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2002 Ford F150 V6 Misfire and EGR Code Troubleshooting: P1400, Cyl 3 Misfire, and EGR Flow Issues

Model: Ford F150 Fault Code: P0300 Posted: 2007-10-15 11:19

I own a 2002 Ford F150 V6 with 52,000 miles. The truck has been exhibiting persistent misfire issues, specifically cylinder 3 misfire and 'misfire in first 1000 revolutions' codes. Additionally, I previously had a P1400 code indicating differential pressure sensor (DPFE) failure due to insufficient or excessive EGR flow. After replacing the DPFE sensor, the P1400 code cleared. However, the cylinder 3 misfire and first 1000 RPM misfire codes remain. The truck shows symptoms of missing under load and at idle. I've tested all plug wires and swapped the #2 and #3 spark plug wires — the misfire remains on cylinder 3. I have disconnected the EGR valve from vacuum lines, yet the misfire persists. Given that the EGR system is still active (though not connected to vacuum), could a faulty EGR vacuum control solenoid be contributing to this issue? No visible signs of lean burn were observed when inspecting the spark plugs. I'm considering replacing cylinder 3's fuel injector, but I don't have a noid light or dedicated injector testing equipment — so my only option is swapping it with another cylinder to see if the misfire moves. I've also read about carbon buildup in EGR passages on older Ford V6 engines due to prolonged use. As a result, I'm planning to remove the upper intake plenum to inspect for clogged or restricted EGR ducts. Any suggestions or diagnostics would be greatly appreciated — especially regarding whether the misfire is related to emissions system faults or a more fundamental ignition issue.

Related fault codes

P0300P0401

Comments (16)

Anonymous 2007-10-15 12:00

Could it be a faulty coil pack? Have you checked for vacuum leaks in the intake system?

Anonymous 2007-10-15 12:08

Replacing the DPFE sensor likely resolved the P1400 code. Try swapping cylinder #3's fuel injector with another cylinder to test if the misfire moves. Also, swap a coil pack with a known good one and check if the misfire shifts — this can help isolate whether it's an ignition or fuel delivery issue. Good luck and please update your progress.

Anonymous 2007-10-15 15:12

Is this a coil-on-plug (COP) system? The 2002 F150 V6 uses a waste spark ignition setup, not COP.

Anonymous 2007-10-15 19:42

It's a 4.2L engine with a waste spark configuration — no COP. I haven't tried swapping coil packs yet. However, I'm planning to remove the upper intake plenum as some users have reported carbon buildup in EGR passages on older Ford V6 engines.

Anonymous 2007-10-15 19:43

Mohawkmtrs wrote: Replacing the DPFE likely fixed the P1400. Yes, that was helpful — but the new EGR valve didn't improve drivability. Mohawkmtrs wrote: Swapping injector #3 with another cylinder is a good idea. Also try swapping the coil pack with another and see if misfire moves. Good luck and keep us posted. I could swap the spark plug wires from cylinders #3 and #6 at the coil to see if that changes anything — it would be easier than pulling out the injectors.

Anonymous 2007-10-15 19:46

jeff compton wrote: It's not a coil-on-plug? Have you checked for a vacuum leak? I've sprayed carb cleaner on suspected vacuum lines, but I don't think a single vacuum leak would cause an isolated misfire on cylinder #3.

Anonymous 2007-10-16 09:55

Okay — so it's not a vacuum leak then.

Anonymous 2007-10-17 11:10

Is cylinder #3 located farthest from the EGR valve? I once had an issue with my 3.8L V6 Ford where the EGR port on cylinder #1 wasn't properly sealed — all other cylinders were fine. I believe emissions system faults can significantly impact engine performance. Given that your truck has only 50K miles, it's surprising such a problem would develop — could the actual mileage be higher than reported? This might be worth verifying.

Anonymous 2007-10-17 11:38

When you manually open the EGR valve using a vacuum pump, does the engine stumble or die? You can find detailed testing procedures for Ford V6 engines with DPFE in search results. If the engine stumbles or dies during this test, please post your findings.

Anonymous 2007-10-18 06:28

Kerry Ritter wrote: Is cylinder #3 farthest from the EGR valve? I had a problem with my #1 cylinder's EGR port not being sealed — others were fine. My engine has about 150K miles. I believe emissions play a key role in engine performance, so don't dismiss the possibility of an emissions-related misfire. Removing the upper intake was straightforward for me — I'm unsure if it's possible on your model. It's hard to believe such a problem would develop at 50K miles if the truck was purchased used — could there be more mileage than reported? I suspect this might be true, especially given that odd issues can arise in any vehicle.

Anonymous 2007-10-18 06:29

Darkrooms wrote: When you open your EGR valve with a vacuum pump, does the engine stumble or die? You can find relevant posts via search — the closest I found was one about a Taurus/Sable with clogged EGR passages. I'm going to grab my vacuum pump and test this right away.

Anonymous 2007-10-18 06:46

Good grief! Here's what happened: Has anyone seen a waste spark system where only one side of the coil pack fails? I never thought it would be an issue — cylinder #4 shares a coil with #3. After swapping the wires at the coil, the misfire moved to cylinder #4. This suggests both EGR and coil issues were present simultaneously. I'm now convinced that the real problem was a failing coil pack — I'll need to replace it.

Anonymous 2007-10-18 07:22

Anonymous 2007-10-18 10:56

I wasn't aware that waste spark systems are still in use. As far as I know, they were phased out by the early 90s. If your engine has a coil pack with two posts, it might just be a shared casing — not necessarily direct ignition. How many wires go to each coil? Two or four to five?

Anonymous 2007-10-20 18:23

Darkrooms wrote: I wasn't aware that waste spark systems are still in use. Not at all — my old 2003 MazdaSpeed Protege and current 2003 Mitsubishi Evolution both have waste spark ignition. Darkrooms wrote: If you have a coil pack with two posts, it might just be a shared casing — not necessarily direct ignition. How many wires go to each coil? Two or four to five? Each coil has four low-voltage wires and six high-tension leads connected to three distinct coils.

Anonymous 2007-10-20 18:24

The truck now runs smoothly with no check engine light — I'm very happy. After troubleshooting, the only real cost was $50 for a new EGR valve — which turned out to be unnecessary. The actual issue was a failing coil pack.