Dtc: P0300

[igidy]

So you don't think it would necessarily have any effect on the issue i'm dealing with? I have a new egr. Im guessing it just assists in the applied vacuum on the egr?

 

[pcb]

I do know that an EGR can cause bad idling and throw a P0300-P0304 code. EGR and coils are usually the first things to check when you have those problems,... followed by wires and plugs.
I don't really know what that boost solenoid does, but there is codes to be thrown involving the EGR. Codes P0106-P0107-P0108 cover EGR boost sensor solenoid.
P0401 & P0402 cover EGR flow. Codes P1487 & P1496-P1499 cover the EGR stepping motor. So there's lots of codes for the EGR system however some guys had a stumbling idle that was caused by the EGR and was fixed by cleaning it but they had no codes before the cleaning.
Some guys "delete" the EGR by making a gasket out of sheet metal that is installed between the EGR and it's mating surface. It only has the bolt holes in it without the holes for the passages. It effectively blocks the EGR but leaves it connected and moving so the ECU thinks it's still working so you don't throw a code. (without the exhaust running through it, it isn't as likely to get fouled as well)

 

[igidy]

So, here's something weird. I decided to have a look at my O2 sensor (upstream). I have already replaced my downstream sensor when it malfunctioned due to damage. I unplugged the upstream sensor and ran the car. It still did the misfiring thing and threw a code, but only after quite a while. I read and erased the code (P0420?? or something like that) and then started the car again, with the sensor still unplugged. I could never get it to throw the O2 sensor code again. This should be a pretty sensitive code yeh? And it should throw a code very quickly instead of only after awhile. Maybe there's a PCM or overall electronics issue???? hrmmmm

 

[pcb]

Yea that's weird,... I remember unplugging my first O2 sensor just to see what would happen,... I immediately threw a code but the car kept running in what I assume was limp mode. I just wanted to see if it would keep running if it was unplugged but didn't try to restart the car with it disconnected. I would assume that the code would come back right away,.. at least the one for an inoperative O2 heater, but that may take a bit of time for the heater to warm up so the ECU gives it some time. Same with the O2 data,... the ECU may allow for a warm-up period for the O2 to start sending data.
I remember another guy was trying to track down a misfire code and it turned out to be a bad plug wire. I remember too someone (Hatchkitten I believe) took her car in for the misfire code and it turned out to be a bad wire in the harness for the coils.
There is so many ways of throwing a misfire code that it is really hard to diagnose. (knowing whether it is random or cylinder specific helps a lot).

 

[igidy]

Turns out both of the brand new ignition coils I put on were bad/faulty. I purchased some Duralast coils at Autozone and it ran okay for a bit. I had to bring the car in to a dealership for them to diagnose the car with a bad coil. It was the 1/4 coil. They replaced it and afterwards every time I would let off the gas my revs would drop to around 300 - 400 rpm. I drove like this for awhile but when I started to blow A/C fuses I started looking into the car again. I decided to go ahead and replace the other coil and sure enough my rev dropping issue has disappeared. Also, I am not blowing A/C fuses anymore. So much for "brand new" parts eh?