Sluggish acceleration?

[{tpc}]

Ok so I seem to have been experiencing this for awhile now, can't quite nail it down. When I first start up the truck in the morning, everything seems fine for the first few miles. Then I go to get on the expressway, and it feels sluggish. If I nail the throttle it downshifts and feels fine. I drive like a grandma so maybe thats it, but it still just feels like its not accelerating like it should.

It has no codes and no CEL or warnings or anything. The 02 sensors seem to be acting appropriately, but I am unclear on the 5.3 if there is more than just 2.

In the winter months on occasion I would get a throttle position sensor cel, which I could clear and it would go away for a bit. Since the weather has warmed up, hasn't happened. I have yet to clean the throttle body or the maf sensor.

Things I have done in the past few months:

Changed air filter and spark plugs.
Changed front/rear diff fluid, transfer case fluid, transmission fluid and filter.
Some new front end parts and new tires.
Ran some techron through the fuel system.

I've also noticed a slight decrease in fuel mileage. About 1 - 1.5 mpg. This seemed to occur after I got the new tires, and I was hoping it wouldn't happen as a result of the tires, but maybe it did as I have read comments on some tire sites that people saw increase or decrease depending on tires.

I have a couple of broken exhaust manifold bolts. I don't think its leaking or leaking that badly if it is.

There is a very slight vibration in the gas pedal, seemingly at all times. Occasionally it goes away, either that or I forget about it lol. But when I drive the wifes envoy, it isn't there, so I'm not imagining it.

Thats about all I know. At first I thought it might be because of the exhaust manifold or a partially plugged cat. But if the cat was plugged and if the manifold was leaking, wouldn't the leak mask the cat?

I've considered taking it to the meineke shop down the street to see if they could tell me if the cat is plugged or if I need new 02 sensors. Everyone gives them good reviews, but I have this feeling that the only way to figure that out is shotgunning the parts or at least that's what they will want to do.

I have no history on whether or not the coolant temp sensor or thermostat have even been changed. Seems to be acting correctly though. (I made a post of fans running alot). The fan ran quite a bit yesterday actually but it was pretty hot and humid out, so I kind of expected it. Truck has the electric fans.

Truck is 2007 5.3l with 199k miles on it.

 

[Gerbil21]

Don't have a 5.3 but it may be the transmission staying in lockup, next time push the brakes a bit, that should release the torque converter from lock up (you should notice a rpm increase) then when you give it gas it shouldn't hesitate. You can also try driving in 3rd which still has lockup but it dosent go there as much only at higher speeds

 

[{tpc}]

Why would the trans stay in lockup from a dead start? I think there might be a way to see if its in lockup via the torque app...

The weird thing is, I've had the truck for over a year now, and this has not happened the entire time. So either I caused it somehow, or something is causing it because its old, worn, or needs maintenance.

 

[Gerbil21]

Why would the trans stay in lockup from a dead start? I think there might be a way to see if its in lockup via the torque app...

The weird thing is, I've had the truck for over a year now, and this has not happened the entire time. So either I caused it somehow, or something is causing it because its old, worn, or needs maintenance.

I thought that you were driving on a on-ramp and giving gas, didn't know it was from a dead stop. Also I'm not sure how torque shows it but they should be info on tc lockup

If it's from a dead stop then yes t.b. and maf cleaning is a good idea also I doubt the exhaust leak will mask a cat since it dosent seem like it leaks that much but it may let air in causing weird readings on the o2 sensor

 

[{tpc}]

Well I was driving on the on-ramp and giving gas, however it starts from a dead stop most every time. Its a right hand turn circle ramp.

I know the truck doesn't lack power, because when I womp on it, it will move out. I also made a 4 hour towing trip both ways and it performed fine. Hard to tell sluggish when your dragging 6k pounds behind you thought lol.

It's not overheating, and tranny temp seemed fine when I was towing. I think it might have hit 201 once. Usually runs in the 190's when towing.

 

[Gerbil21]

Well I was driving on the on-ramp and giving gas, however it starts from a dead stop most every time. Its a right hand turn circle ramp.

I know the truck doesn't lack power, because when I womp on it, it will move out. I also made a 4 hour towing trip both ways and it performed fine. Hard to tell sluggish when your dragging 6k pounds behind you thought lol.

It's not overheating, and tranny temp seemed fine when I was towing. I think it might have hit 201 once. Usually runs in the 190's when towing.

Well I don't know what it is then but I do hope you find the awnser, trans temp seems great 220 would be concerning

 

[Mooseman]

Have you tried manually downshifting it when accelerating onto the highway? Maybe the tranny is getting lazy downshifting. Does it do it when cold or also when fully warmed up?

There are 4 O2 sensors total, one in front of each cat and one behind. Only the front ones have any effect on engine performance. The rear ones only record cat efficiency. You could get a backpressure test done for the cats.

 

[{tpc}]

Have you tried manually downshifting it when accelerating onto the highway? Maybe the tranny is getting lazy downshifting. Does it do it when cold or also when fully warmed up?

There are 4 O2 sensors total, one in front of each cat and one behind. Only the front ones have any effect on engine performance. The rear ones only record cat efficiency. You could get a backpressure test done for the cats.

I have not tried manually downshifting...it feels like it is in the correct gear. There are only 4 of them so should be easy to count.

It seems to perform better when cold. When i leave the house in the morning, it always seems fine. Then about 3 miles down the road is where I get on the x-way...thats when I notice it.

 

[Mooseman]

Being cold, pressure might be higher and shifting better and then drops off a bit. If you're accelerating, it should at least kick off the TCC and also downshift if pushing on the go pedal enough. Maybe the TCC solenoid or valve is a little sticky.

 

[{tpc}]

So your thinking is it's internal to the transmission? Like an issue with the transmission pump itself?

If you recall, in my thread about the fan, I was commenting on possible t-stat or coolant sensor weirdness. Couldn't that also be an issue? I know it affect's fuel mixture, but I'm not exactly sure how it might be affecting my issue in this case.

If at first its saying "richen fuel mixture" because the engine is too cold, then the engine is warmed up and instead of saying "lean it out" its still pouring in more fuel, won't that cause poor acceleration as well? It would also explain a decrease in mpg, as well as the issue being masked during the colder winter months, right?

Thanks for talking me through this. My plan was to clean the maf and throttle body, but now its raining like heck so it will have to wait a bit.

I suppose the tps sensor could be at fault partially as well. Can't wait to see how nasty it is in the throttle body, and I'm hoping cleaning it will prevent reoccurance, at least for a little while, of the tps sensor issue. It actually hasn't popped up in months, but I'm not looking forward to buying a new throttle body to fix it.

 

[Gerbil21]

So your thinking is it's internal to the transmission? Like an issue with the transmission pump itself?

If you recall, in my thread about the fan, I was commenting on possible t-stat or coolant sensor weirdness. Couldn't that also be an issue? I know it affect's fuel mixture, but I'm not exactly sure how it might be affecting my issue in this case.

If at first its saying "richen fuel mixture" because the engine is too cold, then the engine is warmed up and instead of saying "lean it out" its still pouring in more fuel, won't that cause poor acceleration as well? It would also explain a decrease in mpg, as well as the issue being masked during the colder winter months, right?

Thanks for talking me through this. My plan was to clean the maf and throttle body, but now its raining like heck so it will have to wait a bit.

I suppose the tps sensor could be at fault partially as well. Can't wait to see how nasty it is in the throttle body, and I'm hoping cleaning it will prevent reoccurance, at least for a little while, of the tps sensor issue. It actually hasn't popped up in months, but I'm not looking forward to buying a new throttle body to fix it.

That sounds like a good starting plan I would also check Upstream o2 sensors in torque if there original then they should be replaced. Also TPS may need a replacement since you said in the winter times you get a code it may be moisture getting in. Check for codes now that it's raining and then check voltages on the TPS.

Also with those miles if the trans is original maybe it's time to get a shift kit, the ctpowertrain kit on eBay is good and should help extend the life of it especially since you tow.

Mines had 134k and the valve body gaskets were bad and there were about 3 checkbooks stuck in the separator plate

 

[Sparky]

So your thinking is it's internal to the transmission? Like an issue with the transmission pump itself?

If you recall, in my thread about the fan, I was commenting on possible t-stat or coolant sensor weirdness. Couldn't that also be an issue? I know it affect's fuel mixture, but I'm not exactly sure how it might be affecting my issue in this case.

If at first its saying "richen fuel mixture" because the engine is too cold, then the engine is warmed up and instead of saying "lean it out" its still pouring in more fuel, won't that cause poor acceleration as well? It would also explain a decrease in mpg, as well as the issue being masked during the colder winter months, right?

Thanks for talking me through this. My plan was to clean the maf and throttle body, but now its raining like heck so it will have to wait a bit.

I suppose the tps sensor could be at fault partially as well. Can't wait to see how nasty it is in the throttle body, and I'm hoping cleaning it will prevent reoccurance, at least for a little while, of the tps sensor issue. It actually hasn't popped up in months, but I'm not looking forward to buying a new throttle body to fix it.

What he's describing would be more in the valve body, not the innermost guts. It is the place that I've tinkered in on all my 4L60E transmissions so far and I have the parts for the Silverado waiting now too hehehehe.

I have noticed these engines warm up surprisingly fast. I remember the old v8 in my parents' dodge van that took forever to get any heat out of. I could see it being warmed up in 3 miles easy enough to be going to closed loop. If it is burning too rich yes it'll bog down, but that's usually when it is being a real fuel pig. With just a 1mpg decrease I don't think that's the case at all.

 

[{tpc}]

Well tinkering with the insides of the tranny is likely above my pay grade. I can deal with acceleration, I can't deal with being without a truck for a week after I screw it up lol. I did the maf sensor and the throttle body, put it back together, in process of the relearn. Actually i think its relearned or will be in a drive cycle or two. Even with the idle being a little high though, it didn't seem like it made much difference. Actually once again it felt more "normal" prior to warming up, as I hadn't started it today until after I did the throttle body. I was doing a few cycles of up to 50 mph for a bit, down to stop, etc, when it warmed up. Then it felt weird again.

I think its shifting ok, its just like second doesn't have any "balls" unless your nailing it 1st on through to 3rd.

The slight peddle vibration is still there....maybe its motor mounts or something.

Does anyone know approximately what the shift points should be? I don't know if it would help to know, but I could see if it seems correct. Or maybe its is the downshift causing it, ie I command xx percentage of throttle and instead of downshifting it just stays in 2. I just can't see it downshifting into 1st at 20 mph. I can't say exactly, but my "feel" is that its 20-40mph where it feels sluggish.

 

[Gerbil21]

Well tinkering with the insides of the tranny is likely above my pay grade. I can deal with acceleration, I can't deal with being without a truck for a week after I screw it up lol. I did the maf sensor and the throttle body, put it back together, in process of the relearn. Actually i think its relearned or will be in a drive cycle or two. Even with the idle being a little high though, it didn't seem like it made much difference. Actually once again it felt more "normal" prior to warming up, as I hadn't started it today until after I did the throttle body. I was doing a few cycles of up to 50 mph for a bit, down to stop, etc, when it warmed up. Then it felt weird again.

I think its shifting ok, its just like second doesn't have any "balls" unless your nailing it 1st on through to 3rd.

The slight peddle vibration is still there....maybe its motor mounts or something.

Does anyone know approximately what the shift points should be? I don't know if it would help to know, but I could see if it seems correct. Or maybe its is the downshift causing it, ie I command xx percentage of throttle and instead of downshifting it just stays in 2. I just can't see it downshifting into 1st at 20 mph. I can't say exactly, but my "feel" is that its 20-40mph where it feels sluggish.

If you can do plugs, brakes and a oil change and understand what happens then you should be able to do the shift kit I did it on jackstands with barley enough space under in the street. And it wasn't all that clean with the breeze throwing dirt everywhere. There's a great thread on offroadtb

http://forums.offroadtb.com/viewtopic.php?f=27&t=4507

 

[{tpc}]

Thanks for the vote of confidence. I'm just nervous about the trans, and after almost starting and failing to the the tranny fluid/filter change a few weeks ago, I'm not sure I want to climb back underneath it again. FWIW, I could probably pull the pan off without needing jackstands. I just hate that I have to bend the shift bracket out of the way to pull it. But thanks I'll look at the link.

 

[Gerbil21]

Thanks for the vote of confidence. I'm just nervous about the trans, and after almost starting and failing to the the tranny fluid/filter change a few weeks ago, I'm not sure I want to climb back underneath it again. FWIW, I could probably pull the pan off without needing jackstands. I just hate that I have to bend the shift bracket out of the way to pull it. But thanks I'll look at the link.

I never needed to bend anything. Once most of the fluids been drained I only had to lean it to a side and get it out and around the bracket only. But this is something I would recommend you have a helper with

 

[{tpc}]

Yes on a lot of trucks, there isn't a need to bend anything. And if you could get to the T45 (or whatever they were) torx bits that are contaminated with road dirt and crap and mounted on top of the transmission that you can pretty much only see with a led flashlight attached to a mirror, and get them out, then you wouldn't need to on my truck either lol.

Unfortunately that isn't the case as they must use the strongest locktite known to man on them, and you can only fit a 3/8 ratchet at best in there. Even then you would be lucky to get a 1/4 turn.

The other option, which seemed just as fun, was dropping the exhaust crossmember, which, if I had to choose one or the other it would be that. However tweaking the bracket a bit out of the way was 100 times easier than both those things, so I opted for plan c.

However I read through the right up, and while very nice, there is no way in hell I'm doing that. Hell I might not even attempt it on a spare tranny sitting on a bench. I know when things are over my head and thats sure as heck one of them.

I routinely drive a 1/4 mile back to my house to double check if i closed the garage door lol. I could just see...did I put that ball there? What about the spring? Did I drill the hole?

LOL I'd be pulling what is left of my hair out.

 

[{tpc}]

Ok so last night and this morning were relatively cold, sub 60's. Truck acted like I would expect it to, even after being warmed up. Didn't notice the sluggishness.

That said, I did clean the maf and the tb, so maybe that has actually helped. I'm guessing I might still have issues and the tb may need replacing because a couple of times, depending on the angle of the truck (front elevated) the idle would stay high like 1500 rpms. I know it is still relearning (or was when this happened) but when the truck is on a more level plane it would slowly approach normal idle (600 rpms) after I would stop or park.

As best I can now describe the initial problem, its like when I am merging onto the e-way I get up to about 40 mph...at this point it has already hit 4th gear, and then when the lane allows, unless I stomp on the gas, at slowly makes it's way up to 65 (or whatever). It is like it should be dropping a gear but doesn't. This is (was) happening after the engine was warmed up and the outside temps were 70+ degrees.

Supposed to warm up the next few days, so that should give some indication of whether or not the cleaning of the maf and tb helped or not. So far, it seems it has.

 

[Gerbil21]

Ok so last night and this morning were relatively cold, sub 60's. Truck acted like I would expect it to, even after being warmed up. Didn't notice the sluggishness.

That said, I did clean the maf and the tb, so maybe that has actually helped. I'm guessing I might still have issues and the tb may need replacing because a couple of times, depending on the angle of the truck (front elevated) the idle would stay high like 1500 rpms. I know it is still relearning (or was when this happened) but when the truck is on a more level plane it would slowly approach normal idle (600 rpms) after I would stop or park.

As best I can now describe the initial problem, its like when I am merging onto the e-way I get up to about 40 mph...at this point it has already hit 4th gear, and then when the lane allows, unless I stomp on the gas, at slowly makes it's way up to 65 (or whatever). It is like it should be dropping a gear but doesn't. This is (was) happening after the engine was warmed up and the outside temps were 70+ degrees.

Supposed to warm up the next few days, so that should give some indication of whether or not the cleaning of the maf and tb helped or not. So far, it seems it has.

Just wondering but how did you do the relearn? You dont have to disconnect the battery, just pull pcm a & b fuse for 30min. After you put them back turn the key to on but don't start, wait for the hvac to finish it's sweep so the doors don't break. Then start it and make shure all lights and the radio are off and let it idle for 5 minutes to do the idle relarn after that drive it like normal for the transmission to relearn.

Also I had the idle go high on me too idk why but it stopped doing it

Also next time it feels like it won't downshift, let go of the pedal and try again that works for me I'm guessing it's a mix of pcm tuning for mpg and torque management

 

[Chickenhawk]

What is your coolant temp gauge reading? Attach a photo.

Accelerating up to highway speed slower than normal is usually a clogged cat converter. It may also be a transmission issue of course, but my money's on the cat.

If it is running too cool, that would explain why it runs better in cold weather. It gets a richer mixture. Unfortunately, it will get that richer mixture all the time, and will soon roast a cat.

As for the vibration in the pedal, it may be motor mounts but the odds are favoring a bad bearing. Turn off the radio and listen for a humming sound that sounds exactly like a truck with mud tires driving beside you.

 

[{tpc}]

Coolant temp gauge reads straight up and down when warmed up. Maybe a half tic to the left but depends on the angle you look at it with.

As for the relearn I did what alldata said to do a couple of times, then I did a bunch of drive it up to 50 back down to 0, stop and go type stuff. Since then I've been driving it normally.

If its running too cool the gauge isn't showing it, thats for sure. With the torque app, when the weather was warmer, it typically runs in the 195 range. Not sure what it is doing right now.

As for the bad bearing, is there any other way to check for it? With the weather cooler, and after the cleaning and relearn driving, it actually seems to be much less.I kinda feel the same vibration in the steering wheel, I'll have to try and check it to see if its there when stopped.

 

[{tpc}]

The vibration seems to also be in the steering wheel but not as prevalent as when driving.

Since the cleaning, it seems to be running better, though the weather has still been on the cool side.

I really can't tell if I have the humming sound or not. I don't think it's making one, but I've not had a bearing go bad before. I have a couple of trips coming up in the next two weeks, so hopefully its not a bearing issue that shows up during the trips. If it doesn't show up, I'll probably just replace them anyways, just to be on the safe side.

I think it is/was laggy downshifts after all, coupled with a less than pristine throttle body. I think the TB might be "sticky" or something and maybe staying "open" too long which is interfering with the downshifts as I am off the throttle. I think maybe this affected it during the opening up of the throttle as well, and since the cleaning, that has subsided a bit. It does seem more responsive.

 

[Mooseman]

I drove the 07 Tahoe at work and did notice that the downshifts aren't as good as my Saab's. I had to push a little more on the go pedal to make it downshift. It's also more of a dog but could be the weight or gearing difference.

 

[Gerbil21]

I drove the 07 Tahoe at work and did notice that the downshifts aren't as good as my Saab's. I had to push a little more on the go pedal to make it downshift. It's also more of a dog but could be the weight or gearing difference.

Im shure it's the pcm tuning difference with the v8 trying to make the 4L60e last