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2000 Pontiac Sunfire codes...

10-07-2006, 08:34 PM
I was working on a 2000 Pontiac Sunfire, my mother-in-law's. She said it ran like crap so here's what I found out after looking at it. I checked all the fluids except the trans because it has a cap down there and I removed it to see, but couldn't see anything. They usually give you some kind of a mark to go by. Not so lucky here though, I hate these kinds of cars. Meaning cheap cars are hard to fix. So, didn't really get to check the tranny fluid! I used a scan tool by Actron and got the codes PO300 and PO440 twice, meaning there were three codes it pulled. The first, PO300, was a random/multiple cylinder misfire. So I figure it needs plugs and wires, but they look new, so maybe coil(s). The second and third were PO440 evap inefficiency. Scanner said both and I was confused since it gave me the same code for 2 and 3 of the codes. The display had an icon after the third code of which I have no idea what it is except to say that it looked like a small case b over a small case d, or musical symbols! So, my question is what could be causing the misfire if the plugs and wires are new... and what is the evap code, maybe a bad canister or I checked the gas cap and it was tight? So, I'm pretty much not getting any answers to the actual causes here. If you can offer me some input or direction, I'd appreciate it greatly because at this moment, I don't know what to do with it, except drive it off a cliff!
Thank you.

Blue Bowtie
10-08-2006, 12:33 PM
The PCM will store numerous instances of faults and display them multiple times. It seems that the P0440 has been detected on more than one occasion. The two different codes may be related, or perhaps not.

P0300 is a multiple/random misfire. Misfire occurring on several cylinders at an inconsistent rate can be a symptom of many problems. Ignition is a possibility, as well as fuel delivery, and even vacuum leaks or the EGR system.

Even though the plug wires appear new, there is a possibility of insulation failure along the wires, or at the boots on either end. Inspect them closely and verify they are sealed against moisture. You can even observe the ignition wires, coils, and spark plugs in a darkened area to see if there are indications of spark leakage.

The same applies to the plugs. Check them closely for cracked insulators, signs of moisture or arcing, and make sure the gaps are correct. Plug tips and insulators which are contaminated with coolant or excess fuel can create misfire by shunting the spark energy to ground rather than creating a spark at the gap.

The fuel system could be suffering from inadequate pressure. Fuel injectors could be leaking, streaming rather than producing a fine mist of fuel, or partially clogged. Any of these can create an improper fuel mixture and misfire. Typically, injector problems are confined to one or two cylinders, and error codes related to those are not random, but point to a specific cylinder(s), such as P0301, 301, etc. A general fuel pressure problem would be more likely to create the random/multiple condition. A leaking fuel pressure regulator can also cause that, but would likely also create a rich condition and subsequent error code such as P0131.

A vacuum leak almost anywhere can create a lean mixture and subsequent misfire. For this reason, the two codes could be related. A P0440 indicates a general fault in the evaporative emission control system. That typically means the EVAP system could not produce and maintain a vacuum when it should. That can be due to a vacuum line damaged or removed, a damaged/leaking EVAP canister, leaking fuel tank or EVAP hose to the tank, a leaking fuel filler cap, and numerous other possibilities. You should be able to use your scanner to read the vacuum in the EVAP system while the engine is running.

In a nutshell, closely inspect teh ignition system, and test running and standing fuel pressure after shut down.

10-08-2006, 07:26 PM
Thank you for the insight. You certainly have done your homework and you have given me alot of ideas on what to check for and look at. I appreciate your response.

03-25-2016, 05:46 AM
2000 Pontiac Sunfire Gt 2.4 L inline4 vin T misfires with p303 and p300 codes. Well, save some time and money and change the ignition coil cover pan 19166100 N. These are on ebay for around $30 and most likely will fix your problem as they short out lots of time. It is an easy, cheap first thing to try!

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