Throwing a code... is it a head gasket issue?

[preacher35]

Yesterday, I noticed my 2005 4.0 (128k) was having a very slight hesitation/shudder (and I mean very subtle) upon accelerating from a stop. Check engine light came on as well as VSC track lights. They had come on a couple of months ago for a day or two, but then disappeared, so I didn't think much of it. Well, today, I went to my mechanic and had him scan it. P0300. Multiple misfires. I know that this could be caused by several different issues. My question is this: is there anything that I can look for, myself that would make a more definitive diagnosis that it may be a blown head gasket? Exhaust looks normal and no funny smells to report and idles as smooth as when I drove it off the lot back in '05. Advice and suggestions are welcome!

Thank you in advance,

Preacher

 

[Boggs]

I haven't tried it but I hear a "leak down test" is the best way to check hg.
I have seen some do it yourself kits at the local auto parts stores. Or have a shop perform it.

 

[preacher35]

I read somewhere on this forum that you can smell the coolant for "hydrocarbons" which would be indicative of a bad HG. What the hell do hydrocarbons smell like??

 

[Inv4drZm]

I read somewhere on this forum that you can smell the coolant for "hydrocarbons" which would be indicative of a bad HG. What the hell do hydrocarbons smell like??

Oil or gas

 

[fdbyrne]

I read somewhere on this forum that you can smell the coolant for "hydrocarbons" which would be indicative of a bad HG. What the hell do hydrocarbons smell like??

I don't believe that you can usually smell for the hydrocarbons. They hydrocarbons are burned during combustion and converted to heat, CO2, and water along with traces of other things. When they test the coolant for 'hydrocarbons' they are really only testing for an excessive amount of CO2 which is odorless.

I've been through the head gasket thing and this doesn't sound like it's a head gasket to me. When a head gasket goes it will usually misfire in only one cylinder and a code will fire to tell you which one. Random misfires like the one you have are usually something else.

 

[iBison]

If it was a P0306 I would say more likely than with a P0300 since that would indicate cylinder 6, the most common for head gaskets. P0300 is random or multiple misfires. We did the radiator gas test and it was OK. We used a borescope to see coolant in #6, but I was confident of the cause already. My exhaust looked fine as well.

With mine it would run a little rough when first started up and go away within 30 seconds or so. It was pretty obvious, not terrible, but also not just a slight hesitation. Have you been losing any coolant that isn't an obvious leak?

 

[Troymclure]

I read somewhere on this forum that you can smell the coolant for "hydrocarbons" which would be indicative of a bad HG. What the hell do hydrocarbons smell like??

Smells like exhaust fumes. If its there its very easy to smell. Normal coolant smells somewhat sweet.

 

[preacher35]

If anyone is interested, here is what the problem turned out to be: Apparently, I purchased some "bad" gas. I was a little suspicious of this as I remember one of my old girlfriend's car (Honda Accord) had identical symptoms. Turned out she had water in her tank. So, I ran my previous tank of fuel down to almost empty and headed over to a DIFFERENT gas station. Filled it up, codes GONE. Slight stuttering upon acceleration, GONE. My heart palpitations, GONE. Hopefully, this will help someone else in the future!