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5.3l Chevy Tahoe No Guts on STEEP Pull...

FleshEater

Ordinary Average Guy
Joined
May 21, 2020
Member Number
832
Messages
3,242
Loc
Pennsylvania
Okay guys, I’m having an odd issue.

Today I towed my trailer and full gear up about an 11% grade. No codes come up on the DIC, this never happens any other time, only when I tow up this mountain. It’s a rutted up, rough driveway up a mountain. Basically it feels absolutely gutless, even in manual 1st.

Is the motor due for a rebuild, too much weight at that grade and a dead stop? Gearing?

I’m at a loss. I don’t think it’s fuel, because I had a full tank, new fuel pump and lines. Maybe something like a solenoid that could be doing this?
 
I used this Tahoe prior and didn’t notice an issue until last time and this time. I put my foot to the floor and it feels like it has zero power.
 
Knock sensors picking up rattles and klunks and pulling all timing? Exhaust touching the frame and rattling is enough for the knock sensors to pick up.
 
How much weight is trailer and full gear?

This time we unloaded the machine at the bottom of the mountain. Trailer was about 1,000lbs. Gear was clothes for 3 guys, tools, fluids, 6 cases of beer and 5 cases of water.

If it’s the knock sensor, how do I remedy that?
 
Okay guys, I’m having an odd issue.

Today I towed my trailer and full gear up about an 11% grade. No codes come up on the DIC, this never happens any other time, only when I tow up this mountain. It’s a rutted up, rough driveway up a mountain. Basically it feels absolutely gutless, even in manual 1st.

Is the motor due for a rebuild, too much weight at that grade and a dead stop? Gearing?

I’m at a loss. I don’t think it’s fuel, because I had a full tank, new fuel pump and lines. Maybe something like a solenoid that could be doing this?

Maybe because it is really hot the fan clutch was locked up and the pcm pulled some timing?
 
Maybe because it is really hot the fan clutch was locked up and the pcm pulled some timing?

It’s a 2010, GMT 900 with an electric fan...

The knock sensor makes sense. The trailer bouncing could even set it off.
 
Might be a dumb question, but was traction control going nuts? Did it drive fine everywhere else? I’m thinking with that grade, on a rough road, it could be slipping and tc trying to keep it from slipping.
 
It’s a 2010, GMT 900 with an electric fan...

The knock sensor makes sense. The trailer bouncing could even set it off.

I don’t think a trailer bouncing will set off a knock sensor. They are separated by rubber motor mounts and buried in the valley of the motor. A sensor could be going bad though.

This sounds more like torque management plus not quite the right gear ratio for the job.
 
I don’t think a trailer bouncing will set off a knock sensor. They are separated by rubber motor mounts and buried in the valley of the motor. A sensor could be going bad though.

This sounds more like torque management plus not quite the right gear ratio for the job.
+1
A knock sensor affects timing. But only at that instant when it detects the engine knocking. if it adjusted timing to the point that you lacked power you woild probably hear/feel the engine bucking or run rough.

I think your trans decided to try it in a higher gear. Shift manually or stop the skinny pedal till she kicks down
 
Might be a dumb question, but was traction control going nuts? Did it drive fine everywhere else? I’m thinking with that grade, on a rough road, it could be slipping and tc trying to keep it from slipping.

Traction control never kicked on.

It towed fine through all the mountains, plenty of power.
 
I don’t think a trailer bouncing will set off a knock sensor. They are separated by rubber motor mounts and buried in the valley of the motor. A sensor could be going bad though.

This sounds more like torque management plus not quite the right gear ratio for the job.

Now, what if the motor mounts would be bad, which mine probably are the original mounts with 132k on them? This car towed this up the driveway perfectly fine when they had it smoothed over at the beginning of the year. Now that it's all rutted up and washed out, I'm having issues.

If a sensor was going bad, I feel it would give intermittent issues, but it doesn't.
 
+1
A knock sensor affects timing. But only at that instant when it detects the engine knocking. if it adjusted timing to the point that you lacked power you woild probably hear/feel the engine bucking or run rough.

I think your trans decided to try it in a higher gear. Shift manually or stop the skinny pedal till she kicks down

I was manually shifted in 1st, pedal to the floor.

I'm going to put new motor mounts and transmission mount on and see if it helps for the next tow.
 
I was manually shifted in 1st, pedal to the floor.

I'm going to put new motor mounts and transmission mount on and see if it helps for the next tow.

It wont
 

The only other thing I can think of is simply losing momentum. When the driveway was smoother I was able to slightly maintain momentum. Now? The washouts are so bad I’m crawling.

So you think a regear is needed? That was my first thought, but I’ve never experienced this before.
 
Does it have low range?
 
This Tahoe is neither AWD or 2WD, but has no 4lo. I know...it's weird. I've never seen it before, either.

The gearing issues makes no sense on this, because the motor won't even rev, it just bogs down. If I was under geared in the axles, I feel like the motor would still rev.
 
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Well, I forgot to put it in my phone, but I'm guessing I did plugs about 16k miles ago. Maybe less. Also did new serpentine, idler pulley, all fluids, etcetera all the time before towing trips. Just put a cold air intake on it, too.
 
What sucks is that I can't even test out anything I try to fix until I tow back down to WV. I have no hills that steep or bumpy near my house to even try this on.

Motor mounts and trans mount probably needs done anyways, so I can at least try it. Hell if I know what else to do other than tow with the truck down there.
 
Do you notice any change between holding it at ~75% and at 100% throttle?

do you have a scan tool with capability to live stream PIDs? To monitor # of misfires. Misfire can occur when there is high load and failed to arc across electrodes. And to look at MAF, MAP, o2 sensors, and which loop it is in. If I remember correctly WOT automatically put it into open loop, but that may be for older cars, though.

did you actually turned the TC off? You was going up in 4wd or 2wd? TC can kick in undetected and held power back all the way up thinking there’s risk of tire slippage. Imagine just like you will on snow and ice, as if you’re to floor it & TC kick on to stop tires from slipping and bring it down to a slow spin despite the pedal is held against the floor.

oh yeah, one more thing, what about your trailer brakes and what controller you’re running? Steep & bouncy enough to pissed off the controller and it apply trailer’s brake ?
 
so did the issue appear after your cold air intake?
I wonder what the IATs are.
 
Do you notice any change between holding it at ~75% and at 100% throttle?

do you have a scan tool with capability to live stream PIDs? To monitor # of misfires. Misfire can occur when there is high load and failed to arc across electrodes. And to look at MAF, MAP, o2 sensors, and which loop it is in. If I remember correctly WOT automatically put it into open loop, but that may be for older cars, though.

did you actually turned the TC off? You was going up in 4wd or 2wd? TC can kick in undetected and held power back all the way up thinking there’s risk of tire slippage. Imagine just like you will on snow and ice, as if you’re to floor it & TC kick on to stop tires from slipping and bring it down to a slow spin despite the pedal is held against the floor.

oh yeah, one more thing, what about your trailer brakes and what controller you’re running? Steep & bouncy enough to pissed off the controller and it apply trailer’s brake ?

I don’t have a scan tool. No difference between 75% and 100%.

My traction control never kicked on. Next time up that mountain I can turn it off, see if it helps.

This happened before the CAI.

Tahoe is currently in Colorado and running great.
 
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