Belt tensioner pulley causing erratic idle?

[Blackwell808]

Hear me out guys, but is it possible for the bearings in the belt tensioner pulley to cause an erratic idle? A friend brought it up that maybe it’s binding because it’s wearing out and causing a draw on the engine basically. I am only having idle issues. And I notice when the engine is surging in the lower rpms, it makes a squeaking noise from the pulley area. Metco pulleys everywhere else but factory tensioner. The car pulls great still and drives fine. As I said to him I’ve noticed when I’m coasting from say, 50mph in 4th, the car will coast smooth then suddenly feels like an engine brake comes on and starts to slow down a bit faster. And goes back and fourth. If that makes sense. But at idle, it’s just like it’s right there to a smooth idle but something is keeping it from staying there. I’ve checked vac leaks, iac, intake boots, and cleaned my maf. Even put new o2 sensors in and quality e85. So I’m at a total loss on what my issue is. So any advice would be very helpful

 

[Blkkbgt]

Hear me out guys, but is it possible for the bearings in the belt tensioner pulley to cause an erratic idle? A friend brought it up that maybe it’s binding because it’s wearing out and causing a draw on the engine basically. I am only having idle issues. And I notice when the engine is surging in the lower rpms, it makes a squeaking noise from the pulley area. Metco pulleys everywhere else but factory tensioner. The car pulls great still and drives fine. As I said to him I’ve noticed when I’m coasting from say, 50mph in 4th, the car will coast smooth then suddenly feels like an engine brake comes on and starts to slow down a bit faster. And goes back and fourth. If that makes sense. But at idle, it’s just like it’s right there to a smooth idle but something is keeping it from staying there. I’ve checked vac leaks, iac, intake boots, and cleaned my maf. Even put new o2 sensors in and quality e85. So I’m at a total loss on what my issue is. So any advice would be very helpful

First of NO, not a chance would a binding bearing cause you idle issues. The belt would simply slip around it and most likely come off completely if that were to happen because the tensioner would no longer be able to perform its job correctly at that point. If you have concerns about the bearings of ANY of your idler pulleys take the belt off and hand check them for play and noise. Other than that put it out of your mind.

Second, the fact that it feels like someone is putting the brakes on your car when coasting tells me you have more than idle issues. Based on you description I am not sure where to tell you to start other than with some data logs if you have that capability.

 

[Blackwell808]

First of NO, not a chance would a binding bearing cause you idle issues. The belt would simply slip around it and most likely come off completely if that were to happen because the tensioner would no longer be able to perform its job correctly at that point. If you have concerns about the bearings of ANY of your idler pulleys take the belt off and hand check them for play and noise. Other than that put it out of your mind.

Second, the fact that it feels like someone is putting the brakes on your car when coasting tells me you have more than idle issues. Based on you description I am not sure where to tell you to start other than with some data logs if you have that capability.

Other issues like? It’s not like someone’s hitting the brakes it’s just getting a little more resistance when slowing down than normal. I’m just tossing ideas around at this point not trying to sound dumb. I’ve checked all I can. My short term trims were within spec. Long term I didn’t watch too hard but I saw 1 I think. Short term was maybe between .95-1 at idle if I remember right? I could be wrong so don’t quote me. These are from what I can remember from earlier today

 

[01yellercobra]

When it "hits the brakes" it might be going into coasting fuel shut off (CFSO). You can tell because the wideband will show full lean. Some tuners have it more aggressive than others.

 

[Black02GT]

When it "hits the brakes" it might be going into coasting fuel shut off (CFSO). You can tell because the wideband will show full lean. Some tuners have it more aggressive than others.

Id say you're right. Still sounds like something else going on though to make it kick out of CFSO and back in and idle funny.

 

[Blackwell808]

When it "hits the brakes" it might be going into coasting fuel shut off (CFSO). You can tell because the wideband will show full lean. Some tuners have it more aggressive than others.

Then that’s probably what I am feeling.

 

[Blkkbgt]

Is this something that popped up on its own or was work done on the car right before?

 

[Blackwell808]

Is this something that popped up on its own or was work done on the car right before?

Literally just popped up. It was never a perfect dead on idle but it’s gotten noticeably worse and now it’s just constantly hunting for an idle sometimes dying. It’s better with the ac on. With it off it’s just all over it seems like. I was driving it and I got a check engine light for both banks being lean. Replaced o2 sensors and put vp e85 to make sure fuel wasn’t the issue. No help. Have checked for vacuum leaks as well. There is no egr or evap. Cleaned the maf and checked all intake boots. I’m just at a loss at this point. Probably going to take it to a dyno shop and find out what’s going on. The previous dyno tuner whom I can’t get ahold of suddenly said something about my maf being maxed out already and it would need a hardware retune to have a perfect idle but it wasn’t bad enough to bother me until here recently where it’s gotten worse. It has the gt500 slot style maf. Custom 4” intake.

 

[Blackwell808]

Literally just popped up. It was never a perfect dead on idle but it’s gotten noticeably worse and now it’s just constantly hunting for an idle sometimes dying. It’s better with the ac on. With it off it’s just all over it seems like. I was driving it and I got a check engine light for both banks being lean. Replaced o2 sensors and put vp e85 to make sure fuel wasn’t the issue. No help. Have checked for vacuum leaks as well. There is no egr or evap. Cleaned the maf and checked all intake boots. I’m just at a loss at this point. Probably going to take it to a dyno shop and find out what’s going on. The previous dyno tuner whom I can’t get ahold of suddenly said something about my maf being maxed out already and it would need a hardware retune to have a perfect idle but it wasn’t bad enough to bother me until here recently where it’s gotten worse. It has the gt500 slot style maf. Custom 4” intake.

Is this something that popped up on its own or was work done on the car right before?

So i guess it wasn’t sudden but as soon as I purchased the car and got it here to Arizona, I noticed the idle getting a little more erratic. I took it to a dyno for an evaluation to make sure everything was all good with the fuel, air/elevation change. It came from Wisconsin. The guy is the one who said something about the maf. Idk if after driving it’s having trouble learning to this air here compared to what it learned in Wisconsin

 

[MG0h3]

So i guess it wasn’t sudden but as soon as I purchased the car and got it here to Arizona, I noticed the idle getting a little more erratic. I took it to a dyno for an evaluation to make sure everything was all good with the fuel, air/elevation change. It came from Wisconsin. The guy is the one who said something about the maf. Idk if after driving it’s having trouble learning to this air here compared to what it learned in Wisconsin

Took my car from sea level to 4’k where I live no issue other than lost a couple psi in boost.

I know you had it on the dyno but what all was checked? Maybe you need a better tuner to work on the whole thing

Also possible you have an idle air control issue since having the AC changes things.


“BLM is doing God’s work”
2KblackGT

svtperformance.com mobile app

 

[Blkkbgt]

Literally just popped up. It was never a perfect dead on idle but it’s gotten noticeably worse and now it’s just constantly hunting for an idle sometimes dying. It’s better with the ac on. With it off it’s just all over it seems like. I was driving it and I got a check engine light for both banks being lean. Replaced o2 sensors and put vp e85 to make sure fuel wasn’t the issue. No help. Have checked for vacuum leaks as well. There is no egr or evap. Cleaned the maf and checked all intake boots. I’m just at a loss at this point. Probably going to take it to a dyno shop and find out what’s going on. The previous dyno tuner whom I can’t get ahold of suddenly said something about my maf being maxed out already and it would need a hardware retune to have a perfect idle but it wasn’t bad enough to bother me until here recently where it’s gotten worse. It has the gt500 slot style maf. Custom 4” intake.

The fact that the issue is sudden tells me you don't have a tune issue. Tunes don't magically go bad but components do. I am going to guess you have a vacuum leak because BOTH banks are throwing lean codes.

I know you said you checked for leaks but you should probably do it again. Check around the blower and manifold not just the lines. Also check the vacuum at idle and see if its low.

 

[Blackwell808]

Took my car from sea level to 4’k where I live no issue other than lost a couple psi in boost.

I know you had it on the dyno but what all was checked? Maybe you need a better tuner to work on the whole thing

Also possible you have an idle air control issue since having the AC changes things.


“BLM is doing God’s work”
2KblackGT

svtperformance.com mobile app

Everything was checked on the dyno. He said everything looked good. But I’m tempted to take it to someone else. With the car idling and me unplugging the iac it won’t die but it’ll get very close to dying.

 

[Blackwell808]

The fact that the issue is sudden tells me you don't have a tune issue. Tunes don't magically go bad but components do. I am going to guess you have a vacuum leak because BOTH banks are throwing lean codes.

I know you said you checked for leaks but you should probably do it again. Check around the blower and manifold not just the lines. Also check the vacuum at idle and see if its low.

I may see if I can get a smoke test done to it. I’ve looked over all my lines and spot sprayed carb cleaner and couldn’t find/hear anything

 

[Blackwell808]

The fact that the issue is sudden tells me you don't have a tune issue. Tunes don't magically go bad but components do. I am going to guess you have a vacuum leak because BOTH banks are throwing lean codes.

I know you said you checked for leaks but you should probably do it again. Check around the blower and manifold not just the lines. Also check the vacuum at idle and see if its low.

Vacuum is at 20 so it’s good

 

[Blackwell808]

Bump