Flashing check engine light

So last night I was doing some xmas shopping for my wife and on my way home I was getting on the highway and the check engine light came on an started flashing. I got off the highway and pulled in to a parking lot the car war running rough it was shaking the whole car. I took it slow and got it home. Today i changed the spark plugs and wires and it ran better but still not right at idle it runs fine for a few seconds then rough but not as bad. I got a code scanner and found the codes P0300(Random/Multiple Cylinder Misfire Detected), P1781(Engine Torque Signal Circuit), and P0700 (Transmission Control system Malfunction). I cleared the codes to see if after replacing the plugs it would come up with another code and nothing but it still not running right. I it an 04 Aveo with 71,000 on it and the timing belt and every thing was replaced just shy of 60,000. Any one have any ideas?

How did the plugs look? Odds of 4 plug going at once isn't as likely as the coil pack going. (can happen in extreme cold) either that or the wires are shorting out...

But getting another code or checking the system is better then throwing parts at it, mist water on the wires and coil pack while it's running if you see sparks, replace that item.

The plugs needed to be replaced after looking at them and it was cheap

Yeah, I have an idea, but you won't like it. That is pretty much what our 04 started doing, at 107K. Like you, I changed the plugs, I had changed them and the wires around 97K. They looked okay, but the plug in number 2 looked a little "different". Took it in to the dealer for diagnostics. They diagnosed it as a burned valve, and estimated the repair at $2500. Well, I did not like their diagnosis, and took it to my mechanic. He advises that there is a problem with a valve, but the real problem is the loss of compression in the number 2 cylinder. It reads 25psi, while the other 3 are reading 125psi. In my world, when you have a large disparity in cylinder compression, and you shoot some oil into the cylinder and the compression comes back up... that usually indicates a ring problem in that cylinder.

Pulling the motor right now, then disassemble and inspect, and plan to rebuild it. Based on estimates form my mechanic, and the machine shop, I can rebuild this motor, and have it balanced for less money than buying a surprise (surprise, I don't work!!!) engine off ebay, and installing it. Since she loves the Aveo, we are going to do it right.

Good luck, I hope your problem is different from mine.

Oil in the cylinder account for rings yes, but the compression coming up does not always mean rings need replaced.

Although 25 is really low.

Putting the oil in helps account for the fact that a compression test does not account for running conditions. Rings can expand with heat to bring compression up, also if the engine has oil squirters then that can't really be accounted for during dry cranking. Etc

While it points to rings, a cylinder leakdown test should be done to point to the exact problem

For the op. I was stating if all four plugs looked bad then a common piece probably fouled them. Check your coilpack.

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Originally Posted by jimig1

So last night I was doing some xmas shopping for my wife and on my way home I was getting on the highway and the check engine light came on an started flashing. I got off the highway and pulled in to a parking lot the car war running rough it was shaking the whole car. I took it slow and got it home. Today i changed the spark plugs and wires and it ran better but still not right at idle it runs fine for a few seconds then rough but not as bad. I got a code scanner and found the codes P0300(Random/Multiple Cylinder Misfire Detected), P1781(Engine Torque Signal Circuit), and P0700 (Transmission Control system Malfunction). I cleared the codes to see if after replacing the plugs it would come up with another code and nothing but it still not running right. I it an 04 Aveo with 71,000 on it and the timing belt and every thing was replaced just shy of 60,000. Any one have any ideas?

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From my experience 3 weeks after buying my aveo at 108,000 miles, I had a p0300 (multi cyl misfire), I had to to replace the ignition coil, while I was at it I replaced the plugs. due to having a multi cyl misfire though, it killed the air/fuel ratio sens (up stream o2) and it also killed the cat ($300 from discountconverters.com direct bolt on)

I have not had a chance to really look at it nut from test driving it i notice that it only has the problem at idle if you have the car in park and give it a little gas less then 500 rpms the roughness goes away

+1 on the ignition coil. If you've changed the plugs and wires, next in line is the coil. Our '07 started throwing p0300 shortly after we got it and it turned out to be the coil.

Like Paul's experience shows, you really shouldn't be running around in it while it's misfiring, a $100 job can turn into $500 pretty quick.

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Originally Posted by exodus0784

+1 on the ignition coil. If you've changed the plugs and wires, next in line is the coil. Our '07 started throwing p0300 shortly after we got it and it turned out to be the coil.

Like Paul's experience shows, you really shouldn't be running around in it while it's misfiring, a $100 job can turn into $500 pretty quick.

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True, thruough my job, I got the coil for $100, the air/fuel sensor for $95 and as previously mentioned the cat from discountconverters.com for $300. Unfortunately, i didnt have the ability to just stop where i was, I was out of town so I had to limp it home, under low throttle it was fine, but under heavy acceleration is when it would misfire. I also had to limp it home so I could get my aveo to work to fix it, I wasnt about to take it to a shop and pay for something I could do myself for no labor LOL

I got a spare ignition coil if you're interested...

Well I got a new coil last week and the car ran great when to the auto parts store cleared the P0300 Code that showed up again before replacing the coil. So I was driving to work pull in to the ramp and look over and the check engine light is on again :mad: but the car is running fine. I'll be running to the auto parts store tonight to get the code scanned.

If it's no longer flashing (no longer misfiring), I'm guessing the O2 sensors or the catalytic converter are shot from the extra fuel getting pushed through the exhaust.

Well ill find out what the code is and post it up tonight

well I was just at the auto parts store and i got a P0420 Catalyst System Efficiency Below Threshold (Bank 1) so it is the O2 or cat. I'm going to go to my uncles house and use his scanner it is much better then the auto parts store.

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Originally Posted by jimig1

well I was just at the auto parts store and i got a P0420 Catalyst System Efficiency Below Threshold (Bank 1) so it is the O2 or cat. I'm going to go to my uncles house and use his scanner it is much better then the auto parts store.

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bank 1 sensor 1 will be an air/fuel ratio sensor (upstream O2), bank 1 sensor 2 will be an O2 sensor (downstream O2) P0420 will be a feed coming the downstream(after cat), it throws the code when your converter is no longer performing. check out discountconverters.com i bought a direct bolton on cat for my 04 aveo for $300 shipped

Is it a sure thing that it is the cat and not the O2? I'm going to get his scanner then I can monitor the O2 and see if it is the cat or the O2

could be the o2, but if it was flashing the cel it seems there was a misfire from exhaust no being able to escape, if it is the cat then you might have a catastrophe if you dont fix it.

I plan to fix it but i don't want to replace parts just because especially since they are not cheap

well the -p0300 code could be back pressure as well, any loss of power?

you could try running a 1" drill bit through the honeycomb of the cat, not emissions friendly, but would prevent siezing the engine if as builds up too high.. you can use that time to access if the cat is clean or clogged. to replace it or not.

I have not noticed a loss of power. With this car i think that I'd notice since there is not a lot to begin with

you might have just washed the secondary o2 with fuel then. if you were dumping that much fuel. the primary would have been hot enough to burn it off.

Ill find out Sunday with the snap on mt2500 scanner if the o2 sensors are reading correct

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Originally Posted by jimig1

Ill find out Sunday with the snap on mt2500 scanner if the o2 sensors are reading correct

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the cat is easy to check, 3 bolt top, 3 bolts bottom and it comes right out. youll know imediately if the cat is bad by looking inside of it

The problem with taking the cat off is it is cold. Today the high was 25 and for the rest of the week between 4 and 9 degrees. I have the o2 sensor ordered and it will be here this week.

Having the same issue, what was the result of your snap-on scan Jimig1?

I found a really cheap price for the OEM sensor here!

List for $86
Sale for $30.28





http://www.discountcatalyticconverte...nts=partfinder

I had a flashing check engine light and it turned out to be my air temp. sensor it mad my car run like crap my car wouldnt shift right or anything it wash horriable you might wanna look into that as well if have bot fixed the problem yet that sensor is 14.99 at Auto Zone

its always about reading the codes and interpreting that information. not throwing parts at the problem.

Well the car is running like new now after replacing the plugs, wires, coil, and o2 sensor.

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Originally Posted by jimig1

Well the car is running like new now after replacing the plugs, wires, coil, and o2 sensor.

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I replaced the rear o2 sensor, and the plugs. I think wires are next cause it sometimes still missed a little under heavy load. I did learn a neat trick to reset the codes, disconnect the red battery cable from the battery and short it out to ground for a few seconds, works like a charm.

I just swing over to o'rileys and clear it with there scanner

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Originally Posted by jimig1

I just swing over to o'rileys and clear it with there scanner

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The dude at autozone said their not allowed to clear the codes, never thought to just ask to use the OD.

at o'rileys if you are going out to use it in the lot they just take your ID and a Credit card and they give them back once you return the scanner

Just scanned my engine light and it also read p0300. Replacing the coil this afternoon. Hopefully I haven't damaged the cat.

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Originally Posted by Sal_fresco

Just scanned my engine light and it also read p0300. Replacing the coil this afternoon. Hopefully I haven't damaged the cat.

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Just replaced the coil pack. I am still experiencing hesitation and a occasional misfires. Do I need to replace the plugs and wires as well. I'm just wondering if there is anything else I should try. I am not getting an engine light but I can tell its not running properly.

Unfortunately misfire can be caused by many things. If you start hanging parts, you may spend quite a bit of $$ before the problem gets resolved. Best to diagnose first but OTOH, plugs and wires are basic maintenance, so depending on how many miles are on them, it might be a good thing to try next. If that doesn't work, you should get some systematic testing done.