Dears,

here I am again with my troubles....I changed my ECM AND the vehicle speed sensor located in the tranny...and still after 25-40 minutes of highway driving without any problem, troubles appear...

history recap :

1) a couple of months ago I was loosing my speedometer after 25-40 minutes of drive...when I say loosing I mean the needle wildly jumping to zero for a couple of seconds/minutes....during that period the car is still driving, but I have no gas response anymore for a couple of seconds (I floor the pedal and nothing) ( when I slow down the engine stalls...I restart the engine and no more problem till the next drive...no Engine Service Soon light was coming at that moment...it happened a couple of times and then I decided to look for a ECM replacement
2) after 2 months I found a ECM module and swapped it...the PROM was not working so I kept mine....unfortunately same behavior, except that now the ESS light comes on...but no error code has been stored, damned !
3) I finally succeeded to get another speed sensor (not so easy in Belgium if you don't want to pay a very high price, got lucky found one in a junkyard)....still the same problem except that today, instead of having the speedo needle going to zero mph, it stayed blocked at the same speed for a couple of seconds, same for the tachometer, but no gas response and engine stalling just after...

I removed today my ADS Superchip, reset everything and will try another trip at the end of the week..I cannot afford to come late to work for a couple of days...

Any help will be much more than appreciated....I am getting lost here with the risk of having to get rid of my firebird if I cannot solve the problem soon...

I also changed the fuses, without any difference...

Many thanks

John
3.1 V6 Firebird 1990

 

id check that dashboard. it should send a vss pulse to the ecm. sounds like your losing poower.

 

Hi,

could you elaborate ? I believed the speed sensor located in the trany was supposed to send pulses to the ECM and that the dashboard meter was just an "output"....if this is the case why is the gas pedal not responding for a couple of seconds or other werid behavior like I described ?? Am I missing an element in the loop here ?

Thanks for your help

John

 

your loosing power to the dash and the ecm. id be checking the fusable links comming off the starter motor for open shorts.

 

I'm thinking the same thing. 2 spots that should be checked for "intermittant" problems-

1. Upper frame rail, passenger side- there's a fuse screwed to the frame with a red and orange wire coming from it. This gives power to your ECM and fuel pump. Check the fuse to make sure it's okay. Make sure there's no corrosion inside the fuse holder. Wiggle the fuse holder as the car is running to make sure the car doesn't have a problem.

2. Follow that fuse's red wire to the radiator support- it goes into a positive junction block. The terminal on the end of the red wire might be bad. I had this problem. If I wiggled the wire at this terminal, the car would shut off.