EFI 460 help
Thread Starter
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Mountain Pass
Joined: Apr 2016
Posts: 241
Likes: 2
From: Duluth, Minnesota
EFI 460 help
I am new to the whole fuel injection deal here and generally new to trouble shooting and I don't have a keen ear for the miss vs ping vs fuel starved sounds so bear with me please.
I have an 88 f350 with the efi 460. First of all, changed fluids, new vacuum lines, absolutely no codes, engine runs fine when cold, but when warm, when in 3rd, 4th, and 5th, the rpms go down, and it sounds like it is fuel starved from what I think, but it is hard to distinguish sounds as the exhaust broke right after the gutted cat so it is hard to hear. While in 3rd from half to full throttle at around 30 mph, it will display symptoms and eventually stutter once or twice, then pull through with power.
I have a video of the symptoms, this is in 4th gear, and to stop whatever is happening, I ease off the throttle just a very small amount.
I have an 88 f350 with the efi 460. First of all, changed fluids, new vacuum lines, absolutely no codes, engine runs fine when cold, but when warm, when in 3rd, 4th, and 5th, the rpms go down, and it sounds like it is fuel starved from what I think, but it is hard to distinguish sounds as the exhaust broke right after the gutted cat so it is hard to hear. While in 3rd from half to full throttle at around 30 mph, it will display symptoms and eventually stutter once or twice, then pull through with power.
I have a video of the symptoms, this is in 4th gear, and to stop whatever is happening, I ease off the throttle just a very small amount.
Thread Starter
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Mountain Pass
Joined: Apr 2016
Posts: 241
Likes: 2
From: Duluth, Minnesota
Sorry, I meant that there were no bad codes, did pass with an 11. Can't hear inside the truck, but would the fuel pressure also bring down the tach though? Doesn't make sense if my coil is slowing down on behalf of the fuel pressure. I don't think it is the intank pumps as it happens regardless of the tanks, could be high pressure pump maybe... i'll get a gauge on it and see.
Post Fiend
Joined: Jun 2003
Posts: 8,209
Likes: 12
From: Black Hills of SD
Have you replaced the fuel filter? I know you say the cat is gutted but the symptoms resemble a partial obstructed cat. I've seen them "gutted" but still have a big chunk of the monolith sideways at the outlet causing blockage.
Thread Starter
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Mountain Pass
Joined: Apr 2016
Posts: 241
Likes: 2
From: Duluth, Minnesota
Ok update, so I ended up getting a code again, it was the Intake air charge sensor. Replaced and no change. I also did the trick by grounding pin 6 on the eec self test, and ran the pumps. I got a consistent 39.5 psi. Other people have said with this method you should get 40-45 so I think I'm in the clear for that. I found out my local JY that I'm in good with is getting a blown up 460 block from one of the jy workers' f350. Very easy access. I am going to come home with an extra IAC, Injectors, hopefully an egr if it isn't ripped off when the motor got pulled, and TPS. Any more ideas on it? As far as I know, the pumps running would be at full capacity right? So max fuel pressure would be 39.5? I think that is enough?
Fleet Mechanic
Joined: Jan 2013
Posts: 1,305
Likes: 8
your fuel pressure is below spec (if only slightly).
as the fuel pump warms up it could be having trouble keeping up to the demands of the engine. you could try hooking up a gauge and driving with it taped to the cowl/windshield area and see what it happening with things warmed up and under load.
as the fuel pump warms up it could be having trouble keeping up to the demands of the engine. you could try hooking up a gauge and driving with it taped to the cowl/windshield area and see what it happening with things warmed up and under load.
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Fleet Owner
Joined: Aug 2005
Posts: 23,666
Likes: 301
From: Easton,Ks
Fuel pressure gauge are never right on but 39.5 is very close as the PSI at sea level with that test on a standard day, should be 39.3psi. To get over 40psi you would have to go to death valley Calif or have blower on it. It has a 39.3 lb spring in the fuel pressure regulator.
But as stated above you need to have the pressure gauge on it as you drive to know what is happening.
But as stated above you need to have the pressure gauge on it as you drive to know what is happening.
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Cargo Master
Joined: Jun 2013
Posts: 3,174
Likes: 15
From: Somewhere n North America
Engines are easier to diagnose over the internet when all the codes are listed, and in order of test.
KOEO - (O) Self-Test Codes =
KOEO - (C) Continuous Codes =
KOER - (R) Self-Test Codes =
Make sure your A/C, Heat, Radio, etc. are turned off when testing.
KOEO - (O) Self-Test Codes =
KOEO - (C) Continuous Codes =
KOER - (R) Self-Test Codes =
Make sure your A/C, Heat, Radio, etc. are turned off when testing.
Thread Starter
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Mountain Pass
Joined: Apr 2016
Posts: 241
Likes: 2
From: Duluth, Minnesota
Ok got my gauge on it and I'm getting 32 psi whether hot or cold, I get 40 when I give the throttle a ram. When people say 40 at wot, do they mean the whole travel of rpms at 40? I get 40 when I give throttle but then 32 when held anywhere above idle
Fleet Mechanic
Joined: Jan 2013
Posts: 1,305
Likes: 8
at this point i would probably be testing the throttle position sensor. it could have a bad spot(s) on it and you wouldn't necessarily get a code.
hopefully, subford or vjsimone will return and help out ... their troubleshooting skills make mine look sad.
hopefully, subford or vjsimone will return and help out ... their troubleshooting skills make mine look sad.