First off let me say that I love this site. I have been a member for quite some time, but I rarely post anything. So far I have been able to find everything I need without even asking. With that said I guess its about time I speak up. I own a 2000 F-250 4x4 CC 6speed. Its pretty much a stock truck. 6637 mod, ccv mod, and muffler delete. Is all that I have done. I am also running an edge juice w/attitude. I know I need to scrap it for a dp, but the only reason I even have that one is because it was given to me.

Now for the strange part. I was reading on here about shimming the fpr, and I had a few 4-40 screws laying around so I decided to give it a shot. I ground it down to .070 in. and put it in. I didn't really notice a difference in power or throttle response, but the engine ran a lot quieter and more smoothly. Well, after the test drive I decided to take it out until I can get a fuel pressure gauge installed. I figured better safe than sorry. I took out the shim, cranked it up to check for leaks, shut it down and went inside. The next day I left for work, and right away I noticed a difference with the truck. It feels like I turned the chip up a notch. It idles better, runs better, and had a noticable increase in power. So now I'm wondering what it could be. All I did was turn up the pressure, and then put it back to stock. What could have changed?

I have always felt that the truck was weaker that it should be. The biggest thing I ever tow with it is a 10K travel trailer. And lets just say I havent been inpressed. It struggles just to tow that. I have had it in the shop more than a few times and no one has been able to find anything wrong with it. So I just accepted the fact that its just the way it is. But now I'm wondering If there is more to it. It is obviously something the scaners never picked up, and if thats the case what else is there?

Also I have changed the exaust back pressure sensor and cleaned the tube. I also changed another sensor, cant remeber the name now... the round one in the front right side of the the engine valley.

Sorry I went on so long, and thanks in advance for any input.

 

you've prpoably made a noticable mod to the PCM look up table, which isn"t a bad thing. In about ten stop start cycles, the pcm will reaccomodate itself to your driving style and all will be back again to normal.

I have mine set to LTFT of - 38 and I get great economy, but it is sorta gutless. If I battery discinnect it and then drag the trailer around, ltft goes to +10 and I have gobs of power, but poor economy.

 

You will have to forgive me. I get the basics of what your saying, but not the technical aspect. I think what your saying is that the pcm adjusted itself for the higher fuel pressure, which is why its running so well? So what your saying is that it will go back to being the snail it was. But also I've notice an increase in fuel economy. Maybe its just my lack of brain power, I just want to know why it ran so slugish before. And would a test drive of maybe 5 miles with the shim in really make that big a change in the pcm?

 

That can't happen. There is no sensor for fuel pressure, so the PCM is completely blind as to what the actual fuel pressure is.

No, it won't have any "learning curve". If it did, then every time you changed tunes it would have to complete several drive cycles learn the new parameters. The PCM is actually about as dumb as a brick. What more than likely happened is that you inadvertently fixed a problem. Maybe the FPR spring was not seated properly before you ever messed with it, so your fuel pressure might have been too low to begin with. Or when you cleaned out the EBP sensor tube or replaced the ICP sensor (from your description it sounded like the sensor you replaced is the ICP), you may have fixed an issue there as well.

 

ICP! Thats exactly what it was, just couldn't think of it. Thank you for clearing that up for me. I wasn't sure if the pcm in these trucks were able to learn or not. I changed out the sensors a long time back, probably about a year ago. So my best guess would be the spring not being seated correctly. It is a big difference, but it still feels weak. Is there anything else I can check? When I say weak I mean if I hit an overpass with my 10K trailer I lose 10 mph before I hit the top even with my foot to the floor.

 

That can be any number of things. What kind of boost pressures and EGT's do you see?

 

I dont think I have any boost leaks. I can get it as high as 23 psi, but romping around town between 6 and 8psi. Egts can easily hit 1000 even in stock tune. Romping around town between 600 and 800.

 

What setting is that when you see 23 psi of boost?

Also, 1000 degrees isn't that hot yet (assuming your probe is mounted pre-turbo). What tuner setting to you normally keep your truck at, and what's the highest EGT's you can reach on that setting?

 

23 psi is in setting 5 75hp.. I usually keep it in setting 3 drive. which is 55hp. and it will easily go through the roof. I never let it get above 1300, but at wide open wot I know it will.

 

Also I still have the stock exaust with the muffler delete, I know that probably makes a difference. And the probe is pre-turbo.

 

With the Edge, I'm not sure what others are seeing in that setting. Hopefully some of them can chime in. However, to me going well over 1300 degrees on just a 75hp setting seems a tad high.

 

I always just blamed it on the factory exhaust. I'm just curious as to what could cause it to be so sluggish.

 

Well, I developed a problem just in the past two days with my truck acting sluggish. Come to find out the PCM thinks my coolant temps are at 280 degrees. LOL

Not that you have the same problem (who knows), but it can be something obscure like what I found on my truck today.

 

Yeah, I have a feeling its caused by something small like that. All I did was mess with the fpr and it made such a big difference. I would just like to know what I could have changed when I removed the shim. Unless of course is was that the spring wasn't seated properly.

 

The factory exhaust straightpiped is supposed to flow 20% less than 4" exhaust.

Its worth it if your hunting for HP, but the muff delete should suffice.