Hi guys I’ve searched hi and low trying to find out if my case is normal. So I did a command max tail pressure test on my scanner and when I commanded max 22k psi the truck started to shake And lope pretty good. My question is is this normal or do I have an issue?
Lb7 lopes when I command max rail pressure?
- Thread starter Wrivett
- Start date
It's hard to say if it is normal or not. Every LB7 I've messed with runs rough at max rail pressure at idle. It is hard to specify exactly how rough is normal though.
I do know that at 80 MPa all of them seem to idle just fine. When you command the change, they may shake for a split second, and the engine sound will change, but within a second or so, it should be smooth idling again, just louder.
I'd try commanding 80 MPa instead of 160 MPa. If it idles OK at 80, it's probably nothing to worry about. The max rail test is usually to diagnose fuel leaks or failed CP3 pump. If it fails to achieve 160 MPa at idle when commanded, the CP3 is very weak, the injectors are returning way too much fuel, and/or there is a fuel leak. Idle quality isn't really meaningful in this test.
I do know that at 80 MPa all of them seem to idle just fine. When you command the change, they may shake for a split second, and the engine sound will change, but within a second or so, it should be smooth idling again, just louder.
I'd try commanding 80 MPa instead of 160 MPa. If it idles OK at 80, it's probably nothing to worry about. The max rail test is usually to diagnose fuel leaks or failed CP3 pump. If it fails to achieve 160 MPa at idle when commanded, the CP3 is very weak, the injectors are returning way too much fuel, and/or there is a fuel leak. Idle quality isn't really meaningful in this test.