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P0302 Fault Diagnosis: 2006 Ford Mustang 4.0L Engine - Spark, Fuel Pressure, and Sensor Readings

Model: ford mustang Fault Code: P0302 Posted: 2016-09-25 05:39

I'm experiencing a P0302 misfire code on my 2006 Ford Mustang 4.0L engine. I've already replaced all relevant sensors including O2, MAF, MAP, EGR, and checked the spark plugs and ignition wires. I also replaced the fuel injectors and cleaned them using a homemade injector cleaner system. All cylinders show consistent compression (140-150 psi), and the engine has only 43,000 miles on it. I've confirmed spark at cylinder #2, which is the center plug on the passenger side. The old plug showed good burn patterns. Fuel pressure reads 55 psi at idle—higher than typical specs (which usually range between 27-37 psi). After cleaning the MAF sensor and replacing the EGR diaphragm (which had a pinhole), fuel trim values improved slightly, but long-term fuel trims remain elevated (ST FTRM1: +2.3%, LTFTRM2: +1.6%). The FRP pressure increased from 66 to over 70 psi at idle. I have a scan tool and can provide freeze frame data including MAP voltage (8.6 V), ECT (216°F, matching coolant temperature sensor), and fuel trims. I replaced the MAF sensor as part of the EGR repair. No other sensors show hard faults or misfires. The engine was originally from a 2007 Mustang (same model year and engine size) and was installed after being pulled from a previously destroyed motor with camshaft studs missing and visible carbon buildup. I'm now considering whether the issue lies in the catalytic converter or powertrain control module (PCM), though I believe it's less likely due to the lack of symptoms on other cylinders. I'd appreciate expert input on fuel pressure, sensor readings, and whether a cylinder-specific injector swap or further diagnostics are needed.

Related fault codes

P0302

Comments (10)

Anonymous 2016-09-26 09:38

Does cylinder #2 have spark? What did the old plug look like? Is there injector pulse at #2? A compression test would help rule out mechanical issues.

Anonymous 2016-09-26 13:45

I confirmed spark and good injector pulse. The old plug showed strong burn patterns. I removed all three injectors, cleaned them with a homemade cleaner, replaced seals and insulators, and swapped O2 sensors from side to side—only one side had an issue. I used a smoke detector system (with propane and carb cleaner) and found no exhaust leaks. No fault codes for MAF, MAP, or other sensors. My suspicion now leans toward the catalytic converter or PCM. Any insights from others would be appreciated.

Anonymous 2016-09-26 13:58

Compression is consistent at 140–150 psi across all cylinders. The engine has only 43,000 miles and was originally installed in a rebuilt motor with no major history of issues.

Anonymous 2016-09-26 14:15

The PCM is unlikely to be the root cause—only one cylinder misfiring due to a cat is improbable. Let's start with basic diagnostics: What model year and engine type? Is the vehicle stock (no aftermarket modifications)? What brand of spark plugs were used? Do you have a scan tool or code reader? Was this motor swapped from another 4.0L engine of the same year? I'm skeptical about using homemade injector cleaner—what was the cost vs. time investment? Did you try swapping an injector to another cylinder to isolate the issue?

Anonymous 2016-09-26 16:47

2006 Ford Mustang, 4.0L engine, stock configuration. I used Platinum plugs (0.40 ohm) with a new power pack and ignition wires. I swapped injectors to another cylinder—no improvement in misfire symptoms. The motor was sourced from LKQ—a 2007 4.0L engine with 43,000 miles. It's known for strong factory specs. I've also replaced the fuel filter; pressure is stable at 55 psi when running.

Anonymous 2016-09-26 17:01

I have a scan tool. The original motor had severe internal damage—camshaft studs were pulled out, and cylinder walls showed significant carbon buildup, which made it look like the engine was previously overheated or burned.

Anonymous 2016-09-27 07:43

What does your scanner show in the freeze frame? Specifically: ECT (coolant temp), MAP B2S1 voltage, and fuel trims. Is 55 psi at idle accurate? Typical idle pressure is between 27–37 psi. Is cylinder #2 the center plug on the passenger side?

Anonymous 2016-09-27 08:29

Thanks for the input—I'll update with more details once I finish working on this vehicle.

Anonymous 2016-09-28 11:48

Cylinder #2 is indeed the center plug on the passenger side. The fuel pressure rose to over 70 psi after EGR repair (was initially at 66 psi). MAP voltage reads 8.6 V—this seems correct. Coolant temperature sensor shows 216°F, matching ECT readings. Fuel trims: ST FTRM1 = +2.3%, LT FTRM2 = +1.6%. After cleaning the MAF and replacing the EGR diaphragm (with pinhole), long-term fuel trims dropped from +16 to near baseline. RPM increased from 3500 to over 4000 after MAF clean—this is concerning. All readings are from idle freeze frame data. I was busy with another vehicle and couldn't respond yesterday. Hope this helps.

Anonymous 2016-09-28 13:31

Fuel pressure is a key area to investigate. While I'm reviewing specs, my quick check at idle shows only 27–33 psi—your reading of 55 psi appears high and may indicate an issue with fuel system calibration or sensor accuracy. Combined with elevated fuel trims, this warrants further attention. I'll update with full specifications when possible.