91 RX7 starts up, revs to 2K and then dies out. Any ideas?
 

Do you have an AFM? I have turbo II so not sure the differences. This causes this exact condition. Make sure its connected and no disconnects.

With the AFM plugged in the car starts, revs to 2k then dies. With it unplugged the car starts, holds idle, but sounds like its cammed(headers only for now) and smells like its running super rich, could the AFM be bad?

Here is what Satch said on this subject.

The AFM flapper door could be stuck somewhat as it should open w/o too much effort. The flapper door does get pulled open at startup via the vacuum suction created within the engine thus you are correct to believe a large vacuum leak is a possible cause. Make sure the intake duct is secure to the AFM and throttlebody. Also, on some models there is a T connector located underneath the intake duch as it approaches the throttlebody where a hose take air and sends it around to the other side of the engine. I put the post below.

https://www.rx7club.com/general-rota...e-afm-1060685/

I know the door opens and closes fine, but I was reading that it could still be bad regardless, the car will not idle with the AFM plugged in, it revs up to 2k and then dies out. With it unplugged it idles and wont die out but the idle is super low, hence why it sounds like its cammed and lopes like a big V8.

Have you double and triple checked vacuum lines? Maybe a bad booster line?

Finding vacuum leaks left and right lol. Do you mean brake booster vacuum line? I think if the AFM was working properly it would idle better, it wont idle when it's plugged in. If I start the car without it, it idles.. not well but it does, if I plug it in while its running it starts to sound better and then dies out.

It will not idle even with one leak. Check all lines. Take them off and inspect them under a light. You'd be surprised to see that they are badly cracked and could explain why it's able to idle(a very very small leak). Brake booster line runs to the lower intake manifold on the passenger side. It's the biggest vacuum line ... you can't miss it. It's on the firewall side. Just follow the vacuum line from the brake booster.

I wouldn't worry about anything else until you address ALL leaks. You'll be running in circles. I don't think it's your MAF.

I'll make sure to check them all, it just doesn't make sense to me that when you unplug the MAF the car will at least idle. I read that a lot of the MAF had failures and the updated ones were marked with a white dot, I believe I have the older one. Like I said when we plugged the MAF while the car was running the idle started sounding better and then it died out. If we started the car with the MAF plugged in it would rev up to 2k and then die out by itself

The FSM has a procedure to test the MAF. If the resistances check out then it's probably good. It's just that you mentioned you were finding leaks left and right. If that's the case then you shouldn't be wondering why it's not idling. If you fix all the leaks and your problem persists then you can logically move on to other things that could be the culprit. Are you getting a code 08?

Haven't had a chance to check the codes, ill do that and see what its's saying.

Now it's starting with the MAF plugged in, and idling a bit high and backfiring a bit, I revved it up to 3k and it died out. Could this be vacuum related?

Do you have a vacuum diagram for your model? It does sound to be vacuum related. I would suggest you check out the diagram and go through all the connections and see if you might've overlooked something. If you do this you can rule out it being vacuum related with a bit of confidence.

Has the intake been removed? Has the upper/intake manifold been removed? It seems intake related for sure. The backfiring, meh, could be something else doing that. I would focus all of my attention on inspecting the whole intake system start to finish and all vacuum lines.

TPS has nothing to do with idle until the engine is warmed up

David I ended up buying a smoke machine for cheap off craigslist just for testing my vacuum lines. I have heard of people blowing smoke as well into it. I just don't smoke and this works like a dream for me. I simply unplug the brake booster line and connect one of those air mattress pumps up to it. Then I have the other end connected to the smoke machine so it blows smoke through the vacuum areas. If any smoke is seen pouring out of an area that is where my leak is. You will also need to plug where the MAF connects if you have it off or just after is so the smoke doesn't come out there. I have used this a few times. It has found the leak every time if I had one. I had one under the throttle body there which is hard to get to. All those spider lines for the OMP all of that is vacuum. One of those came off and smoke was pouring through one time I checked when I had a high idle condition. I knew it was sucking in air from somewhere, but not really where. In my experience i have had a few vacuum leaks and they all caused high idle conditions due to be getting to much air. I once left the main brake booster off which caused a huge leak. I finally pulled started my car and it took and minute and sounded awful trying to run. Finally after like 20 to 30 seconds the idle went way up. I couldn't get the idle below 1800 no matter how much I adjusted it. I knew something was wrong. I took a break and let it cool down and then remembered I did not hook up the main hose after I had it all apart. This is why I could not get it started until I pull started. Anyways the moral of the story is vacuum related can make it hard to start maybe or give it high idle. This is all it effects though and wouldn't cause the cutting out of your car I do not believe. Vacuum is easy diagnosed if you can plug the AFM and blow smoke through it somehow.

Ohh since you have an S5 stepping on the throttle cuts the fuel which allows you to start if its flooded a little.

Fix your vacuum leaks jesus.

If you can get the engine to idle, spray carb cleaner around the engine bay. if the idle changes, you have a vacuum leak.

Are you low on coolant(buzzer)?

Good to hear that you found a leak. Are you actually using a vacuum diagram? I mean, it's goes without saying but it would make your life a whole lot easier man. Learning how to troubleshoot right is important. How is one expected to know where all the vacuums lines are on an engine? You will save lots of time and money. You'll also understand your car better.

We filled it with coolant (new radiator)... I know the oil sensor connector is not hooked up, was wondering what that white connector was. I also know the oil was somewhat low to begin with, sometimes it buzzes sometimes it doesn't throughout this whole process of getting it running. Doing an oil change this weekend and hooking up the sensor, just need to find where it plugs into.