Hard shift uphill

Hello I have recently purchased a Toyota Tundra 2004 4.7L automatic 4wd.
I replaced the starter, spark plugs, coil packs and air filter. It fires up great has lots of power. But going up hill at 35mph to 40 mph rpm hit 4500 and then after shifting I have gas pedal to the floor it accelerates very slowly. But on flat ground no issue smooth all the way to 80mph. Check engine light is off but code for knock sensor and O2 sensor 2 bank2. I’m stumped and looking for advice

 

I had a '00 4.7L Auto 4WD, so essentially the same truck.

Mine developed an occasional funny shift from 1 to 2 only when going uphill, kinda' "clunk" in. I took it to a trans shop and even hooked up to a laptop they couldn't find a problem and wouldn't take my money.

I would shift it manually from 1 to 2 when going uphill, and by running it up a tad higher before shifting it didn't do it... a little more line pressure I presume.

Does it feel like yours is slipping after it shifts, or just not a lot of power?

It could just be a gearing thing... There's a bit of a gap in the powerband on these Gen 1's where it doesn't quite have the oomph to pull strong in the next gear when going uphill.

 

Doesn’t feel like a slip as much as something holding it back after the shift.

 

Transmission fluid level was low but no change when I topped it off. I’m planning to do a filter and fluid change buying used I don’t know if it’s been done before.

 

Might just be that flat spot in the gearing/powerband. While the torque of the 4.7's is "decent"... they don't really make a lot of HP.

 

Didn’t seem to have the issue before I changed starter but I didn’t know how this would affect shifting

 

Could be the spark plugs are gapped incorrectly or simply the motor doesn’t like them - as silly as that sounds. What plugs did you use, and did you check the gap?

Or like @SD Surfer mentioned, it could just be a flat spot in the power band. I’m not as familiar with the Gen1 transmission gearing, but being a 3 speed with OverDrive, it’s pretty common on many vehicles for the engine to drop below peak torque on the 1-2 shift. When I was shopping for a truck, that was one thing I liked about the Gen2 tundra vs say a Chevy 2500 gasser - the Chevy had a lull between 2nd and 3rd where it dropped below peak torque even if you redline it in 2nd. But, like I said, that’s pretty common for a three speed transmission.

 

That would be my guess, as that was very much my experience in my Gen 1.

Those 4.7's also don't make their peak torque until fairly high revs... (I wanna' say it's like 3,400 RPM's?) So with just the 3 speeds there's some definite flat spots in the curve. Not much of an issue on the flats, but throw some incline in the mix and it becomes much more noticeable.
Granted, 3,400 isn't that high... the 5.7 makes peak #'s @ 3,600 rpm, but I think it makes more sooner, where the 4.7 does not. I remember with my '00 you could very distinctly feel it come on much stronger when you hit the sweet spot.
I seem to remember reading somewhere that the 5.7 makes like 80% of it's power even down around 2K???

Fortunately the 1st Gens don't mind being wound up all day long when there's work to be done. Great trucks... I kinda' miss the ol' girl.

 

Check to see if rodents got under the manifold and chewed up the knock sensor leads. It's a legitimate problem on these trucks.

However, the fact you just replaced the starter makes me think you might've improperly reattached the harness for the knock sensors and that has the knock sensor code pending.

But I also think that's a separate issue from the other, since the "lag/stumble" when stomping on gas" is more indicative of a fuel/spark issue, or MAF issue. But given you just did a bunch of ignition related stuff, we need to ask.

Is this symptom something new, that just started after your recent work?

What is the EXACT brand and part number of plug you bought?
More importantly WHERE did you buy the plugs and the coil packs?

Vast majority of the time, stomping on the gas and getting no response is spark related. Don't get me wrong, it could absolutely be fuel pump (it's never the fuel filter) and it could be, like, MAF degradation or needs cleaning, but ... I'm leaning towards spark/ignition.

 

I used iridium plugs and gap was good. Did have rat signs under manifold had to shop vac out the seeds underneath it maybe damaged knock sensor I’m going to replace it and change transmission filter and I’ll post my findings this weekend thank you for all your suggestions got lots to think on now

 

Bought from where?
What brand/part number?
Was this happening before the recent work?

(just looking to double-check on the 2nd Q, and the 1st Q is because there are several known sources of counterfeit product, 3rd so we know if this is a constant issue or recent occurence)

Don't bother changing transmission filter. It's just a metal screen and there is zero value in dropping the pan to change it.

 

@00boomstick these questions are very important here.

Also curious if the intake gaskets are set right or if that could be part of your issue. After changing the starter the gaskets might not be right.

 

Update changed transmission filter and fluid seams to have fixed the issue. Was several quarts low so maybe an air bubble or lack of fluid to torque converter. Thank you everyone for your input

 

Yeah, that'll do it for sure!

Glad you got it sorted out.