I have a 2008 XL 4.2 auto trans with 60,000 miles on it. We purchased a new travel trailer with a total weight just under 5000 lbs that we pulled for about 2000 miles this summer. On the last trip we noticed the truck was missing pretty bad going up hills or under load. After we got home I started to notice the miss at times even not towing. Did a tune up with Motocraft plus and wires and seems to still have a miss at an idle and very low RPM.

What would be best to check next?? would Coil be logical? Motocraft Coil is about $70 on rock auto.

 

Well, the 4.2 is a good ole iron block, iron heads push-rod engine with one cam and two valves per cylinder. The computer control and EFI have been great on it. Anyway, the design tends to narrow down possible culprits for the miss compared to the 3-valve/2-cam V8 with 8 coils. So you find yourself in more familiar territory if you have ever worked on pushrod V8s in the past. Did you change the coil wire when you did the plug wires? Check it again for poor contact or corrosion. You might have a sticky valve or lifter - do you use an oil flush before changing oil? Are you using 5W-20 Motorcraft oil and filter? How about fuel system service? If none, you should start by using a strong cleaner and follow up with full-time use of a cleaner/stabilizer.
Just some random thoughts.

 

last few oil changes since I have owned it have been Motorcraft oil and filter. I will put a can of Sea Foam in the gas to see if that helps. Today the check engine light came on so I will see if I can get auto zone or a place like that to pull the code tomorrow and see if that reveal anything. I did not change the coil wire - is that something that needs to be addressed? it looks like its a wiring harness that plugs into it.

 

Autozone pulled the code... #6 Cylinder - put a new plug in it and all is well


check engine light went out about 5 miles later - Phew! I will still dump some sea foam in it just to be sure on the fuel system though... thanks for the advice!

 

My 2006 did the same thing a few years back and it ended up being the #3 coil that had gone bad. That was I guess about 5 years ago. They replaced the #3 coil and plug and it's run great ever since! As 1 saxman implied, the 4.2 is basically bulletproof. I read of all of the problems people on here are having with the Triton series V8's and the V6 has none of those issues. I will say that in my opinion, a 5000# trailer is probably asking a bit much of it though. It will do it with the automatic as you have, but probably not happily. I've got the 5-speed and my rated towing capacity is useless. And that's with 3.55's and the towing package.

 

I was really skeptical when I purchased the camper... it was so close to the max tow that I was not sure if it would actually pull it or not but took the chance. Believe it or not it tows that trailer like nothing! if I run between 55 and 60mph I Can get 10mpg and it will pull it at that speed all day long without issue. 65 does fine but MPG starts dropping off and 70 it will do but you can tell its really starting to push hard. We did a good deal of towing this summer and it did great! Even in hills it will hold 55 - 60 no trouble...

 

Wow! That's pretty good for a '6! Mine does okay on the hills, as long as I don't have too much of a load in the bed. With a heavy load on a long, steep hill, it will start to get a bit winded. I usually pull the hills in third gear, which is my strongest. I live in an area with a lot of long, steep hills too. My next truck I'll get one of the Ecoboost engines to give me better mileage and more power under load.

 

Good deal and glad it was an easy fix. Amazing that the new plug was bad! I've never seen that before. Your set-up is a natural for a fuel additive because burning so much fuel must be making carbon deposits in the combustion chambers. I've been using Sta-Bil Marine for Ethanol fuels in all our vehicles and equipment for years. Almost nine years in the truck. Never had any fuel system problems yet. Started using it when it came out at the stores and used regular red Sta-Bil before that, going back to the '90s. I mean in every tankful, every time. It keeps fuel systems clean and catalytic converters sweet. The engines always run like new and no 'fuel-system maintenance' has ever been done to any vehicle.

 

I use a bottle of STP Fuel Injector Cleaner in mine about every 5-6000 miles to do the same thing. It works great, I swear by the stuff! I've used it in every vehicle I've ever owned. Since I document all of my fuel expenses I just make a not on the receipt whether or not I used any additive. Although I've thought about using some of the better additives on the market, like Sta-bil or even Marvel's Mystery Oil. Does anyone have any experience with that?

 

Thank you for being a loyal STA-BIL® customer! We appreciate you using our fuel additives. Please do not hesitate to reach out if you ever have any questions.

Have a great evening!

If you're willing to give STA-BIL® a try we would suggest STA-BIL® 360° Performance. This additive will keep fuel fresh, will help clean the fuel system, has water handling capabilities, and rust & corrosion inhibitors - both above and below the fuel line. For more info on that item please see the link below. Please let us know if you have any questions.

STA-BIL 360 Performance | Gold Eagle

If anyone is interested in a free sample please just shoot us a PM with your name and address and we'll get that entered in.

Have a great evening!

 

"If you're willing to give STA-BIL® a try we would suggest STA-BIL® 360° Performance. This additive will keep fuel fresh, will help clean the fuel system, has water handling capabilities, and rust & corrosion inhibitors - both above and below the fuel line. For more info on that item please see the link below. Please let us know if you have any questions."


Thanks I will check that out. I have used Sta-Bil in this vehicle the few times I've had to stop driving for health issues and always been very impressed by its ability to keep the fuel fresh enough to allow the vehicle to start right up after sitting for as much as 8 months. I will check out the websites you provided, thank you.