Shaky Sonata

Hi all!

I just became a member of the car talk community and thought I could tap into the collective expertise here. I have a '04 4 cylinder hyundai sonata and it vibrates at low rpm. I thought it was an engine miss so I replaced the spark plugs and cleaned the throttle body and put in some fuel system cleaner. My current theory is that I have a leak somewhere in my intake but I don’t know how to start looking. Am I on the right track? The vibration only happens at low rpm, idling is bad. There’s an intermittent rocking and I’m afraid that there might be some permanent damage if I don’t rectify the situation.

Any help would be greatly appreciated,
Hapless in NJ

When did this vibration start? Did it occur after you had your timing belt changed?

Check your owners manual to see if it requires a check of the valve lash. If it does, start there. This does sound like a valve problem.

Is your check engine light on?

Have you had any recent services? Did the symptoms come on suddenly or gradually?
Is there a check engine light?

Timing issues are possible. Could be an Intake manifold gasket.

I think more information is key here.

This engine has two timing belts - one is the actual timing belt, the other is to drive the balance shaft and oil pump shaft. The engine will vibrate, as the OP describes, if the balance shaft and/or oil pump shaft are off by a tooth or two.

It seemed to come on gradually. I haven’t had the timing belt changed since I got the car. It has 194000 miles. I thought the secondary timing belt could be involved

As Metalhead999 asked, is there a check engine light?

Look closely for a vacuum leak. When checking for a leak, be sure to also temporarily disconnect and plug the vacuum line going to the brake vacuum booster (to determine if the booster diaphragm is leaking).

Negative on the check engine light. I’m going to have a big service day this week to change the brake pads, oil pan gasket, timing belt(s), and hopefully get the old girl running at 100%. Any other ideas guys?