Hey Fellas, I own a 99 superduty 7.3. Lately I've had a series of problems. Ist problem I had was that the engine would shut off, I would let it sit for 20 min. then it would start and run for a 1/4 mi. Fuel pump and filter were replaced and continued. So we changed the cam sensor, the injector harness, 1 injector, the map sensor. After all those repairs have been made, truck runs fine until tranny shifts through all gears to overdrive and at 45 mph through 60 mph. the engine seems to spudder, if you put the pedal down, it runs good. I attempted to find leaks with soapy water, none were found. The only thing that I found was the the "Y" manifold does not have constant vacume........should it? As you can see we've done alot and almost there, if you guys can help it would be greatly appreciated!! Thanx Guys!!

 

Can you read the fault codes..? It is a good place to start..And Welcome to our Forum..

 

no the turbo builds pressure so should have positive pressure

should be more specific should only read vacuum from idle a first crack of throttle

 

At no time should a diesel engine have vacuum. There is no throttle plate to block the flow of air into the engine so it's impossible to produce a vacuum.

 

probly not supose to but mine will show brief vaccum just when I crack throttle off idle

 

OK, no vacume. One thing that I forgot to metion the scanner picks up a code, says back pressure malfunction. 470 on a matco scanner. I'll get more accurate info, didn't write info down.
You guys are a big help!!

 

I would suggest cleaning your ebp tubing that goes from your sensor to the front of the pass. side exhaust manifold.. I find it easlier to just remove it to clean.. Some guys run a weed eater .095 dia cord down the tube. Does not take that long to remove it, unless the fitting on the manifold is rusty.. If that does not fix it, you might consider replacing the sensor..

 

If you let completly off the pedal does it go away. And if you give it a little fuel it shudders the worst? If so you got another bad injector hideing in their. That sounds exactly what was wrong with mine i payed hell for over a month trying to find the little bugger too. If you can run a Change in Rotation Violicity test(you need a really good scan tool) and a CCT(Cylinder Contribution Test).

 

<TABLE><TBODY><TR><TD vAlign=top width="100%">If you let completly off the pedal does it go away. And if you give it a little fuel it shudders the worst? If so you got another bad injector hideing in their. That sounds exactly what was wrong with mine i payed hell for over a month trying to find the little bugger too. If you can run a Change in Rotation Violicity test(you need a really good scan tool) and a CCT(Cylinder Contribution Test).
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Yes sir! that is exactly the problem,Thanx again guys! I'll try cleaning the lines first, but you are probably right another $200.00 injector. I sure hope one of these is the cure, if not I'll be sure to hound you guys again.

 

<TABLE><TBODY><TR><TD vAlign=top width="100%">I would suggest cleaning your ebp tubing that goes from your sensor to the front of the pass. side exhaust manifold.. I find it easlier to just remove it to clean.. Some guys run a weed eater .095 dia cord down the tube. Does not take that long to remove it, unless the fitting on the manifold is rusty.. If that does not fix it, you might consider replacing the sensor..
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Which sensor is that boss?

 

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Which sensor is that boss?[/QUOTE]

If you are looking for the ebp sensor, it is located behind and down from your belt idle pulley. (right next to the heater hose). Under the sensor you will find the tubing that goes to the pass. side from exhaust maniford. Carbon build up in the tube causes the sensor to malifunction.

 

Thanx Guys, after I get back from repairing my truck, I'll be back and let you guys know how it turned out.

Thanx I appreciate all your help!!!