I have noticed a gradual decline in power in my truck, 2000 7.3 6 speed, over the past 2 years. I have been hauling the same load to the same place and it just doesnt have the stuff it used to. It has a few miles on it, ~235k (bought it with 173k cause i knew the owner), but has been serviced very well (oil, fuel, t-case differentials, etc.) I have tried all sorts of injector cleaners hoping that was it; didnt help. I bought a boost gauge and it makes good boost, new turbo at 195k. I just cant pull the grades that i used to but it has gradually gotten worse.

Does anyone have any ideas? My next idea was to maybe make up a gage to test the HPOP, if i can find a set of directions to do that. The last time i sent an oil sample was at about 220k and it was very good; this truck has had synthetic oil its whole life.

I have no idea.......please help

Matt

 

Gonna bump it. I am curious to other may say.

 

I had the same problem with my truck. Gradual loss of power and also fuel economy. If you have a stock exhaust system, check to see if it is somewhat clogged. On my 99, it had a can type thing with honeycomb material inside. I was told that it was some kind of converter or flash arrester. I don't know. I couldn't even see light through it with a spot light shining through one end and me looking in the other. I got a hold of it with a pressure washer and blew all kind of crap out of it. It was better, but I just deleted it completely instead of reinstalling it. I got a lot of power back. I hear the turbo whistle a lot more now, but I really like that sound. My up pipes are also leaking, but I am going to take care of those this weekend. Don't know if this helps, but figured I would share anyway.

Good luck

 

on your uppipes, you going with the bellows up grade or just replacing the gaskets?

 

For now, I'm just going to replace the donuts. I have an early 99 so I plan on upgrading it to a bigger tubo off of a 99.5 or later. When I get the money saved up that is. I plan on replacing the stock up pipes with the bellowed ones when I do to that project. It will be a while, so for now, I'm just going to stick a $20 bandaid on it.

 

I am suffering the same fate myself, but I think mine is an extremely obscure problem. However I will share with you Some of the common things to check, and observe. I am sure others will chime in as well. First though, the best thing you can do for yourself is get an Auto Enginuity. First I will list a few items to observe, then things to check.

1. Does the truck start fine in 5-6seconds? This can indicate either low compression, bad glow plug system, HPOP slow to produce pressure, IPR going bad or plugged.

2. Does it settle into a nice smooth idle? Rough idle can indicate worn injectors, aerated oil in the HPO system, air in the fuel system(common). A rolling idle can indicate a severely plugged fuel filter, IPR or ICP going bad causing hard to control ICP pressure.

3. How much boost is it making? Is the truck stock or modified? Boost on a stock truck should approach 18psi. If not, then you could have a plugged air filter, need to readjust the wastegate, check out the Vacum lines that control the wastegate, and look at your up-pipes at the back of the turbo.

4. If you take off your oil filler cap, how much blow by do you see? Should be a light mist that you can easily put your hand over. This indicates ring wear

5. Does the truck ever stumble, miss, run erratic, buck, or otherwise run poorly intermittantly? Usually this is caused by an electrical gremlin of sorts. It is not uncommon for the UVCH(valve cover harness) plug to work their way loose inside the Valve cover though this will result in codes.

6. Have you ever pulled codes? If so what do you get?

7. Do you get smoke from the tailpipe and what color when starting, idle, or under acceleration? You should see some light colored smoke on startup that quickly fades away. A bunch of white smoke at startup is likely a bad glow plug system. Under acceleration on a stock truck you should only see a very faint haze of dark colored smoke, if any at all. If you are getting heavy smoke on acceleration or towing grades, then you likely have an air restriction, either intake, or exhaust - malfunctioning EBPR, or fouled muffler.

8. Does the engine seem to have a top end knock or cackle that is unusually loud? This may be hard to detect if you are used to it, but try to compare the sound of yours wit a few others on road, at a stoplight, in a parking lot, etc. This usually indicates excessive air in the fuel.


Assuming the engine otherwise runs fine, but is low on power or mileage, here are a few common things to test for, Either with a scanner(AE) and or manually.

1. Up-Pipes leaking. This is very common on the 7.3 and has time and again been reported to cause loss of power, and economy. If you are loosing exhaust pressure to the turbo, you are making the turbo far less efficient. This can be evidenced by a heavy soot buildup at the up-pipes going onto the turbo collector at the back of the engine. You can visual the drivers side, but will need a mirror, or reach your hand in back(cold engine) on the passenger side. Do not under estimate the significance of this leak.

2. Intercooler and intake spider boot leaks. These are likely coated with Oil and leaking. from the Facotry, Ford chose to route the PCV through the entire intake tract, and over time this builds up with oil, causing boost leaks, and reducing the efficiency of the intercooler. Again, if excessive this can cause a loss in power. If possible, go to the local hardware store and buy a 4"-2" rubber plumbing reducer, then a 2inch to 1/2" PVC plumbing bushing, 1/2" to 1/4" brass bushing and an air chuck. Fit all parts together, and connect to PCV bracket mounted on drivers valve cover. Make sure to either plug, cap or use some needle nose vice grips to block the PCV hose going to the crank case. Now using a regulated 20psi source, pressure up the intake and check for leaks. Or simply order a new boot kit from a sponsor, such as dieselsite.com. Rerouting of the PCV will help prevent this in the future. Do a search for CCV mod. Tons of writeups. For a little extra leak insurance, lightly coat the pipe and intake side of the connections with a coating of RTV. Again, lightly or removing the boot in the future may require surgery.

3. Check Fuel Pressure. These engines are very forgiving on fuel pressure. They will run, idle and drive just fine with low fuel pressure, and just have low power. Checking fuel pressure from the #4 ports on the back of the fuel bowl is easiest, but not the best. The best method is to use the factory plugged fuel port on either the passenger front, or drivers rear head, opposite of the OEM feed lines. These ports are 1/8NPT. This will tell you what is left at the injectors, after pump, filter, and engine usage. If possible, monitor pressure under load. anything below about 50psi at the rail under load is too low. At idle you should see 60-75psi. If you do this, make sure to use a liquid filled gage, a standard gage with destroy itself quickly from the pulsations. There is no OEM sensor to monitor fuel pressure.

4. Fuel Air Check. Air in the fuel is another common problem on the 7.3 PSD's. The easiest way to check for excessive air in my experiance is by removing the return line from the fuel bowl, top drivers side and putting in a loop of clear tube. The fitting size is standard compression fitting, either 5/16 or 3/8 can't remember for sure. Get a 1 foot length of clear(5/16OD) nylon tubing from a hardware store, a compression nut, insert, ferrule for the fuel bowl end, and then a compression union for the fuel hardline end. Maybe $5 all told. Connect the one end to the fuel bowl, loop the tube, and connect to compression union on tube side, then remove the nut and use the OEM nut on the hardline side. This will allow you to see the fuel being returned and how much air is in the fuel. Excessive air means you need to perform the intank and pre-pump mods(Hutch). A search will reveal TONS of info here as well. Sorry for the vagueness on the sizies, it has been about 3 years since I last did that trick.

5. Exhaust BP sensor check. This is something more recently discovered that plays a role in fueling. On the Front of the motor right to next to the Vertical heater hose, and in front of the HPOP gear cover is the Exhaust backpressure sensor. It will have a tube coming out the bottom leading to the passenger side exhaust manifold. These tubes can and do get coked up and completely plug off the sensor. This is one area where the AE comes in handy. Factory spec says to Hold the engine at WOT for 30 seconds and watch the back pressure. The EBP should rise more than 4, but not exceed 26psi. If you do not have an AE, then you can carefully remove the sensor, start the engine and take a look to see if you are getting any exhaust from the tube. Or you can back probe the sensor with a multimeter set on VDC, and measure the voltage. Have someone rev the motor while monitoring the voltmeter. YOu should see an obvious increase in voltage + or - at least 2vdc with the revving of the motor. Make sure wires are clear of Fan.

6. HPOP. This is another area where you almost need the AE. Do you have a code 1211? if not, then this is not likely a problem. The pressure should be about 500-600 at an idle, stock or modified. Under full load, you should see about 2800-3000 for a stock truck. Many modified trucks will see a lower pressure. On a stock truck, if this is over 2500, then there is no significant power loss resulting from the Hpop.

Well that is about all I have for now, hopefully that helps you a bit and maybe a few others as well. I have since gone WAAAAYYYYY beyond that for my own ride......

 

i would also check ur exhaust backpressure tube. If it clogs up it will hurt power as well and fuel mileage. the sensor is located right behind the fan and the tube runs from the the passenger side manifold. Take it off and clean it and see if it helps.