[aldersonfilm]

Hey guys! New here and just purchased a 2005 V6 with 155K miles on it. I love it, but it's got some quirks... It has a pretty significant rumble when idling. Needle is steady, but the whole car shakes, sometimes worse than others. Today it threw out a P0301 code (misfire in cylinder #1.) I checked the plus and was gapped at .043. If I'm not mistaken, it's supposed to be .054, no??? I regapped it and pulled the #2 plug. This one had almost no gap at all. I regapped it too, but I didn't go any further than that. I suppose that right there could be there problem, but any other suggestions?

Also, makes a funny whirring noise when accelerating, especially in 2nd.

 

[aldersonfilm]

I should add. The previous owner ALWAYS ran 91 in it and I've started putting 87 in it, which it is supposed to take. I'm thinking maybe he gapped the plugs less in order to get a quicker ignition for running a higher octane fuel... Who knows. Could this change in fuel cause a misfire?

 

[Immortal]

If all your Plugs are that low gapped, you will receive a bad spark, which leads to a bad fuel burn, and could cause misfire.
Try to gap them back to the Stock Value, basic maintenance may help too. Checked/changed Airfilter, Fuel Filter? Throttle Body?
I´m curious why the plugs are so tight gapped, normally you only do that while supercharging? :heha:

 

[az.dsrt]

Also, if the previous owner always used 91 octane, is it possible the car has a tune on it?

 

[aldersonfilm]

Hmmm.... Now you guys have me curious haha. The car would rumble a bit even before regapping, but seemed to get worse when I dumped 87 in it. As the last of the 91 burns off, it's getting worse and triggered a misfire code, but I don't know if they are related... Also, there is a whine, that sounds like a turbo, but I don't know these engines well enough yet to know if that's the case. The guy hardly spoke any english, so who knows what kinda stuff is on there. Should I gap them down again...? How do I tell if it does have a tune on it?

 

[az.dsrt]

If it was me, I would replace the plugs with ones properly gapped. Completely eliminate that as a potential problem. You've got enough miles on it and I assume you don't know when they were last changed.

On the tune, as far as I know the only way to tell is to hook up a tuner to it or contact the seller. In my book, someone selling a car with a custom tune on it without the tuner is doing something very bogus.

 

[yellstang05]

If this only happened after you put in the 87 octane fuel, I would be quick to think it was the gas. It could be 1.) too low of octane if it is tuned for a higher octane or, 2.) be consistently bad gas.

To help eliminate other problems you can:

1. Try throwing some 91 or 93 octane in and see if it runs normally. If your car is tuned for a high octane, then it can have a hard time running with too low of octane. But with EFI systems now, it usually compensates and readjusts. This problem would be more likely to happen in older cars. You may also be able to reload the factory tune and run on good ol' 87.

2. Check the ignition system (wires, coil, and plugs). It wouldn't be a bad idea to change the plugs too. I've heard after 100k miles they should be replaced.

3. Check to see if any vacuum hoses are loose, this could cause a rough idle.

4. Fuel again, might be a bad injector where you having the misfire. Check the connector to the injector too before replacing it.

 

[aldersonfilm]

Now I'm really worried. My temp gauge doesn't work and I haven't had a chance to replace it yet. Checked the coolant reservoir today: Bone dry... I'm assuming I'd get a check engine light or coolant temp light or at least a faulty coolant sensor light if it did overheat. But now I'm freaking out that maybe I blew a head gasket or cracked the head. No visible coolant in the oil and no coolant came out with the spark plugs. The engine does hiss a bit when I shut it off though...

 

[JimC]

As far as your coolant issue check the thermostat housing. Probably it has split on the back side. It is a common thing, especially given the mileage and easy to do.

Do you have the stock intake or an aftermarket one on the car? A picture of the engine bay will tell us.

For safety I would replace all spark plugs. The Autolite 5143 is not expensive so for about $12 you can eliminate that as a problem

Sent from my SPH-D710 using Tapatalk 4 Beta

 

[aldersonfilm]

Well... Took that car in today and learned a few new things. The number 4 cylinder also threw a code on the way over and when we pulled the plug, it was rusty. Yup... Sooo water in the piston. Looking like I've got a blown head gasket, maybe a cracked head.