1991 F250 460. I did a scan, not getting any codes. New cap, rotor, plug wires and plugs gapped to spec. I've been running fuel injector cleaner but not sure if I'm wasting money. Took off and cleaned the TPS and sprayed cleaner into the throttle body. New PCV valve. New o2 sensor. used 2 cans of starter fluid and couldn't find any vacuum leaks, but don't hear any either. Only odd noise sounds like one of the injectors on the right side kind of makes almost like a buzzing noise.


The idle will sometimes sputter, sometimes not, it's very sporadic. It seems to do it more in the first 5 minutes of running.
Vacuum test shows a very steady 18 inches. Compression check shows all cylinders very close to 155.

Any ideas what it could be? It's actually pretty light but I'm very **** about my machinery. Plus I'm going to be driving this truck to Texas soon.

 

Nothing? Should I just wait for the problem to get worse and register a code? I'm thinking if I fix this I can get better mpg (get about 10 mpg on freeways driving 55, 460, E4OD, and 4.10 rear gears).

Idle is sort of like this --------------------0---------00------------------0--------0-----------------------------------0-----0---0--0------------------0----0----------------------------------------0-

with the "0" being like someone is hitting the truck with a hammer that I can feel.

 

try running better gas if it gets better bump timing up 1 or 2 deg

 

I have seen a few cases of worn bushings in the distributor causing whacky idle and running issues as you described. The buzzing injector is also a concern to me.

 

I checked the timing by unplugging the SPOUT connector, and it held steady at 10 degrees, no bounding around. Fuel injection is new to me, as far as working on cars go. I'm really at a loss on this one. I think I may have to take it in.

 

I just went through something similar, pulled all smog equipment and cleaned up my vaccum lines, cleaned or replaced all sensors, haven't done the timing bump yet. I ended up replacing the injectors, they were original and the truck is an '88 so it was time. Put in accel ACC-150824 replacement injectors and it cleaned everything up, and they really seem to work well. I've heard bad reviews on them, but the price was good and install pretty easy, except that I was standing on a bucket to reach into the engine compartment and it went out from under me; nice scrape on my chest from the hood latch...

 

I just bought a 97 with a 460 and it has the same issue I asked my mechanic he said it is common withthose engines. It kinda feels like it has a very miled cam at times

 

One other thing to look at....these engines are very susceptible to ignition cross-fire. I would make sure the wires for adjacent firing cylinders are adequately spaced from each other. There are numerous TSBs out there for the 5.0 and 5.8L engines but the 7.5L engine can have the same issue due to similar firing order.

 

I finally got a code 32. Something to do with the EGR. Other than my crescent wrench that is not going to be able to fit up in there, I don't have a wrench that fits it. Looks to be about a 1" nut.

I can't get to the nut directly behind the EGR. My idea was to take the whole tube out and loosen ithe nut at the exhaust manifold that i can actually get to. Unless this code means something else. Any suggestions?

 

I went to a car repair shop. They said my EGR is stuck open, but didn't replace it. They said my PCM is going out but the part is obsolete by Ford.

 

I'm having the exact same problem. 1995 F150 5.0. Intermittent rough idle and jerking when driving. I've replaced a lot of stuff and so far still having issue. real pain in the butt. Runs smooth as can be sometimes, then will start stumbling again at other times.
Replaced distributor, voltage coil, O2 sensor, Throttle position sensor, fuel regualtor, alternator, battery, EGR valve, plugs, plug wires, etc...