P0300 Code and no start

My step dad called me and said the car would not start. It cranks but no fire. Awesome, so I leave my physics lab to go take care of it.

2004 Chevy Aveo 5 speed w/ 107k miles

I can't see anything visually wrong with it. Rented a scanner from autozone and I got codes

P0300
P0420

P0300 is a random cylinder misfire
P0420 is something with the catalyst( replaced 20k ago after it decided to go into melt down mode)

The intake hose from the air cleaner to throttle body has a nice gaping crack in it and a few vacuum lines I can visually see have cracked and some torn rubber connectors as well. I need to get this car back on the road asap.

thank you

did you check for spark to each cylinder? i am thinking bad coil pack.. but it could be flooding, which would kill the cat in 20k miles as well.. did you have the repair done that killed the first cat? or just replace the cat?

The dealership did the work for the cat about 30k ago. They replaced the cat, o2 sensors, and spark plugs.

I will check for spark tomorrow, the car was running just fine yesterday.

What is the best way to check for spark? I've never actually done that (I've owned diesel mercedes for a while)

do you have a timing light?

no, but I can probably rent one from autozone.

I have an iPhone so tomorrow when I go back to the car I will post my updates on the forum. I'm praying its only the coil pack.

well if you get a timing light, pull the cover over the wires, hook it up to each wire individually and see if the light flashes.

If you get all 4 flashes, you have spark, when on cylinder 1, check it for time on the crank pulley timing mark..

if you are properly timed, (i am assuming it turns over freely with no noise) and have spark. Mist the coil pack and wires lightly with water, if you have a light show, something needs replaced (whatever is lighting up)..

If not enough light to cause a no start condition.. then i am pretty sure you need to check the o2 sensors.

Ok, I will do that.

as well as pull the timing cover and inspect. I didn't hear any weird noises.


how does one remove the upper timing cover?

you dnt need to pull the timing cover, just figure out where to point the light on the crank pulley. it is notched for tdc, and there will be a spot on the block it lines too. (easy to figure out if its in time).

Ok(I do need to do the timing belt asap)

My step dad did say after the incident with the clogged cat the car never felt the same. Wasn't as quick off the line and he just drove slower. He never actually drove the car hard, nice smooth shifts, never bouncing off the limiter or running it to the redline.

reading through all your posts again makes this situationally difficult. If the car didn't run like "new" after the cat repair 20-30k miles ago. And you are at 107k miles without doing the timing belt, or even 107k miles on a few original parts. The problem could stem from a few areas.

Start with what i already told you, but i would probably at this point verify no ad engine noises while cranking over, and check the timing belt. It might look ok, but just slipped, so verifying timing marks is more important.

it could be the primary o2, depending on what the previous check shows. Did he have both cats replaced? i think that year had two cats, others do. it would be helpful (and VERY quick) if you had a scan tool with real time data. But i know that is probably out of your reach.

i would also suggest "feeling" and "listening" to your injectors, to see if they all click the same way. This is worst case scenario, but A stuck injector could cause your current problems as well as the original cat failure. But you need to be experienced to diagnose an injector issue.

I'll see if I have some fuel line laying around to use as a makeshift stethoscope. I've diagnosed nailing diesel injectors before.

I wish he had told me that it wasn't feeling the same after the cats were replaced (I do believe both were replaced). I am very meticulous about my car(94 E320 Cabriolet) and my family members.. not so much apparently.




To remove the timing belt cover I just remove the two bolts securing it and leave the engine mount?

yeah the top cover come off without the mount, i'm 90% sure (i have the newer engine).

Well, I went to the car today and it was down pouring, awesome. I had stopped by a mechanic a friend reccomended and he gave me a card for a tow truck he uses. I went to the car, its still raining so I say screw it and tow it to him.

Get the car there, pop the hood. Charles removed the oil cap and tells me to bump the engine over. Did that and the cam did not move. Great.. just great. Theres your random misfire. We push the car into the garage and remove the valve cover to do a leak down test. Cylinders 2 and 4 are at 90/100 psi.. Good good... Go to cyl 3 and its at 75, not good.

Pull out the TSB's and in '07 there was a tsb for random misfiring and etc. Calls for all the valves to be replaced with I guess an updated valve to cure the sealing issue. Note that in '09 the catalytic converter went into melt down mode. The dealership replaced all of that under warranty. But they did not, and I repeat did not tell my parents about the TSB while it was still under warranty. My mother was there for the work and everything they did. She does not even recall them saying anything about a timing belt job or anything. Great, now I need call them and get the records from them on the car if I can to see if they did mention any TB or valves in the work order for the cat.

So, Charles is pulling the head and sending it out. He has done this job before on an '04 Aveo so he knows what is involved and I am looking at $1300 out the door. I'd honestly probably be able to do this myself but I don't have the time with work and school(finals are in like 3 weeks) I have my own car I need to deal with at the moment too(rebuilding the top hydraulics).

He will be calling me later with an up to date quote on the job. If need be I have a friend at a chevy dealership and I can probably get all of the parts at cost if need be.


I know I am new on this forum and I really appreciate everyones help but I will say this.. I hate timing belts, I will never own a car with a timing belt. All of my Mercedes have been double row timing chains.

I'll keep everyone posted.

i dont see how the timing belt failure is at all related to the TSB? plus that tsb was in canada anyhow wasnt it? if your referring to the one brought up here a few times.

thats one of the things i told you to look into, listening for engine noise if you cranked it. Did you check the belt itself? if you have been dry cranking it as long as i would think, did you do a wet test on the compression test?

We didn't hear any weird noises but the compression on #3 (75 out of 100 psi) was not ideal according to him. The teeth on the belt were stripped at the crank pulley.

I don't know what to do when it comes to this car. It's built to be disposable but I cant just cast it off and get another car.

Got the updated repair estimate.. $1400.. Paid the diagnosis fee and towed it home.... A friend is going to help me pull the head and ill send it to the same machine shop the mechanic uses. He gave me the name and number. My friend(s) that are helping me have experience pulling heads and making the car run after.