CEL and rough running under 2000rpm

[Randy960]

My 98 4.0 is throwing both a PO174 (engine lean, bank 2) and a PO304 (cylinder 4 misfire) code. They usually come back within 5 or 10 minutes or clearing them. The engine seems to rough up to 2000 rpm, and fairly smooth above, but still down on power. I pulled the spark plugs to find that the cylinder 5 plug was cracked and the (screw on style) end of the plug was stripped out. So I replaced all of the plugs and I'm still having the same problems. The only thing I can think of is the fuel injectors, or a messed up o2 sensor confusing the computer. Can an o2 sensor get damaged by dumping raw fuel on it?

 

[JaBradt85]

IAC valve or MAF

 

[Earl43P]

Bad plug wire
Coilpack
Bad injector (swap with one of the others and run it to verify)
Low compression
in that order is how I'd approach that problem.

 

[Randy960]

Its not the IAC valve, or a vacuum leak, because the engine run normal at WOT, and it doesn't. I've switched plug wires around to no avail, plus they're only a year old. plugs, air filter, and fuel filter are new. Fuel pressure is good, vacuum is good. So Tomorrow I'll do a compression test, try to get a voltage reading from the maf, and then roll a die to figure out if i want to buy a maf, injectors, or a coilpack first. Any more ideas?

 

[Randy960]

injectors. I had a set of injectors overnighted to me because im doing a lot of driving sunday and monday, and they fixed it. If I had to guess, I would say that the fuel filter that I took off was probably so clogged with crap that it blew through and clogged the injectors. I think is was the original, because it was a motorcraft part, and the previous owner doesn't seem like the "ford original parts" kind of person. I was thinking I had replaced it when I got the truck, but I hadn't. Anyway, thanks for the help everyone.

 

[97fordrunner]

How did your truck idle when cold? and warmed up? My truck is a '97 and it sounds like it is doing the same thing yours was, My fuel filter was old when it started to run like crap and I replaced it so I am leaning to the same problem that you had, how much did the injectors run you if you don't mind my asking?

 

[Randy960]

It seemed to run about the same reguardless of temp. I got my rebuilt injectors from lucky7autoinjectors on ebay for 112 shipped overnight.

 

[97fordrunner]

ok thanks