01 LS Rough Idle

[GalateMLS01]

So here's the deal, I am like everyone else lucky enough to buy one of these spectacular vehicles. (Sarcasm for anyone who didn't get it) Currently the problem I have is Rough Idle with an intermittent po173 code, bank 2 sensor 1. While the car is at idle there is a noise that leads me to believe that I might have a bad pulley somewhere. Also if the 02 sensor was bad, why would it be and intermittent code. Wouldn't it be on all the time?

[shorod]

Welcome to the forum!

Which engine does your LS have? Are you sure it's a P0173? I don't see that that code exists for the Lincoln LS.

-Rod

[GalateMLS01]

It's the 3.9 V8. The code is PO153 O2 sensor bank 2 sensor 1. I need to take the belt off and try all the pulleys to see if one is locked up. It's odd that the cel comes on and the goes off. It started recently after I took the air intake tubing off. I have checked to make sure all hoses and plugs are conected and they are, so I'm stumped with that. Any ideas?

[GalateMLS01]

Ok so, I've taken the belt off and checked all the pulleys, none of them are locked up. So I started the car with no belt. Once the motor reved down, the rough idle came back. The noise seems to be coming from the intake horn, maybe, but I do know for sure that it's the top end of the motor. Any ideas?

[GalateMLS01]

I think the problem is in the timing chain, the noise is coming from the front of the drivers side valve cover, right where the cam gears sit. I don't know if its the chain, chain tensioner or the chain guide. Anybody ever had this problem?

[shorod]

The code P0153 can be due to a variety of things. P0153 actually indicates a slow response from the O2 sensor, Bank 2 sensor 1. This can be due to, according to the factory service manual:

• Contaminated HO2S sensor.
• Exhaust leaks.
• Shorted /open wiring.
• Improper fueling.
• MAF sensor.
• Deteriorating HO2S sensor.
• Inlet air leaks.

Since you mention that this started just after you had the air intake off, I really think you need to reinspect/reinstall the intake tubing and verify the Mass Air Flow (MAF) sensor is plugged in and there are no rolled lips or something of the tubing.

Can you describe the noise a bit better? Does it sound like a high frequency rumble, a tapping noise, etc.? If a high frequency rumble, I'd suspect a tensioner or idler pulley, possibly an alternator bearing.

-Rod

[GalateMLS01]

It's kind of like a swishing sound, it repetative and i've taken a dowl rod and placed it on top of the valve cover to listen to exactly where it's coming from. The loudest spot is on the two cam gear humps. The way the car acts is as if a bearing siezed up and is putting friction on the chain causing it to idle rough and a bit slugish, throttle response is ok but when coming to a stop it idles way down and comes back up.

[shorod]

A disconnected vacuum line or problem with the intake air tubing could cause the rough idle though, as well as explain the check engine light, and be consistent with that happening just after you took the intake system off. How soon after you had the intake system off did the noise start? If you had taken this car to the shop and they had the same parts off and the noise started the same duration following, would you sign it off as coincidence, or would you take it back and make them reinspect their work? If the latter, you should reinspect your work. No one's perfect.

Maybe the noise you're hearing is an air leak rather than a bearing or timing conponent issue.

-Rod

[GalateMLS01]

I would have to say it was about 2 -3 weeks ago. I've rechecked the intake and found the reason the cel was coming on, one of the clips on one of the hoses broke, but the noise is not related to that. I'm waiting for some nicer weather to take the vavle cover off and inspect the cam gears.