Hey guys just in the past 2000 miles or so my 5.4 has been running poorly. I changed the fuel filter and it helped a little but still running poor. Also my exhaust doesnt seem like it sounds the same. I was wondering if the O2 sensors may be going bad at 110,000 miles but I dont have a check engine light coming on.

Any suggestions please!

 

How does the air filter look?

Can you expand on what "Running poor" means.

Like "engine shakes" or "slow acceleration" etc.

 

The air filter is clean I see it every day.

"Running poorly" means yes i do have slow acceleration, i noticed the performance really bad climbing hills, the motor doesnt pull at all and shifts down into 2nd gear. Usually 3rd gear pulls good but not anymore.

 

Are you using one of those K&N oiled filters?

 

No I have a K&N FIPK and the filter has about 9,000 miles on it. I havent cleaned it, but it still looks really clean.

 

I guess I don't know what a FIPK is but I will guess at a MAF for starters and point you to this link.

http://autorepair.about.com/library/faqs/bl827d.htm

When were your spark plugs last changed?

 

How long has it been since you did a tune up. The plugs could be worn out

 

The FIPK is just a cold air intake, or high flow intake. So I can see the filter all the time.

I imagine the spark plugs are the original plugs. I have only had the truck for 7 months.

 

I would start by cleaning the MAF and see if you get any improvement. I would also pull a spark plug and see what it looks like. The spark plugs are good for about 100,000 miles I think.

The Fuel Injection Performance Kit does not need to be oiled then?

I will mention a couple of other items.

Catalytic converters / exhaust might be plugged up or low fuel pressure.

Oxygen sensors may need to be replaced.

Do you get a check engine light?

 

I was kinda thinkin if its somethin electrical a check engine light would come on. I just was outside I moved my air filter around and unplugged some spark plugs and plugged them back in. I didnt start the truck again but I'll see if the small tinkering changed somethin.

 

Check engine light does not come on.

 

Im thinking more and more it might be clogged cats because you said you notice a change in the way the exhaust sounds. Did you smell anything like rotten eggs during the last 2000 miles?

 

put a vacuum gauge on the engine and tape it to the windshield and drive it. when started the vacuum gauge should read around 18" of vacuum, give or take. when the throttle is snapped it should drop to little or nothing. when the engine is held at about 2000 rpm the gauge should drop and then work its way back up to normal or close to it. while driving at a steady speed the gauge should read steady, if the exhaust is plugged the the gauge will slowly start to drop as the engine is loosing power. to make sure the exhaust is the problem loosen it up and lower it at the manifolds and drive to see if problem is gone. also i've seen bad fuel pumps, most of the time they have good pressure but little flow. use a fuel pressure gauge to check the pressure and flow. in my experience it should flow 1oz. per second. should be able to fill 16oz pop bottle in 16seconds.

 

This actually sounds alot like what I have been experiencing intermittently in my truck. Which is the same setup except has 125k. Mine had a tune up at 100K, so I don't think it should be plugs. My K&N should be fine too. I cleaned the MAF about a month ago, so its a tossup there. I think the plugged cats could definately be my problem though. I did notice a slight exhaust gas smell the other night while it was running bad. My power loss is mainly low in the powerband, less than 2300 rpm. It seems to come and go somewhat. I thought it was running pretty well today. Any Ideas? How much low end will I lose cutting the cats off?