95 riv surging

[fishboybug]

hey there, i have a 95 sc riv and it seems to surge when accelerating. took it to the dealer and the gave me the code p1640 and told me that i need a new pcm. a cpl months earlier i had an ex gm mechanic check it out and he told me that is was some kind of supercharger bypass module or something like that. i don't know the code he got or the exact words he used for the part. is the dealer trying to make some extra money on me or do i really have to swap the whole pcm. if the swap is needed, could you point me in a cheaper direction than the dealer. i only paid $500 for the car 2 years ago and just want to get it trade ready. thanks

[neo307]

I found this on another forum,.. P1640

"That's the QDM 2 failure. IF...that is the correct one.. it should encompass the boost soleniod, TC clutch and evap purge soleniod.

On a previous 95..I was plagued with the light as you are. The torque converter clutch is easy to test. Drive over 50 and watching rpm's tap the brake pedal lightly..do the rpm's come up 2-500? Ok..TCC works.

Evap purge is easy to test..let the car warm up..and run for a couple minutes. Hold a finger on the purge soleniod on top of the canister..does it vibrate sooner or later? Ok..that tests good.

BCS... it works fine every time you press the pedal you go into boost right? On a whim..I swapped mine and the light disappeared.

Your issue is probably one of the above three items. the bsc and evap sol are easy enough to swap for testing. "

P1640 can also mean the ECM is faulty, from what I understand.