strange gulping noise from air filter area after engine warms up. stops when idle sensor is unplugged. replaced sensor but didn’t help. Runs ok but when you get to 40 mph misses and runs rough. computer and all 6 coil packs and plugs replaced. 6 cyl 30. engine
Odd, you do not have the CEL illuminated with those symptoms… Your CEL might be faulty, have the codes checked, you may have fault codes.
Thanks for taking the time to reply. I’m not sure what the CEL is, however there are no warning lights at all. I might add that the vehicle starts to run rough and kind of miss at exactly 40 mpr. I did have a guy check the codes and he came up with nothing. Replaced the vacumn hose on the egr. Also last year the computer and all coils and plugs were replaced. Vehicle has only been adult driven and not hard.
CEL = Check Engine Light.
Fortunately the vacuum line to the EGR valve has been replaced, so if that was done correctly we can rule that out. It could be a vacuum leak with in the intake manifold or somewhere else. However I am thinking the EGR valve itself is bad. When the car starts running rough tap the EGR valve with a hammer, if the valve is stuck the tapping might free it up and if this is the case the engine should immediately improve. The gulping sound is throwing me off a little bit though, I truly have no idea what that is.
Yes, felt pretty stupid about the CEL after I replied! Tapping on the EGR didn’t have any effect but the guy who was trying to figure it out promised to come back and do a pressure test. I agree that the valve probably be replaced as it’s not a major expense. Also, the engine runs ok until you get up to 40 mph-right on the dot. No one who has heard the gulping has ever heard anything similar. It warms up and starts it in a very even pattern. Gulp, gulp, gulp every few seconds. I surely appreciate your thoughts on this.
One more thing I wish you would help me understand-why does the gulping stop when the idle control module is unplugged? I did replace it as I said earlier but when reconnected it started back as soon as the engine warmned up. The guy took it off to be sure the gasket was in right.
You may be feeling torque convertor shudder, if there were a misfire the check engine light would be flashing. The PCM/misfire monitor is far more sensitive to misfires that the driver.
Thanks for the input… I’m in a very little town-not a garage here-nothing but a Chevy dealership!
If i understand the purpose of the Idle air control valve correctly on this vehicle is that it controls the idle rpm of the engine by finely controlling the amount of air going into the intake manifold electronically. If so i would assume that while the gulping sound is there the engine rpm would fluctuate? Can you see or hear that happen?
The only thing I can think of, and this out of the box thinking on my part, is that you have a faulty Mass Air Flow sensor (MAF). the MAF is sending erroneous data to the ecu and because of this the IAC is fluctuating between more air and less air and thus creating a gulping sound. This is my wacko theory, and yes this gulping sound is quite strange to me.
Can you also better describe how the engine runs rough? Does it drop RPM, or does it seem to buck? Give it your best shot at describing it.
Hi there. It’s runs really rought-kind of like a miss. And loses power at well. This starts at exactly 40 mph.
Replaced the idle sensor as the gulping sounds goes away if you unplug it. Replaced it and gulping starting back as soon as new one was connected. Haven’t done anything with Mass air flow. By the way, the idle valve made no difference in the mrp-even when I unplugged it. Is there a way to check the MAF? Thanks again.