P0300 Cjeck Engine Code
 

I have a 2001 Protege MP3 with 90K miles and ithas the 2.0 liter. The check engine light comes on periodically and with the OBD reader I get P0300, Random Cylinder Misfire. I have replaced the spark plugs and it still happens occasionally. Typically the car runs and idles smoothly, but sometimes when idling over a minute, it will start to shake and act as if it will stall and the light comes on. I tried forcing the idle up with the throttle stop, but then I started getting check engine code for hi idle speed, so I set it back.

The only other thing I notice is it has the stock air cleaner housing on it. On one side there are two clips and the other side is supposed to have two loops in the base and "pegs" in the cover the go into these loops so the other side latches down tight. One of the loops is broken off, so I can hear vaccum noise coming in where the cover does not seal down tight.

Do you think it is this slight leak at the air cleaner or is it a O2 Sensor or EGR Valve? Is there any of these that are common with this 2.0 liter engine?

RE: P0300 Cjeck Engine Code
 

Well, looks like you have a smoking gun. Doesn't mean it is the criminal, but it is a good place to start. Try to sealup that air cleaner housing or, better yet, go to the junkyard and get a replacement. Another likely suspect would be a coil pack. They start to act up when you get the heated up.

RE: P0300 Cjeck Engine Code
 

Thanks... Put a new Air Filter in and sealed off the housing yesterday. If that fixes it, I will replace the housing as you suggest. Thanks for the idea of the coil potential issue after engine gets hot. I did not think of monitoring how hot the engine is to help diagnosis a coil issue. That's good thinking.

Many others comment about the EGR valve, but I am wondering if that is the problem if I would be getting a different engine diagnostic code other than a PO300. Plus, I looked at the EGR Valve yesterday and did not see how it would be removed easily. One link on this site mentions removing the two 12 mm bolts that hold the air intake nozzle onto the throttle body, but I did not see how it could be removed with the throttle linkage and cable attached. Not sure if the EGR valve is mounted to this intake via the 4 phillips head screws, but they were so tight, I was concerned with stripping the heads of the screw. I hate phillips heads.... should have used allen heads or hex bolts.

RE: P0300 Cjeck Engine Code
 

http://protege5.ugly.net/#ac

Here's a link to a 2002 shop manual. Most of it should apply to your car also. especially the OBD codes. You can see how to get to the EGR. If it was EGR related, more than likely you'd be getting an EGR code. Do you have your own reader, or are you relying on the guy at the parts store. Parts store guys tend to read the codes wrong. The readers are worth the money. This one is good for the do it yourself. http://www.amazon.com/Actron-CP9125-...640&sr=8-3

RE: P0300 Cjeck Engine Code
 

Thanks... yes, I have my own code reader and it is a P0300, multiple cylinder misfire, so since this does not reference the EGR valve, I think my next step is to replace the coils and plug wires. Thanks!