UncleEinstein

I took my 2011 HHR LT, 2.4 liter into the dealership for a random misfire problem. The traction control said it needed servicing also. The Chevy dealership said they did not know how to "service" the car. I thought that was a bit odd. Now they say they cannot find out why the car misfires randomly, never specifying a specific cylinder. We are up to around $ 650.00 so far, and still have no real idea. They said today, that they think it is either the throttle body needing replacement, or the dreaded engine control module itself. Anybody else having this problem?

whopper

Welcome. The traction control light is probably lit up? and the random misfire was indicated by what? An engine check light code of p0300? It really helps to include ALL the relevant information right off the bat, and the current mileage on the car.

$650 so far!!! Wow - and nothing fixed? Generally a misfire problem is due to a dirty throttle body (which can be easily cleaned), or a dirty Mass Air Flow (MAF) sensor, which can be easily cleaned as well. Can you let us know what they have done so far? Beyond those items, of course there are spark plugs but usually that is isolated to a single cylinder, so I would not suspect them unless they have over 100,000 miles on them.

Get back to us with the additional information and we will see what suggestions/advice we can give.

donbrew

Fixing the misfire would be "servicing the Traction control". P0300 does not mean "random" misfire it mean "unidentified" misfire.

A mechanic blaming "the computer" is just plain lazy and stupid. Same with replacing the throttle body.

First step to diagnose is a compression and leakdown test. Cleaning the throttle body might help couldn't hurt if done properly. For $650 thyey should have hooked it up to an oscilloscope to check the injectors and coils. and done a compression test.
They ripped you off if they charged that much money and said goodbye.

Question to answer:
Do you hear a rattling noise when you first start up that goes away upon warm up?
Is coolant mysteriously disappearing?
Is the oil mysteriously growing? Odd color?
ANY other codes?

UncleEinstein

Hi, well they looked at everything, and said they were baffled as to what it was .The dealership changed the plugs, and cleaned the throttle body. Still nothing. Then they said the throttle body would not go to "zero" when closed, actually that it wouldn't close period. So now, they are looking into a used throttle body, and hopefully we won't have to get a Engine Control Module too. I don't think we should have to pay an endless amount of money, just because they had trouble figuring it out. Also, I had already replaced the Mass air flow sensor recently.

donbrew

I am assuming that there are no other codes besides P0300, you don't seem to want to answer any questions.

Go to another shop with an "old guy" that knows how to use an oscilloscope. The fact that they are even suggesting a new ECM is an indicator that they are rip off artists.

A bad throttle body has several different codes that indicate exactly what is wrong
A bad ECM has another bunch of codes.
Any Electronic part has codes.

If they don't do a compression and leakdown test they are not worth your money. The most likely cause is a leaking head gasket; that's why I asked the questions that you did not answer.

Get your car out of that shop!!! They do not know what they are doing!!!!

UncleEinstein

I'm sorry donbrew, there is no rattling noise,the coolant isn't disappearing. However, it did have alot of white in it, and nobody at another dealership could figure out what the stuff was. There are no other codes, except the traction control servicing light came on before. They said they didn't know how to service it. We did have the compression test done at an "old timers" shop, he didn't seem to find anything. I think you are right, these guys are clowns, who only want to empty everyone's wallet. Yes, the only code was the P0300.

donbrew

The White stuff could be oil or the result of a overheat or mixing of coolants.

Don't pay them for any repair without a written guarantee that it will work, they are throwing your money at it.

The only thing that can cause a misfire without causing other codes is a head gasket, or a leaking valve guide, or a slacking timing chain (could be the balance chain) The CEL is what causes the traction light..

You never did affirm my assumption that the code is P0300 only.

Doc brown

That would have been my cue to go elsewhere. Now that they've take you for $650, cut your losses and find someone who actually can find the issue.

UncleEinstein

Amen brother, amen.....

UncleEinstein

I just took my 2011 HHR LT, to the dealership to solve a random misfire problem. They did this and that, changed out the throttle body, but now the throttle is out of control. I have had the car in there two weeks, and I cannot trust them to know how to fix it. They just caused it. The idle goes higher every time I start the car, and WILL NOT kick down. I am afraid the next time I start it, the engine will explode, no trouble codes. Apparently the computer thinks this is normal. It also gives itself gas in drive AND reverse, without any gas pedal help. What should I do ????