SOHC_4dr

my friends car has a turbo'd Z6. the idle (cold or hot) fluctuates from 1000 to 600 frequently. he is also getting a leak, it is suppose to get 7 psi but sometimes its only up to 4 and a few times it creeps to 11. its been tuned on 7 psi and just happened a few days ago. anyone have any idea what could be causing the fluctuations and creep? i unplugged the MAP and it died and wouldnt start unless it was plugged in. on my Y8 it'll keep running when dissconnected. is his bad or is it just because its OBD 1?

da_dude

Of course unplugging the map sensor will kill the car. Have you bleed the coolant system? Clean the IACV? Check for vacuum leaks.

SOHC_4dr

unplugging it didnt turn off my Y8. which is what confused me. didnt bleed the coolant. i could try cleaning the iacv and i cant find any leaks. the waste gate flutters also. what could cause the leak and creep?

nothing_shocking

well maybe your MAP sensor is bad and not your friend's

SOHC_4dr

no. i dont have an idle issue

turbociv910

well your car should not run with it un plugged, you DO have something wrong there.

Check for boost leaks.

SOHC_4dr

my engine isnt the only engine to keep running with it un plugged. i know of a B18C that still runs and another Y8 and they dont have engine problems or cel.

SOHC_4dr

MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR. The MAP sensor is mounted on or connected to the intake manifold to monitor intake vacuum. It changes voltage or frequency as manifold pressure changes. The computer uses this information to measure engine load so ignition timing can be advanced and retarded as needed. It performs essentially the same job as the vacuum advance diaphragm on an old fashioned mechanical distributor.

On engines with a "speed density" type of fuel injection, the MAP sensor also helps the PCM estimate airflow. Problems here may cause an intermittent check engine light (light comes on when accelerating or when the engine is under load), hesitation when accelerating, elevated emissions and poor engine performance. The engine will run with a bad MAP sensor, but it will run poorly. Some PCMs can substitute "estimated data" for a missing or out of range MAP signal, but engine performance will be drastically reduced.

MAP Sensor Strategies: Some MAP sensor problems are not the fault of the sensor itself. If the vacuum hose that connects the MAP sensor to the intake manifold is loose, leaking or plugged, the sensor cannot produce an accurate signal. Also, if there is a problem within the engine itself that causes intake vacuum to be lower than normal (such as a vacuum leak, EGR valve that is stuck open or leaky PCV hose), the MAP sensor's readings may be lower than normal.
http://www.aa1car.com/library/1999/cm69910.htm

so yeah a car can run with it unhooked or in bad condition.

The_Honda_Guy

First of all, the idle problem is most likely related to your IACV. If you don't know what this is and the problems they have, you shouldn't own a Honda. On any vehicle that has a IACV, if it gets clogged up with carbon buildup it will idle high, low, or surge. Try removing the IACV and cleaning it first. Also, check for carbon buildup on the throttle body and plate.

Make sure you check for vacuum leaks too. Surging idle can also be caused by vacuum leaks, which I could definitely see on a turbo car, especially if you did a really goofy job of doing the vacuum lines for the MAP.

SOHC_4dr

yes i know the IACV and its operation. i just needed ideas on where to look first for his issues. thanks all i'll see what i can find