Whining noise, slow acceleration, MPG's getting worse. What to do next?

POW

Original poster
Member
May 23, 2014
38
So I have the whining noise going on under the hood & the cars acceleration seems to be very slow lately. I noticed MPGs have dropped as well. Mixed (in Houston traffic) I should be averaging around 15ish & highway 17-18. This already isn't very good but last couple fill ups averaged around 13.5-14.

I am assuming & going to start with changing the idler pulley to address the whining noise. Can anyone link me to the part I need to order?

Would this also impact my acceleration and/or mpgs? What else should I do right now? 02 sensor?

Car currently sits at about 122K miles.

Here is everything that has been done:

New tires at 95K, rotated every 5K since.
K&N air filter at 99K (has not been cleaned since)
New water pump, thermostat/CTS, coolant & transmission flush, serpentine belt, & radiator at 102K miles
New front right wheel bearing at 103K
Spark plugs replaced at 103K
Throttle body cleaned at 103K
New battery (duralast gold) at 120K

I am also due for my next oil change (mobil 1 synthetic) & will be doing that very soon.

I know the biggest issue is I have not done the transfer case fluid or the differential fluids!!!!! I don't ever use the 4wd but yes I know getting these fluids done are very important & a top priority. I have the transfer case fluid sitting at my house just need to do it!

What else should I do or think about doing? I have no codes or lights showing up & other than the recent whining noise & acceleration the truck has been running smoothly & in good shape. Just want to be as proactive as I can in keeping it that way.

  • Transfer case fluid
  • differential fluids
  • idler pulley
  • 02 sensor?
  • clean air filter
  • oil change/filter
  • Oil pressure switch/sensor (had this issue once, seems to be bad sensor, have it in the garage just need to do it)

Can anyone link me to the correct 02 sensor & idler pulley to order? I prefer to order through amazon if available.

Thanks for the help. You guys have always been my go to when I have any issues/questions and always lead me in the right direction.
 

Robbabob

Member
Dec 10, 2012
1,096
What temperature do you run at? The needle should be just below vertical when warmed up ~10 minutes of driving.

If it's running low, even without a CEL alarm, the truck will run rich and clog the cat, THEN your mileage will drop.

Good luck!
 
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Reactions: Mike w

POW

Original poster
Member
May 23, 2014
38
Mike, thanks I am going to order those right now.

Rob, I believe my temp has been right at the 210 mark or around there. I haven't noticed it fluctuating and I generally keep a close eye on my dash/gauges now.

Thanks to both for the replies!
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
There are lots of things that could affect mileage. Look at this thread for lots of things to check.
 

POW

Original poster
Member
May 23, 2014
38
Mike w said:
Hey Mike, or anyone else,

Are you sure the one you linked above is the upstream?

I think this one is the upstream:

http://www.amazon.com/ACDelco-213-1698-Original-Equipment-Heated/dp/B000NW4PJC/ref=pd_sim_263_2?ie=UTF8&refRID=170S0JB1TFC0B2TB5XH6

I believe the one Mike posted is the downstream but can someone please confirm before I order them.

Also, should I order & replace both? Or only the upstream?

Thanks,

Alex
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
The one you posted is the upstream. I cross referenced with RockAuto and for that number says UPSTREAM IN MANIFOLD.
 

POW

Original poster
Member
May 23, 2014
38
Mooseman said:
The one you posted is the upstream. I cross referenced with RockAuto and for that number says UPSTREAM IN MANIFOLD.
Thanks, Moose.

If I am going to change one, is it best to change the upstream first? Or should I do both?
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
The downstream one, unless it actually fails, you can leave alone. All it does is report if the cat is working and throws a code if it's below a certain threshold. Does nothing for fuel mixture.
 

Mike w

Member
Jun 24, 2014
287
POW said:
Hey Mike, or anyone else,

Are you sure the one you linked above is the upstream?

I think this one is the upstream:

http://www.amazon.com/ACDelco-213-1698-Original-Equipment-Heated/dp/B000NW4PJC/ref=pd_sim_263_2?ie=UTF8&refRID=170S0JB1TFC0B2TB5XH6

I believe the one Mike posted is the downstream but can someone please confirm before I order them.

Also, should I order & replace both? Or only the upstream?

Thanks,

Alex
Sorry Alex that is correct i copied the wrong link, i had multiple tabs up. Please report if it improved MPG
 

POW

Original poster
Member
May 23, 2014
38
Mike w said:
Hey guys,

I ended up ordering this part & finally got around to putting it in last night. As soon as I fired it up the whining noise caused by the bad bearings was gone but there was a screeching sound like the pulley wasn't a good fit. I used the same washer/dust shield & greased it up good before I put it back in..

At first we thought maybe we had it too tight so we loosened it a turn & the noise was better but still didn't sound right & seemed like the belt was getting hotter than normal.

We took out the AC Delco pulley & compared it to the OEM & the ACDelco has a raised rim around the bearings inside the pulley where the OEM did not, it was flush. We believe that is the culprit & that the ACDelco is not the correct fit. Can anyone confirm?

We ended up putting the OEM back in (still have the whining noise) & I am going to pick up a new one at Autozone.

Anyone recommend the best one to use?
 

Inert_Static

Member
Jun 22, 2013
249
POW said:
Hey guys,

I ended up ordering this part & finally got around to putting it in last night. As soon as I fired it up the whining noise caused by the bad bearings was gone but there was a screeching sound like the pulley wasn't a good fit. I used the same washer/dust shield & greased it up good before I put it back in..

At first we thought maybe we had it too tight so we loosened it a turn & the noise was better but still didn't sound right & seemed like the belt was getting hotter than normal.

We took out the AC Delco pulley & compared it to the OEM & the ACDelco has a raised rim around the bearings inside the pulley where the OEM did not, it was flush. We believe that is the culprit & that the ACDelco is not the correct fit. Can anyone confirm?

We ended up putting the OEM back in (still have the whining noise) & I am going to pick up a new one at Autozone.

Anyone recommend the best one to use?
I just replaced mine last week. Some of the pulleys had exposed bearings and I did not trust that design. I got the sealed one from O'Reilly's.

http://www.oreillyauto.com/site/c/detail/GATE/36227/03307.oap?year=2008&make=GMC&model=Envoy&vi=1441132&ck=Search_03307_1441132_-1&pt=03307&ppt=C0328

and it worked like a champ.
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
I used an aftermarket one and I couldn't reuse the dust shield. Works fine otherwise and the shield is really useless.
 

POW

Original poster
Member
May 23, 2014
38
I just swapped out the ACDelco with a Duralast from Autozone & it sounds brand new. Seems to have helped with power as well but maybe that is just a mental thing as I am not hearing this awful whine as I hit the gas.

Thanks, y'all.
 

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