Ok Guys , I dont have a PS but my buddy does. He has a 99 7.3, the prob he is having is rough idle. He said it seems to miss at idle, vibrates and shakes the gear shift. After you rev it up like above 900 rpm it feels like it smoothes out. At highway speed it seems to run ok, he is not sure if it does actually stop missing or you just dont notice it at high rpm. Any help as far as what to check first etc would be appriciated.
New guy with ????? on 99 7.3 ps miss
- Thread starter 4x7.3NE
- Start date
SD70Ace
Big yellow Diesels
Start replaceing injectors.....$$$$$
93turbo_animal
Registered User
does he still have the dual mass flywheel in it? If so one going bad can cause or amplify a rough running condition. more info would help mileage ect.
cm1hedge
Full Access Member
X2 on DMF
Double-S-Diesel
parts seller
no dual mass on a SD
need to get it on a scanner and do a cylinder contribtuion test
need to get it on a scanner and do a cylinder contribtuion test
cm1hedge
Full Access Member
My bad!
trackspeeder
Stone crusher.
rebel_horseman
Rt. Wing Extremist
A friend's old 94 PSD had a similar problem. He had it scanned and one of the injectors was going bad. He pulled it, opened it up and cleaned it real good, then replaced it and it got him down the road for a little while. Putting a computer on it would be the first step then go from there.
How do you do this buzz test? I searched but didnt find it, does a dealer have to do it or what?
1320Cummins
Pro Parts Thrasher
You need the proper scan tool to run this test.
Most auto shops will have this tool.
Buzz test and cylinder contribution test are the same thing.
He can start by replacing the valve cover gaskets. Probably 7 out of 10 times I have traced a miss to bad valve cover gasket. You can get the gaskets at your local auto parts store.
Tim the 2lman
Registered User
Acutally they're not the same test. A buzz test is done KeyOnEngineOff (or KOEO) and tests the electrical side of the injection system possibly revealing wiring continuity problems, IDM problems, or injector problems. It's an audible test to see if an injector is weak or not functioning for instance.
Cylinder contribution test is performed KOERunning and narrows misses down to a specific cylinder that is not equally contributing during it's power cycle. Contribution tests may reveal low compession, due to a bad lifter or burned valve, cracked piston, as well as faulty injectors.
I like to run them both.
Double-S-Diesel
parts seller
could also be a loose UVHC, had 2 just this weak, one ran crappy for 2 miles the was fine, the other came and went
Continuity Test.
If it's a 99.5 you will more than likely get a false continuity test on #6 & #8 unless you have updated to the AE injector for #8 cyl.
If it's a 99.5 you will more than likely get a false continuity test on #6 & #8 unless you have updated to the AE injector for #8 cyl.
