Hey guys, I'm having an issue where if I either ease into the throttle up to 3000 rpms, it breaks up when it gets there. I have 40psi of fuel pressure at idle and it maintains that pressure even when it's breaking up. If I go wot the engine also breaks up. According to my torque pro app, the commanded spark advance drops way down when it starts sputtering, so it seems like the computer is pulling the timing. Does this sound like an ignition issue, or a wiring issue? I've got fresh 93 octane fuel in it.
Check fuel pressure at idle with the vacuum line to the regulator disconnected.
With the boost referenced fuel regulator under vacuum the pressure is lower and it increases with boost. Please let us know what the pressure is when running with the vacuum line disconnected.
I'm not 100% what pump is in there, i bought the car with the swap already in progress. The PO said it was an SUV fuel pump that was recommended on the forums, but he couldn't remember which one. I'll test the fuel pressure again when I get home today thanks
Scratch that, I'm an idiot. I unplugged the wrong hose. 40 key on engine off, 50 engine idling with the fpr vacuum line unhooked. Probably a bad fpr then?
If your fuel pressure is up to spec and the exhaust unrestricted then you need to take the next step. I realize that many DIY mechanics don't like hearing this but a full diagnostic scan of the PCM will pinpoint the trouble. The symptoms you describe can be one of any number of things. Failing to do a scan is working in the blind. .
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If your fuel pressure is up to spec and the exhaust unrestricted then you need to take the next step. I realize that many DIY mechanics don't like hearing this but a full diagnostic scan of the PCM will pinpoint the trouble. The symptoms you describe can be one of any number of things. Failing to do a scan is working in the blind. .
Correct me If I'm wrong, but the fuel pressure at idle going up to 50 with the fuel pressure regulator unhooked would mean that it is something related to that regulator.
No, that is the expected behavior, the fuel pressure rises with boost. It should be higher at atmosphere (which is with the line disconnected).
Are you able to monitor fuel pressure while you are experiencing the issue? If the fuel pump is not up to the ask, or on its way it could provide the correct fueling during idle but drop under load.
But if you are really having fueling issues it can be damaging to the engine to go under load. If you do a quick check and your fuel pressure is good there are other things to look at.
I personally always have a wideband O2 sensor installed in my modded cars. With that you could see if your AFRs are too lean or too rich when the issue is happening, and that would help with the next steps.
I was able to verify that as boost increases, so does fuel pressure. I had 50 psi at 3000 rpms and it was still climbing when the misfire started. I'm going to begin diagnosing the ignition components, I believe that may be where my problem is
Sounds familiar with what I used to get so here's what my issue was. But to be clear, diagnosis should always find a problem prior to random part replacement.
If your coils are relocated and no longer on the engine, make sure they have a dedicated ground running to the ICM wherever they're mounted. I relocated mine to the firewall and it would puke all over itself as soon as I got above about 1 pound of boost. I was also burning occasional spark plug wires, like they were fuses. Running a new ground resolved everything.
