P0300 Random Misfire 2.4L Quad 4 SOLVED!

[MDCole9761]

Wow....

Hmmm.....well, the oil in the resonator is usually due to oil getting through the PCV valve- which should be cheap to replace. The extra amount of oil might also be contributing to that since there is more oil flowing up into the top of the engine, so the oil level is higher.

As far as the smoke coming out of the engine oil cap- I'm not sure about that. I think I've seen a little come out before, but it was brief and not very substantial.

The accelerating over 4000 RPM is definitely an issue- I'm starting to wonder if the crankshaft position sensor is faulty. In this engine, the crankshaft position sensor provides a signal to the ICM to control timing- and may also be responsible for telling the computer what RPM the engine is rotating at. In turn, this data is part of the fuel calculation. So, it's quite possible that an intermittent signal (whether due to wiring or a bad sensor) could be throwing everything off. Now, it memory serves me right, there is a DTC code for the crank position sensor- which I would expect to be one of the codes set if it was faulty. But that's not to say that it always does!

Oil in the exhaust sounds like it may be what you were thinking (bad gasket or loose piston ring). This would in turn coat the O2 sensor and cause problems (since it too is involved in fuel calculations).

I guess the obvious question with the oil related stuff would be did you see oil buildup on the O2 sensor and/or spark plug(s)? When checking the oil level, does it seem to be leaking/burning/using oil? If so, then most of your problems may be attributed to an oil burning/leaking problem. Oil on the spark plug(s) could cause it not to fire, which would cause the engine to stumble, which would cause the computer to compensate by increasing the idle air.

The 4000 RPM barrier still sounds like a computer/sensor issue since it's a precise number and the fact that it goes fine up until 4000RPM and then just "flutters" there. Sounds like the same thing as the "rev limiter" that limits RPMs when in neutral (which is on purpose).

Man- I wish I could actually see the car. It's so hard to diagnose things over the internet! You don't happen to live near Fort Wayne, IN do you?

[markw09]

Yes this works ,we replaced timing chain, head gasket, coil packs, plugs and boots, nothing worked,checked online and saw this solution tried it instantly work, thanks guys.

[Hvactech]

Man, I just wanted to thank you and thank God!!! My local Chevy dealer actually told me the engine was bad and it would cost between $3000 for a used engine and $4000 for a new engine!!! They also told me I had no compression in #2 & 3 cylinders! I don't think the pulled a single plug, they were so tight and rough coming out. I had it towed home and started doing some searching. I also borrowed Auto Zones code reader for a refundable deposit which was great since I couldn't get the car out of it's own way to take it in. Of course I got the PO300, "random multiple misfire" code. I hadn't change the plugs yet since new;( so did that, ohmed out the coils and everything was right on the money but still rattling and rolling and of course the "check engine" light still "flashing". I'm so glad I didn't have to drive it very far when it failed, only a few miles and hopefully didn't kill the "cat". I checked autozone web site and found the Part Number: CB9 and my local store had it for $55 bucks. You have to put it together which only took a few minutes, kinda got me when you had to put the thermal grease on and push the contact springs into it. I did see what appeared to be the same on the old one. I got it all back together and she "FIRED" up beautifully just like it should!!! Drove like a charm. I'm really disappointed in my local dealer and plan on giving them a call. My wife was ready to start selling the seats/tires and anything else she could. Thanks again and Thank God for the fabulous info posted here and on the web. Looks like the "Plastic" housing must break down right around 100,000 miles. We had the same as the original poster, 105K, couldn't believe it. It is 11 years old but we bought it new and have taken care of it and sure didn't want to go looking for something else or putting a new engine in it. God bless you all, Ben Tebbens.

[danielsatur]

I hope you fired your dealership!

[Hvactech]

Yeah, we just left the dealer after finally meeting with the Service Manager, almost seemed like he didn't want to see us. Somehow he had heard that we got it going and the gist of the repair...I guess we still live in a small town, about 7000 I guess I don't know, he seemed sincere and said this thing just doesn't happen! It's pretty hard to believe it that's for sure!!!. We're supposed to get our money back and the extra towing fee for bringing it home. A big disappointment but thank God it's running like a champ!!! Have a great day, Ben.

[624147588]

My son owns a 1999 Alero and after replacing the ignition module, spark plugs, and ecm I final came across this thread... replacing the ignition coil cover solved the problem... Thanks

[yehorkswife]

My husband has a 2001 Alero 2.4L and we've had the 'coil tower' replaced 3 times! It was between $600-$800 each time. We now have to do it for a 4th time.
I think we'll try doing it ourselves and save $500+. So glad to have found this thread so I know what part we needed to look for and autozone's website for instructions!

[PanJimbo]

I had this error here in the year 2014, and tried replacing the spark plugs, didn't do it. Then I tried the housing and boots, didn't work either. Next day I changed the ignition coils and that did it.

[alero1964]

Please help 2001 Alero 2.4 Saturday night filled the gas tank and drove 20 miles home. Sunday left for work and made it about 8 miles when the engine started losing power. I pulled over turned the car off checked the oil and made sure it was not overheating.

Started it back up and it definitely had a misfire. Since then I has searched the internet. I have put new plugs in it, I have new plug boots and a new coil housing. Code reader keeps giving me random misfire. When it would be specific it gave the 303 #3 cylinder misfire.

Today I took the packs out and swapped them and put them back in. My thinking was that if the coil pack its self was bad that the misfire should show up as #1 cylinder. I wiped the codes drove it 1/4 mile and the light started flashing and it still had a miss. Scanned it and sure enough misfire #1 cylinder. I think Great! I went to autozone and bout a new one. I installed it and tried again only to still have a random misfire

Anyone have a guess? How about a test I can do?

[alero1964]

Problem solved It is my son's car and when we picked up the new coil pack he installed it. But he replace the wrong one. We switched them this morning and its back to running right.

[65comet]

Glad you are fixed, and thanks for posting that you solved it.

[gmbob]

I had this issue as well. I changed the spark plugs, the "corks" ( aka plug wires), the coils and the coil cap. Still running the same, bad. Took it on the highway, got it up to 70 and the engine light went on. I took it to autozone , had them read the code. It said MAP sensor was bad. So I got one of those. When I went to locate it and replace it, I saw the hose running to it was cracked. Bingo, replaced the hose , returned the MAP sensor and my car runs like new. Lesson learned here was, I spent over $160 for parts and it was only a couple dollar hose! ( Check that first if I were you)

[dansimons]

I am having a few of the same issues with my daughters 98 Sunfire 2.4L

It's been driving me crazy for weeks now... It seems to be fine at time and then out of the blue it will either not start, or run but run really crappy. It doesn't seem to lose any power it just stutters and jerks and backfires at times when driving down the road and almost dies at times or does die and is really hard to start back up.

My wife has a 2001 Alero with he exact same motor so I have swapped around the whole assembly that contains the coils, coil housing, ICM, boots etc, also changed the crank position sensor, throttle positioning sensor, put in new plugs and boots, new air filter, new fuel filter. We tried running fuel system cleaner in it and it got really bad the next day, but then if you leave the car sit for a day or so it will run fine for a couple days before it starts acting up again. Could it be a bad heated oxygen sensor? Maybe the Cat is starting to get plugged up?

Also, the last couple days it has started having an issue with the heat in the car, sometimes it takes for ever for the gauge to move, but when you accelerate it will shoot right up to normal range and blow heat, but will then fluctuate up and down and blow cold or hot air when it wants to.

Any ideas at all would be greatly appreciated.

Dan

[Deanna_m0]

Thank you! My issue exactly. I'm not an electronic guru nor mechanic, so my solution while more expensive was cheaper than paying the mechanic. I would suggest this order of operations unless you just want a once and done solution of purchasing everything. 2) Remove spark plugs, clean or replace. Purchase 4 plug on coil boots and install. Button the car back up and try to turn it on. 2) If that does not work, buy the ignition coil housing. Put the new boots and old coil packs in the new housing. Button car back up and try to run. The housing seems to be key to fixing the issue. And while I don't have testing to support it, I believe the new springs (coils) that come packaged with the housing are what makes this work. They have more tension then the old ones and cause the ignition coil packs to 'float' a bit where they are seated. I guess this because I could not find any damage to my old housing. 3) If that does not work a cylinder or two may have become crapped up and frozen due to the backfiring (mine failed compression testing). Marvel Miracle oil or similar, if placed in the cylinder (an ounce or two) via the spark plug orifice, left to soak a few hours, then buttoned up and turned on, may free the pistons. Expect a lot of smoke while clearing the pistons. 4) Test the ignition module and replace if bad - this is the most expensive component and not returnable. Have the new one tested too before you walk out the door with it. 5) Ignition coil packs - I did not need to replace these, so I have no suggestion. Mine runs! Good luck with yours.

[Mywitsend]

Ok, I'm at my wits end with my 2000 Alero 2.4L. Need advice.

The car started jerking while driving and idling rough. Autozone hooked it up to their computer and it registered a code (P0303 multiple misfires in cylinder 3). So the print out recommended replacing the fuel injector in cylinder 3. I did that as well as replaced all the o-rings on the other injectors and cleaned them and the fuel rail also. Put evrything back together and it is still having the same problem. Next, I replaced the coil pack that services cylinder 3, it still didnt work. Replaced the spark plugs, spark plug boots, and coil pack housing. I had the ignition control module tested and its good, had the other coil pack tested and its good as well. Put it all back together again and still the problem is not solved.

Hooked it up to a computer again, only now the code popping up is not as specific. The code that pops now is P0300, plus now it sounds like one of the plugs is arcing eventhough I checked them thoroughly to make sure they are all connected properly. Im not even sure if the arcing sound is due to an issue with the plugs and not some other electrical issue. Just to be safe I returned the spark plug boots I bought and got a new set and with the new set it still is making the arcing sound.

So, does anybody have any wisdom that will lead to a strike on what the problem is? I took it to a mechanic and he could not diagnose it and I did the checks and replacements he recommended. The mechanic did a compression test on cylinder 3 and it tested good.

Wisdom...?