Chevy Aveo Misfire or Normal

luckinsluckins Member Posts: 63
edited March 2014 in Chevrolet
I noticed that my 2004 Aveo has some kind of misfire or uneven idling, especially when cold. Sometimes, it hesitates if I were to take my foot off the gas and "let it roll" on it's own, but not when I push on the gas.

I am currently trying to run a few bottles of decent fuel injector cleaner because I'm wondering if water got into the gas due to sitting for a long while with a bad gas cap and heavy rains. It seems to have gotten slightly better after I put some cleaner into the tank. It doesn't hesitate or stall at any other time and runs smoothly on the highway. When it warms up, it is better, but not non-existent.

Is it normal for this engine to run unevenly or feel like it has a misfire? I've noticed one other GM MPFI vehicle having an uneven idle, too. I'm used to throttle bodies and carburetors, so I don't know if it's behaving correctly.

Also, aside from getting a fuel injection service, are there any good fuel injection cleaners I can get from an auto parts store?


  • luckinsluckins Member Posts: 63
    I got the wires all off and have a new set of wires now. I only managed to change one spark plug because the tool kept getting stuck in the hole. The only way to get it out was to take the spark plug out with it. Is there a trick to keeping the tool from getting out of the hole?

    The one spark did change, I tightened with the wire. I'm pretty sure it was OK because after I tightened it, I check it with the tool and it was almost as snug as if I were to have used the tool. The only thing was that I had to take the plug out again because the tool got stuck and I reinserted it with the wire even tighter than before. If I can't get the tool to work when I tighten the others, I will use the wire to tighten them. The all sit on top and are held in with snugly fitting wires and a cover, so I doubt it will pop out.

    If anyone knows of any problems of doing it that way, let me know and I'll work on getting the tools to work.

    The car runs slightly better, but still runs unevenly. It might take a couple of days for the computer to adjust.

    It was a 20 minute job that took 2.5 hours because the tool kept getting stuck! And, I still have three other plugs to do.
  • luckinsluckins Member Posts: 63
    I found a tool that is all one assembly and I may get that and use that to tighten while using the regular socket wrench to loosen them. I might not be able to do it for a day or two. So, I hope that one plug doesn't blow out and I can get the wires off the other three. I put silicone on them, so I think it'll be alright, plus, they're new.
  • wave54wave54 Member Posts: 211
    There's a TSB on that issue regarding valves that need to be replaced. Since you're not used to the car and it's been sitting, I'd wait awhile and run a few tanks through before having that checked out.

    Are plugs and wires recent?
  • luckinsluckins Member Posts: 63
    I don't think that TSB is related to my problem, it's actually not as bad as the problem mentioned in both the bulletins I saw.

    I had them inspect the car visually when I took it into the dealer today for the BTSI solenoid and they said everything looked fine. I also found out that they didn't do a fuel injection service, yet. And, just a few minutes ago, I checked under the cover at the wires and they looked like they haven't been changed in a while, so I want to do that. The problem is that I can get those darn boots off the plugs! :mad: So, I can't see if the plugs need changing until I get those boots off. I don't want to damage the wires unless I am really committed to changing them, which I'm not at the moment.

    Is there a trick to getting those boots off? Also what size socket do I need for the plugs, I have a 13/16" spark plug socket, but I wonder if I need another kind.

    I have a feeling that once I change the wires, plugs, and get the fuel service, that this car will be running normally.
  • mc_ensormc_ensor Member Posts: 2
    I've been to a few aveo forums and seen a lot of threads concerning misfires and such. I had the same problem with my '04 aveo and finally figured it out!!! I got the run-around from 4 places before somebody diagnosed it right. It started for me with a check engine light: code p0300, I think. It's a "random multiple-cylinder misfire" code. I lost a lot of hp and had a nasty hesitation. Turns out, engine valves were the ticket. A valve went to [non-permissible content removed] and that allowed oil to leak into the spark plug, fouling it out. Somehow, the O2 sensor got screwed up also. All together, it ended up costing me just under $700 for a good fix. New valves, plugs & wires, a new O2 sensor, and an injector service for good measure. Hope this helps!
  • luckinsluckins Member Posts: 63
    Thanks! I don't actually get a code on my misfire and I'm aware of the valve problem. Actually, the misfire is, more or less, taken care of. I put new plugs and wires on it and made sure they were snapped in tight. I also took it on a very long drive and I think that helped with some gas contamination that might have gotten into the tank while it was at the dealership. I still might need a fuel injection service because once in a while, I will feel a miss, but it's very minor. It also doesn't hesitate as much. But, things change from day to day . One day it can be perfect, the next day less so.
  • framingtonframington Member Posts: 1
    Check engine light came on, went to Dealer for the 07 Aveo with 6000 miles on it. They said there was a misfire. They said needed a valve. They replaced the head (took 10 days to fix because all parts had to come from Korea). Dealer manager said the new valves have been redesigned due to defective valve causing carbon build-up and weak valve springs. A month later back to the dealer with what I thought was a blown head gasket (loud noise and fluid leaking). The service manager claimed a spark plug was not installed properly. But how did that account for the fluid leak? He said problem may return even though valves redesigned. Another 10 days for service; for a spark plug? He suggested STP or other type gas treatment put in quarterly. Any other suggestions?
  • busirisbusiris Member Posts: 3,490
    My suggestion....Get another dealer!

    Loose/bad spark plugs DO NOT create fluid leaks!!!!

    End of story.
  • luckinsluckins Member Posts: 63
    I agree, a bad or mis-installed spark plug would probably only cause a miss, if even that. And, how does one not install a spark plug right unless it's just loose? I mean, they only go in one way? And, there's no fluid involved with it whatsoever. I'd bet that they didn't put the head or head gasket on correctly when they did the valve job.

    GM says not to use those additives. I've used them and they can actually make a problem worse. All most of them are is soap that can be put in the gas tank. And, they only work for fuel-related problems, not bad valves.

    I know these cars can have valve problems, but, in honesty, it's not a common occurrence considering all the Aveos out there with well over 60,000 miles, now, who haven't had this problem at all. If what that dealer said was true, a lot more Aveos would be coming into the shop and people wouldn't be getting a run-around like I am hearing.
  • mc_ensormc_ensor Member Posts: 2
    I did the same deal at first. Replacing the plugs / wires worked temporarily for me as well, but the problem kept returning. Once the valves allow enough oil into the plug sockets, you'll have to replace them again and again.
  • luckinsluckins Member Posts: 63
    I actually took it in to have a fuel injection service and now it runs almost perfectly. I does have a funny hesitation thing, sometimes, when I first start it, but otherwise, it's about as good as a car with MPFI can get, I think.
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