i have a 2004 hyundai sonata. every time i go to refuel the car stalls. After the 2nd attempt to start it up I have to pump the accelerator until it starts & rev the engine to keep it going. this happens each time i go to get gas. i took it to the dealership & they quoted me $700 for a faulty mass air flow sensor & to clean an intake valve. i replaced the very expensive mass air flow sensor & still have the problem. Does it sound like the intake valve & if so, which one? air, fuel? I am at a loss & if anyone can help it would be great. i feel the dealership is trying to make money. by the way the fuel pump & strainer was replaced in 2007.
This seems to be a problem with the EVAP system. If the check engine light comes on, and the code is P0446, there is a TSB 06-30-005 (Technical Service Bulletin) dealing with that. This is an except from that TSB.
NORMAL SYSTEM OPERATION:
In an evaporative emissions system, fuel vapors and air in the charcoal canister are drawn into the intake manifold through the canister purge valve. The vapor/air drawn from the charcoal canister is replenished by fresh air being drawn through the EVAP air filter and canister close valve. Normally, there is a small but measureable amount of vacuum at the differential pressure sensor during purging.
During the system leak check (the vehicle must be driving at a steady speed over 1800 RPM), the canister close valve shuts and purging occurs until the system is drawn to 1.8 volts (measured at the differential pressure sensor). The vacuum will remain at 1.8 volts for up to 30 seconds (depending on the fuel level). This is NORMAL operation, and should not be confused with the diagnostic procedures described later.
In a system that sets P0446, the amount of vapors being purged from the canister is greater than the volume of fresh air entering into the canister. This causes the canister to build up vacuum. When the canister increases in vacuum, the remainder of the system (fuel tank, hoses, separator, etc.) will also increase in vacuum. The fuel tank pressure sensor measures and reports the vacuum level (in volts) to the ECM. If the vacuum level reaches beyond the ECM threshold, P0446 is set into ECM memory. If this condition occurs on two consecutive drive cycles, then the ?Check Engine? light will illuminate.
I think that you need to have your dealership explain to you in more detail just exactly what is the problem. “Intake valve” doesn’t really refer to anything in this case. There are multiple intake valves, probably one for each cylinder in this engine, so I doubt that they would have referred to them as a singular.
Could they have been referring to the throttle body? Or the Idle Air Control motor?
Even still, the fact that it only happens when you fill up with fuel immediately leads me to think that it’s a problem with the charcoal vapor recovery system. Unfortunately, I can’t offer much more than that.
While I don’t usually buy in to the whole “they’re trying to rip me off” thing, the fact that they replaced the MAF sensor for this problem is a little troubling.
EDIT: I see that hellokit is a much faster typist than I. 
Part of the problem, other than higher prices, of going to the dealer for repairs, is that you give the symptoms to a Service Writer (who is usually Not a mechanic) who abbreviates all that you tell s/him, and s/he, then, passes that incomplete picture to the mechanic. Your problem, probably, reached the mechanic as, “Engine is hard to start”. That’s very helpful, isn’t it?
This disconnect in the communications (and price), is one of the reasons we refer people to independent shops/mechanics. There, the person you talk to is a mechanic, or there is a mechanic at their elbow, and that person can get a much better picture of the symptoms from you. The better the input (from you), the better the outcome (repair).
[Mr.Josh, It’s not typing speed, it’s ‘copy and paste’ speed. The “intake valve” is likely the “idle air control valve” (another bad GUESS by the dealer].
okay so you guys are right in saying it is not the intake valve because i did take it to an independent mechanic & they told me it sounds like the EVAP system as well. Now I have the dealer calling me & offering to replace my fuel filter for a small fee. I think i will go with the EVAP/charcoal vapor recovery system & see what happens with that. Thank you both & i will let you know if the problem persists.
Are you refueling with the engine running?
I was thinking this too - you really should not do that (it’s illegal, too!). Either way, it is the EVAP system.
Besides that, if he is, the CEL will trip EVAP system fault codes.
Overfilling the tank?
I was thinking more along the lines of breaking into the sealed EVAP system with the engine running to refuel. That would trip codes.
Yeah, carbon bed saturation occurred to me too regarding what sounds like fuel delivery problems.
Actually i have never run any of my cars I have owned while refueling. I was always told it was dangerous. But I must admit I did try it once with this problem to keep it running so it wouldn’t stall. Low and behold it shut off as soon as the fuel began to pump into tha car. kind of freaked me out so I didn’t try that again. Also, my check engine light has only come on once & only for about an hour & never came back on. Does this sound like an expensive fix, this EVAP issue? I need to prepare for the worst.