3

This problem started a month ago. My Aveo started revving and jerking when it was sitting at a light on my way home (2 blocks from my house) and the engine light came on. I drove it home. The next day I went to drive it to the mechanic and the engine would not turn over. I had it towed to the shop. They replaced the battery, terminals and the ignition coil.

Less than a month later, we are driving to the beach and the engine starts jerking a revving again and the CEL came back on. We were in a place where we couldn't pull over, so my husband tried to drive it to a shopping plaza. The car would not go over 35mph. We had it towed back to the mechanic. They replaced the ignition coil again (said it was faulty).

Less than a week later, it happened again. The engine is jerking and revving and the car can not shift out of second. This time the engine light is not on. We got it back home (made it 5 miles from when we picked it up)

Do I bother taking it back to the mechanic? or do I see if I can get the engine light to come on? I have no clue of it is a third bad ignition coil or if there is another issue. Without the engine codes, I'm stumped.

What steps can I take to diagnose this issue?

Improve this question
8
  • Hi. I think you should take it to a different mechanic (unless there is a warranty on the previous work). Is there a chance you will attempt to repair yourself?
    – David Winslow
    Commented Jul 27, 2015 at 20:49
  • It is under warranty, but at this point I am willing to try and do the work myself, just not sure where to start. The belt, head gasket, and plugs and wires were changed out 3 years ago and less 30,000 miles.
    – Aveo Owner
    Commented Jul 27, 2015 at 20:53
  • If you can take it back and have further work done without having to pay more money, I would do that. The first thing I would check is the ignition coil. If this third one is bad there is something shorting it out and you will have to find the root cause of the problem. Usually it's the wiring to the coil. Are you able to get the code history, either from the car or the mechanic?
    – David Winslow
    Commented Jul 27, 2015 at 23:57
  • I asked for it the last time and I was told "it was the ignition coil." they wouldn't give me the exact code that popped up.
    – Aveo Owner
    Commented Jul 28, 2015 at 0:05
  • Thank you for providing so much detail in your question! It really helps the community to narrow down the possibilities as to what may be going on...
    – Zaid
    Commented Jul 28, 2015 at 8:33

2 Answers 2

Reset to default
4

Bad coils are just one of many things that could be to blame.

I'd say stop changing coils. It is highly unlikely that they were the root cause of the problem to begin with.

The symptoms provided are consistent with a misfiring engine. This usually means that there is an issue with the mixture of air and fuel reaching the engine (more on that in a bit).

So how come the car runs fine after returning from the garage?

I have no way of proving it, but this could be explained by the garage resetting the fuel trims.

In some vehicles, disconnecting the battery for a few hours is enough to reset the fuel trims; others require a scan tool. Either way, these fuel trims are re-learnt over time. While relearning, the car may operate well while the fuel trims are reasonable. As they worsen over time, the misfiring will return.

So what could be wrong?

If I were asked to highlight the probable culprits, they would be:

  • unmetered air

    So the engine computer is sensing less air than what is actually present. Ask the garage to perform a smoke test on the intake to test this theory.

  • faulty lambda sensor(s)

    These sensors are also commonly referred to as O2 sensors. If possible, hook up the vehicle to a scan tool and check if the sensor voltages are flitting between 0.2 and 0.8 V. If they aren't, the lambda sensors will likely need replacing.

  • faulty MAF/MAP sensor(s)

    If there are no intake leaks (result of the smoke test), an under-reading sensor can explain why the engine is misfiring.

Please note that this list is not exhaustive, but is a very good place to start hunting down such issues. All the best.

Improve this answer
2
  • I had to replace the O2 sensors 5 years ago along with the gas cap (recalled). I was thinking that was the original culprit and not the ignition coil. The gas cap has a tendency to fall out if I go over a large bump. I asked them to check the gas cap, but they told me it was fine.
    – Aveo Owner
    Commented Jul 28, 2015 at 20:06
  • @AveoOwner : Well, O2 sensors normally don't go bad within 5 years. Ask a mechanic to perform a smoke test and we can take it from there.
    – Zaid
    Commented Jul 29, 2015 at 1:37
0

Mechanic changed out the spark plug wires. This stopped the jerking and revving. The engine light came back in after I drove it 20 miles. I requested a smoke test, but I was told that it wasn't necessary. At this point, I'm just going to handle this myself.

Improve this answer

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .