Rough Running V10
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Elder User
Joined: May 2004
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From: Phoenix, Az
Rough Running V10
I recently (2 weeks or so) replaced the heater tube that goes under the intake manifold. Truck ran fine first day, then developed a miss. Turned out to be a bad COP. Replaced that and still had an annoying roughness. After driving it, it seems to run fine when cold, then gets a bit rough after it warms up. Idle in gear is a bit rough. Worst part is getting on the freeway. Going down the ramp, about 55 mph, high gear, about 1500 rpms. Give it a bit of throttle to pick up speed, it runs very rough, until it downshifts and rpm's come up. But it has a roughness at light throttle, low rpms. Truck was running fine before R&R intake manifold. No codes or pending codes on the scanner. I'm not sure where to start looking for the issue. I am suspicious of a disconnected vacuum line at the EVR, but can't see it without removing parts.
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Elder User
Joined: May 2004
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From: Phoenix, Az
A thought has crossed my mind. If- my helper got the vac supply line connected to the EVR, but NOT the vac line going to the EGR, there would be a vacuum leak when the EVR signalled the EGR to open. Is it possible, that a 1/8" vac line being open, cause a rough running situation? I am thinking hypothetical at this point, until I can actually see the vac connection. But, I may go out this afternoon, and hook up a vac pump to the EGR signal line to see if it is open.
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Elder User
Joined: May 2004
Posts: 749
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From: Phoenix, Az
Got into it today. Had to take off a couple of easy parts, but verified the vac lines are on correctly to the EGR controller, and the fuel pressure regulator. So, now I am finally getting a code for random misfire. Great code, could be a bunch of stuff. I checked the fuel pressure KOEO, then started it and fuel pressure is in spec. I did find a fault in the emission canister purge valve. I removed it, and the little vacuum line port doesn't hold vacuum. You might as well say its a vacuum leak. The line going to the TB spacer holds vacuum @ the purge valve, and excess pressure from the tank line vents to the TB spacer hose.
I basically blocked the line to the TB spacer and also the small vacuum line. So, the purge valve is out of the picture.
The truck still runs rough, and doesn't throw another code, but I haven't driven it yet. I did notice when the engine runs smooth, the STFT is low, .50 to 1.5 or so, + or minus. The LTFT is pretty stable from 0 to 1.5 +-. When the roughness starts, the STFT goes nuts, up to +9, and up and down. Im not sure what is up unless an injector is sticking open.
I basically blocked the line to the TB spacer and also the small vacuum line. So, the purge valve is out of the picture.
The truck still runs rough, and doesn't throw another code, but I haven't driven it yet. I did notice when the engine runs smooth, the STFT is low, .50 to 1.5 or so, + or minus. The LTFT is pretty stable from 0 to 1.5 +-. When the roughness starts, the STFT goes nuts, up to +9, and up and down. Im not sure what is up unless an injector is sticking open.
Hotshot
Joined: Jul 2013
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so 99 truck with how many miles?
could be a dozen or so possibles
when was the last time the intake, combustion chamber de-carbed?
piston rings probally have a good layer of crud.....ever engine flush before oil change
seems like the engines ford said need 5W30 are running crappy compared to the engines they are saying to run 5W20.
could be a dozen or so possibles
when was the last time the intake, combustion chamber de-carbed?
piston rings probally have a good layer of crud.....ever engine flush before oil change
seems like the engines ford said need 5W30 are running crappy compared to the engines they are saying to run 5W20.
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