5.8 (351) Mystery
11-28-2015, 03:19 PM
#1
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5.8 (351) Mystery
Have an unsolvable issue with my engine on my 1995. Engine was running fine in the morning and an hour later it seemed to run only on 6 or 7 cylinders. Is runs rough, has a loss of power and driving light on the petal (but put the load like going up a slight incline, accelerating or trying to maintain speed) it shakes/chugs likes it has a serious engine miss. I replaced the spark plugs, wires, cap & rotor - still runs the same. Changed out the ECU - still runs the same. Changed the TPS (due to KOEO code) - still runs the same. Had a fuel rail/injector cleaning and changed the fuel filter at a mechanics garage - still runs the same. Searched for vacuum leaks - none found. Filled the fuel tank with drygas and all kinds of fuel injection cleaners ran tank full after tank full for the last month - still runs the same. I just replaced all the spark plugs again just in case there happen to be 1 or 2 bad plugs - still no change. But all spark plugs pulled were light tan in color and that tells me they are firing correctly. I rechecked the ECU again looking for more codes - but keep getting 111 (System Passes). But I finally did find a vacuum line that at some point became unhooked and plugged it back in. It was on the rear passenger side of the engine heading to the big hoses were there was a vacuum selenoid of some sort for the emissions system. So I am lost and looking for input.
11-28-2015, 03:58 PM
#2
Senior Member
I would suspect something like a bad valve push rod. I'm not sure sure if that would set off a code.
I would try removing the spark plug wires one at a time and see if you can determine if a cylinder is misfiring. I would suggest a compression test, but this is easier.
I would try removing the spark plug wires one at a time and see if you can determine if a cylinder is misfiring. I would suggest a compression test, but this is easier.
11-28-2015, 06:49 PM
#4
Like Jayber said, test your fuel pressure. Go buy a gauge. For what you just spent trying to guess your way through, you could have bought 5 or 10 of them.
You need 30 to 45 psi If you turn the key to on and have less than 40 psi, you have a problem. If you have close to 30 or less, you found your problem.
If the fuel pressure is good, do a compression test.
If one cylinder comes up low, do a wet test so you can distinguish between rings or valves being the issue.
You need 30 to 45 psi If you turn the key to on and have less than 40 psi, you have a problem. If you have close to 30 or less, you found your problem.
If the fuel pressure is good, do a compression test.
If one cylinder comes up low, do a wet test so you can distinguish between rings or valves being the issue.