my 300 started running rough and fuel milage and power dropped. then I gave it a tune up and milage went to 16-17. I was impressed but It did not fix my problem. . Now Im thinking it may be a fuel problem. So I change filter started using berrimam B12 to help clean my system. This to has not yet made a difference. I notice the miss mostly at lower speeds but can fill it at highway speeds. It feels like I hit a small bump in the road when it misses. Is this a fuel injector problem or vacum problem. If this is the injectors is there a way to clean them my self or any suggestions would be appeciated. Also I would like to know what a downpipe is or maybe a photo or link thanks

 

Check your vacum lines by spraying them with carb cleaner or ether. Do one at a time.
If the engine picks up speed when you spray a vacum line-that line has a leak

 

It would help tremendously to know something about the vehicle. What year and model?

Fuel injectors rarely are a problem, but seafoam works marvels at cleaning out engines. Put a can in the tank, and dump another can into the brake booster vacuum line. That'll clean 'er out real good.

Did you use quality parts or the cheapest junk that Autozone sells? Quality tune-up parts make a huge difference in how a truck runs.

 

I have a 1995 f-150 short wide 4x4 300 standard 3.55 rear. Tune up parts came from napa could not see paying $40.00 for a cap and rotor from ford. I am not familiar with seafoam and why put it in the brake booster?

 

something else you should do is remove the intake air temp sensor and clean with throttle body cleaner or just replace it they are about 12 -14 dollars.

 

Make sure that your TPS is working correctly. The reason that you put the seafoam into the booster line is because this line connects directly to your plenum, thus feeding all of the cylinders. Seafoam is good stuff. I add one to my gas tank everytime I change my oil. Add another 2/3 can to my engine oil, the remaining 1/3 down the carb.
When you add the seafoam to your booster line have someone in the truck to keep up the rpms(this vacum "leak" will want to shut it down). Slowly pour into the line, I use a funnel for this. After you've added it, shut off the truck and let it sit 5 min. or so. Reconnect the booster line and fire it up. It will smoke for a few minutes-A LOT. This is fine, that smoke contains a lot of carbon build-up. I would highly suggest that you do this somewhere with plenty of ventilation and far enough away from complaining neighbors

 

the can says just to use 1/3 in the booster line......should i just do that or give it more?.....mine is a 95 with only 111,000 miles on it so i couldnt imagine it has to much build up in it.

 

ok after running it through the vac. line and and putting the rest in the gas tank i went from about 150-160 miles per 3/4 tank to 195 miles on 3/4. I guess getting all that buildup out really helps.