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Car Speed does not match as RPM goes up

10-12-2009, 07:35 PM
I have a 97 Lesabre. I got a used motor from a 96 Park Ave. The 3.8 motor was strong, powerful motor. No problem passing other cars on the freeway or in town.
When I push the pedal to the floor, it shifts down. I could hold the throttle and the car would pick up speed, continued for as long as I had the throttle down (once went from 55 to 115, with the car increasing speed rapidly all the way).
As the RPM goes up, the speed rapidly went up.

With the 96 PA Motor, the car drives good. If I push the throttle down a little, the car picks up speed good (Not as Hot as the old, but just slightly less then before, but seems OK). I notice a little, but someone driving the car who never drove the old motor would think it was nice.

Problem: When I push the pedal hard, when it kicks down, the RPMís increase at a faster rate, but the car speed doesnít match it. The speed increase is very, very slow. The car gets to a point where the motor is high RPM and it canít go any faster. I let off the pedal, and it will shift up, but not going very fast. Nothing like the rocket ship I once had.

Sitting at a light, I wanted to do a test. When the light turned green, I floored it. I went a little ways past the intersection; the motor was high RPM (I think they call it floating?) but the speed was barley increasing. The car couldnít go any faster, when I creped up to 39 MPH!!

On the Highway, if you push down, the car almost slows down, but the RPMís increase way up. I just barley go past them a mile or two faster.

As the RPM increased, the car went a lot faster. Now, the RPM goes up faster then before, but the speed doesnít match. The most problem is about half throttle and above (Half throttle doesnít mean exactly at half, just meaning when you really put your foot into it).

What could be wrong?

Thank you,

10-12-2009, 07:38 PM
Sounds like the trans is slipping or stays in a lower gear too long, tough to tell without driving it.

10-12-2009, 07:44 PM
Thanks for replying.
Trans is consistent, doesn't feel like slipping. Feels like the gear is lower, but not staying in to long, because even right off the start it's way slower. Hardly any increase in speed.
The power is like an old car with the timing retarded.

10-12-2009, 08:13 PM
When you replaced the motor, did you do a crank variation learn?

Hard to saw what problems you may be experiencing.. Could it be a possible clogged cat?

Are there any other symptoms or anything else you notice?

10-12-2009, 08:34 PM
No, noting else noticed.

With the "new" motor, I had him replace the CPS.

If it's off, shouldn't it give a code? I didn't know about, "crank variation learn" until I just read about it. It says you would get a code.

10-13-2009, 10:21 AM
No need to do a crank variation relearn on a 96. I agree, your problem sounds like exhaust backpressure. Like Jrs3800 (Don) mentioned, have you checked the cat? If I remember correctly, your other engine pumped oil or coolant into the exhaust. If so, the cat may look like the on in the pic below! :eek7:

10-13-2009, 12:31 PM
I would agree on the cat but how does the engine achieve high rpms in any gear as he describes. Tough to tell what is really happening here.

10-13-2009, 12:43 PM
If I remember correctly, your other engine pumped oil or coolant into the exhaust. If so, the cat may look like the on in the pic below!
Bolt broke off the timing gear at 115MPH.

10-13-2009, 01:02 PM
This might seem like a stupid question but, if it doesn't *seem* like the clutch is slipping, how can I find out if it is?

A friend who has a car like mine said when his clutch started slipping, he got a code. Is that true?

10-13-2009, 03:37 PM
Bolt broke off the timing gear at 115MPH.Yeah, I remember that! Did you break any valves, or other parts that may have found their way into the exhaust?

The cat in the pic above came from my Ultra several months ago. The symptoms were similar, loss of power & MPH in all gears; however rpm would still climb to 5800-6000 rpm, it just took a lot longer! You can have your trans scanned, but if you don't have any trans DTC's, it's a waste of money. Your friend is correct, if you had clutch slip in the trans, you should get several DTC's.

10-13-2009, 05:33 PM
There where pieces of mettle in the water jackets when we took off the water pump. Could see pieces looking up inside the motor.
I still have it, but never took it apart to see what happened. I wanted to know what I should take off it before I get rid of it, but never got an answer to my thread.

If it goes to long, may lose it tho (On the floor at a shop).


10-13-2009, 09:05 PM
Pull the intake & heads & post pics of what you see in the combustion chambers.

10-13-2009, 10:31 PM
I Promise I will if I can get this problem fixed.

10-14-2009, 04:26 PM
One part I don't know about is the ECM or eprom thing. Wonder if it could be the computer or eprom for my car does not match the "new" motor?
Still don't' know what different changes where made on a motor made in 96 and a motor made in 96? (97 Car manufactured in 3/96).

10-14-2009, 05:27 PM
You have a 1997 LeSabre right? You are simply using a 1996 motor?

The 1997 PCM should have a crank variation learn sequence performed being that you replaced the engine.. Hard to say how much of an affect it will have on the way the engine performs.. I still have not done the Crank variation learn on my Van that was swapped to the 97 PCM.. I need to but so far it runs ok..

You may have some other issues, and any more thoughts or changes you have noticed could be helpful.. Its always hard to help over the net as opposed to actually being there to see the problem in action..:)

10-14-2009, 05:53 PM
No, I don't notice any other problems. Runs good otherwise.

Reading up on the crank variation learn sequence, it seems that will help so you don't get false misfire codes. Since I don't have that problem, doesn't seem like that could be it.

Thanks for replying. I was hoping I'd get someone who knew right a way what it was.
Kind of like when some one posts, there car locked up and all the fluid was gone out of the radiator.

02-14-2010, 07:30 PM
Want to be conscious of not posting in an old thread, but still working on this. I had a pressure test done, checked out OK.

Mechanic will look at it this week. He thinks it might be running lean. Maybe a O2 Sensor, TPS or something like that.

Another guy said he thinks it's the torque converter.


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