Question: I notice driving home from work last night

[Marv02]

I notice driving home from work last night.
The Up shift light was going on and off my car has the 700R4 trans in it why is the light flashing every now and then.
The shift lever is in the overdrive position.
And the Instance MPG would be at 22 MPG then drop down to 7 then back up to 22 MPG also.
Could the transmission going in and out of Lock UP ??.
The RPM stay the same.
But I do think the Toruqe converter is going bad I just saving up money again to buy a new transmission I woulding if this has anything to do with the new issues that showed uo last night.

 

[TedC]

Marv02, This sounds like an ECM issue. The issue is how serial data is being processed (or not processed) by the ECM. Search for one of my old posts on this topic and see if this isn't your issue. Gordon Killibrew helped me pin point this issue on my 1989.

 

[Marv02]

Marv02, This sounds like an ECM issue. The issue is how serial data is being processed (or not processed) by the ECM. Search for one of my old posts on this topic and see if this isn't your issue. Gordon Killibrew helped me pin point this issue on my 1989.

Will it ever end I did pull the ABS light bulb out the oterh day i woulder if this is also causing the issues.

I gotten tired of seeing the ABS light on.

I pop the bulb back in and see if this fixes it.

 

[TedC]

I installed a rebuilt ECM for $88 and has worked great now for 3+ years. The local parts store even let me keep my old ECM because it was the original unit. If your upshift light blinks when you have an automatic, this is a tell tale sign that the serial data logic is messed up. If you have a scanner, try using it. I found that my scanner would not sync properly, and if it did, would not post any serial data. Also, my MPG readings would bounce all over the place. During an ECM rebuild process they remove all the protective coating on the circuit board and run several tests. The protective coating used in early C4s does not age well and can cause all kinds of issues. If it passes all the tests, they recoat the board and add a rebuild sticker to the case.

 

[Marv02]

I put the Anti Lock Brake light bulb back in all fixed now but I have to look at the stupid anti lock brake light once again.