Overdrive

[james1965]

it's a 2005 SLE with a 4t65e, i'm not even sure if it is the culprit, but here goes...
if you are cruising around 1600 rpms in overdrive and start to climb a gradual hill, the normal time when the car would or should downshift, the car gets confused it seems, it ( feels ) like it bucks or maybe it stumbles.. if I give it a bit more throttle though it downshifts and all is fine. I don't seem to have the issue if I just drive around in 3rd. Transmission has prolly around 50k miles on it, had a new filter put in it 2 years ago. the thing is, I've read people say the MAF could be a issue as well. I dunno. there are 0 engine / trans/or any other codes in the computer or even in the history files. it's been about 8000 miles ago I put new wires and plugs in it. the car runs great. just feels like it tries to downshift and can't. any thoughts?

[96 SSEi]

you can unplug the maf and see if its better,
if you are at 1600 rpm, you would have already shifted out of overdrive - maybe in 2nd - problems shifting up could be caused by low fluid level.
check level and condition of fluid - give it a change and see if improvement follows.

[nos4blood70]

This issue is usually caused by something in the ignition system. Might be worth a shot to replace the plugs/wires again and take a look at the coils and ICM.

[michtom]

X2

[MKMike]

X3
Problems with operating under load are typically ignition problems.
With the longer service intervals these cars have, it seems that they often don't get serviced at all.

The easiest and least expensive things to do are to check and replace the following:
ACDelco spark plugs NEVER Bosch
Wires
Fuel filter should be replaced
If the fuel flow is restricted because the filter has gotten plugged up over the years. The engine gets starved for fuel when under a load.
Can't hurt to also install an ACDelco PCV valve--though this will not solve the issue at hand, it's simply required maintenance

Look at Rockauto for better prices.
Their Pontiac Bonneville Club Vendors forum post contains a discount code.

As mentioned, there may be coil or ICM troubles.

I've read people say the MAF could be a issue as well. I dunno. there are 0 engine / trans/or any other codes in the computer or even in the history files. it's been about 8000 miles ago I put new wires and plugs in it. the car runs great. just feels like it tries to downshift and can't. any thoughts?

Only some scan tools will read transmission codes.
A Tech 2 certainly will.
Don't know which others do or don't.
Yes, a bad MAF sensor can cause transmission issues.

[MKMike]

I forget to mention that your MAF sensor may have gotten dirty over time.
This will cause driveability issues.
You can get some MAF sensor cleaner (other cleaners leave dirt-collecting residues) and clean the MAF sensor wires/ elements.
Our sensor is removed with 2 inverted Torx screws.
Just remove the screws and the sensor comes right out.
Don't disconnect the throttle body because coolant runs through parts of it.
This video is good
https://www.youtube.com/watch?v=_TO7ZC5N-aA

If the MAF sensor is bad, either get a good used one from Harofreak00 (Andrew) , or a reliable junkyard and then clean it with MAF sensor cleaner.
If you buy a brand new sensor--buy a Hitachi MAF sensor.
Don't even bother with other brands because they're junk

This is the Common Problems thread that every Bonnie owner should read
2000-2005-other-than-gxp/topic25362.html

[james1965]

@MKmike, I have a Snap-on Solus pro and it is current to date. wouldn't a coil pack issue, a plug throw a code? I am not leaning towards a fuel filter because if I give it just a nudge more throttle it shifts down and takes off without missing a beat. I have Never in my lifetime put a Bosch anything on anything. I can't recall the brand I used on the wires though, but I do know it would not have been Bosch, my dad had many issues with that brand of stuff. I do know the plugs I put in just a few years ago are ACDelco. last year I only put 2500 miles on the car and maybe only 6000 the year before. those plugs should be golden. however I know sh*t happens and it could be a plug too.

Transmission shifts perfectly though upshifting through the gears all the way into overdrive. it's just under a slight load when it would normally down shift 1 gear ( into 3rd ) that it acts like it tried to down shift but can't or it does and then shifts back and forth from 3rd to 4th. however it is very hard for me to tell, it could very well be the ignition system and its the engine bucking... Hmm. I wonder how good my camera phone is. maybe I can record a short video. i'll try to reproduce it later today if the roads are not too snow covered.

on a side note, it makes no difference whether the car is warmed up or cold right out of the car port garage.

[nos4blood70]

This issue doesn't throw a code. When I had this problem, it was caused by my ignition wires. They worked fine in all other conditions, but they would make the RPMs wonky in low RPM/high load situations. I would double check if you could. Otherwise clean the contact points on the coils, and between the coils and the ICM (ignition control module) that they sit on.