Transmission drive/revers at idle controlled by the ECM??

[Jan Larsson]

Might be a stupid question but when I stand still and change from drive to reverse and back the engine twists pretty bad (and I get a clunking sound as well) ... I spoke to a former Buick engineer working on the 1989 TTA program (and also the GN engines) and he said there's a setting in the chip that might be the issue ... I got a standard TurboTweak chip in mine made for my setup ...

So in short would there be anything the ECM / prom would control when just changing from drive to reverse and back a few times making the engine torque over hard?

I'm sceptical to what he told me but thought I would ask you all anyway

 

[pacecarta]

hes mistaken
chip only controls the lockup solenoid , besides that it just sees the 3rdand 4th pressure switches
the ecu can also see when you are in park

fix your motor mounts and trans mount also check the amount of rotation play in driveshaft ( worn ujoints ,excessive gear backlash)
on the TTA also check the torque arm bushing

what is your TPS setting (should be .46 or lower when running )
whats the Idle RPM.. if high check your IAC count , if iac is bottomed out (zero) then the rpm cant be controlled by the ecu

 

[Jan Larsson]

I thought he might be as I could not for my life figure out how that could work lol.

I put all new engine mounts (stock rubber style aftermarket) in there when I rebuilt the engine and this been happening from day one ... trans mount and cross member donouts are all new (I tried stock ruber and now have aftermarket poly on there) ... torque arm bushing is also new (poly) and the driveshaft were balanced and have all new u-joints front and rear.

So a bit lost unless one of the engine mounts where bad from the factory .... might take the passanger side one out and replace it with a new one ...

TPS is still set correct but will double check to make sure ... idle RPM is around the 700 mark so should be good. IAC count I need to look at as I can't remember right now.

Appreciate the pointers, any other ideas?

 

[dvernst]

Jan my car has always done this also. So does Bo's. (Ttameasap). Mine did it with the stock rear, and now I have a 9", and Bo has a s60. Same exact sound. I think it's a characteristic of the torque arm suspension. The torque arm really transfers a lot of sound.