Just got a '93 F350 with a 460 EFI 225K miles. It smokes and burns oil. The fuel seems a bit rich to me cause I can small it in the exhaust. I plan to do a tune as I am not sure one has ever been done, probably but?... Also there is black suet coming out the tail pipe. I am guessing this is oil pulled past the valve seals. I have read that these will dry out and crack and do not re-wet.
I plan to do a ignition tune up, cap, rotor, wires plugs. I am also going to replace the stock coil "original i think" with a 48KV TFI upgrade. The OE is 38KV I have read. Think I will gap the plugs at .055" instead of the .044" spec. I know it needs this tune up but don't think it will fix the over fuel or the smoke issues.
A good indication of bad valve guide seals is a puff of oil smoke at startup after the truck has been sitting.
For the fuel problem pull the vacuum pipe off the fuel pressure regulator and look for signs of gas, if any found replace the FPR.
Might also be a good idea to check for trouble codes. Go to fordfuelinjection.com and from the list on the right click on Self Test. You can also read there about the FPR.
hopefully some of the experts will give their opinion soon.
I wonder if the oil suet is messin with the O2 sensor?... its sounds like the heads need to come off and be freshened up. If your gonna do a tune-up id check the compression too... with 225K your motor is probly gettin tired, its possible that some of the oil is gettin by the pistons when the motors running too.
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Dan
1996 F-250, 351W under the hood
No smoke after sitting. Noticed that the truck didn't smoke at start up tonight after sitting a few days. I just moved it around in the driveway and it wasn't pumping out any suet after running for just a few minutes.
That's why I'm thinking seals and not guides. No suet when there isn't oil in the top of the motor and after running for just a minute or two the oil isn't thin enough to sneak through the cracks. That's my theory for now until I find out I'm wrong.
I'm not sure how all that suet will effect the o2. I will check the fuel system.
Yes I agree about the compression check, while I'm doing the plugs I will check each one and note it. Also, with 8.5:1 compression what should it be about 160 psi or so?
I'm going to eventually get rid of the EFI for a carb/distributor so I don't want to go nuts trying to optimize the system, but I do need to get passed inspection here in Texas. Since its pre '96 they do a simple sniffer test, its not bad but wont pass spitting suet.
I will let you know what I find when I get into it.
Agreed accept that the oil isn't being burned. It spitting suet.
The suet indicates inefficient combustion. Just as black smoke indicates inefficient fuel combustion. The hydrocarbon chains in the oil are not being rendered efficiently. If it were a little oil being consumed in the combustion cycle the oil would be more fully combusted, rendering energy from almost all the long or large hydrocarbon chains. This typically emits blue smoke.
In this case either the volume of oil or low ignition temps are not allowing for efficient combustion of either fuels, the gasoline or the oil. This is perhaps why the exhaust smells fuel rich, there may be nothing wrong with that system t all, it may just be the large volume of oil in the combustion chamber, lowering ignition temps and eating up oxygen keeping a large portion of the intended fuel from being ignited. It may also be over fueling exacerbating the situation, but the large volume of oil present in the combustion chamber would be causing a problem regardless.
I may be all wrong, but this is what makes sense in my head for now.
Little update, did the tune up. Plugs 6 and 8 were so badly oil fouled that there wasn't even a gap anymore, just built up carbon bridging the gap, nice...
The compression looks good, no blow by. In fact I checked the the vent tube from the oil fill tube to the air filter box, there was actually a very small amount of vacuum on the line at idle. This bolsters the leaky valve seal argument, either that or the bottom side of the of the intake gaskets have gone bad and its sucking oil and air.
Also, its smokes worse after letting off the gas and the engine is being driven faster by the gearing and the throttle body is closed. This apparently forces the engine to suck more oil was no oxygen to burn it.
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