1988 FC RX-7 will not stay running
 

I just bought an 88 FC for 600 bucks. It's surprisingly complete for that price. Only problem is the mold, a couple cracks, and it won't stay running. I rushed into the deal without doing a compression test. ~_~

However! I just checked it today and it's at 120 psi!
I honestly didn't think I could get an RX-7 until a few years down the road. This one just happened to present itself.

So, at first it wouldn't start so I changed the fuel pump.

Then it wouldn't stay on so I changed injectors.

Then it seemed to be running extremely rich with black smoke, shaking, and no power. So I changed the fuel pressure regulator, spark plugs, coolant temp sensor, and O2 sensor. It seems to stay on longer but still running terrible.

Whenever I unplug the mass airflow sensor, it runs perfectly but suddenly cuts off after 5 seconds or so. So I tried a new mass airflow sensor but it made no difference.¯_(ツ)_/¯

I'm thinking it's the ECU because there were a couple rusty looking points on the board. I soldered them but it made no difference.

I adjusted the TPS and it ran nicely for half a minute but now it won't start again.
When it runs nicely it tries to reach warmup rpms but buckles and can't make it.
I should mention that the car has electrical issues. Sometimes the door lights come on and the key-in-ignition beep works, but sometimes it doesn't. Also, the washer fluid light seems to be functioning as the battery warning light. lol

In short, I have no idea what's wrong but it could be the TPS.
Please send help quick. I really like this car. (´⌒`｡)

HALP ME. (´°̥̥̥̥̥̥̥̥ω°̥̥̥̥̥̥̥̥｀)

Don't you see my tears?

Hit me with the truth! I CAN TAKE IT. ::>_<::
I'm changing the TPS today but your input it still valuable!

Make sure that your spark plug wires are going to the right plugs. You'd be surprised how often they are mismatched.

There are labels for L1, L2, T1, and T2 on the coil packs as well as beside the plug holes on the engine.

Also check your plug wires with a multimeter. It doesn't sound like a fuel pump issue, but you can test that too by checking if there is voltage at the pump, and jumpering the yellow connector near the Air Flow Meter w/key to ignition. You should hear the pump start whirring as the fuel system is pressurized. Again, it doesn't sound like it's the fuel pump, but it's an easy check.

If you have a timing light, you can try re-stabbing the Crank Angle Sensor and resetting the timing, as it might be off if the engine was messed with by the previous owner. There are many threads about that.

Factory Service Manual PDFs are available at Foxed.ca

If all else fails, the easiest way to check if it is the ECU is to try and find another one near you and plug it in.

I checked the coils and changed the TPS sensor today. It didn't fix it so I'm going to go through the diagnostic procedures in the service manual tomorrow. I have a diagnostic computer that can connect to the diagnostic port on these cars that I will try as well.

I checked the vacuum today and it looks like there isn't enough and that's why the ECU is injecting too much fuel. I can't find the leak though. The brake booster looks like it has been leaking but vacuum was not restored even when I plugged the line. I'll look into the manual in more detail tomorrow.

EDIT: Turns out I was out of gas and that's why it was running leaner. I filled it up and now it's extra rich again. *bangs head against the wall*

I did a smoke test and found that the MAP sensor line was blocked. I replaced it but it didn't solve the problem. It looks like the ECU for sure. It should arrive by Thursday

Man, you're changing way too many parts haha.

How did you do your compression test?
Were all of your sensors tested to deem them garbage?
Did you test your old TPS?
Not enough vacuum? ...
You soldered your ECU?
And the MAF... did you test it?

Too much is going on here. Please tell me you didn't throw your TPS in the garbage.

(Most important question: How did you do your compression test?)

Honestly, the only sensor I tested was the TPS.
I think the only parts I needed to change were the fuel pump and injectors.

My dad tested compression while I cranked the engine. He said each push was strong.

We've been throwing way too many parts at this car so we took it to a rotary shop and they immediately said it was the ECU. It's only $60 so I'm hoping that's it.
I resoldered the points on the ECU that looked rusty. The area around the ECU is very rusty and damp which is why I checked it.

Try the ECU. Hopefully the car wasnt a victim of flood damage, because thats what it sounds like.

I'm in Florida and it's so humid you'd think we were flooded every day. haha

How long did it take them to diagnose that? Ecu is at the bottom of the function table.

I hope they didn't rip you. Doesn't sound like Ecu but I've been wrong before.

I dropped it off in the morning and they called by noon. I won't pay for the ECU if it doesn't fix the problem

When you did the comp. test did you hold the valve open observe the evenness of each stroke? 60 dollar fix would be sweet.

It turns out that it was the ECU. They put in a new one and made some throttle and idle adjustments and its running nicely! Thanks for the help.
It still has a couple issues like the clutch some electrical things but so far its drivable. I'll probably be sticking around here.