Trouba

Ok, I have a 2007 Silverado with the 4.3 V6, and every time I shut off my engine, I hear quite a loud "poof" somewhere around the area of the air filter/intake. What can this be?

I had never had problems with it before I had my dealership look at a problem I had with the 'circulate' setting on the AC not shutting outside air out, and also they replaced the belt because it squeeked.

Any thoughts? Thanks

MalibuMaxxSS

backfire thru the throttle body?? or MAF..speaking of AC could be your condensor as well, sometimes they make funyn noises, leak water...man that makes people paranoid....MY TRUCK IS LEAKING SOMETHING....LOL

the AC wont recycle inside air, none of them do,only outside air.....the belt no biggie,

Trouba

What causes backfire through the throttle body? And what about the Mass Air Flow? How does this work?

Thanks...

thrasherff

Some intakes allow for more of an amplified "sucking of air" sound. My roomate's Honda when shutting of takes a last gasp of air and you can hear it about 30ft way.

And yes I give him crap for driving a Honda.

MalibuMaxxSS

your 07 truck should NOT do it so if it is take it in to check it out, did you change the air intake in any way?

Trouba

No, I did not change anything about the air intake, or anything else for that matter. I read some about this and it could be a broken sensor at the intake and it be a timing problem or 'lean fuel' problem, but this is quite rare with these modern fuel injected engines. Gotta take it in tomorrow and see what they can do. I HAVE problems with the AC, by the way, but I don't think it's the condenser because it is the outside air coming in when on 'circulate', and I hear whistling sounds coming through the AC when driving; like it's not shutting the outside air out completely. Very annoying and the dealership said something like, 'we calibrated it on the computer, but these cabins aren't completely airtight, and we only heard a slight whistle at 80, so you don't want to go 80...' some bull like that...

MalibuMaxxSS

Well he is right 80 is to fast........ fukin stealerships hey... .....just Tell him if he thinks GM suck so bad and are not air tight and should have problems like this then maybe you should see someone over him...and last time I drove thru the US, 80 was pretty mcuh the going speed on the highways, crazy drivers......gotta love Canada, where it is common for people to travel the speed limit in BOTH lanes making sure not to pass each other

Trouba

Malibu, about the 80mph, I was not driving 80 when I heard it, I was driving anywhere between 60 to 70mph. The guy that test drove it drove 80!

Anyway, I went back to the dealership the day before yesterday, they kept for a day and a half, and this is what they told me:

-AC whistling issue: They called GM about it and GM said that when you put your AC on circulate, somewhere between 9 to 11 percent outside air needs to come in, as regulated by federal standards. BUT, something about the valve that closes off inside the airducts is perhaps not seated properly, therefore causing a whistling sound. They gave the dealership the option to open up the dash, mess around in there with some insulation tape and try to make it more quiet. What do you think I said to that? [&:] Better to leave it like it is then, don't you think? It could mess it up way worse for them to work on it. GM also said that, in time, some of these systems settle in and the sound goes away. Basically it is forced-in air from driving.

-POOF sound from intake: OK, they couldn't figure out what this was so they had to call GM about this as well, and the engineer there told the dealership mechanic that this is a normal occurrence. That air blows back out through the intake toward the filter is due to the balancing of the crankshaft, and as this happens, air gets pushed back out through the intake; however, supposedly this is not air mixed with fuel, since the moment you turn your motor off, it cuts off the fuel and spark. They said it is less noticable on the V8's, if noticable at all, but the same thing happens there. But the V6 has a different intake arm, according to them, so you can hear it better. Hmm.

Personally I really thought it was some kind of intake manifold leak/afterfire/backfire issue, because I had some pitch black soot around the exhaust while I have CLEAN synthetic oil in the engine. If they were more thorough they should have done an emission test as well and such. Argh.. what a headache. I know we are on a Chevy forum so I won't say what brand of truck I will have next time around... [&o] Really, if I knew all this and the way it drives, I would NEVER have bought this truck. So, there you go GM.

ZX1100F1

This is not correct.

The defroster won't go into recirc but the A/C will.