F150 V6 4.2L Hard to Diagnose Engine Misfires

02-05-2014, 11:01 PM
Been a common problem for years and recently got one in the shop for the concern with the EGR port plugging up and then dumping all the egr into the one cylinder that is not plugged causing a misfire off idle. Many know of this concern but I have yet to see a good example of it. I show you some easy diagnosis before you pull the upper plenum to inspect the ports.


05-03-2014, 09:54 PM
I had this problem with my (235,000 miles) 97 f150 4.2L, and with your advice, I isn't a problem any more. (3 ports were clogged and 3 ports were open) Thank You

05-05-2014, 08:47 AM
P0306 is a very common code to get for this situation. As stated above, having the other ports clogged up makes all the exhaust gas being recirculated to be forced to go into one cylinder. This is usually number 6 that is nearest to the EGR valve. All these extra exhaust gases start to build up on the spark plug tip until it finally won't fire anymore. Thus the misfire code. I really just wanted to add a post to include that code for anyone doing a search on it for the 4.2L V6 Ford. Bad design in my opinion, not thought out thoroughly.

05-05-2014, 08:15 PM
Bad design?? I'm not so sure. I have a 97 F150 4.2L and never had this issue. Darn truck is rock solid. And when/if I do have that issue, it doesn't look like it is going to be such a hard thing to fix.

No truck or car is problem proof but some are definitely more resilient. I would have to say the 4.2 L is a pretty good little engine.

Just my opinion.

05-06-2014, 08:59 AM
I also like the 4.2 in my 98 F150. I get 22 mpg average on every tank. But if we don't complain about things we feel are designed incorrectly, they will do it again. Plus there are a few unscrupulous mechanics and shops that would take this simple problem and use it to empty the wallet of some average person. If it wasn't in the design in the first place, it wouldn't be a problem later. There are many V6 engines that don't handle the EGR gases in this manner. When I see some of these things, I get the feeling the engineers are encouraged to come up with some flaws that will only show up after warranties have expired to promote new purchases. One that really gets me is VW and their permanent transmission fluid. The first eight years of the New Beetle they said the tranny fluid should never be changed, and had it sealed so you can't even check the fluid. Now well past warranties, people have to pay upwards of 3 grand to get them fixed or junk them. Sorry for this additional rant, but my dad didn't investigate before he bought a 2002 with what he thought would be an easy cheap fix.

05-06-2014, 09:14 PM
I hear you, and yes you are correct it does make sense to complain about design issues. I guess I'm just happy that this old truck of mine has been so reliable. I love the rust, dents and dings because that just adds character.

Seriously the only work I have put into this truck are routine maintenance such as oil changes, brakes, etc.

Changed out the power steering pump and hose. That's it.

Pretty good for 17 years.

05-06-2014, 09:20 PM
Also I would like to point out that 17 years with very minor issues is what makes a customer want to buy the product again.

I can only hope that someone important from Ford reads these threads (doubt it, but can hope).

It is only because of my great experience with my own ford truck that I will most likely buy another F150.

That's all for my rant.

05-12-2014, 12:07 AM
I have worked on many brands most are just complete junk! I like working on Fords they seem logically built and for the most part tough!

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