Low RPM, Uphill Load - Chugging/Exhaust Noise

[tystaco]

2000 Limited with 160k, west coast with no rust on the exhaust (unsure about internal). Noticed a month or so ago, driving up hill at low RPMs, I get a chugging noise....now, I would say it really sounds like an exhaust leak, except it is not constant at all. This noise exists at no other ranges and goes away as soon as you let off or can get the transmission to downshift.

I've poked around at the exhaust system and can't see anything out of whack. Noise comes from directly in front of you, so I thought maybe a manifold leak? Is it possible that a bad engine mount could allow some torqueing that creates a leak, but then goes away once it shifts out of that position?

I will try and get a video of it this weekend, as well as do the old in park engine mount check.

Really hoping it isn't anything major. Runs perfect otherwise.

 

[JohnOfTheJungle]

I think mine does something similar to this. I'm going to grease the u-joints soon and see if that helps, seems like others have had that help with the rumbling sound.

I also get the clunk when coming to a stop and also when letting off the brake to take off from a light, so I'm pretty sure it needs it.

 

[Buckaroo]

Noticed a month or so ago, driving up hill at low RPMs, I get a chugging noise....now, I would say it really sounds like an exhaust leak, except it is not constant at all. This noise exists at no other ranges and goes away as soon as you let off or can get the transmission to downshift.

The noise could be from metal to metal vibration associated with the exhaust system although I would typically describe it as a rattle - the level of vibration can change with RPM/speed/gear. Recommend you try to rock the exhaust back and forth with your hand from underneath (careful when hot!) and see if there is movement that would allow it to come in contact with the frame, etc. Also make sure all hangers are in place. You can do this with the truck off.

Buckaroo

 

[tystaco]

I think mine does something similar to this. I'm going to grease the u-joints soon and see if that helps, seems like others have had that help with the rumbling sound.

I also get the clunk when coming to a stop and also when letting off the brake to take off from a light, so I'm pretty sure it needs it.

The clunk might be your slip yoke....look up timmy the toolman on youtube.

Mine has much more of an exhaust chug sound than a rumble.

 

[tystaco]

The noise could be from metal to metal vibration associated with the exhaust system although I would typically describe it as a rattle - the level of vibration can change with RPM/speed/gear. Recommend you try to rock the exhaust back and forth with your hand from underneath (careful when hot!) and see if there is movement that would allow it to come in contact with the frame, etc. Also make sure all hangers are in place. You can do this with the truck off.

Buckaroo

I crawled under it and shook stuff the other day, nothing seemed to move or be broken. Definitely not a rattling sound. I will check the engine mounts this weekend.

 

[tystaco]

Okay...so no video yet, but it did it going up the first climb into the coastal range on Saturday...started in around 50 mph, did not go away with downshifting this time. Tried to get it to do it on Sunday going up a few of the hills I have heard it on in the past, ~30-40mph, did not hear it at all.

It also seemed more of a rattling sound on Saturday. I will solve this, but it will likely take me a few weeks as it is my wife's ride and I only get a shot at driving it at speed every other week or so. Also...still putting back together my truck from the wheel bearing/LCA Bushing/tie rod end replacement, so that has my priority over something I don't think is a major concern just makes it sound like crap.

 

[tystaco]

Is this a plugged catalytic converter?!? I am looking at some videos and hearing similar stories...some starting with hill climbs.

I am lead to think this because we are also smelling a firework odor after hill climbs.

 

[tystaco]

Closing the Loop

I took the vehicle in to an exhaust shop to have it checked over...they tossed it on a computer and found Active and Pending P0171...bank lean codes.

Turns out my CEL had been removed by the PO, so I was thinking I didn't have a code (this is why you should get a scangauge or blue tooth scanner).

Chasing the P0171, I cleaned the MAF and replaced the front O2 sensor...didn't fix it...so I replaced the MAF and cleared the P0171 code.

I then had the muffler replaced because it seemed rough...in the end, my chugging up hill problem is gone...I believe it to have been the MAF causing some havoc.

 

[SpidermanGeek]

I took the vehicle in to an exhaust shop to have it checked over...they tossed it on a computer and found Active and Pending P0171...bank lean codes.

Turns out my CEL had been removed by the PO, so I was thinking I didn't have a code (this is why you should get a scangauge or blue tooth scanner).

Chasing the P0171, I cleaned the MAF and replaced the front O2 sensor...didn't fix it...so I replaced the MAF and cleared the P0171 code.

I then had the muffler replaced because it seemed rough...in the end, my chugging up hill problem is gone...I believe it to have been the MAF causing some havoc.

Could have been your muffler all along. Uneducated guess, but sometimes condensation builds up in the exhaust system from sitting overnight, that kind of thing. If the truck sat for some periods of time, over time the innards of the muffler could have rotted and broke. If stuff was loose in there, it could have essentially clogged part of the muffler exit during uphill climbs. Thus creating a back pressure that would see you having adverse effects that could sound like they came from the front. The engine could have been chugging from the restricted exhaust. Similar to what happens when a cat gets clogged.

Plausible? I dunno, I'm spitballin' here.

 

[tystaco]

Could have been your muffler all along. Uneducated guess, but sometimes condensation builds up in the exhaust system from sitting overnight, that kind of thing. If the truck sat for some periods of time, over time the innards of the muffler could have rotted and broke. If stuff was loose in there, it could have essentially clogged part of the muffler exit during uphill climbs. Thus creating a back pressure that would see you having adverse effects that could sound like they came from the front. The engine could have been chugging from the restricted exhaust. Similar to what happens when a cat gets clogged.

Plausible? I dunno, I'm spitballin' here.

I agree 100%, which is why I went after the muffler (might have been the cat, but I went for the cheaper solution first).

As I went through troubleshooting this, I kept thinking it sounded like an exhaust leak from the engine bay, but only under load and uphill....so the same conclusion...a clog causing back pressure/misfire?. I would have stayed on that line had I not gotten the code reader. I have never experienced a misfire (as far as I know) but I may have been feeling it during the chugging? Either way, the problem is gone after either the MAF or muffler change....but I wasn't waiting in between as I wanted the problem gone...as soon as I cleared the code I replaced the muffler.