99 Lumina LTZ 3.8L Surges at idle sometimes
maxman
03-09-2007, 09:57 PM
'99 Lumina LTZ 3.8 L V6. 186,000 miles
Runs well most of the time. However, sometimes when it is started, it surges and jerks. If I rev it a few times, it goes away. I noticed a sound under the hood of air when this happens. I finally caught it with the hood open before it went away. Air was surging through the intake duct upstream of the filter. The filter is clean. When the surging stops, the engine will idle low, then high, then low, then high, etc, until it like catches up, and everything is fine.
Seems to happen most when the engine is not quite cooled off after it was up to operating temperature.
Another thing that I noticed is that when I shut the engine off, I hear the air surge. Like a valve is dumping air. For sure the surging air noise is coming through the intake duct, even with the cover off the air filter box. I can start the engine back up, run 1 minute, shut it off, and I hear the surging air. It never did this before. This sound of surging air sounds exactly like the sound when the car is running rough as explained in the previous paragraph. In this case, the car will start and idle just fine, but when I shut it off, I hear the surge. This can be repeated multiple times.
There is a device mounted on the side of the intake, opposite the springs and stuff for the throttle. What is the device? Does it come apart cleanly? It this device prone to failure? Could this device be my problem?
The service engine light is on and the last time that I checked it, it was the MAP sensor. I removed the sensor and cleaned it with MAP sensor cleaner and the service light went away. It was back about 50 miles later. I will check it again to see if something has changed.
Runs well most of the time. However, sometimes when it is started, it surges and jerks. If I rev it a few times, it goes away. I noticed a sound under the hood of air when this happens. I finally caught it with the hood open before it went away. Air was surging through the intake duct upstream of the filter. The filter is clean. When the surging stops, the engine will idle low, then high, then low, then high, etc, until it like catches up, and everything is fine.
Seems to happen most when the engine is not quite cooled off after it was up to operating temperature.
Another thing that I noticed is that when I shut the engine off, I hear the air surge. Like a valve is dumping air. For sure the surging air noise is coming through the intake duct, even with the cover off the air filter box. I can start the engine back up, run 1 minute, shut it off, and I hear the surging air. It never did this before. This sound of surging air sounds exactly like the sound when the car is running rough as explained in the previous paragraph. In this case, the car will start and idle just fine, but when I shut it off, I hear the surge. This can be repeated multiple times.
There is a device mounted on the side of the intake, opposite the springs and stuff for the throttle. What is the device? Does it come apart cleanly? It this device prone to failure? Could this device be my problem?
The service engine light is on and the last time that I checked it, it was the MAP sensor. I removed the sensor and cleaned it with MAP sensor cleaner and the service light went away. It was back about 50 miles later. I will check it again to see if something has changed.
maxwedge
03-10-2007, 10:00 AM
You cannot clean a map sensor, something wrong there, 2cnd pull the idle speed control from the TB and clean it and the passages, clean the throttle body also. Post back the exact codes also.
maxman
03-14-2007, 09:47 PM
OK. According to Advance Auto diagnostics device, a code in history shows 102. No current codes. I lost the print out, but it said something regarding "MAP or VAC sensor".
I removed the IAC (idle air control solenoid) aan cleaned the build up of carbon from the plunger and the seat inside of the manifold. There was quite a bit. The car seemed to run great and went over 70 miles without the check engine light. It rested for a bit, but when I started it back up, the check engine light came back on.
It has started to do the surging thing again as described previously. As before, not all the time. Still hear the dumping of air through the intake about 5 seconds after I shut off the engine.
I am going to remove the IAC and clean it again. Any other suggestions?
I removed the IAC (idle air control solenoid) aan cleaned the build up of carbon from the plunger and the seat inside of the manifold. There was quite a bit. The car seemed to run great and went over 70 miles without the check engine light. It rested for a bit, but when I started it back up, the check engine light came back on.
It has started to do the surging thing again as described previously. As before, not all the time. Still hear the dumping of air through the intake about 5 seconds after I shut off the engine.
I am going to remove the IAC and clean it again. Any other suggestions?
Automotive Network, Inc., Copyright ©2025