Ford Powerstroke Diesel Forum banner

21 - 30 of 30 Posts

·
Registered
Joined
·
22 Posts
My ‘97 had a similar sounding problem. My local powerstroke wizard found out it was the exhaust back pressure valve getting stuck. Cleaned it up and lubed it. Problem solved. Hope it helps.
 

·
Registered
Joined
·
1 Posts
I would hope they monitored things like injectors, boost, etc. When you mash it to the floor going up a hill shouldn't it downshift?

I'm not skilled enough to offer advice but I know when I go to the floor it downshifts out of over drive.

No matter what, update the thread here because it may help someone else out in the future.

Sent from my SM-N960U using Tapatalk
Try a fuel filter I had similar problem
 

·
Registered
Joined
·
8,572 Posts
Didn't see this suggestion but I would if you haven't already. The ECM and shifting in these trucks is not intuitive. Its really dated and you have to find ways to MAKE it do what you want without breaking things esp towing. Hence why the 5r100s just turn OD off and not much else changes if any after the fact vs the next gen 5r100 switching to tow mode changes everything dramtically.

When you are going up hill and OD off and you notice the bog down with you foot against the floor try releasing the throttle for say 2 seconds and rolling into the throttle rather quickly again. (think mashing the pedal but with finesse). I noticed some 7.3ls even my own with a large trailer or heavier equipment the 4r100s won't downshift on its own, so I release the throttle for a second and mash it and wallah! im in the gear/powerband I want to for the remainder of the hill. (When I say mash it, I don't mean truly mash its kind of a softer mash just really hard to describe) The driver can REALLY MANIPULATE the shifting with the 7.3ls if they learn their trucks. (you've had you'rs longer than most so you know your truck).

There is always a chance I have just had a bad spring in the valvebody or ecm qwerk but its gotten my truck to downshift when I wanted vs when the truck wanted to and my trans fluid is still red, transmission is shifting great.
 

·
Registered
Joined
·
448 Posts
Didn't see this suggestion but I would if you haven't already. The ECM and shifting in these trucks is not intuitive. Its really dated and you have to find ways to MAKE it do what you want without breaking things esp towing. Hence why the 5r100s just turn OD off and not much else changes if any after the fact vs the next gen 5r100 switching to tow mode changes everything dramtically.

When you are going up hill and OD off and you notice the bog down with you foot against the floor try releasing the throttle for say 2 seconds and rolling into the throttle rather quickly again. (think mashing the pedal but with finesse). I noticed some 7.3ls even my own with a large trailer or heavier equipment the 4r100s won't downshift on its own, so I release the throttle for a second and mash it and wallah! im in the gear/powerband I want to for the remainder of the hill. (When I say mash it, I don't mean truly mash its kind of a softer mash just really hard to describe) The driver can REALLY MANIPULATE the shifting with the 7.3ls if they learn their trucks. (you've had you'rs longer than most so you know your truck).

There is always a chance I have just had a bad spring in the valvebody or ecm qwerk but its gotten my truck to downshift when I wanted vs when the truck wanted to and my trans fluid is still red, transmission is shifting great.
What if camogirl were to install a php Hydra chip and use a tow tune? I don't tow so I don't know what it does to the shift strategy.

Maybe if all else fails that could be a solution.

Sent from my SM-N960U using Tapatalk
 

·
Registered
Joined
·
8,572 Posts
What if camogirl were to install a php Hydra chip and use a tow tune? I don't tow so I don't know what it does to the shift strategy.

Maybe if all else fails that could be a solution.

Sent from my SM-N960U using Tapatalk

Generally speaking the tow tune will work better than the the normal 7.3l truck using the OD off mode. The tune adds X amount of power more commonly 25-50hp, and then it changes when the transmission shifts at various rpms/speed wise, changes when/how often the torq converter locks, also raises the pressure for shifting. There is a little more too it that im not familiar with but that would be one solution if the truck is really fine. This is assuming the truck is stock otherwise. I don't really feel there is an issue with the truck to be honest though. I think the OP mentioned the truck didn't use to do this and thats probably somewhat correct but clutches get worn, pumps don't product the right pressure amounts 100%, springs loose tension etc.

My biggest reason is I can get my truck to do nearly the same thing with a lighter and heavier trailers very easily. The truck just doesn't work like it really should because is nearly 20 yr old technology. If you ever get a chance to drive even a 6.0l the 5R100 tow mode is leaps and bounds ahead of just turning off the OD like on the 7.3ls that don't have modifications. I have a modified valvebody built for towing by John Woods, the 6.0ls trans cooler, and a wicked wheel 2 turbo wheel, with a straight pipe, AIS severe duty intake. basically the truck is built for towing and I can get it to replicate the scenario in this thread etc. Thats just my 2 cents if its even worth that.


PS the OP list all thats been done and tried but didn't actually say what???

Whats the boost while towing? too low could mean boost leak or the red tube issues.

what are the EGTs when towing? Too high could indicated leak in intercooler, cracked pipes, boost leaks in general

What is the IPR and ICP reading at idle, cruising and at pedal pushed to the floor?

Does the throttle position unit have a deadspot/short so its not actually telling the ECM that more throttle is applied so the ecm thinks its fine to not downshift etc

There is alot of things that we can only assume without any of the above information posted though.
 

·
Registered
Joined
·
36 Posts
Discussion Starter #27
Just want to thanks everyone for all the input....I am currently working with someone that worked at Ford for many ears and started his own business...he is very well respected here in southern az but he is so dang far....but after my first local mechanic decided he was not interested in helping me any further because my truck did not throw any codes- I figured this Ford Guy was my only hope- in spite of the distance....first when I went over there he replaced the entire fuel tank sending unit- since the original pickup screen was failing and crumbling h thought perhaps some rubber was lodged in old sending unit- better safe than sorry- we replaced the whole thing...ran great, but same issue....hooked up the travel trailer and I could only get to 2200 RPM's at 55 MPH going up a grade, and wasn't even really steep- foot was on the floor....there have been people that have suggested straight exhausts...tuners...and a bunch of other things....but again, I know what a beast this 7.3 can be....I've had it since 2002...all I am looking to do is get the same performance out of it that I have had since 02....I have towed heavy loads...and it had always pulled like a beast- with stock exhaust and no mods...something is not right- I just want to restore it back to the way it has always performed....so far I have had a new sending unit installed...new fuel filter...fuel lines blown out....new motorcraft fuel pump....This ford guy doesn't seem to feel that changing out any sensors would solve anything as they all look very healthy on the computer(which I am not convinced that a weak sensor would always throw a code- so I am not sure I agree with that)….but he seems to feel that new injectors would be the next step if my truck doesn't pull right tomarrow with the travel trailer hooked up....I just picked the truck up today with the new fuel pump-

So again- thanks everyone for your suggestions...but this problem has recently developed under a load- it always towed beautifully, with lots of power- all without any mods.....and I want to find the problem and bring it back to the place that it has been since 02. I know how it drives...I know how the tranny is supposed to shift, even though it is a dinosaur....I am the only one that has ever been behind the wheel of it's 112,900 mile life and I know my truck....and right now it's driving like crap under a load- and I need to figure out why.....so depending on what I can research, I would like to try a few sensor replacements before I drop a lot of cash on new injectors, I really do not feel that new injectors are the problem....someone earlier in this thread mentioned a MAP sensor....I am going to educate myself on that part...that would just make my day if my fix was that easy....and I could change that part out myself....
 

·
Registered
Joined
·
36 Posts
Discussion Starter #28 (Edited)
I had the same problem with my 2001 7.3, turned out the (MAP) Manifold Absolute Pressure sensor hose connection was cracked. It’s connected by a 2’+ section of hose that had shrank over the years. It’s mounted on the left-hand side of the firewall. Without it sensing a difference in pressure as you execrate Turbo boost is almost non-existent. Forgot to mention a scanner wont detect the problem because electronically it’s in working order. View attachment 767964
So changing the MAP sensor completely fixed your issue of power under a load going uphill?? Or did you just change the cracked vacuum hose??
 

·
Registered
Joined
·
615 Posts
The bottom line is you need to monitor fuel pressure, IPR percentage, ICP values, and boost pressure while you are experiencing this loss of power.

If those numbers report back in spec, I would do a buzz test. If the buzz is weak, replace injectors. If the buzz test is good, perform a compression test

Your problem should be able to be identified by watching those things while you are towing up hill


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
40 Posts
I like the cracked MAP hose suggestion. I like it so much that I'm going to check the hose on my 99 over the weekend. I have a trip coming up in two weeks, and I've noticed the truck seems a little lethargic on grades compared to what it used to be. This (cracked hose) is the kind of deficiency that can creep up without being obvious.

CamoGirl: Have you checked the air filter? If you have an aftermarket deal with a cloth outer cover, pull off the cloth and check the element underneath it. The PO of my truck had the filter element get very badly blocked by winter snow-scuzz build up under the cover. He called me for tech support (I work on his boats) from the side of I-70 in Vail Pass when it wouldn't pull the Airstream at over 10 MPH. After about 20 minutes of looking and checking and asking questions he finally pulled the cover back and said "I think I found it...". The outer cover looked fine, and he had looked at it several times. But the pleats in the filter under the cover were blocked with solids.

Do you have an Exhaust Gas Temp gauge? If you're not running a tuner, probably not. An EGT gauge can give helpful indications on where problems may be. Higher than expected EGT means low air delivery or boost, or too high a gear. Low EGT is inadequate fuel delivery, almost always fuel filter restriction.

Observing exhaust for smoke or color can be difficult. But how about at night with headlights behind you? Makes observing smoke in the mirror much easier. More black than expected, is low air delivery or boost.
 
21 - 30 of 30 Posts
Top