Bad Miss on my 2003

[MrTeeThyme]

My 2003 4.0 with 214k miles developed a bad miss upon startup. It threw a P0303 error (cylinder 3 misfire) and if you hold a paper towel up to the exhaust, it sucks it in. That leads me to believe it's a stuck exhaust valve. Once it warms up, it goes away. I tried some Marvels mystery oil to see if it helped but it doesn't.

I also had a P0231 (fuel pump secondary circuit low) error and a P0316 (misfire detected on startup - first 1000 revs).

I cleared the codes and started it up. It had the miss until it warmed up, but didn't throw any codes this time.

Does this sound like it could be a valve spring? If so, can it be replaced without pulling the head? Would a lifter behave like this?

Thanks.

 

[MrTeeThyme]

Update:

Took the truck to an indy. He called me today and said it was misfiring on two cylinders but not throwing a code. He replaced the plugs and used a test coil to no improvement. He said he then put a temp fuel pressure gauge on it and took it for a test drive. He said the pressure drops very low and he is 95 percent sure it will fix the problem I described in the op. He quoted me $665 for everything.

If it fixes the problem, I'll be satisfied, I just don't see how a fuel pump issue would clear up once the engine gets up to operating temperature.

 

[ncranchero]

OUCH ! !

Code P0231 = The PCM monitors the fuel pump monitor (FPM) circuit. The test fails if the PCM commands the fuel pump ON and B+ voltage is not detected on the FPM circuit.

Causes =
Open B+ circuit to the fuel pump relay
Open FP PWR circuit between the fuel pump relay and its connection to the FPM circuit
Damaged fuel pump relay
Damaged PCM (engine will start)

I just don't see how a fuel pump issue would clear up once the engine gets up to operating temperature.

Me either........... better have an understanding that if a pump doesn't fix it then that cost is on HIM ! Any fuel in the vacuum line to the fuel pressure regulator or the fuel pulse damper?

You sound closer to the cause than he does. Why is a weak fuel pump going to cause a suck-back @ the tail pipe?

 

[MrTeeThyme]

I haven't heard back from the indy and I know it doesn't take three days to install a fuel pump so I'm guessing it didn't fix the problem. Since I have my new ST to drive, I will wait patiently.

 

[ncranchero]

Hope they don't want to charge you for the stuff they throw at it.