Idle lopes, Rough Idle #3 cyl. misfire Please help!!

[BlackoutTBEroc]

Hello , I love this site.Thanks to who ever can help me. My truck at idle just don't seem right. It kinda feels like i had cam work. But not really . you know how the car kinda bounces when its cam. It lopes you can look at the antenna and it shakes like we have 70mph winds. and the exhaust pipe does the same.I did have at one time a #3 cyl misfire. i have changed the spark plugs,cleaned the throttle body.Never got the SES light again. I cant find anything about the same issue on the forums. and the ones that did have the same issue never got a response. i hope someone can help. my truck runs pretty good except for that and getting a bird squeak when the ac is on. I think that is when its engaging and disengaging.






05 Lt Chevy Trailblazer I6 4.2

138,000 miles.

 

[Wooluf1952]

Hello , I love this site.Thanks to who ever can help me. My truck at idle just don't seem right. It kinda feels like i had cam work. But not really . you know how the car kinda bounces when its cam. It lopes you can look at the antenna and it shakes like we have 70mph winds. and the exhaust pipe does the same.I did have at one time a #3 cyl misfire. i have changed the spark plugs,cleaned the throttle body.Never got the SES light again. I cant find anything about the same issue on the forums. and the ones that did have the same issue never got a response. i hope someone can help. my truck runs pretty good except for that and getting a bird squeak when the ac is on. I think that is when its engaging and disengaging.
05 Lt Chevy Trailblazer I6 4.2

138,000 miles.

Is the serpentine belt original? At that mileage it probably needs to be replaced and could be the reason for the chirp.
The lope could be the engine mounts. Have you checked them? Is there a lot of movement when you rev the engine? Does it smooth out when driving and seem worse when idling in drive or reverse?

 

[BlackoutTBEroc]

thank you for your help. I use to have that squeak when it was warming up. So I changed the belt and that fixed it. I was thinking the same thing. Its weird how it squeaks. like in overdrive while in motion. around 30mph.. ima check on the motor mounts. i dont feel the lope while driving. its only while in park or at a stop light. its kinda hard to tell in drive.

 

[The_Roadie]

The big clues to bad motor mounts are that the roughness doesn't show up on the tach, it's exactly 10 Hz, worse in DRIVE with your foot on the brake than in idle, and it might get better when warm than if it's near freezing.

 

[BlackoutTBEroc]

The big clues to bad motor mounts are that the roughness doesn't show up on the tach, it's exactly 10 Hz, worse in DRIVE with your foot on the brake than in idle, and it might get better when warm than if it's near freezing.

I have read so much of your stuff. I think the motor mounts are good. but it was def worth the try.I appreciate ur time.. i dont feel anything when braking. When i am at a stop. you can actually feel it in your body if you try to stay still. its like lope, lope, lope,Thank you.

 

[The_Roadie]

Your lope sounds like that I might call a surging. Also much lower frequency than 10 Hz. The motor mount 10 Hz vibration is also a rotational vibration you won't feel in your body as a fore/aft surging. At your mileage, if you've never replaced your CPAS I'd try that as a relatively cheap shotgun attempt. It would cost you more than that to pay a mechanic to hook it up to a Tech II to do an in-depth diagnostic.

 

[BlackoutTBEroc]

I have thought that. But wanted to get more peoples opinions. it hasn't throw a code(SES) in about 9 months. I do have my own scanner. But its the one from advance Auto.. the pro version. lol..All says ok. Just dont understand because every other Tb. does not do the same thing. I change tires for a living and I have been in so many tB and I havent seen the same kinda issue. you can actually see the miss. if I look at the tail pipe you can see the studder..My antenna flops from side to side.. I have notice it stalling out while its warming up when the a/c is on. Thankls again.

 

[MacMan]

What brand of plugs did you install? Did you remove the throttle body from the engine to clean both sides of the throttle plate, and did you have the battery disconnected for at least 35-40 minutes while you did it?

 

[BlackoutTBEroc]

Yes I did leave Battery off for more then 30 min

 

[BlackoutTBEroc]

Thanks for ur reply. I used the ones that everyone on here says to use ac delco it was def the right part # I wish it was the wrong spark plugs. Yes I took the whole throttle body off. Cleaned it as much as possible any more .. I appreciate ur time.. I have been reading all of the forums I can for about a year know. I know a lot from all of the knowledge from the great people on here . Thanks again to all the members for the support..

 

[BlackoutTBEroc]

I Hope I can Get this Figured out..