Plot thickens misfire and rough after revving 2k plus

[stuee1]

ok, i posted before about errors on my wifes holden epica 2.0 L6.

I wiped all the error codes and the problem i seem to have is,,
when i start it runs fine, if i rev over 1500rmp it starts to cough and splutter then when i let it idle is is very rough like its misfiring and also a random knocking sound at the top end like a lifter or something.

the ecu keeps spitting out 5 and 6 misfire codes.

hopefully someone can shed a little light or give me some ideas to try to diagnose more.

thanks in advance anyone.

 

[Calaber]

Why dont you look to see if someone went to the trouble of answering your original post before starting a second thread on the same problem?

 

[stuee1]

Why dont you look to see if someone went to the trouble of answering your original post before starting a second thread on the same problem?

Because its a different thing now than the op because all the errors have gone except one and didnt want to confuse people.

 

[Calaber]

Interesting. You ask for help as you obviously don't know what the problem is, but then you decide that it's something else. So why not at least TRY the suggestions before posting again. Otherwise, why ask for help? Some of us here have actually experienced electrical problems with late model cars before and from my own experience, one small fault can result in a number of warning lights illuminating simultaneously, even though the systems are unrelated.

Ignition systems have their own peculiar ways of driving you nuts. Why don't you try the two things I suggested the first time? Just because different sets of error codes keep coming up doesn't mean that the problem isn't related to the same thing. If it's misfiring, test the coil pack and the cam position sensor. Both have a major effect on firing, they're easily accessible and are not the dearest things to replace if they are stuffed.

 

[mudguts1966]

Hi Calaber , My wife also has a Epica which has had a similar misfire , it ran roughly for a second or two with the noisy nock you describe upon starting , I have had it looked at several times with no real answer to what it was (electrical or mechanically) , began to hate the car more than what I already did .
I have tried something that has eased the symptom's greatly with only a single bad start in the last three weeks , I will give you a bit of history , I have always ran my cars on PRENIUM grade fuel , I remembered a sticker on the fuel filler saying car was capable of running on ETHANOL but never did because I always wanted to have the best ,the tank was empty so I decided to try a half a tank of normal UNLEADED , it has been the difference , do you run your car on Prenium ???
I am not a mechanic , the change of fuel is not going beyond the cars hand book , but possibly the high octane fuel is to much for the engines starting tolerance . if it works would be glad to know

 

[Calaber]

Hi Calaber , My wife also has a Epica which has had a similar misfire , it ran roughly for a second or two with the noisy nock you describe upon starting , I have had it looked at several times with no real answer to what it was (electrical or mechanically) , began to hate the car more than what I already did .
I have tried something that has eased the symptom's greatly with only a single bad start in the last three weeks , I will give you a bit of history , I have always ran my cars on PRENIUM grade fuel , I remembered a sticker on the fuel filler saying car was capable of running on ETHANOL but never did because I always wanted to have the best ,the tank was empty so I decided to try a half a tank of normal UNLEADED , it has been the difference , do you run your car on Prenium ???
I am not a mechanic , the change of fuel is not going beyond the cars hand book , but possibly the high octane fuel is to much for the engines starting tolerance . if it works would be glad to know

Hi mudguts.

The original thread poster was stuee1, not me. He was the member with the problem. He seems to have gone very quiet since his last post above so I don't know if he's even still active.

However.....

You say that your car developed the original problem when running on 98 premium and now that you are running 91 unleaded, the problem has gone? (or at least diminished.) That's a bit odd - the higher octane rating with Premium is usually unnoticeable in a car designed for 91, though you might get some small performance improvement. (Highly doubtful with an Epica ) Generally it's a waste of money using the higher grade fuel but not harmful at all for the engine. I'm not familiar with the Epica engine at all. It's a 2.0 or 2.5 litre inline DOHC six, I think, and that's about the limit of my knowledge. Maybe something to do with the timing chain if it has variable valve timing. Perhaps the camshaft adjuster is faulty but that's a very rough guess.

Have you had any error codes read to see if defects have been recorded? How many k's on the car?