I drive a 2006 Acura CSX. K20Z2 engine and automatic transmission.
The car has been doing this for the past month or so. It started when I come to a stop, the RPM would drop below spec to around 500 to 600 rpm and you get the low rpm vibration. Then it would return to normal after a few seconds. And it would only do it 10% of the time at operating temperature. If it did not return to normal then when I step on the gas it would hesitate off the line. It kept doing it and never gave me a code and the CEL never came on.
Last week it got bitterly cold where I live (Manitoba, Canada) and it finally worsened when I was driving to work. The engine light came on flashing and gave me P0301, P0302, and P0304. The car also idled rough below spec, struggled to accelerate and I could smell unburned gas. I had a short ram intake thing on so I thought the MAF sensor could be dirty or fouled so I replaced it with a clean one and cleared the code. When I was driving home the misfire returned and this time it was P0301, with the same rough idle at a stop and hesitation during acceleration.
Since the motor that's in the car was from the junkyard and I never changed the spark plugs in it, I went ahead to replace all 4 plugs with NGK iridium and also the ignition coil of cylinder 1. The old plugs looked crusty with the exception of the plugs from cylinder 1, which was covered in oil. The car ran slightly better after the plugs were replaced but it won't rev past 5000 rpm. And during my test drive when I came to an adrupt stop, the idle speed plunged back down to 500 and the engine sounded like it was going to stall. It refused to accelerate when the light was green and would only pick itself up after 10 seconds or so. But if I stopped gradually, it seemed to be able to handle itself better and would idle at normal RPM at 700 - 800.
And as of now it did not give me any code but the hesitation is so bad that I do not feel safe driving the car in rush hours traffic.
Any suggestions on where I should look next?
It sound like the engine is out of time. At the same time it sounds like a computer problem. I know these engines have issues with the cams, weak motor mounts and mains seals. There are a few other minor things. Its possible your exhaust cam needs to be replaced. When the cam start to have issues or are failing the usually make a taping knocking sound. Poor acceleration/hesitation and nosie are the common symptoms
Its a junkyard engine so it's possible the engine is just bad or something wasn't connected. Scotty said it best you need a fancy scan tool . A deep scan and watching live data is the only real way to figure this out.
Well you say that hesitation is bad but there's no codes. But finally got like me with high level scanner. Let them road test it with his fancy scan tool connected. It will record all the data. When it does has hesitate. That will be some data on there that shows where the problem lies such as it might show one particular cylinder has misfires in it. Then you know it was in that area. Realize unless the data is more than 25% plus or minus it often will not trip a code. But you will feel it yourself. But a good mechanic can read that down and show what's wrong even though there are no codes
Thanks for replying. Thought I would give an update. Took it to the mechanic and he found an exposed wire from the remote starter that's fried with bare metal exposing. This wire was shorting the ignition and fuel circuit. The mechanic taped up the wire and the car drives fine now.