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Hello i have a Santa fé 2.7L V6 from 2007 where i get Misfires on #2 and #4 on idle. For me it sounded like Vaccum problem but i did not find anything and let a garage smoke test it and there is no vaccum leaks. Changed spark plugs and swapped place for the injectors, cleaned the maf and trottle body. When i could not find anything i drove the car to Hyundai garage and after about 1 hour called and said that the ECU is faulty and looses ground in injector 2, nothing about injector 4 and only at idle?.
Now im thinking about to do what they said and replace the ecu, but the cost of this is about 2 000 dollar and i have read the in the cars "Repair manual" that the injector will cut of after 46 seconds if something is wrong. I asked the hyndai garage about this and they did not know anything about this.
The car misfires only at idle and works perfekt if you don't have to stop at red lights and such.. Should i belive them and replace the ECU or keep looking?
Misfire at idle only may well be a valve problem. Did yiou do any mechanical testing? Maybe leak down test and compression check is something you want to start with.
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
The following user(s) said Thank You: Andy.MacFadyen
I have done compression test. But only on cylinder 2,4,6. What i can remeber it was In spec but 2 and 4 was a bit lower then 6. I will buy my self a leakdown tester and do both compression and leak down.
Good to know that im not the only one that thinks ecu replace should not be needed. 2 000 dollar and no warrenty becaus if you put VIN number in the new ecu it can never be changed on these cars
Now i have done new Compression readings on the bank with the misfires. All 3 cylinders have about 9.5 Kg/cm3 And specs says about 12. Leakdown says about 25% leak on all 3 and the air comes out trough the oil. And a tablespoon of oil in the cylinders gives me compression reading over 12.
Is it safe to say that it's the piston rings are worn or broken?. And could the "small" lekage of 25% cause the car to only misfire on idle?
With misfires on one bank only at idle, I'd agree with Juergen's suspicion of a valve problem, or possibly mechanical timing. Before digging too much deeper, I'd be tempted to pull the upper timing covers and verify the belt marks.
Does a power balance test agree with the misfire codes you're getting? What are your fuel trims at idle?
A cylinder with less than 6 bar ~ 90psi will not produce enough heat to create proper combustion. Although your compression readings are substandard, it is not the cause of your SINGLEcylinder misfire, I believe, nor that the rings are broken. Is there a possibility the cylinder walls were already fuel washed when you did the compression test?
I recommend a running compression test, including a snap throttle test, this will give you cylinder specific information on breathing. Furthermore put a vacuum gauge on the engine and report back.
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
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