I`m still having problems with my `89 F-250 4x4. It has a 351W with a C6. When it starts cold it will run terrible for a few minutes and then the idle will even out. After running it for 20 minutes or so with no problem it will start to spit and sputter under acceleration. I cannot figure this stupid thing out, I`m about ready to set it on fire. Gotta match?

The things I`ve changed are a follows....the O2 sensor before the cat, which I changed yesterday. MAP sensor, Intake Air Temp sensor, Coolant Temp sensor, Fuel Pressure Regulator, Spark Plugs (properly gapped), EGR valve and EGR position sensor or (EVP), Ignition Coil.

I can`t think of anything else off hand. If I remember anything I`ll post it. What else can I possibly look at?

 

What codes if any is the computer showing?

 

you changed the plugs, how old are the wires and cap/rotor?

 

The plugs are about a year and a half old. The wires and cap and rotor were not changed by me, they were changed when I bought the truck. I inspected the cap and rotor and all looks good.

 

I performed a test on it this morning, here's what I got from the scanner...

KOEO test

DTC 34:
1) /cars only/ Insufficient EGR flow or EVP voltage high (sonic) or pre-sensor voltage high or out of specification.
2) /trucks only/ EGR control circuit fault (ex. V8 models)
3) Defective EGR, pressure transducer sensor
4) /trucks only/ EVPP control system fault/ voltage higher than closed limits on V8 models

DTC 14: I could not locate this code, the OBD tool said to go to their website, the code was not there, I performed a search on the web as well.

DTC 34: PFE, PFE sensor is/ was out of range

DTC 96: Fuel pump secondary circuit fault/ high speed fuel pump relay open
_______________
KOER test

CYL 8: There was no description for this, just the code

DTC 12: V8 RPM out of range (throttle kicker)

DTC 44: Oxygen sensor signal indicates rich- excessive fuel, restricted air intake or inoperative thermactor system

DTC 34: same code as KOEO test

 

Forgot to mention, the smog pump (air thermactor?) has been disconnected. Not sure if it matters any.

 

Ok maybe it's just me but... if you disconnected the smog pump you are probably kicking some of those codes because the o2 sensor doesn't have the o2 pump running anymore....

You say kicking under load and rough idle????

Maybe it's just me (and this is outta left field) but anyone else thinking fuel/fuel pressure/fuel delivery problem?

Have you changed the $6 fuel filter?

 

lol i was just going to ask about the filter lol

 

i would unbolt the exhaust right before the cat.. i had a thunderbird that would run fine for 10-15 mins then get really hard to keep running.. i looked under it and found out the cats were clogged!! they were glowing orange.. had them removed and it ran fine there-after

 

The smog pump was already disconnected when I bought it. I didn't even know that these trucks had smogs until I discovered it was there. The pump is still attached, the hoses were cut and the pulley was bypassed.........I'm guessing it seized up.

No, I have not changed the fuel filter yet, I will change it this week.

As far as the rough idle, it starts fine in the winter and usually runs rough for a period of time 10 minutes after use, then the idle evens out and it runs great. During the summer the roughness begins sooner after starting the truck, then it will go away after about ten minutes. Then I drive it for maybe 15-20 minutes and the truck will be fine, then all of a sudden it will want to skip and misfire under acceleration. The problem seems to occur with precise punctuality. It happens at the around the same time, almost every time.

 

If you say it fires up fine in either condition, I'd be inclined to suspect fuel delivery like the others are suggesting. Your codes are a bit deceptive, I think, due to that smog pump being bypassed. If I were you I'd just start at the basics. Test for your air, fuel, and spark and see what you get. Whatever you do, don't start throwing parts at it until you've troubleshot your problem. I would, however, look into new wires. Me personally, I like to do new wires whenever I get new plugs and vice versa. Just my .02 though. Good luck and keep us in the loop, ESPECIALLY if you figure it out.

 

This would be a good idea... If you have catalytic converter(s) you might want to unhook the exhaust and run it... However cats collapsing usually robs the engine of power at all times. I somehow suspect that the PO probably cut the cats out if he bypassed the smog pump... If you do have clogged cats it will rob you of power since your engine can breathe. Kinda like eating to many beans and not being able to fart...

I would change the fuel filter and put some sea foam in the next tank of gas. It will clean the fuel system out and remove any water that might have gotten in your tank from bad gas or sitting to long. I just did a write up and there is one on RJM about how to clean and "rebuild" your injectors. I have heard of several cases where a rusty tank has let enough fine particulate get through the tank screen and clog a fuel filter and even the injectors. However you are idling fine so I assume your injectors are fine so we'll leave that alone for now.

Also your air pump can be taken off, taken apart, lubed up and reinstalled. This won't fix your 02 sensor and EGR code problems, but if your cat is still there it needs the extra 02 to burn the hydrocarbons up... Doesn't make sense to have a cat without a air pump or vice versa... Also RJM has EGR eliminators... Probably to late for that ship since you already replaced those parts... Heres the website anyhow. http://rjminjectiontech.com/

Wires only need to be replaced every 100K maybe... IF, you have put good ones on to begin with... Don't be cheap! I use 9mm Ford wires when I can on my trucks. If not Accel 8mm wires work good to. I also use zip ties to do custom gappers (yes i did pick that tip up from Joe on PowerBlockTV!)...

 

I'm not sure what brand wires were put on the truck, they were already there when I bought it almost two years ago, I can only assume they are cheap. The next two things I will change is the fuel filter and the plug wires.

Also forgot to mention that last summer I shot half a can of throttle body cleaner through the top end. That didn't help. I also used a bottle of Marvel Mystery Oil fuel treatment, its supposed to help clean the injectors. I used Chevron Techron in a different tank of gas as well. None of these treatments had an effect. I will try the Sea Foam though.

 

Personally I stay away from the magic potions. There are two very defined schools of thought on liquid treatments of many sorts, so it's up to you.

 

liquid treatments on a whole are probably going to be a bandaid fix but if you have water in the tank that is making the engine jump and sputter you need more alcohol in the tank to bind with the water to remove it from the system... IE Sea Foam or Heat...

The fuel filter is a common cause and a cheap thing to eliminate from the equation. Plus if you don't know how old it is, it's best to replace it...

Another thing to think about... Do you have 2 tanks and does the problem persist with both tanks? It doesn't sound like a fuel pump problem but inconsisten fuel/fuel pressure can cause the problems you describle. I had Thumper die on me several times and not want to start... It was only the high pressure pump mounted to the frame rail...