macattack0821

Drove the car in the rain the other day, and I started noticing that when I applied throttle I would get a really slow response, in terms of speed and rpm's, and then all of a sudden the rpm's would jump and the car would accelerate. Stopped and let it sit for a minute, and the car started to vibrate pretty bad while idling, plus the check engine light came on. Took it to the auto zone, hooked the scanner up to it, and it came back with a P0300 code, the random multiple misfire.

Took the car to my buddies house, we figured that my MAF sensor or air filter had gotten wet from going through a puddle and had pulled it into the throttle body. Pulled the air filter out Sunday and cleaned it, along with cleaning the MAF sensor. Turned the car on, and the check engine light was off and it was running fine.

Today, car started doing the same thing, very bad throttle response and very rough idling, along with another check engine light. I don't know if it's maybe the coil packs? I'm really at a loss here, tried the search function to see if I could pull up another thread but not so much luck. Anybody have any suggestions?

LS6427

iTrader: (2)

Sounds like a failing 02 sensor.

And NO.....you will not always get a code or SES light until it totally fails.

Get it scanned with an OBDII scanner while the engine is running to see how the 02 sensors are switching.

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macattack0821

Funny you say that, when I had it hooked up to the scanner at auto zone it did show a code for a faulty O2 sensor in the heater bank, talking with some of the guys at work O2 sensors came up as maybe a possible cause as well. If it isn't that sensor would it be something in the fuel system, injectors or fuel pump maybe?

2birdJosh

check plug wires for cracks i had problem like yours in rain and humidity. It turned out after replacing coils and 02 sensors my wires were bad. I felt pretty stupid not thinking of them!

macattack0821

Yeah, I've been looking to put some iridium spark plugs in the car for a while now, so this is giving me an excuse to actually get them and check out that whole system for anything else that might be wrong, including wires. Thanks for the info man!

sopes

Pull all the coil connectors and look for corrosion, then go after the plugs and wires if theyve never been done, but it soulds like a coil issue more so...

LS6427

iTrader: (2)

The symptoms you are having are CLASSIC for failing 02 sensor(s).

And you had a code for that.......

Change the 02 sensor associated with that code......whichever bank, whichever sensor.

Problem solved.......

Cheapest 02 sensors you'll probably find......and the best sensors.........

Denso sensors.......www.rockauto.com
They should be around $35.00-$40.00 each.

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macattack0821

Sounds like a plan, appreciate the information man, not being the most mechanically inclined wasn't helping me in this situation haha

2birdJosh

let us know when you figure it out and what it was.

macattack0821

Well somewhat of an update I guess, my buddy and I worked on the car yesterday, cleaning off the idle sensor (very dirty), and ran the car while unplugging each coil pack individually to see if we saw a change in idle speed. We didn't hit the very back coil on the left side, we both just don't have small enough hands, but we didn't see any change at all with the other 7 packs.

Unplugged the MAF sensor plug from the connector on the lid, expecting the car to bog down a bit....except nothing happened. Idle remained the same with the connector plugged in as with it unplugged. This little episode right here made my buddy think it was the MAF sensor after all.

Cleared the code out of the car, and put a new air filter in it. I have driven the car for the last two days now and haven't had an issue, other than it seems to idle very low (right at 500 RPM's or so).....not sure what the deal is now

macattack0821

I have ordered O2 sensors though, seeing as how it was either pay 40 dollars for a sensor or 190 dollars for a MAF sensor (which my buddy thinks is the problem), as well as bought some CRC MAF sensor cleaner to try and maybe clean that thing up a little better as well

LS6427

iTrader: (2)

It's normal for there to be no change when you unplug the MAF......the MAF is only used for when the engine is cold until it reaches something like 122*F....mid to high rpm accelerations and wide open throttle. Otherwise, the 02 sensors are doing all the work to keep the engine running at the right air/fuel ratio.

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macattack0821

Ok so makes sense then that an O2 sensor would be the main culprit? I've been driving the car for the last couple days with little problem, except for it seems to idle very low.....I have felt the misfire twice in the last couple days but only for maybe 1/2-1 second, and it hasn't set the check engine light off