Acceleration problem - is it so tough?

[public]

Sorry the EGR did not work out for you. By the way my 1998 also has the 4T60 and it does not behave as you describe (at least not anymore)

[bignoisey]

I said my 2000 century has a 4T65E, on my way home today I tried noticing when mine upshifts in each gear. It's so mmooth its hard to tell but It never went to 4th (OD) at a slower speed than 45 mph and the lockup occurred some time after that, but I'd need a tachometer to tell exactly when since its so subtle. If your lockup is happening at 35, I'd say thats too low a speed - no wonder you can't accelerate. Maybe some other century oeners can try light acceleration like I did and report the results. Any GM tech's out there who have access to official specs for minimum upshift & lockup speeds?
After consulting my Chilton's guide, it looks like Century's may come from a couple different GM plants and from the best I can tell the '99 model can have either transmission. There is only one engine oprion though 1995 - 2000, the 3.1L 160HP V6.

[public]

Sorry I was not clear. I understand that your 2000 has the 4T65E, however I just wanted to offer my experience with the 4T60, which is possibly what we are dealing with. The 4T60 can be identified by the plug location and the presence of a vacuum modulator. I just wish we could help get this car to function properly.

[occupant]

Just be glad you don't have an older A-body Century with the 2.5 engine and 3-speed automatic. 1-2 comes about 10-12mph, 3rd comes around 20-25mph, lockup engages between 30-35, depending on year and whether AC is on or not. Those cars cannot accelerate hardly at all in lockup until over 40mph.

My 1995 Century has the 2.2 Cavalier engine with that 3-speed automatic and is programmed slightly better. Engages lockup at 35mph under light acceleration with AC off, 40mph with AC on. I'm used to it, and sometimes I will turn on the AC if I'm driving a steady 35-39mph so it won't engage.

The 3100 is a torquey engine for its size and type, but low rpms will still cause this lag. You may consider driving in "D" (3rd gear max) when you know you won't exceed 40-45mph. I forget the AT shift pattern on the 97-up models. Should be P R N @ D 2 1, you can choose "D" until you get on freeways. If there is no "D", there may be an overdrive off button somewhere, or a "3" position which is the same as "D".

Or, with practice and experience you will determine the right amount of throttle to keep your lockup converter from engaging.

Also, a light tap on the brake (with the left foot) will disengage the lockup converter long enough for you to squeeze in a little more throttle.

I like early shifts and early lockups, because I drive relatively slowly for the best possible mileage, and unless I'm going up a hill, my 247,000 mile 4-cylinder accelerates just fine in lockup from 40mph on up to 60-70. It is a very rare (a couple times a week, and I drive 1200-1500 miles weekly) occasion when I am forced take the car out of lockup with more throttle or a tap of the brake.

In other words, it's normal. So get used to it, or try one of the suggestions offered here (like keeping out of overdrive til you're going over 40mph). Test drive a new 2004 Century, or any other mid-size 3.1/3.4 with a 4T60 GM offering (Lumina/Impala/Intrigue/GP), I'll bet it will do the same thing.

[seniorbigs]

I think you may be fighting something that is normal. The manufacturer's need to eek out as much fuel economy as possible and low rpm's help them to achieve that. If you drive in 3rd gear rather than OD, you should get a little mord spirited performance. Third gear driving usually lets the ECM/TCM provide a little more aggresive shift curve.

[roaddirt]

Several days ago I test drove friend’s 2001 Buick Century. I could feel when it go in overdrive around 40 mph (mine do that at 35mph instantly) but it would “unlock” and start accelerating as soon as I slightly pressed acceleration pedal.

On the holiday weekend I drove to NC and the problem was present all the time even at speeds 70-80 mph. It felt like lack of power and hesitation especially driving even slight uphill. There is definitely something wrong. I still switching between “engine problem or transmission problem” question, but it is definitely a problem.

[hobieracer]

Like big says, maybe it is going in a bit early. I have a regal 4t65E with rough shifting probs, one thing I've learned is that mine learns. Over time the car modifies the way it shifts based on clutch wear and driving habits. Maybe yours learned to be slow, you can have these learned points cleared, I think it may take a while to see what comes of it... i am not expert though, it is just another direction to go in.

[Bisbee2001]

I have the same problem as I have read from the very top of this discussion. I have a 2001 Buick Century. I am not a "car" person, but all I know is that recently my car has had some serious acceleration problems.

I live in Bisbee, AZ, which is high in elevation. I travel to work, 60 miles round trip, and consists of extreme hill climbing. As with the first post, if I push down on the "sweet" part of the pedal the car will hesitate to accelerate. RPM go up and down down, very quickly. Also, I have noticed a drastic loss in MPG. I usually get 29 mpg, but I'm down to 26 mpg. Also, the problem seems to be getting worse. Just taking off it is starting to not want to accelerate. Also, if I push the pedal way down, as in to pass, the car will only drop into 3rd gear.

Today, I could only go 70mph; not enough to pass. Needless to say, I started thinking about the fuel filter (I noticed this problem in my 65 vw bus), and maybe the sparkplugs.

However, after reading the online posts, I am wonder what I should do myself. I am seriously debating seeing a mechanic, but now I am wondering if I should save my money and see what comes of this conversation.

BTW: I replaced the fuel filter about 30k miles ago. (My car has 82k)
Thanks...
JB

[public]

Yeah, when my EGR went bad I could barely get to 65 mph. As I would go up over a bridge I could not maintain 65, it would slow down to 55 or so before I got to the top. Good Luck. You may need it, My Century is one problem after another.(see post in nonspecific section re: which Buick should I buy?)

[JettaGTman]

Hey Roaddirt. My wife owns a 1996 pontiac bonneville which happens to have a 4t60e tranny and acts up like yours. I have done a bit of research online and have seen that the problem has been caused by the internal shift solenoids on many occasions. but try to catch it quick because, although there may be no relation, my wifes car lost 2nd 3rd and 4th, which if you look up is also caused by solenoids. apparently there is a common grounding problem with the 4t60e's. I hope that you find this helpful. replacing the torque converter while the tranny is being serviced would also be reccomended if you can budget it at the time.

[BNaylor]

Originally Posted by JettaGTman

Hey Roaddirt. My wife owns a 1996 pontiac bonneville which happens to have a 4t60e tranny and acts up like yours. I have done a bit of research online and have seen that the problem has been caused by the internal shift solenoids on many occasions. but try to catch it quick because, although there may be no relation, my wifes car lost 2nd 3rd and 4th, which if you look up is also caused by solenoids. apparently there is a common grounding problem with the 4t60e's. I hope that you find this helpful. replacing the torque converter while the tranny is being serviced would also be reccomended if you can budget it at the time.

Welcome to AF.

Sorry but our community rules prohibit raising old threads that are too old. This one dates back to over two years ago. It serves no purpose and there is no continuity in the discussion.

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