'96 TCU into '92 Q...some hesitation when driving

[werepe]

Hello to all Q45 techs here. Thank you guys for all you do here. I love this forum, it has really helped me a lot.My question this time: I installed a '96 TCU into my '92 Q yesterday hoping to get that 1st gear take-off. I drove it for a while and noticed that the drive wasn't smooth. It felt as though it was hesitating to move. It didn't drive as smoothly as it did with the original TCU. Do you guys think if I change the ECU to a '96 ECU, that'd fix the problem...or would that be a bad idea...is there an interchange issue? I have access to a '96 ECU. Should I just look for a TCU from '93-'95? Please advise! Which ECU can I install that'd make a difference in my performance? Thank you so much for helping!

[maxnix]

The ratios in 1st and 2nd gear are out of whack with what it expects. Should only matter at WOT. Also, 1996 is generally a 16 or 32 bit system whereas pre 1994 was 8 bit. Don't know if that is the source of your problem.

That may be why the later series of 1993 TCU is the recommended one for 1990-1992 G50.
Modified by maxnix at 8:16 AM 4/2/2008

[Q45tech]

The 96 Q does NOT have VVT so the ecu would not send signals to 92 engine VVT solenoid so power from 1500-4800 rpm would be lower.

The 96 ecu expects coils with integrated transistors vs 92 has on cover ignitors/transistors.

1996 has extra senssor not found on 90-95 so codes will be set and fail safe will occur.

All in all A VERY BAD IDEA TO EVEN PLUG IN A 96 ECU in a 92.

To get the correct 1st gear start FIND A 1993 TCU

[werepe]

thanks for the prompt responses. Is '93 TCU the only one recommended? How about one out of a '94 or '95...would those work just as well also?Thanks!

[Haitian_King]

thanks for the prompt responses. Is '93 TCU the only one recommended? How about one out of a '94 or '95...would those work just as well also?Thanks!

Get the 93. The 94-95 TCU was programmed differently because they had slightly different ratios than the 90-93.

[mxr662]

With the 94 tcu and stock ecu I hit the rev limiter before shifting. Nico ecu fixed that

[Q45tech]

With 94 tcu [and 90-93 transmission] hitting stock rev limiter is common without raising the redline to 7300 because the 6550 shift times 1.05 [gearing expected] =~ 6878 obviously close to 6900.

Used and abused trannies with more than 60k are even more prone to hitting limiter since they shift slower......time from solenoid command to actual gear change event vs engine revability.