Sorry for the long winded post but thanks for reading.

Ok so recently my 93 F150 5.8L 4x4 e40d has developed a really rough idle and seems like the valves are burnt when I am driving. I can run about 5-10% throttle and the engine seems fine, once I get above that it just sounds like what I would guess would be the exhaust valves leaking. Its hard to explain the sound but kind of sounds like combustion escaping or possible clogged exhaust. It does not seem to be tied to the rpm's. I can get the truck to rev up and shift through gears with the little throttle.

I have had an EGR code come up. I tried cleaning the valve (hosing it down with cleaner) thinking I fixed it, since that code went away. I still get codes but I will pull them again to see if there is anything new. I replaced my passenger exhaust gasket months ago due to leak and need to do the same to the driver side.

I know with a bad EGR I would get lean combustion which would take out my valves. I did have this happen before but not as bad. I just sucked seafoam through my intake and fuel and it went away. That didnt work this time, but made it a little bit better.

Anyway before I start dumping money getting valves machined does anyone have any other thoughts on what it could be? I may try to buy some used heads since that may be cheaper than all new valves and machine work.

As I write this I remembered that when I did the exhaust gasket I didnt care about putting hose clamps back on my air injection system (I misplaced them). I was told that would cause my cat to get junked up if air leaked out of the hoses, but I thought it would last long enough for the weather to get nice so I could cut the cat off. We dont have emissions here in Iowa.

Thanks
Dan

 

Hard to say, cutting off the cat could be a good start to make sure it's not clogged. Also check your fuel pressure under load, but burnt valves really are vary rare and would show big symptoms, and not like this.

Thinking more along the lines of plugged cat or fuel filter.

 

I agree with the big O. However if you are still concerned with a possible valve problem then do a compression test.

 

Sorry to brig up an old thread but I thought I would give my findings so far. Sorry for being late doing this but between selling a house, getting married and buying another house I have been kinda busy.

I cut the rear cat off and that helped out a lot. Went from running REALLY BAD to just pretty bad. I also swapped out my fuel filter. Found out that just by jiggling the fuel filter the rear line fell off so thats not good. Anyway it still doesnt run the greatest. 10% throttle its fine and sometimes it seems that its fine up to 40% or so. I have noticed that if I start getting to half a tank it runs really bad. I make a 1 mile trek to get gas and it runs better. This is leaving me to believe that its definately a fuel pressure problem but it could be related to the cats as well. I cant cut the front cat off otherwise I will only have 1 foot of exhaust so once things slow down I will hopefully get a replacement under there.

Thanks for everyones help.

Dano