P0303, P0302, P0301

[Dick Berg]

Hello Forum!
1997 EB Explorer. 4L SOHC engine, 160K miles.
My step-Grandson is now driving the rig and he's reporting the above error codes.
Actually, the P0303 has been around for a while. It pops-up with no driving symptoms, and then doesn't recur for weeks or even a few months. Recently, it's also showing the P0302 and P0301 codes, with again, no driving symptoms.
The fuel injectors are original and it's curious that all of the codes are on the right bank of the engine. Is that a clue as to what's going on?
We just ordered all new injectors since they could be the cause of the error codes.
We're also planning on replacing the fuel pressure regulator since we'll be in the area.
Are there some other causes that will result in these codes being set?

Thanks,
Dick Berg

 

[C420sailor]

Any unusual oil or coolant loss? Smoke from the exhaust?

Check the coil pack for cracks. May be worth grabbing a spare from the JY for troubleshooting. Always good to have one on hand anyway.

 

[Dick Berg]

C420sailor - Thanks for the reply.
I should have mentioned that when only the P0303 was popping up, we replaced the plugs, wires and coil pack.
That didn't seem to have any effect on the P0303 frequency, but now the other two codes are popping up as I noted.
BTW, we're having problems finding the fuel pressure regulator, RockAuto doesn't even show it.
I'm going to contact a dealer to see if they have it.

Thanks,
Dick Berg

 

[C420sailor]

IIRC, that part is virtually unobtanium. Someone on here had a helluva time finding a replacement

 

[C420sailor]

Got any fuel trim data? Any other codes?

When I hear of misfires belonging to one bank, I’m thinking coil pack, injector wiring, head gasket, intake manifold gasket, jumped timing.

A FPR going out would show a systemic issue(s)

 

[Mr. Alligator]

IIRC, that part is virtually unobtanium. Someone on here had a helluva time finding a replacement

Yes, the fuel pressure regulator was a tough project.

The regulator is bolted on the passenger side front of the fuel rail. The OEM regulator has a steel braided line permanently attached, and is not available. I replaced mine with a equivalent regulator (from a Volvo, as I recall). If you do the research, you will find the equivalent part. But it does not have a steel braided line attached. Took it to a hydraulic fabricator to have a steel braided line attached.

Solved - Fuel pressure problem.

Your issues do not sound like fuel delivery problems. Good luck.

 

[Dick Berg]

C420sailor and Mr. Alligator - Thanks for the responses.
I don't have any fuel trim information, and the only codes set are the ones that I identified.
It's not losing any fluids.
It's curious that there are no drivability symptoms and once reset, the codes don't recur for days if not weeks or months.
I may be missing something, but it doesn't sound very serious to me, like jumped timing. Do you agree?
Anyway, we're going to replace the injectors and the intake manifold gaskets, look closely at the condition of the intake manifold and sealing surfaces, clean thoroughly, and hope for the best. I know, hope isn't a very good strategy...
We're also going to replace the fuel filter first which should relieve the fuel pressure at the fuel rails.
As I noted earlier, the injectors are original, and based on my research, they're past end of life at 160K miles.
Could an intermittent, irregular spray pattern from the injectors cause the noted symptoms?
It's very curious that the codes are all from the right bank. Just a coincidence??? Hmmm...
Based on the non-likelihood of finding a replacement fuel pressure regulator, we're not going to mess with it.

Thanks again,
Dick Berg

 

[boominXplorer]

Timing is probably off slightly enough to register missfires but still drive ok. Any o2 sensor codes by chance?

Got to consider your issue is most likely connected across the board on the passenger side of the engine (cyl 1,2,3). That side shares the same camshaft, o2 sensors and catalytic converter.

 

[Dick Berg]

boominXplorer - There are no O2 codes or any other codes except for those noted.
Understood that it's likely something unique to the right bank, but we're still going to replace the injectors.
We don't have the ability to pull the engine, so any work on the right-side timing (camshaft) is essentially off the table.
If it was an O2 sensor, shouldn't it have set a code?
If replacing the injectors doesn't resolve the codes, then we can consider replacing the O2 sensor even if it didn't set a code.

Thanks,
Dick

 

[boominXplorer]

Have a way to check compression? Check all the cylinders and write them down and compare. I don't think just because you can't do a job doesn't mean it's not your issue. You could always switch o2 sensors from the other side and see if the problem moves. Make sure the plug wires are routed correctly as well, the numbers will be on the coil if it's OE Ford.

 

[C420sailor]

Replacing the injectors is good PM. Mine are well past due at 333k…I’ll get around to it lol

 

[Dick Berg]

boominXplorer - To clarify, I didn't suggest that because we're not in a position to pull the engine to deal with a possible right-side timing problem, that it couldn't be the source of the problem.
We're only in a position to do what we're capable of doing.
Your suggestion that it could be the O2 sensor on that side is very interesting. But wouldn't it have set a code of it was faulty?
Since it's relatively easy to replace the O2 sensor, that's certainly something that we can do if replacing the injectors and intake manifold gaskets doesn't resolve the problem.

Thanks for your insights,
Dick

 

[C420sailor]

Oxygen sensors can degrade extensively before throwing a code

The general guidance is just if you’re upstream sensors have over 100k, they’re probably worth replacing.

 

[Dick Berg]

C420sailor - Great information, thanks for sharing it.
All three of the O2 sensors were replaced about 75K miles ago.
I'll order all three of them and install them in conjunction with the injectors.

Thanks again,
Dick