My 200 has a bit of a bumpy idle, not exactly rough but it bounces around. I got new 4-hole injectors and that calmed it down a bit, and replaced the TPS after I ruined it when a water crossing got too deep. Im wondering what else it can be, I cleaned the IAC valve recently too. It idles in the right spot but when im stopped it shakes and you can feel it throughout the whole car. IAC sensor? Motor mounts?

 

I'd check the tranny and motor mounts. Someone recently advised that if you start the engine with the hood open and you can see the engine vibrating your motor mounts are bad. For the tranny the general advice is to take a big screwdriver or pry bar and stick it between the frame or cross-member and tranny case and if you can move the tranny at all then the mount is bad.

 

My 01 does the same thing. Here are some things I have done. I dont think the issue is anything mechanical but more electronic related. I get no check engine light for a mis-fire either.

- Rebuilt engine. Solid 150 psi across the board
- New spark plugs (Champion copper)
- Cleaned and flowed injectors
- New motor mounts
- Verified fuel trims arent going crazy
- Verified tps is good

Things I am doing next

- Refresh grounds
- Coil rail replacement

If it still idles the same after all that, I am going to say its normal since it runs perfectly fine.

 

Maybe not in5-Speed's case being a new motor but the OP may have a carbon build up in the cylinders.

 

I replaced the ground to body cable on mine and the dipstick ground and it made a big difference for starting and for my high/rough idle. Its a super easy job too.

 

My wife's 01 is beginning to start a little rougher in the mornings and has a slightly noticeable skip that can only be heard from the tailpipe. It's at 211,*** miles and I'm about to start replacing sensors proactively. I changed the plugs about a year ago because the electrodes were nearly gone. Only ones I could get were the champions at the time. I'll probably switch in some NGK this summer.

I haven't decided where to start. Possibly the crank or cam sensor. Also it probably would be a good idea to replace power and ground cables. And also water pump, thermostat and temp sensor are in need before tradgedy strikes since it's got the 0331. I'm hoping I don't need to do the coil rail yet. Also it's the 50 state emissions so I should probably do the O2 sensors. As far as I can tell they're original and the exhaust should be fine for a couple more years.

Hopefully that will help. I also need to focus more on gaskets and seals. And the rest of the sensors are much easier to replace if one of them happens to go bad suddenly.

 

Do you know if valve cover gasket would help? It seems like it could cause vacum leaks since 2+ hoses go in there.

 

Those are not for vacuum. They're for crankcase ventilation. So a bad gasket wouldn't affect how it runs. If anything if one of those were clogged maybe the engine would be more sluggish.

 

Ok, thanks