1996 VDP problems.I replaced a defective ECU with a used one and it seems to work fine except one issue. Idle is at about 750 but gets interrupted every ten seconds or so with a stutter, then resumes ok. It has stalled coming off the gas at a light but restarts no problem. I've seen in some threads that the EGR valve can cause this problem and cause the P1775 fault code. Is it possible that the new ECU has a different setting to the EGR or maybe none that is causing the issue. If that is hardwired into the EPROMs what should I do?
Also, I don't see that these issues would cause the speedo to stop working? Is there any connection or should I check the
wiring behind the dash.
Is it better to just replace the EGR or just try cleaning it.? Appreciate any advice and if that can cause the error code and/or speedo fail...

 

I had an issue with failing intake manifold gaskets causing a stutter every 32 seconds at warm idle.

Idle should be 700rpm in Park, 580rpm in Drive.

 

The EGR valve is upgraded in the TSB R - 493 and may be a miss match in how it is controlled properly

TSB coming

You may see a sticker on your ECU and under the hood that may indicate if done

The speedometer , cruise control and 1 of 4 speed sensors for the traction control and anti - skid is the left rear speed sensor , this sensor can break on removal as plastic ..................................ask me how I know

Any TC and anti - skid lights ?

A good sensor will read 1300 ohms as a basic meter reading and will generate about 1 volt AC if wheel is spun in the correct fwd direction

 

05.1-26 amend4 (R493)

The EGR valve does have a position sensor which does allow a ELM 327 device to read the commanded vs. actual EGR position value , EGR_ Error perameter ID target value 0 % in all engine ranges but I would not expect a 0 value in real world