5.9 motor shakes when started up
#1
5.9 motor shakes when started up
This just started the other day. I turned it off to repair the steering box and add new fluid then when I turned it back on I noticed it shaking. Right when I turn it on, it shakes with the RPM's and then when it settles down and idles it's fine. When I give it gas it shudders and shakes through the RPM's. It does the same thing in neutral, drive, and park. When I'm driving I can feel it in the gas pedal and steering wheel and it's more prominent at lower speeds like starting from a stop. It does it when it's cold at start up and when it's warm. No difference.
What could suddenly cause it to go from running great one second then shaking/shuddering the next?
This is what I have done so far.
Plenum repair
Valve cover gaskets
New injectors
Tested all the throttle body sensors. TPS, IAC, MAF. All in working order.
New Cap and Rotor
Plug wires routed according to the TSB
Checked for vacuum leaks with carb cleaner. Found none.
Used a code scanner. No codes.
Reset the battery didn't help.
Could it be?
Bad coil?
Cap and Rotor failure of some kind?
02 sensor?
If I had hair I'd be pulling it out right now. Any ideas?
What could suddenly cause it to go from running great one second then shaking/shuddering the next?
This is what I have done so far.
Plenum repair
Valve cover gaskets
New injectors
Tested all the throttle body sensors. TPS, IAC, MAF. All in working order.
New Cap and Rotor
Plug wires routed according to the TSB
Checked for vacuum leaks with carb cleaner. Found none.
Used a code scanner. No codes.
Reset the battery didn't help.
Could it be?
Bad coil?
Cap and Rotor failure of some kind?
02 sensor?
If I had hair I'd be pulling it out right now. Any ideas?
Last edited by Vegas360; 09-10-2012 at 10:44 PM.
#2
#3
I took the coil out and it was in bad shape. replaced it and although it idles better the shaking still exists. While the motor was running I pulled each plug wire one at a time and couldn't tell if anything was wrong. I can't get my arm up there to unplug the upstream 02 sensor. Still working on a creative way to get to it without having to unbolt the exhaust.
#6
#7
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#8
Just removed the downstream 02 sensor and still got the same shake.
Had a buddy here today and although the MM aren't in the best shape they do not move around when I give it gas. I am not ruling it out though. The motor does not have excessive play. Neither does the tranny. Here is what I have covered so far:
TPS
IAC
MAF
Both 02's
Spark plugs
Wires
Coil
Cap
Rotor
Cam position sensor
H balancer
Seafoamed through brake booster and gas tank
Rebuilt 703 injectors installed over old stock injectors
Battery and Alt tested with multimeter
Removed steering arm to test for pump vibes through arm on start up
Removed the PCM plugs and sprayed them out with electric cleaner
Wiggled every wire to all the sensors including the injectors
Wiggled the PCM harness
Pulled all plug wires while it ran and listened for any indication of failure or miss
Listened for vacuum leak and sprayed carb cleaner generously all over vac hoses, right and left intake gasket and front to rear intake. No change in idle.
Here is where I am at
Had a buddy here today and although the MM aren't in the best shape they do not move around when I give it gas. I am not ruling it out though. The motor does not have excessive play. Neither does the tranny. Here is what I have covered so far:
TPS
IAC
MAF
Both 02's
Spark plugs
Wires
Coil
Cap
Rotor
Cam position sensor
H balancer
Seafoamed through brake booster and gas tank
Rebuilt 703 injectors installed over old stock injectors
Battery and Alt tested with multimeter
Removed steering arm to test for pump vibes through arm on start up
Removed the PCM plugs and sprayed them out with electric cleaner
Wiggled every wire to all the sensors including the injectors
Wiggled the PCM harness
Pulled all plug wires while it ran and listened for any indication of failure or miss
Listened for vacuum leak and sprayed carb cleaner generously all over vac hoses, right and left intake gasket and front to rear intake. No change in idle.
Here is where I am at
Last edited by Vegas360; 09-11-2012 at 09:35 PM.
#10