99 & up 7.3L Power Stroke Engine and DrivetrainDiscussion of the 99 & up 7.3L Power Stroke diesel engine and drivetrain in the 1999-Up Super Duty trucks and Excursions. No gas engine discussion allowed except on transmissions and drivetrain that pertain to all models. Please confine discussion of topics in this forum to those items that are specific to the 7.3L Power Stroke engine.
OK, been trying to diagnose this thing and every idea ends up with more questions.. HeLP!
Idle is slightly rough, like a miss. If you slowly ramp up the RPMs (in neutral, drive, whatever), the vibration gets more and more pronounced. When you get to about 1100 or so (where the shake is the worst), RPM suddenly jumps to about 1400, then ramps up fine again and smooths out above 2000 or so. Same thing when you slowly back off, hit 1400rpm and then drops right to 1100 and wont hold in the middle. It's near impossible to get it to hold between 11-1400, if it will do it at all. This is where the vibration is horrible, shakes the whole truck. We kept thinking it was a t/c problem because when it hit lockup it shook like hell, but with more thought and playing with engine speed I think it's because right when it hits lockup at an easy cruise, it lands the motor right at that RPM range where its the worst. After it hits O/D and drops to ~1300rpm, shakes like crazy and gets worse when you give it throttle. If you ease it on and get it closer to 2000, it smooths out. So doesn't seem to matter if its in neutral or any gear, does it all the time, just really pronounces it under load.
No codes/SES light either!
Also noticed that once in a while it will do the same thing from about 700-1000 RPM, if you ease the gas slowly off it won't hold within that rpm range.
Replaced UVC wiring last night, slightly smoother idle but no real change in symptoms. [img]/ubbthreads/images/graemlins/shrug.gif[/img] [img]/ubbthreads/images/graemlins/shrug.gif[/img] ARGH!!!
Check the main wiring harness for rubbed spots. A likely spot is where it crosses the driver's side valve cover. Some of the guys have found injector circuits shorting out there. Don't remember if they got an SES light or not though.
Also check the harness connectors for proper fit of the pins. If some have gotten loose, they might cause your symptoms.
On the other hand, those things should have set a code. What are you using to read codes? Not all readers work on the PSD.
Checked wiring over valve cover right beneath the connector... Couple wires have rub spots but not thru the insulation, wrapped them up good, no difference.
Code reader "Actron" - From just doing a quick search it looks like those don't do IDM codes, but either way, wont a code set the SES light
Not all codes set the SES, but generally those associated with the injector circuits will.
You may have mechanical problems that the PCM won't pick up without specific tests. You should have a cylinder contribution test run to check your injectors. If one comes up with that test, then you'll have a spot to look at. It may not be the injectors, but the CCT will (no make that should)pinpoint the cylinder(s) that are causing the problem. Compression test and other mechanical inspection will get you closer to the cause of your problem. If you swap the indicated bad injector with another, and the CCT code follows the injector, then that would confirm it as a bad injector.
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Linear Mode
