kewebb

Hey guys, I have an 88 rx7 non turbo that I’m having some issues with and was hoping one of you could point me in the right direction. Basically the problem is if I give it anything more than roughly 25% throttle then it begins dying. If I rev it up with the little throttle I can and then give it more than 25% throttle then it completely cuts out and until around 1500 rpm where it begins popping and banging, kinda like a rev limiter until I let off the throttle again. I’ve attached a video showing this.

I can rev it all the way to red line with ~25% throttle. It looks to me when it starts falling off is just after the secondary throttle blades open.

I’ve replaced the fuel filter, fuel pump and injectors and confirmed it has about 40 psi at the rail. I’ve also replaced the tps and calibrated it. Replaced the maf, plugs and confirmed it has spark. I’ve set the timing correctly as well.
the car also has the omp, air pump, egr, and air bypass deleted. (Still has bac valve)
I’ve gone as far to try another known working ecu and it didn’t help anything.

any ideas help, thank you.

Hot_Dog

Have you tried pulling error codes? This is normally the first step in a troubleshooting process. Here's a link with more detail: FC3S Pro v2.0:&nbsp How-To - Zenki FC3S Error Codes

kewebb

I figured it didn’t have any codes because the engine light wasn’t on but I’ll definitely give this a go. Thank you

Hot_Dog

I don't believe that the S4 has a check engine light.

rlynchster

You could try the old starting fluid trick. . . . Trying not to set things on fire, spray little squirts around select areas and if you get a bump in RPM's all of a sudden, you've found your air leak.

Sounds like it's an air problem. . . specifically, too much air problem. . . .Popping and bangs are consistent with too much air.

Did you replace your MAF with a new reman unit? . . .I had an old MAF do something similar to what you are seeing.

Might also want to change the water temp sensor behind the alternator. This might be a contributor, but not the root cause.. . . But if changing it makes an improvement of sorts, it could make it easier to find the real culprit. A bad sensor would make the car think it's cold when it fact it is not and thereby mess with the air fuel ratio.

kewebb

I checked for vacuum leaks and changed the coolant temp sensor, nothing changed. I tested the codes and it gave me a code for the afm so I pulled it out and tested it as the fsm says and I could that the iat built into the afm was bad. I just replaced the afm so I guess bad luck, I ordered a new one. My only question is if the iat was bad and everything else was fine, why didn’t I get a code for the iat?

rlynchster

Define "bad" with the IAT .. .An IAT on the upper intake could simply read different/wrong ohms relative to temperature and the ECU wouldn't know it's off. The IAT in that location in my opinion is for fine tuning the mix and probably wouldn't make the car undriveable. . . It might throw a code if it were unplugged though. I seem to remember somebody saying that the ECU goes to a default map for that IAT input when it is unplugged.

My guess is on the MAF you are replacing. .

kewebb

the iat I was talking about was the internal one on the Maf, when I measured the resistance as the fsm says to it read 0 resistance. I totally forgot there was another iat on the actual intake so that answers my questions as to why it gave a Maf code. I got a new one coming so hopefully that fixes it. Thanks for your help