JUST BOUGHT A '92 RS 25TH ANNIV. WITH TEE TOPS AND IT HAS A V8 305. THIS IS MY FIRST ONE. LESS THAN 78,000 ORIGINAL MILES. RUNS GREAT BUT AT TIMES THE PRESSURE GAUGE WITH MOVE AROUND AND I GET THIS IDLE SURGE FOR ONE SECOND THEN IT QUITS. GOES AWAY AFTER I DRIVE IT FOR ABOUT 5-10 MINS BUT THEN THE SERVICE LIGHT COMES ON. WAS TOLD THAT IT MAYBE THE OIL PRESSURE SENSOR. WHERE IS IT? I HAVE TO FIX IT BEFORE I CAN GET IT REGISTERED. EMMISSIONS TEST. ANY HELP?

 

Edit: oh, I looked at the schematic wrong

looks like this

 

Welcome to TGO!

The Oil Pressure Sending Unit (pictured above) has nothing to do with the ECM - there is not any oil pressure anything that the ECM gets any readings off of - so that has nothing to do with your idle surge.

The OPSU pictured above is the ONLY one in your car - older models had two, but TBI cars only had one - it feeds signal to the guage, and also directs power to the fuel pump when the ECM and fuel pump relay arent working right. BUT - this doesn't have anything to do with your surging idle problem, as fuel pressure is regulated inside the TBI. This OPSU is located just above the oil filter driver side block.

Check the codes for the SES light - https://www.thirdgen.org/service-eng...ht-error-codes - more than likely you'll find your idle issue there.

And I'd guess that the surging idle is causing the change in the oil pressure reading, not the other way around.

And get rid of the caps lock - no need to yell here.