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.

 

absolutely no codes = bad.
pass code "11" = good; so please clarify that part.
i am leaning towards fuel pressure ... check fuel pressure with a gauge at the schraeder valve on the fuel rail.

 

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.

 

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.

 

The previous owner gutted it, I can see through it. The end of the cat is still the hottest part (temp gun) so I may pry it off. Fuel filter replaced twice now

 

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?

 

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.

 

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.

 

I'll see what I can do. Might have to zip tie the hood down.

 

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.

 

I have fully tested all codes, I have none, code 11=pass koer, koeo, and continuous memory.

 

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

 

with no trouble codes and fuel pressure looking good it might be time to go old-school and put a vacuum gauge on it.

 

I get a solid 18"

 

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.