Backstory:
Restoring my late fathers 88 vert na with a 13B

Cleaned out and replaced fuel system and many parts.

Car will start, run for a second. Die.

Can hold MAF sensor door open and she runs like a top.

Currently:
My son one day got the car running without having to manually hold the MAF sensor. Said he adjusted the air/fuel. Cool!!

So I thought.

We drove the car for days. No issues.
Then one day it died. Had to have it towed home.

Come to find out my son TAPED the MAF sensor flap so it would stay open! While I appreciate his engineering, it’s still not right!

Now, all signs and posts on here say it’s a vaccum leak, but I’ve looked and smoked and listened and sprayed and smoked and cannot for the life of me find a vaccum leak.

My next train is thought:
Is the fuel pressure not high enough? Did I get a new fuel pump that was too small?
Or is it not getting enough voltage to tell it to make more power or something??

Getting a fuel pressure test done next.
What your guys thoughts to it being fuel delivery related?

 

Have you diagnosed the MAF itself yet? There are a couple of easy checks in the FSM that can be done in minutes with a multimeter.

Fuel pressure issues at start/idle are unlikely in my experience, not to mention the pump doesn’t have to work hard at all to supply enough fuel to idle the car. It can happen, but what you’re describing sounds vacuum/MAF related.

Beyond those two, teeing in a gauge to measure fuel pressure is easy enough. If/when you can get the car running (does more air help things?) I’d also look at redoing the initial set procedure and getting everything set properly so you’re not running in circles dealing with the wonky 80s electrical/mechanical PWM madness that is the FC idle control system.

Not sure what your kid did qualifies as engineering but we’ve all been there Good luck!

 

Yep. Went down that road and even found a former co-worker who built cash registers for NCR and really knows multi-maters to check it.
I even went as far as getting a 'rebuilt' one from rock auto, throwing it in there and still the same results!

But I've been driving the car with the redneck tape job, and more and more I keep thinking its all tied to the exhaust system which is absolutely shot. Because I thought about what you said about fuel...when it runs, it can supply fuel just fine all the way to redline.
However, if the exhaust 'hiccups' or chokes, I get no power until I let off the throttle and try again.
The catalytic converter looks like it come off the titantic.

The left muffler fell off and the whole thing is just bad looking.

I have to get a new exhaust system for it regardless. So my hope is that once I get it replaced that actuators are actuating, venturi effect is venturi-ing and THEN hopefully we have a co-operating MAF sensor.
Because for the life of me, I've been been searching for vacuum leaks with smoke for so long, the car has second hand smoke lung cancer now.

 

its possible it could be a broken cat, try banging on the bottom of the cat with your palm and see if it rattles. i have had cars where the broken pieces inside would turn enough to let the engine run somewhat normally for a bit until they rattled into a closed choked off position, resulting in a lot of bogging and lacking performance. however i never had an RX7 not start/drive with a failing cat.

you can also test it with a pressure gauge in the oxygen sensor port. anything over 0-1 psi indicates a blockage.

check your fuel pressure and fuel pump voltage to see if they drop just before the car stalls out(not after). the pressure should be around 38psi at idle.

look for this yellow connector by the right front strut tower, make a little double spade connector jumper and jump the 2 pins and retest the car and see if it stop stalling:
http://i181.photobucket.com/albums/x...2/DSCF0089.jpg


really need some definitive results in some of those tests.

and don't forget, before you pull all your hair out there is the last resort to at least make the car drivable, pull/drill the plug off the air bleed port and screw the flat head screw in while counting the turns, write the turns in on the AFM and try starting the car with that air screw seated fully. here is a picture for reference circled in red:


you can play with this screw setting to smooth out the idle, but it *should* allow the car to not stall out anymore, this is a bypass/workaround for a vacuum leak that is 100% reversible by resetting the screw to its original position once the issue is resolved. it's better than tape...


there has to be something missing in the tests, are you smoke testing the intake right at the throttle body? there is still the intake snorkel to account for if so.

 

Thank you (as always) for these tips/reminders that I need to go through.
Yes, my home-made smoke machine (pickle jar with mineral oil soaked rags with a heating element inside with air in / air out hoses) I've hooked up from the maf with a rubber glove with the hose coming through a small hole.
I need to redo my smoker, but its produced pretty good white smoke.

Thanks again for the tip on how to adjust the screw to versus using tape. I never noticed that under mine for all the times I've taken it out.

 

it's there, some AFMs look slightly different with the ribs but every AFM i've seen has this capped off air bleed screw on them. if you opt to drill it out, the screw is about 1/4 in below the cap and the cap is only about 3-4mm thick. i just just a drill bit about as big as the cap and slowly drill it til you see inside the hidden port enough to get a screwdriver in there.

 

About 2 years ago I went on Amazon and bought a rebuilt AFM for $109 and was done with it.

I changed the water temp sensor behind the alternator and the AFM and was amazed at how better the car ran during startup, and after warm up.

All for 150 bucks.

I would do that before I touched the fuel system.

If you want to check the fuel system operation put the key in the second position before starting the car and then with your finger push open the vane inside the AFM.. . .You should hear the fuel pump kick on.

This is only for S4's with vane style AFM's (86 to 88)

 

he said he replaced the AFM with a reman one, but the same symptoms persisted. it's possible he got another bad AFM, the pump circuit is known to fail but it's a better chance that there's an issue still present somewhere.

 

Yep. I found a rebuilt one on rock auto and slapped it in there real quick and got the same results. Also with the OHM meter testing on my original looking good, I dont think its actually the AFM at all.
And yes, can turn the ignition to on, push the flap open with a screw driver and hear the fuel coming through. So that works as well.

Im going to get the exhaust system replaced so I can actually work on the car while it runs without dying from the fumes. Continue to look for a vacuum leak.
I've made some contacts with an rx7 pro who I may honestly take the car to for him to review. I've completely given up on this mystery. lol