Great News Update!

user: notanymore is getting a virtual handshake from me.

Put the MAF sensor back in and I found a good length screwdriver to push the flap open while my son started the car.

And we successfully idled and ran at 2500 rpm without touching the throttle for 4 minutes!

So where do I go from here? An all new MAF sensor? Or how to check the wiring/harness?

I’m so happy to hear the car run again. Thank you.

 

Always kinda funny going back through old posts and gotta say NotAnymore was on this a long time ago. Mentioned the adjustment screw on the sensor and sure enough, I never even noticed it before.

The “flapper” seems to spring closed just back fine. Freely moves. Super clean. But do I need to crack it open and adjust the spring more? What can I do to my current setup to adjust?

Hope to get some more time with it tomorrow. Thanks

 

since you have to hold the AFM open to get it to idle it points to air leaks still present in the intake. if you have an air compressor you can build an intake pressure cap with simple plumbing couplers and a tire valve stem, pressurize the intake off the throttle body and spray the intake down with soapy water and spray gun. you should even be able to hear the air leaks. if you can't spot any leaks with soapy water i also use mechanics stethescope without the metal pointer attached(point the open hose end at areas for amplified sounds).

something like this:


and i have similar to these:



this is the best alternative i can find to smoke machines, i have these couplers made up to test n/a and turbo intakes for leaks as it works for both.

if you can't find any more intake leaks you will have to test the AFM, there is resistance values in the testing procedure for the sweep full closed and full open. if the sweep shows erratic resistance or the values aren't correct when closed you should try another known good AFM, preferrably a stock one from another car and not a remanufactured one.

the service manual can still be found here (would be wise to download them all while they're still up):

foxed.ca - /rx7manual/manuals/1988FSM/

and thread with the steps for the test with images from the FSM here:

Testing AFM - RX7Club.com - Mazda RX7 Forum

Personally i rarely find the AFM's to fail, it is 99% of the time something else that needs addressing.

intake leaks are quite common though, after 30 years of hardened rubber and gaskets. another common place for the n/a to leak is the brake booster line off the back of the intake on the passenger side. that S shaped hose gets very brittle and cracks at the bends. it is however now NLA from mazda though. i have looped high pressure fuel hose as an interim solution temporarily, low pressure carburetor rated fuel hose is insufficient.

glad to hear you're making progress little by little.

 

Thanks again NotAnymore for the tips. I’m going to try your techniques if I can’t borrow a smoker.

I just did the test where I turned the ignition to on, and pushed the flapper open with my screwdriver and I heard the injectors spraying fuel.

All the hoses and everything appear to be visually in tact and connected where they’re supposed to be.

But I know a guy with a smoker. Just lives over an hour away. Thanks again for all your posts and help!

 

no problem.

 

Since it’s going to be a minute till I get a smoke machine, I took it out I’m checking the ohm resistance. In which case I’ve looked this over and I’m making double triple sure I’m hitting the right pins.

And my ohm meter is displaying the same #’s wether the door is open or closed.

So I was thinking, should I open it up and check the connections inside? Make sure something doesn’t need to be re soldiered?

 

ill open the FSM and see which terminals it was again, the images from that post are kind of blurry.

 

with the connector on the topside with black cap facing up of the AFM the pins are E1(1, 1st on the left) Fc(2) E2(3) Vb(4) Vc(5) Vs(6) and THA(7 last on the right)

the fuel pump switch is pin E1(1) and Fc(2), closed it should show no continuity, fully open it should show near 0 resistance.


the sweeper for fuel correction is pins E2(3) and Vs(6) should show 20-400 ohms closed and 20-1000 ohms fully open. this range seems kind of redundant but it should rise in resistance as you sweep the door. make sure your ohm meter leads aren't bridging to other terminals or your readings will be off.

so set your ohm meter leads on pin 3 and 6 for the actual airflow signal and resistance should rise from about 30 ohms to near 1000 fully open(at least that is what i recall should happen), pins 1 and 2 for the fuel pump switch which closes as the door swings open to keep the fuel pump turned on should act like a relay turning on when you open the door to bridge the connection.

the issue with opening it is the internals are delicate, the sweeper actually is only held in place by a set screw and there is a ratcheting/calibrated clockspring, so if you do open it try not to bump things inside. the cover is also glued on with a sealant. it's basically a big fuel level sending unit internally, preloaded by spring tension on the flapper door, luckily the spring doesn't lose tension over time.

i have messed with the internals before but only when i had backups on hand, as a way of tuning the engine myself. once you do any sort of tinkering inside there's no way of getting it back to original without some expensive test equipment and proper baseline readings.

basically i don't suggest opening an AFM unless you know it is DOA. the screws won't get you where you want to go, the black cover is where the guts are.

if your curiosity can't be sated here is a thread i posted a few years back that has some images that survived the years:
protip: series 4 airflow meter tuning - RX7Club.com - Mazda RX7 Forum

i probably still have that old AFM sitting on my parts racks somewhere, as i recall just replacing it with another one rather than trying to undo the dickery that had been done.

 

Okay, promise not to laugh, but I don’t even have a digital ohm meter. I just have my dads old analog one.

But specifically looking at this one, the pins 1 and 2, I have zero reading when closed. And I have a reading when fully open. Per what you said and reading, it should be 0.

I got a picture showing it’s set to Rx10k and the ohms adjustment is all the way down.

Thoughts?


the other pins you had me check all show the same reading too. But I’m focused on these because it shuts off the fuel pump and that’s the end of my running.

 

An analog meter is fine to use. Just make sure the range is set correctly.

Most important, touch the leads together and use the ohms adjust and set the meter to zero.

Also, when doing a sweep test, an analog meter is preferred. It is much easier to see drop outs.

As for your readings, If you didn't zero out your leads, those readings aren't accurate. Are they accurate enough to now if it tests correctly? Not sure ..

It kind of looks like you might need a bit more guidance here. If this sits here without other response(s), I might be able to walk you through at least some of it.

 

hard to really know if the meter is accurate, make sure you zero it out like jeff said because 30k ohms for the fuel pump switch sounds a bit high, as does the sweeper readings.

you can keep the fuel pump running by jumpering the yellow loose 2 pin connector near the right front strut tower and retest the car.

 

And that is an important step that I missed/didnt know. When I get home I'll do that and re-test.
Also while I'm posting here, I saw the comment about putting a jumper on that plug by the strut for the fuel pump relay. If anyone could point me in that direction for more clarity?

I havent procured a smoker machine yet, but I've seen some DIY examples with pickle jars or cigars! I might look into the cigar one!
But finally narrowed it down to either being an issue with this sensor or a leak. We'll get it guys!
Thank you all again,

 

the connector should be taped up on the engine harness between the right front strut tower where it jumps across to the engine in that large loom of wires. it likely will be right over where your intake hose from the airbox goes to the throttle body.

i can't find any images anymore as all sites that used to have images purged them, the FSM picture isn't very good and my car doesn't have one anymore since i have a standalone EMS.

 

It's the yellow connector. You might hear the pump kick on. With the hose from the filter off at the rack, you will get fuel out of the hose with the key turned all the way and the jumper in place. Put the hose in a glass jar or similar if you don't have a fuel pressure gauge. Fuel pressure is very important but I am not sure you are there yet in testing.

Just as an aside, just tap the ignition fully on very quickly or your jar will overflow with fuel very quickly.

Hopefully, this is the connector that you were looking for and the test you were looking to do.

Edit: The key will be in the first position not full forward for the test.

 

So now that I know how to zero out the ohm meter prior to testing, the first test with pin one and pin two for fuel was correct and good.

The other test for pin 3 against pin 6 showed no difference. However I can only get this thing to work on Rx10K. And again, I admit I know little about doing these measurements.

But I feel based off hearing the fuel come on and off when I open and close the flapper, that this sensor is good.

My next step is to get a home made smoker tester and see if I can find a vacuum leak somewhere.

Thanks again everyone.

 

you can make one relatively cheap, i made one with some stuff i had laying around like in this video:


currently dealing with a neighbors 1996 nissan D21 pickup that he had another neighbor rebuild the motor on. apparently the guy doesn't know how to remove old gaskets or to put new ones on, the intake is leaking from just about every joint. the KA24 has a MAF system though, so it just idles higher and rougher than the 2nd gen rx7.

 

Update -
We found the hopeful leak!!

I put together a similar pickle jar smoke machine with some harbor freight stuff laying around. Worked well. But pro-tip, that metal lid gets hot! Be careful.

Anyways. It didn’t take too long to see the problem! And as a shock to nobody: it was a vacuum line that Todd forgot to connect! Steady stream of smoke coming right out.

Not technical enough to say what line it is, but it leads straight up to the air/fuel mixture box.
We also found a sleight amount seeping out from the intake manifold gasket that I replaced on the left side. Right was sealed.

I’m going to check the torque on the nuts down a little more, but also hoping when we finally get a good heat cycle it will seal up nicely.

So you’re all wondering: is it running? Well, it’s late and the battery was a little weak. I got it on a charger tonight and hopefully tomorrow I’ll be able to take my wife and mom out for a Mother’s Day ride!

Thanks all!

 

Welp…
still back in the same spot. Can’t get the car to run unless someone is standing there holding a screwdriver on the MAF plate. The revs respond to how much you open or close the plate.
But just cannot simply turn the key and start. It will just “burble”

I dunno. I’m on the cusp up just looking for another MAF sensor just to see.

There’s a Mazda guy in my state of Ohio. I might see if what he can do for me maybe?

Will do another smoke/vapor leak test. But swear I had it.
Disappointed here…

Will keep pressing.
Thanks

 

could be the AFM, just be sure to find the same one preferrably used but from a recently running car. N326 should be the 1986-1988 non turbo one. this is what should be the part number printed on yours. if yours has the wrong one installed it can give similar results, the turbo airflow meters(N318) have higher spring tension than non turbo ones. i would check that someone hasn't swapped it inadvertantly with the wrong one first.

did you ever jumper the 2 pins in the yellow test connector to keep the pump running?

 

Good tips (as always)
I might reach out to the Mazda guy here in Ohio and see if he's got anything on the shelf. I see the part on places like carparts.com, but like you said in an earlier post and here...do they actually check them to make sure they work?
The one I have is totally original that came with the car. Basically muffler fell off and he put in the garage to sit for the next 16 years. lol

I did forget about the jumper pin thing too. I found the harness and meant to try that. But I was still sitting in my chair of depression when I could've swore we found it with the disconnected line!
We'll get it! Gotta stay positive.

Thanks!

 

Yep, most problems have a very simple solution, you just have to figure out where the problem is.

there is still the option of drilling the tamper plug out of the AFM, count and note the turns clockwise until it stops. reinstall the AFM with the screw turned in a turn or 2 and see what happens. this is the same as manually forcing the flapper door open more than it naturally would with the engine running, richening the mixture and preventing the fuel pump switch from closing. this is only a true fix if the AFM is in fact faulty and the cause of the issue, otherwise it's just a simple solution to keep the car running with large vacuum leaks. i don't doubt your leak test results but some places you can't see like a brake booster diaphragm torn internally which will cause a large vacuum leak that is unseen. just be sure the AFM is placed on the intake snorkel, it doesn't do any good to measure air if it's not on the intake.

you can verify this by disconnecting the brake booster hose and capping the port.

when cars sit unused for long periods of time, rubber components tend to start failing, the brake booster is a simple rubber diaphragm.

 

Thanks for the heads up on the brake booster. I have one more thing to check now. The double throttle diaphragm, the EGR, BAC and maybe the ACV leak without visible smoke. My AVC was leaking at the sensor so, that was visible. There was another that I helped with ended up being freeze plugs. There at at least three in the intake, maybe 4. Two of which would not be visible.


I had small leaks from a couple of those and I still could set idle speed, it was a bit low but manageable.

So with the flap open, it simulates more air getting in, therefore there is to much gas? or not enough air? or both? Or a broken AFM or to much air already?

 

Funny you mentioned the brakes. Over the winter I took my master cylinder and booster out. Reason is because the seals on the reservoir failed and all the fluid leaked out.

Ironically I just got the new master cylinder reinstalled, but haven’t gotten to attempt to bleed the brakes yet. This engine running is taking all the attention.

Got home today and did another smoke test just to double double check. Tightened things down and I can’t find anything. And my home mode smoke machine makes a lot of smoke (protip mineral oil). lol.

Also made a jumper for the yellow plug, and I hear the pump working when I turned the key to on.

But still can’t get her to start.
I’m thinking about getting a MAF sensor, be careful putting it in and if it doesn’t work just put it right back in the box.

Thanks all,

 

Just to show I’m not crazy. The car RUNS great when you hold the door open. Revs smooth and responsive and everything works. Oil pressure. Voltage etc.

Im also gonna consider the rich/lean adjustment NotAnymore mentioned. That makes sense too.

 

Hi, most if not all of the rubber diaphragms have a hole in them after 35 years.
Vacuum is applied to the diaphragm until the coolant temperature reaches 140 degrees, any higher and the vacuum is closed off and the spring forces the plate open.

With that in mind, the rip or hole in the rubber will create a vacuum leak until the engine temp reaches 140 degrees.
You will never find this leak on a warmed-up engine!

There is a simple test in the FSM for this.

There is a thread for substituting a new EGR diaphragm in place of the old leaking one.