Code 31 and 24 with intermitent no start.

[SupraChrisMk3]

So here is my problem. For the past couple weeks the car would very intermitently not start. After maybe the 2nd or 3rd try it would start right up and run great. Last thursday it would not start at all and I had to have it towed home. I could not hear the fuel pump turn on when I turned the key either. Got it back home and figured that the fuel pump had failed and replaced fuel pump and fuel filter for peace of mind. After that it started right up and ran great again. But today when leaving work to go home again car would not start. Double checked connections under hood (electrical, vacuum) and still would not start. For the hell of it disconected AFM and car started. Reconected everything and drove home normally. Once home checked codes and found both 31 and 24. I have also been having an issue of when in stop and go traffic having the car stumble and stall out when I push in the clutch to come to a stop. Like the RPMs do not catch the idle at all and that the RPMs just fall untill it stalls out. So what I am trying to figure out is would a bad AFM cause a no start and or the stalling out issue, and if not what would. Still running stock electronics and fuel, mods listed in sig. Any help will be apreciated.

 

[jetjock]

1) The fuel pump isn't supposed to run with the key on.

2) What codes did you expect to get after disconnecting the AFM?

 

[SupraChrisMk3]

I will clear the codes today and run it and check agian to make sure but my big question is that could a bad AFM still be the cause of my occasional no start and stalling issues. I'm just getting a little stumped on what to be looking for because this is just a weird thing that just popped up in the last few weeks. At least now I'm pretty sure it shouldn't be a fuel issue. But then again I guess it doesn't hurt to get some more thoughts from here. Thanks again.

 

[jetjock]

I seriously doubt the AFM is your problem. There's a lot of other things more likely to cause stalling and the ECU doesn't use the AFM signal when starting the engine.

 

[supraguy@aol]

I like to throw this at just about every no-start post:
Check the cps wires. They fray and get brittle, and can cause an intermittent no-start.

 

[iamcuhja]

i would start with the cps like Supraguy said. the harness clip on my cps broke, and it was loose, causing the same issue your having. zip tied it tight and it took care of it.

 

[SupraChrisMk3]

Car has been running ok without any issues the last couple days (knock on wood). So I guess I will just have to go through and double check some of the stuff you guys sugested such as the cps wires and see if it acts up again. By the way I'm an idiot and the code 31 and 24 was my fault when I unplugged the AFM when checking things over so just disregard that. It sill acts up in stop and go traffic sometimes when the idle falls and almost cuts out. I guess I will just have to do some more digging into that though.

 

[89supra7mgte]

Your fuel pump should only run 3-5 seconds with key on (to build psi) then again when cranking and continue when started, and running. When and if you get it act up check, if possible, for spark, and or fuel psi. cps is good place to start as well. But we need to know, if it acts up, what you are losing...... Low fuel psi or flow could cause the stalling in stop and go along with weak connection at cps. from my experience with a bad afm, the car would hardly run off idle, but when and if you could rev it up it would idle all the way down and die.

With a new fuel pump and filter, you can most likely rule out the low psi and flow..... but may be experiencing an intermittent fuel pump relay. Jut something else to keep in mind

 

[Sawbladz]

Our fuel pumps don't run when the key is in the on position. Not how the system works on our cars.

 

[89supra7mgte]

ok my apologies for the mis information. Thanks for informing me on that.

 

[Nick M]

Your fuel pump should only run 3-5 seconds with key on (to build psi) then again when cranking and continue when started, and running.

To explain what he was talking about, as well as the OP, the fuel pump is powered by the circuit opening relay. This is common on Toyota, and not a Supra thing. There is another fuel pump relay, but it is in series after the circuit opening relay. The circuit opening relay switched power and power to energize the relay is shared with the EFI relay switched power. If the ECM does not energize the EFI relay, your fuel pump will not run.

You can see this on the EWD.

The OP needs to look at the circuit opening relay and EFI relay since you are looking for quick check.

 

[SupraChrisMk3]

Thanks for all the tips guys. If it acts up again I will have some test equipment with me so I can find out if I am losing either fuel or spark when it won't start. How would I make sure that I am getting good fuel pressure though? Using the diag plug underhood? I will search the TSRM for some more info. I did replace the ISC valve last summer when I had a surging idle after I fixed my BHG. Do you think that if it went bad again that it could be the cause of my stalling in stop and go situations?

 

[jetjock]

...Your fuel pump should only run 3-5 seconds with key on (to build psi)...

Just to be clear (as was pointed out) the pump doesn't run with the key on, not even for 3-5 seconds.

 

[89supra7mgte]

I know jet, that was my mistake.