Hello everyone,

I am new to the forum as well as new to owning a cavalier. Some background information of the car is it is a 2001 z24 2.4L with a 5 speed manual transmission. I purchased the vehicle knowing it needed some work but now I am a little more then concerned with its issues.

After purchasing the vehicle it developed an irregular idle and sounded like a popping noise in the exhaust. I plugged a scanner into the vehicle and 11 codes appeared. Going through the codes I came to a conclusion the vehicle needed a tune up. I replaced spark plugs, two ignition coil packs, the coil pack housing and the spark plug boots, as well as the IAC. I cleared the codes and started the vehicle, surprisingly there seemed to be no change. I plugged the scanner back in and only 4 codes appeared. They are as follows P0480 (Cooling Fan Control 1 circuit malfunction), P0300 (random multiple misfire. "this code registered twice"), and P0453 (evaporative emissions control system sensor high output).

I have purchased a fuel tank pressure sensor that I will be installing tomorrow to address the P0453 code and hopefully that will clear that problem up for me, I also purchased a Coolant Fan relay to try to address the P0480 code which it did not fix (by circuit malfunction does mean the box the relays in are bad or possible the fan/ motor itself?)

And last but not least my biggest concern is the P0300 misfire code. I am concerned about this code because at idle it is very irregular jumping rpms all over the place and obviously oil is being burned from the tail pipe (blue smoke smells like burnt oil) but if I push my foot on the gas and take the rpms to 1500 the smoke stops and the vehicle runs smooth. (I did check the coolant level and it was at the recommended level, and although the vehicle was in need of an oil change when purchased the oil was not milky in any way) so I have ruled out a head gasket.

I am new to forums and I have read the rules and done my best to abide by them (I apologize in advance if I have broken any of them in this post). I searched through 64 posts on this site dealing with "oil air separators" and am still not clear exactly how they work or their location on the vehicle. What I have gathered is they are similar to a pcv function and they have two hoses from them. I did locate two hoses (one going to the air box, another just hanging in between the manifold. What it appears to me is that one hose goes to the air box on top of the manifold and what has me baffled is the other goes to nothing but there is a hose clamp on the end and a bolt or something stuck in it. What exactly would be the reason for this ( i know this is not factory) and would it possibly cause a P0300 code and cause oil to burn? I also searched through 15 posts in advanced search under P0300 for 2.4L and did not have anything jump out at me to address this issue that I haven't already done.

I am new to this style of system on this motor and I am honestly lost and don't know where to go from here, I am starting at square one and hoping someone can give me some advice as to how to make this car run better, I purchased the car for a great price and don't mind putting some money into it but I also don't want to throw parts at it (more than I have already). Again thank you all who may have some advice, I appreciate any and all input and help I can get.

Happy 2015 to all.

Best thing to do would be to hook a good scanner up and data log the sensors.justto let you know usually whe. A coil pack goes bad on a ld9 they dump fuel like crazy and destroy the catalytic converter. That happened to me. Misfire could be cause by bad spark plug boots, ignition coil module, crank position sensor, camshaft sensor, fuel pump.




On the inside my car looks like a fighter jet.

How does it run under heavy acceleration?

I would check the MAP sensor since it interfaces with the FAN circuit. I would check the ICM like rob stated above.

The vacuum hose from the intake manifold to the MAP sensor may also be bad and compounding your issues. <--Known issue on older 2.4l (LD9)s.

Also, ensure that the ground strap from the IDI cover is making good contact with one of the IDI covers 4 bolts. Also, check other grounds. Like from the Battery to battery tray, and the two that run from the battery to the engine block, and trans. Bad grounds are known to cause idle issues on most cavaliers.








PRND321 Till I DIE
Old Motor: 160whp & 152ft/lbs, 1/4 Mile 15.4 @88.2
M45 + LD9 + 4T40-E, GO GO GO

What plugs did you install?

It is possible that timing is off.

Also you said you replaced the coil housing. Which one did you get? I ask as some aftermarket ones are black. I would stay away from those. The whites ones seem to be better.



FU Tuning

Addicted to meth wrote:What plugs did you install?

It is possible that timing is off.

Also you said you replaced the coil housing. Which one did you get? I ask as some aftermarket ones are black. I would stay away from those. The whites ones seem to be better.

I personally like the black ones, and have had better luck with those. lol A black one is currently on my Cav.




PRND321 Till I DIE
Old Motor: 160whp & 152ft/lbs, 1/4 Mile 15.4 @88.2
M45 + LD9 + 4T40-E, GO GO GO

-MD- Enforcer wrote:

Addicted to meth wrote:What plugs did you install?

It is possible that timing is off.

Also you said you replaced the coil housing. Which one did you get? I ask as some aftermarket ones are black. I would stay away from those. The whites ones seem to be better.

I personally like the black ones, and have had better luck with those. lol A black one is currently on my Cav.

We had a black one fail about a week after we installed it on a car.

I have had the best luck with the stock factory one as it is still going strong 148k later.



FU Tuning

really focus on that p0300, and from what you've described it sounds like an ignition missfire. these kinds of problems are much easier to diagnose if you have a scanner with a missfire graphic or a missfire counter for each cylinder to narrow down to which cylinder to look at more closely. i know you just replaced the entire ignition system with the exception of the icm and ckp sensor, i would double check the gap on the plugs oe recommends .050". be careful when you measure and open the gap that you don't scrape off the platinum coating on the center electrode. also check for carbon tracking, if there was an unnoticeable hairline fracture on the ceramic insulation it will be noticeable now as a black line that wont rub off. check the boots to make sure there isn't a crack or tear, if you found a tear or carbon tracking replace both the affected plug and boot for that cylinder. inspect the coil housing carefully for anywhere that might be arcing to the head. definitely fix that plugged pcv system. one line should go to the air box and i believe the other should go to the right front of the head or the timing cover.

I know on my z24 cavalier I had was getting the p0300 every so often. the second time it started to kick in real bad and flash the CEL at me letting me know there was Danger to the engine.
Tuned out it was somebody putting sugar in my gas tank. So a locking gas cap and a fuel tank flush, change fuel filter, and all the injectors later. The car ran great. Even tried changing the whole ignition to another factory one which did nothing.
I also had the cooling fan code, check the fuse in the engine bay. if it keeps blowing up then your fan is probably seized or shorted. Could also just try tunning the AC on, it should turn the fan on.