rpms drop after driving awhile

[mistagst]

My car is auto everything perfectly fine up untill around 15-20 min of driving. After that anything above 35-40mph the rpms just drop and like to settle at 2k. I get on the gas and is rises back to 3k and above but when i get off it just to maintain the speed it drops back down to 2k and gets pretty sluggish to accelerate. Im thinking a new set of spark plugs and wires will do the trick? Just seems weird it only acts like that after ive been driving it for a while and before that its perfectly fine. Any tips would help thanks

 

[SNAKE_15]

It's hard to tell but replace your spark plugs and make sure your injectors are still good

 

[boost198]

Probably replace fuel filter too

 

[mistagst]

finally got around to working on the car a bit I checked the wires and they seem good. I also changed the spark plugs. took the car out and it is still the same if not worse. I asked I few people I know and what came up often was it could be that my cat converter is getting clogged up due to age. could this be the problem? or is it still something else

 

[96atawd]

Do these cars with automatic trans have a locking torque converter? Like, 1st gear, shift to 2nd, shift to 3rd, shift to 4th/OD, then torque converter lock up? If so, I believe the tq converter wont lock up when the engine/trans is cold, to speed up the warm up time, then the tq converter should lock up once reaching operating temp?

 

[mistagst]

It happends after driving for like 15 min not before

 

[Alex Brunner]

So only while the car is warm? When it is cold, does it behave like you would expect it to? Is this not how it has acted in the past? Does it accelerate fine once you get into the higher RPM range?

I have never driven at auto eclipse, but that sounds pretty normal for an automatic in general. They are designed to let the engine operate at the lowest RPM possible to maintain a speed.

 

[96atawd]

It happends after driving for like 15 min not before

Again, I believe it is your torque converter locking up, as it should. Before the engine/trans reaches operating temp, the tq converter shouldnt lock up. After reaching operating temp the tq converter should lock up if above a certain speed.

 

[mistagst]

Only after i have driven it for like 15 min do the rpms start acting up. When it does and im going threw the gears and hit 40mph the rpms drop to around 1.5k to 2k and settles there but im still trying to accelerate i get on the gas more to keep accelerating and it gets sluggish but fights its way out untill i reach 60mph which normally at 60mph the car is at about 3k rpms but since it started acting it drops to 2k and makes it really had to acclerate when i need to change lanes i will try to post a vid asap

 

[sirbow2]

maybe a stupid idea, but Overdrive? Or do DSMs not have that?