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?

 

Unhook 02 and/or unscrew and see what happens, mine did similar thing last march,but only at idle speed. Just out of the blue was getting random multi misfires.
thru parts at. It's much better now. Also check fuel pressure.

 

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.

 

Alldatadiy.com has symptom related information that can help in your search for answers as well as repair information. Good luck!

 

When you do the plenum repair, new o2's and new or gutted cat goes along with that fix. Unscrew the pre cat o2 and see if it runs better.

 

Update: Got the upstream 02 out and still runs the same. Also took the belt off to check the pulleys and H balancer. All tight. Started it without the belt an still have same condition.

 

Have you checked your motor mounts?

 

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

 

Check fuel pressure?...probably not it, but. Do compression test yet?

 

Have you addressed your plenum yet??