87 NA stops firing above 3000 RPM
 

I bought an 87 NA off a friend a few months back and have slowly been tinkering with it trying to diagnose the problem. The primary symptom is that it can't maintain an idle. I have managed to keep it running by adjusting the idle up to about 1500 rpm but I just realized today that if I step on the gas it revs up smoothly to about 3000 but past that the gas cuts out and it dies unless I let off the pedal immediately. I get the exact same results when I adjust the throttle under the hood. What does this behavior mean??

the bad idle could be a vacuume leak or bad grounds. engine shutting off could be a bad fuel pump, is the car your primary car because if its not a daily driver i can give you some advice on a good list of things to do before driving the car. was the engine ever rebuilt .

No, it is not my daily driver and no the engine has not been rebuilt. It has about 115k miles on it. I'm going to give it a thorough check for vacuum leaks as soon as I have time.

Also, I'm getting the ECU error code for the AFM. Should I definitely replace it or could a vacuum leak or another problem cause the ECU to give me that error code?

And last, I did the FSM TPS adjustment and the car will not idle. It starts and dies immediately. Messing with the TPS I could get it to stay running at about 1100 rpm but I had to loosen the TPS screw until about 5 turns away from coming out.

theres a vacuume line on the driver side of the engine next to the oil filter make sure its connected correctly.
since its not a daily driver have the engine rebuilt, also gives you a good chance to get it ported if you want. another good thing to do is to take out the fuel pump and check for rust and gunk, if it has clean out the tank with some palmolive and a hard brush clean the fuel pump too dont worry about the water. this can cause alot of problems in the future.
ill get back to you on the AFM but i think a vacuume leak could cause the code.

when you get time get under your car make a checklist and check all the mechanical aspects of the car mounts joints ect. thats the best advice ive gotten to keep my rx alive. problems with these cars are already a sure science and the problems are usually mechanical. luck

Why not take a few minutes out of your busy day and check out the afm with a meter at the ECU? Beats writing on this forum and waiting around. AFM faults codes are all electrical.

Hailers is right check the ecu. if your lucky could be a wiring or adjust issue. remember the afm is adjustable too. luck

I had a problem with mine sputtering at about 3k RPM and I ended up fixing it by making sure the battery connections were tight.

also dont forget to check that line next to the oil filter

I replaced the AFM (the original one was not in good shape) and that helped tremendously but there are still issues. The car idles at about 1500 and sometimes decides to move around +- 200 rpm. Excited that the car didn't die immediately, I drove it around the neighborhood a bit only to find that it had no power. In 2nd it takes about 5 seconds to get from 2k rpm to 7k rpm with WOT.

I'm going to go through the entire low-power checklist in the FSM but I'd thought I'd ask if there is anything missing from that list that I should check.

ill tell you right now thats about right for the car to get from 2k-7k. remember an na is very slow, no matter what you think. 1500 is a bit high for idle. try to bring that down maybe? now that you got the afm swapped what other issues still persist?

I can't get the idle lower than that. I have the air adjust screw turned all the way in and it idles there. I understand that this usually indicates a vacuum leak but I still can't find one.

Other than the idling speed, the only serious issue is the brakes but I haven't even begun to look into tuning them.

As for the power, is is usual to experience a faster gain in RPM with WOT around 4k than 2k? As in I can get from 4k->6k faster than 2k->4k.

mines not :D

try to adjust teh cable itself. this might be able to fix your issue.

as far as your theory for revving i believe your right, but then again i have been wrong before.

Yea its normal, the rotary engine in N/A trim makes is best power on the second half of the rev band.

You have a vac leak, there are plenty of vac lines you cant see(a decent amount for the omp injectors which you wont see with the uim on. The best course of action it to just pull the manifold off and replace the old gaskets and vac lines, some emissions delete's wouldn't be bad if you can get away with it in your state. This would also be a great chance to replace the old and probably bad fuel lines, fuel pulsation dampener, injector o-rings, and clean the important engine grounds. One other thing to do is verify the TPS is adjusted in spec(1 volt at the ecu). If the TPS is not adjusted in spec the car can idle rough or actually idle high if it starts advancing the ignition timing. You have a nice weekend of work ahead of you basically.