highspeed=roughrun HELP
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highspeed=roughrun HELP
I have and 89 F350 with 5.8l efi engine. When I purchased the truck a few months ago (after it sat for about 5 years) it got a new rear fuel tank, new rear fuel pump, new fuel filter, also new plugs wires cap and rotor. I cleaned the IAC valve and it runs reasonably well ( idle is still a lil choppy some time) but i has only seen about 200 kms since i bought it. The problem is once it get up to about 80 kmh on the highway is feels like it is misfiring or flooding with fuel as it loses power and becomes very jerky and shutters. additionally it used approx 50 liters of fuel to travel 140 kms (not impressed) any advice is greatly appreciated as I am running out of things to try replacing to fix the problem.
Lead Driver
Joined: Aug 2006
Posts: 5,670
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From: Sand Lake, MI
As always with a problem like this first thing we ask you do is run the self test and check it for any stored codes, if it gets a system pass for "KOEO" and "CM" then move on and run the "KOER" test.
If you do not know how to run a self test see>Ford Fuel Injection How To Run a Self-Test
Fuel pressure, check it and verify its not to high, and it holds within 5psi of spec for 1 minute after shutting engine off.
If you find its way to high to start with or bleeds right off to zero in a few seconds for example, there are some tests aid in determining what the problem is.
If you do not know how to run a self test see>Ford Fuel Injection How To Run a Self-Test
Fuel pressure, check it and verify its not to high, and it holds within 5psi of spec for 1 minute after shutting engine off.
If you find its way to high to start with or bleeds right off to zero in a few seconds for example, there are some tests aid in determining what the problem is.
Posting Guru
Joined: Jun 2003
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From: southwest michigan
Running a test really help narrow things down, since at this point, we don't really know where to start.
BTW, have you made sure mice haven't made a nest in your air filter yet. For some reason, the mice around here like to do that when vehicles sit for awhile.
Elder User
Joined: Jul 2010
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From: Paradise CA
Yeah first get the numbers ran, because with the EFI, the computers can be tricky and will run very weird if its been messed with, or just some little chip is fried, It sounds to me like it could be the TPS, that controls the throttle and air/fuel mixture and that can make it idol funny and can make the motor run with a rich fuel mixture at higher speeds and make it suck a lot more gas, But get the numbers ran and see what comes up, if you do that it can be fixed with a simple part
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Senior User
Joined: Jun 2010
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From: Sodus, NY
Sound like we are having the same problem. So far I have changed the plugs, IAC valve, fuel pressure regulator, and the temp sensor. I ran the codes and I came up with about 10 different codes. One was for the EGR valve not opening properly, and the EVP was not reading right. The EVP gets its reading off the EGR. So my step is going to be changing the EGR valve.
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Logistics Pro
Joined: Mar 2005
Posts: 4,698
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From: Mexico, Missouri
You can check the operation of the EGR valve by removing it and checking to see if the plunger is operational. There could be a rupture in the diaphram, so as to not let it work correctly. IT could also be really gummed up. if you have access to a haynes or chilton manual, it will give you instruction on how to test the EVP and the EGR. I just went rounds and rounds with my SMog system. It all boiled down to damaged/faulty exhaust. Both cats shot, muffler shot.
Another operational check is with the EGR Vacuum Regulator (EVR). Link to this site for detailed information. Extremely useful.
Ford Fuel Injection EGR Vacuum Regulator (EVR)
Another operational check is with the EGR Vacuum Regulator (EVR). Link to this site for detailed information. Extremely useful.
Ford Fuel Injection EGR Vacuum Regulator (EVR)
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tried changing the map sensor too....got a used one and no difference....when the vacuum line is off the map sensor the idle drops and when the vac line is reconnected the idle picks up again...this is normal correct?
Posting Guru
Joined: Jun 2003
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From: southwest michigan
I would fix the EVP first. The EVP controls the EGR valve, if the EVP is not working your EGR valve will not function correctly. If your EGR valve is screwed up, your EVP will still perform just fine.
Posting Guru
Joined: Jul 2008
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You could also try checking your coolant temp sensor. When the truck is cold, it'll run better on larger amounts of fuel than it will when warm; that could explain the harder running when up to operating temp.
