Ford Automobiles banner

1 - 11 of 11 Posts

·
Registered
Joined
·
10 Posts
Discussion Starter #1
I got a 97 t-bird with the 3.8L v6. When im in park the idle is fine. But once i shift into reverse or drive the idle gets rough. theres times where it almost hit 0 for the rpms(mainly in drive) but it never stalls. I cleaned the throttle body and the maf sensor. and seafoam in the gas tank. but still not better.

Please help

the car has 158k miles.
 

·
Registered
Joined
·
4,352 Posts
If your CEL is on, I'd pull diagnostic codes, first.
IF not, I'd give it a serious look for vacuum leaks, and if nothing, then either a compression test or hook a vacuum guage up to it.

Vacuum guage is a lot easier to do on that engine, due to the difficulty of getting to the back three cylinders.

Howto locate a vacuum leak
http://www.fordforumsonline.com/forum/engine-drivetrain/94-howto-how-locate-vacuum-leak.html#post423
HowTo check your IAC
http://www.fordforumsonline.com/forum/engine-drivetrain/261-howto-check-clean-your-idle-air-control-valve-iac-iab.html

How to Use and Interpret a Vacuum Gauge
 

·
Registered
Joined
·
10 Posts
Discussion Starter #3
ok thanks ill look at it. also why is that when i floor it it shifts at like 4500 rpm instead of redlining?
 

·
Registered
Joined
·
4,352 Posts
Shifting is controlled by the PCM.
 

·
Registered
Joined
·
4,352 Posts
I'm guessing that sounds about right. I don't pay any particular attention to it, perhaps later today I will.

I think it usually runs between 2200 and 2500 RPM on the highway in the 50-70 mph range.
 

·
Registered
Joined
·
4,352 Posts
I just took mine for a short ride.
The way I drive it normally shifts between 2000 and 2200 RPMs.
It is just under 2000 RPMs at 50 mph

Under hard accelleration (I didn't quite floor it) it shifted between 4000 and 4400 RPM

hope this helps.
 

·
Registered
Joined
·
1,184 Posts
Depending on what year car you drive,shifting is controled by a number of different things. 60's and 70's My cars mostly controlled by a cable or rod linkage from the throttle to the transmission.As electronics entered into the picture,computers started to control the trans operation,such as ECAT.Enter into OBDII generation and the computers get more sophisticated by adding switches and sensors.fFor you vehicle,it goes something like this.

Shift Patterns
Upshifts
The powertrain control module (PCM) has an adaptive learn strategy to electronically control the transaxle. The adaptive learn strategy will automatically adjust the shift feel to the driver demands. The first few hundred miles of operation the transaxle may have abrupt shifts, this is a normal operation and will correct itself. If the battery has been disconnected for longer than 20 minutes the shift tables will reset and need to be relearned. Upshifting is controlled by the PCM. The PCM receives inputs from various
engine and vehicle sensors along with driver demands to control shift scheduling, shift feel, and torque converter clutch operation.
Downshifts
Under certain conditions the transaxle will downshift automatically to a lower gear range
(without moving the transaxle range selector lever). There are three categories of automatic downshifts: coastdown, torque demand, and forced or kickdown shifts.
Coastdown
The coastdown downshift occurs as the name indicates, when the vehicle is coasting down to a stop.
Torque Demand
The torque demand downshift occurs automatically during part throttle acceleration when the demand for torque is greater than the engine can provide at that gear ratio. The transaxle will disengage the torque converter clutch (TCC) to provide added acceleration, if applied.
Kickdown
For maximum acceleration, the driver can force a downshift by pressing the accelerator pedal to the floor. A forced downshift into second gear is possible below 88 km/h (55 mph). Below approximately 40 km/h (25 mph) a forced kickdown to first gear will occur. For all shift speeds, specifications are subject to variation due to tire size and engine calibration requirements.

Hope this helps.
 

·
Registered
Joined
·
530 Posts
Glad you found the problem.

While your helping your Bird run better, how many miles on the wires/spark plugs, & fuel filter?
 

·
Registered
Joined
·
6 Posts
Tell you what, if none of the stuff above actually took care of the problem, test your IAC valve. Replacing that on my 95 took care of the same problems you had/have.
 
1 - 11 of 11 Posts
Top