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P0300 & P0301 Fault Diagnosis: 2001 Ford Protege LX 2.0L Engine Idle Issues

Model: Protege 2001 LX 2.0L Fault Code: P0300 Posted: 2010-11-11 19:50

Hi everyone, I've been experiencing intermittent Check Engine Light (CEL) activation on my 2001 Ford Protege LX 2.0L, which comes on and off every few days—sometimes staying on for a couple of days before turning off. The symptoms include difficult engine starts and a rough idle, especially when the engine is warm. I've had two diagnostic readings: P0300 (random misfire) and P0301 (misfire detected in cylinder 1). I've conducted several tests: - Measured all spark plug wires and ignition coils using an ohmmeter. All readings were within acceptable ranges, except for cylinder 4's wire, which initially resisted measurement. After gently bending the rubber insulation slightly to one side, a stable reading was achieved. This led me to suspect possible loose or degraded wiring. - Visually inspected the EGR valve—though it appeared worn and difficult to access, I found no major damage. - Applied throttlebody cleaner to clean the throttle body. I tested each spark plug individually: cylinder 1 produced a bright white spark as expected. All spark plugs appear new and in good condition visually. A key observation is that the rough idle only occurs when the engine is warm; at cold start, it idles smoothly around 900 RPM. This behavior suggests a temperature-dependent issue. I’ve attached a video demonstrating this behavior: [https://www.youtube.com/watch?v=7At4SHjb6ho](http://www.youtube.com/watch?v=7At4SHjb6ho) I’m seeking advice on the most likely root cause. Could it be a faulty ignition coil, loose spark plug wire (especially cylinder 4), or a vacuum leak? I’d like to avoid replacing parts without confirming the issue first. Thanks for any insights! - Mat

Related fault codes

P0300P0301

Comments (6)

Anonymous 2010-11-12 06:05

Great photos! Spark plug wires and ignition coils are common failure points on this model. Vacuum leaks from intake gaskets can also cause similar symptoms. I recommend checking for vacuum leaks first. If none are found, consider replacing the spark plugs with the correct heat range and brand, and test by swapping the suspect spark plug wire to another cylinder—this will help determine if that specific wire is causing the P0301 code.

Anonymous 2010-11-12 13:11

Thanks for the helpful input! Before investing in parts or removing the EGR valve, I’d like to gather more diagnostic data. One key detail I missed: the rough idle only occurs when the engine is warm. When cold, it idles smoothly at around 900 RPM. This behavior may point to a temperature-sensitive issue. Here’s a short video illustrating this: [https://www.youtube.com/watch?v=7At4SHjb6ho](http://www.youtube.com/watch?v=7At4SHjb6ho). Any thoughts on what this might indicate?

Anonymous 2010-11-12 13:42

The video link is now back online.

Anonymous 2010-11-13 14:05

I’ve taken apart the EGR valve. The previous owner had already done so—there was a broken screw between the top and bottom sections. After disassembling, I found it difficult to move the valve smoothly; it didn’t appear to have a spring mechanism. I manually pushed it up and down with a screwdriver (with cloth protection), which helped loosen it slightly. I then sprayed WD-40 and cleaned it again using throttlebody cleaner. Here are some before-and-after photos: [link to images]. The valve now appears to be spring-loaded after adjustment. It’s drying out now, and I’ll test the idle performance shortly. Does this sound like a plausible fix? I don’t have formal training on EGR systems, so I’m cautious about my assessment.

Anonymous 2010-11-14 09:25

It's possible that a slightly open EGR valve at idle could be contributing to the issue—but if it were fully open or partially open, I’d expect severe starting problems and poor engine performance. A small leak might not cause rough idling directly. Have you checked for vacuum leaks as a first step? This is often overlooked but can mimic misfire symptoms.

Anonymous 2010-11-14 10:03

Thanks to Jeff Compton’s input! As noted in my update, the EGR valve was indeed the root cause. After cleaning and repositioning with WD-40, followed by a full clean, my 2001 Ford Protege now runs with a steady idle (though slightly high—this can be easily adjusted via idle speed settings). The issue is resolved.