t run and idle.
Wife is starting to wonder when she’ll get her spot in the garage back! lol.
Hey all.
Yeah, I’m just throwing money at parts, but everything that had fuel just was clogged and smelled awful of bad ethanol gas. So I figure it wouldn’t hurt to replace these parts.
I need to rent the tool to do a compression test. I don’t have that or a smoker machine readily available.
I did have a question about back pressure. The exhaust system from the manifold back is rust and just a mess. Needing to get looking at an exhaust system replacement. But with the car starting and wanting to run for 25 seconds then die, in my mind I can’t figure out why it just won’t run and idle.
Wife is starting to wonder when she’ll get her spot in the garage back! lol.
I would think an easy way to figure if its back pressure is to pull the mid-pipe/cat off and try it. I'm not sure if Ohio has emissions testing on cars this old but if the vehicle still has the cat I would look at getting that removed anyways if the state will let you. If you do it though, just be sure to be in a well-ventilated area. cover your mouth and wear ear plugs
i mean you could run a couple wires up from the starter solenoid too(the thin wire off the spade) and jumper that to the positive post on the battery, if assistance isn't available.
