Hello,i have a 99 7.3 with 40,000 on a rebuild,injectors i dont know they do pass a buzz test.what happens is when driving say at 30 mph and im not needing to give it throttle but i dont back all the way off the peddle sort of at a neutral point my engine will sound rough and seems like its not hitting on all cylinders.it runs great when i give it fuel and idles fine its just the point in between it runs erratic.last year when chasing a no power problem i did rebuild the ipr,new fuel filter,icp and harness,cps and what fixed it was new fuel pressure regulator(brass was gaulded and causing fuel pressure to crash).no mods other than a bullydog tuner that never goes past #2 setting.i do have a auto engenuity scanner if you have a suggestion what to look for or already know what my issue is.thanks in advance

 

Hello,i talked to a former ford tech and he said to pull the transmission pan and look for broken snap ring.that it sounds like its trying to do something with the torque converter in and out of stall or lock up?i believe thats what he said.any thoughts.its gonna be a couple of days before my turn in the garage so i was looking for other ideas to look for when i get it in there.thanks in advance

 

I've heard of a snap or lock ring in the trans that is prone to breaking, but no idea if it could cause your symptom.

Another idea is a dirty throttle position sensor. If the TPS has grunge at that particular spot in it's travel the signal will be bad. TPS is mounted to the pedal assembly and some folks have success blowing it clean with a can of contact cleaner.

Pretty sure AE can monitor the TPS voltage.

So the rough running is not related to anything but pedal position? Not temps or location? Can ya hold it in low gear and recreate the problem?

 

Well i took out the tps and checked it on an analog meter and it did appear to a have a bad spot (slow response)so i put a new one in it anyhow(original).didnt fix it.i can run it in low gear and create it,it acts just like a fuel/miss problem.sounds funny and slight buck,i unplugged the icp -no change-i run a/e on it ,buzz test, some did sound different than others and cylinder contribution -didnt find anything,i did have a #8 cylinder rotation velocity but i have read where thats normal for ae to do that on good engines.i used to have a big sun machine i could hook up to gas engines and find a problem with an oscilloscope it would show plug,wire problem and kill cylinders individually,it was cool.im a little disappointed in a/e i cant do what all i thought i could do or im not smart enough to use it correctly(might be that).anyhow if anyone has a suggestion from here im all ears. thanks in advance

 

you could check for chafed wires going to your 40 pin connector. The wires rub on the valve cover. The bottom row go to the injectors and could be shorting one out.

 

Are you talking about a kind of warbling, rattling injector noise when you let off on the throttle. Many 7.3's do this when not much fuel is needed to keep the engine running due to the truck coasting. If you do figure out a cause for this it would be interesting to hear. I have just thought of it as a "natural thing for 7.3's during coasting mode.
Larry

 

Check your UVCH's and make sure they aren't coming loose. Rough running could be them, or as LAMADMAN stated, a chaffed wire grounding in the harness.

 

My drivers side wiring harness under the valve cover on my 99' came loose and I thought the truck had blown up. I pulled in a hotel parking lot and pulled the valve cover off and put back together with a zip tie until I could get back home. Once I got home I pulled valve cover again and did the .50 cent fix worked fine from then on. Grind down 2 quarters and install to take up the slack in the wore out plastic plug end.

 

HI,back again.i checked all above and then took it to a diesel mechanic.he run the snap on scanner and come back with a #8 injector didnt pass cct.recomended new #8 and the uvch.so i did...reluctantly it did not change the surging.my a/e still says #8 cct fail.i then took out the grey cps and changed it to the black one.that got rid of the cct fail and made the perdals reading better.(im pretty sure i could have done that to begin with and saved 250 bucks)swapped it back to the grey and #3 failed with #8.i think that is a ghost.i have unplugged the icp and drove it ,no change.i recorded my hpop and icp duty cycle it starts at about 13% with 700psi and when i floor it it goes to 42% and 2400psi.the graph matches almost on top of each other when i play it back.i can get it to surge while driving but do not see anything recorded that is squirrelly.i do have a fuel pressure gauge on pillar and it varies but never drops under 50,it just acts like its sort of lopping running out of fuel but when i give it gas it runs like a scalded dog.i have read where people had something called "hitching" but im not sure this is it.my main concern is catching a problem before it becomes a bigger one.i only use this towing a boat about 300 miles round trip but i have no desire to break down so far from home.any how if there is anything you all can think of i would appreciate it.thanks for looking

 

fuel filter, air filter, oil?

 

new fuel filter ,new air filter stock (worked before),oil change is about 2000 miles on it since november synthetic rotella t6

 

I'm not sure... I have Single Shot stage 1 Injectors running on a split shot tune and it does then when giving/removing throttle at the start of the pedal. Also idles a bit wonky.

I am stumped by this... Would love to follow along!

Maybe it's the throttle position sensor on the pedal? Can you read the TPS while driving to see what it does?

Does it do it in either tune? Maybe one of those is the culprit?

 

Does it do the same if you use cruise control?

 

You should remedy that tuning issue as soon as you can. I wouldn't recommend running it like that for very long.

 

The moment I get my chip back it's going in. Just waiting on the d@mned snail mail...

I was and still am concerned about it but it's my only running and trustworthy vehicle at the moment.