Your car’s kind of old, which limits the bi-directional tests that Ford offered back then. And the aftermarket scan tools basically don’t offer tests which the car manufacturer didn’t.
As far as I know, the test you described wasn’t available for your particular car
No need to remove them. If you hook up a tester . . . or a similar one, doesn’t have to be OTC . . . and a fuel pressure tester, you’ll see on the gauge if the pressure drop is acceptable or not.
This misfire on #4 and #5 specifically . . . is this a brand new problem, which only started after you installed that new coil?
The coil was the first thing I did before any problems occurred but the car was running fine for a couple weeks in between the first and second misfire issues. It is possible it broke recently though. Also to get to my fuel injectors the upper intake has to be removed. This is the only way to manually test them right?
One mechanic who helped me connected a really fancy scan tool last time about a week ago and he saw a reading for all 6 fuel injectors that just said “no fault detected” or “normal” (can’t remember exactly.) for all 6 of the injectors
Yes and i ideally don’t want to have to pay someone to remove the upper plenum just to do a diagnostic and then if it is the problem, order the part and then pay someone again to remove the plenum a 2nd time to actually install them
I agree with your thinking . . . don’t pay a lot of money to remove the plenum just to test the injectors
As I said before, I’m liking the coil pack more than the injectors
But there is one thing you can do without removing the plenum, in regards to the injectors and rail
When you’ve got the engine warmed up and consistently misfiring . . . as per your description . . . shut it off and tee in that fuel pressure gauge
Turn the ignition back on and make sure the fuel pressure isn’t dropping like mad, due to leaking injectors. Without buzzing them with that special tool, you won’t know exactly which one is leaking. But you’ll know IF one of them is leaking like mad. And hopefully the pressure will be steady, meaning you can more or less cross injectors off of the list. Your mechanic will know how to perform those tests.
Oh, I thought doing a fuel pressure test with a fuel pressure gauge only confirms whether or not the fuel pump is the problem, but you’re saying it also tests the injectors?
Just to confirm, you’re saying to start the car while warm and let it misfire and while it’s misfiring, connect the fuel pressure gauge? And if the fuel pressure is in the normal range then both the pump and injectors can be ruled out? (And likely the coil pack like you said.) If fuel pressure is low then it has to be either the pump or injectors right?
What I’m saying is that a smart guy can use the fuel pressure gauge, interpret the results and reach a reasonable conclusion if the injectors are leaking down . . . or not . . . but not necessarily which particular one is the problem, unless you use that special tool or manage to find some kind of scan tool which will buzz the injectors individually without removing that plenum
But like I said, I think the coil is a far more likely culprit
You can’t hook up the fuel pressure gauge with the engine running
you’d have to shut it off before hooking up the gauge
Then you hook up the gauge . . . tee it in between the pump and the fuel rail
Cycle the key on and off a few times, ending in the on position
What’s the gauge read?
If it’s within spec, the fuel pump is more than likely okay
If it’s not within spec, shut off the line going to the fuel rail . . . good fuel pressure testers have a knob to isolate one side . . . and do that last step again
If it’s now within spec and holding, you know the problem isn’t the pump, but rather past it, probably a leaking injector, or maybe even a fuel pressure regulator. I’m assuming your Mustang has one, because it’s an older car.
Hey I ended up replacing the fuel pump and fuel filter today which brought the long term and short term fuel trims down to normal range! No more warm start misfire!!
However I still have a check engine light coming back even after I cleared it twice. It is P0193 which says there’s an issue with the fuel rail pressure sensor reading high (fuel pressure too high?)
I tested the sensor, which is 3 days old and brand new OEM part, by unplugging the vacuum line with the engine running but there wasn’t any fuel leaking out which means the sensor itself is good. The wires and connectors for the sensor appear to be in good condition as well. So why do I still have this code?
Car doesn’t have low fuel, the sensor itself works properly and I just replaced the fuel pump today. So even though both of the sensor connectors LOOK fine, they are somehow malfunctioning. Maybe incorrect voltage in one or both of them? You think the sensors connectors or harness has to be the reason for the code still on? Because I can’t think of anything else
Yes, fuel pressure is 55 when first turning key on, after 10 minutes it drops to 45 but mechanic consulted Ford book and he said although some cars aren’t supposed to drop, he said the book didn’t say anything about my specific car dropping in fuel pressure after some time to be a cause for concern. Unless it drops rapidly within seconds but he said 10 PSI drop in 10 minutes is normal
Yes, fuel pressure is 55 when first turning key on, after 10 minutes it drops to 45 but mechanic consulted Ford book and he said although some cars aren’t supposed to drop, he said the book didn’t say anything about my specific car dropping in fuel pressure after some time to be a cause for concern. Unless it drops rapidly within seconds but he said 10 PSI drop in 10 minutes is normal
It’s not clear to me, was this just key on engine off reading? I’d be checking pressure engine running at idle and then at some higher rpm point. Diagnostic routine should define rpm points and expected pressure range. Then dead head pressure.
Also just to confirm, is the P0193 code saying that the fuel pressure sensor has detected incorrect fuel pressure? Or is it saying that the computer has detected a malfunction with the sensor itself? (Or the wiring harness/connector)
All that is known is the computer has gotten a reading that is outside of the acceptable range. That is why the first step is to determine if the pressure is in fact lower or higher than specified. If pressure reads correct with independent gauge, then it could be sensor, wiring or computer. If pressure is indeed incorrect then filter, regulator, pump, leaky injector(s), bad injector signal etc. The factory repair manual will have diagnostic trees and procedures for narrowing down and finding root cause.
