The car is a 94 z28 a4. I hooked a scanner to it and it showed i had a code 33 which is MAP sensor or circuit too high and the SES light never came on. I believe that means low vacume. Now i have put heads, cam, intake plus the usual bolt on and mail order tune. Now i know with the cam it wont have as much vacume as it would stock. Now my question is this anything to worry about? And if the sensor is bad would it effect how it runs?

 

DTC 33 = Manifold Absolute Pressure (MAP) sensor circuit (signal voltage high, low vacuum)

The code sets when the MAP exceeds 68 kPa at closed throttle (<4%) for more than 5 seconds. A big enough cam will cause that. A good tuner can minimize the problem, but too much overlap, and its difficult.

You need to read the MAP at idle with a scanner (or measure signal voltage at idle) and see if its over the threshold for the code. The MAP harness connectors dry out and crumble. That can lead to intermittent high and low voltage conditions.

 

ill try and hook the scanner back to it today. What should it read at idle.

 

alright i hooked the scanner back to it and at idle it was reading about 3.08v at highest and around 2.96 at lowest.

 

I have a conversion chart between volts - kPa - "Hg in my online scanner guide:

http://www.injuneer.com/ScanMast.html

3.0V corresponds to 65kPa or 19.2"Hg. You're right on the borderline of the 68kPa that sets the code. While you have the scanner hooked up, wiggle the harness wires, to make sure the connector isn't a problem. I was getting 100kPA intermittently, and it was a crumbling connector.

 

Yeah it read 19.4 Hg. ill try to move the wires around and see what that does. I havent even took the wires loose to check the connector since i disnt know if it was just the cam making low vacume.

 

Well i went out and wiggled the harness and it didnt do much different. It read 20.3hg and 3.06v. Pulled the connector off and it looked fine nothing broken or loose. So i guess that leads me to the sensor itself?

 

No. That tells you your cam is making very low vacuum.

 

so its nothing to worry about then right? The car funs fine and all i just wanted to make sure.