93 4.9L running rough
#1
93 4.9L running rough
I have changed plugs, wires, cap, rotor, coil and O2 sensor. Cleaned the IAC valve and verified that its working. Checked MAP sensor and TPS sensor. Truck is running rough through all RPMS. When I changed the plugs they were black like its running rich. Air filter and fuel filter aren't very old. I am pulling my hair out trying to figure this out without going broke buying any more unneeded parts. I am not a mechanic but Im usually able to fix anything on my trucks. Any help would be greatly appreciated. Im starting to think about the EGR and fuel pressure regulator. Am I leaning in the right direction?
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I haven't checked compression yet. I checked my oil and it smells like gas. If I pull the vacuum line from the fuel pressure regulator there is no change in the way that the engine runs, and Im smelling gas at the tailpipe. I know these can be symptoms of a bad FPR. Can a bad EGR also cause these things?
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Had the same issue you are having....
I dealt with a rough running 1994 4.9 for a year. I replaced everything you mentioned above. It turned out it was the fuel pump. My mechanic replaced it and then it went bad again (never buy Standard Motor Products fuel pumps, they were bad luck for me). Finally, on the third try, we went with a Motorcraft Fuel Pump and problem solved.
If you can, I would check your fuel pressure and see if it is consistent. It might be a good idea to replace the fuel pressure regulator, too. Fixing those two things worked for me.
Let us know what you find out.
If you can, I would check your fuel pressure and see if it is consistent. It might be a good idea to replace the fuel pressure regulator, too. Fixing those two things worked for me.
Let us know what you find out.
#11