LS400_96

My LS is starting to shaking when idling. I got the car at 128,000 miles and havent done a complete tune-up like spark plug, cap, rotor, etc. Do you guys think this is causing the car to shake?

I am thinking about changing the plugs tomorrow to see if this will fix it. I know that the car came with Denso Platinum plugs, but I heard that copper plugs provide better conduction but last only 30,000 miles. I was wondering if anybody changed to copper plugs on their N/A and had problems. Also, do I gap the copper plugs to .043 in like the platinum plugs? I am going to go with the Denso K20R-U11 copper plugs. Is this the right part number?

Leets

have you checked your motor mounts?

LS400_96

How do I check that the motor mounts are bad? Never did this before.

Faceless1

A couple of things could be the cause.
1) Tune up may correct the problem depending on how the car is trembling during idle. Is it a hard shake or soft shake?

2) Motor Mounts could be the problem........A good check I use is looking at them and checking for cracks in the rubber. Thats the obvious check in case your wondering. The other way is start the engine and leave in park. Turn the throttle up to a higher RPM and check how much the engine jumps when you do it.

3)You could have carbon build-up in your engine. A good check for this is to pull off the throttle body and look on the inside of it. If it is black then you would want to clean all that guck!! off. Also run an injector cleaner through your engine to release the carbon that is inside the engine on the pistons and valves.

4)Your MAF could be going bad.......sorry, I miss wrote myself. Nothing is ever going bad. Either it is bad or it isn't. Anyway, your MAF could be bad and causing you to have a poor idle. Check your RPM gauge too see if that is fluctuating up and down.

5)Your IAC valve could be bad. Again check your RPM gauge to see if the gauge is fluctuaing at idle.

6)Last but not least........What type of gas are you using in your car. Gas is a silent killer of engines. Cheap gas or fuel with poor additives to give it that 93 octane rating can give you headaches over time. It may not affect your car at first, but contstant use can really do harm to your engine.

With all this that I have said, keep in mind that you must give more info if you want a true and proper diagnosis of your condition.

LS400_96

Changed the spark plugs with new ND copper plugs. The number 2 cylinder had alot of dirt buildup on the plug and some engine oil was leaking out of the plug threads. Also, cleaned the TB out with cleaner. Boy, that thing was really dirty. Now, the car idles really smooth and pulls harder. Just like new. Next week, I am going to do some more tune-up. Any suggestions on what should be done. The car has 128,000 miles and seems like the previous owner never did the 120,000 tune-up.

carnal_c30

if you still have vibration under idle... in nuetral check your motor mounts...

if it vibrates alot in drive, check the tranny mounts

LS400_96

I think my motor mounts are bad. When I turn on the engine in the morning, I could hear a noise and the engine seems like it moves alot. How many motor and tranny mounts are on the LS? How do I replace them?