P0300 code issues

I have read many posts on this code on TW and do understand the multiple misfire code.

My 2001 2.7 (140,000 miles) started misfiring a few months ago but only until the engine warms up to operating temp. Once warmed up the misfire stops and everything is fine. The misfire is quite apparent when shifting gears. This winter has been really cold and after 10 minutes of driving the problem goes away....the CEL just came on last week.

I am guessing it is not plugs or coil pacs but maybe the MAF ?......I do have the deck plate mod done 2 years ago with no issues.

Any ideas are very welcome regarding my misfire only when engine is cold?

Thanks

 

With the truck idling, tap the MAF lightly with the handle of a screwdriver; if the idle fluctuates the MAF is bad.

 

If you are getting a 300 code, and not a 301 or 302, etc ..... then its a random mis-fire of any or all cylinders.

I'd also look at the EGR, FPR, temp sensors.

You can rule out the EGR easily, by disabling it (block off the vacuum line going to the valve itself) .

 

Thanks guys...tried tapping the maf today but no idle fluctuation after it warmed up and the misfiring stopped.

Will explore the other suggestions as well as tapping the maf when truck is cold.

 

Just went through this on my buddys 4runner with a 2.7, sorry to say it was a head gasket. His would also do it when warm and used water.