The check engine light comes on when idling. Using a tester, the code indicates the IAC was not functioning. I replaced the IAC, the engine idles somewhat better, but at 1000 RPM, and the check engine light still comes on. I re-tested and the code is the same... #35, IAC. Any thoughts?
2007-09-29 02:01:13 · 4 answers · asked by nidantwo 1 in Cars & Transportation ➔ Car Makes ➔ Chevrolet
If there was a vacuum leak or other air leak getting into the engine which wasn't going through the air filter, mass air flow sensor and inlet air temperature sensor in your air cleaner ductwork leading to the intake manifold, then the oxygen sensor would detect a too lean air/fuel mixture and automatically pulse more gasoline through the fuel injectors. That would speed up the engine idle just like when you press down the accelerator pedal and the throttle plate opens. This is called an "unmetered" air leak into the engine, and the computer thinks the air is coming in through the air cleaner as it's designed to do. And the computer also knows the engine is supposed to be idling at hot idle, so it tells the IAC to close off as much air as possible to get the idle down, but the IAC can't do it because of the unmetered air leak. The computer and IAC run out of idle RPM correction range. A shop would use an unlit propane tester wand to pass around the various places at the top of the engine where air could get in unmetered including around the air duct connection to the intake manifold, vacuum connections and the intake manifold gasket areas. If any test point causes a change in idle RPM, you've detected an air leak.
2007-09-29 02:30:51 · answer #1 · answered by bobweb 7 · 2⤊ 1⤋
I own a shop, and think this; The butterfly in the throttle body is probably sticking in the open position. Clean it good with throttle body cleaner, stuff long rag into throttle body to catch the gunk so it don't set off the O-2 sensor, or cause other problems from getting down in the engine. The long rag is easy to get back out too. There is a slot around the butterfly that air travels, and the IAC is inserted into this slot to control the idle speed. If the butterfly is sticking open, then the computer sets a code for the IAC or circuit. Use a propane torch to check for vacuum leaks. Any area that is sucking vacuum will suck the gas from the propane torch into the intake, and make the engine speed up. Pay attention to the EGR valve, it may be sticking open causing it to set the code too. The code 35 can be a tricky little devil sometimes, as other stuff will make the code set due to the computer doesn't know the difference, it only knows excessive air is getting into the engine, thus it sets a 35 code.
Glad to help out, Good Luck!!!
2007-09-29 11:04:57 · answer #2 · answered by Anonymous · 1⤊ 0⤋
Code 35 is an idle problem. It doesn't mean the IAC motor is faulty. You most likely have a vacuum leak. The most likely area is either broken vacuum lines or the gasket underneath the TBI injection unit to the intake manifold is bad.
2007-09-29 12:57:00 · answer #3 · answered by Deano 7 · 0⤊ 1⤋
CHECK FOR ADDITIONAL VACUUM LEAKS BUT WHEN YOU REPLACE IT DID YOU CLEAN OUT THE HOUSING BECAUSE IT IS LIKELY VERY DIRTY AS WELL.
2007-09-29 10:49:13 · answer #4 · answered by Anonymous · 0⤊ 1⤋