Shakes at Idle [Archive] - GrandAmGT.com Forum

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entxoj
08-03-2006, 11:21 AM
Hi,
Got an 01 GA SE with a 2.4. When engine is hot (550-600 rpms), sitting at light in drive, engine shakes. Turn on AC and it gets worse. It does not do it in reverse. It does not do it when its cold (900+ rpms). I had it scoped and it is not missing. Thinking engine mounts? 4 engine mounts inspected, none cracked or look deteriorated. Anyone have any ideas? 84k miles. The direction the engine torques when in drive leads me to beleive the front right(driver side).
Thanks

freakydeaky
08-03-2006, 12:47 PM
If the engine idles roughly when it is hot, then check the following:

Check the PCV Valve for proper operation by placing your finger over the opening (while running). You should feel vacuum on your finger however when released the valve should snap shut. If it hisses at all, replace it. Also, remove the valve from the tube an shake it. It should rattle like there is a loose marble inside. If it doesn't rattle, replace it.

Check the canister purge and vent system. It should NOT apply vacuum to the system at idle. There are many types of control systems for this device however if you remove the hose labeled "tank" and feel vacuum at the port during idle then you need to service the system and probably replace the control valve. If that is the cause, blocking the "tank" port will stop the rough idle.

Check the spark plugs for proper gap.

Run a cylinder compression test.

Check the ignition timing. See the Vehicle Emission Control label for information.

Check the exhaust system for restriction or blockage. A clogged catalytic converter will cause high speed as well as idle problems.



taken from----> rough idle (http://www.misterfixit.com/ruffidle.htm)

entxoj
08-03-2006, 11:36 PM
Thanks for the tips.

I am under the assumption that vacuum leaks or sticky/faulty emissions equipment would cause a rough idle. This rough idle I think would show up when it is scoped. Same if plugs were fouled. And, I would get the same result in reverse.

So,
Scope is clean.
Reverse, neutral, high speed or higher rpms smooth.

Am I off base on my thought process?