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My wife drives a 2010 Hyundai Tucson. Back in March or April it died on her while starting it up. It cranked fine, ran for 5-10 seconds, and then stalled. She was able to then start it up again and it ran just fine.

Since then it has been doing it on and off intermittently, but it seems to be getting worse lately. Last week it stalled again and then when I restarted it the check engine light was on. I took it to get checked and it was the MAP sensor. I had that replaced yesterday and the engine seems to run a little more smoothly, but the issue still persists.

It feels like it happens only when the engine is warmed up. If I drive it from home to a store and am only in for a couple minutes it feels more likely to happen. Sometimes it will stall twice in a row and giving it gas to force it up to about 1200-1500 RPM seems to help it stay running. It doesn't have any driving issues - once it's started it is good to go.

Today it happened to me again. After it stalled I turned the key without starting it to see what would happen. I heard an electronic hum type noise repeating - as if it was trying to start something up and having trouble.

From my research into the issue, it is likely either an airflow or fuel related issue. The intermittent stalling seems to sound more like the IAC (or in my case it seems to be integrated with the Throttle Body and called an Electronic Throttle Control). The electronic hum might sound more like a fuel relay/pump issue?

My background with working on vehicles is limited. I'd like to get better at it and be able to do more myself. If it's the throttle body/IAC it seems fairly easy to clean and possibly replace it. The fuel relay looks easy too, but the fuel pump sounds difficult and expensive.

I guess my questions are: do my scenarios sound likely or do you think I'd be better off look at something else first? How do I troubleshoot and test each part to figure out what is wrong? I'd like to get this resolved myself if possible, but I don't want to get in over my head either. Any suggestions are appreciated!

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    I'd definitely give a go at cleaning the throttle, just be careful not to move the plate with your hand. I'd also suggest investing in some diagnostic tools like a single channel digital storage oscilloscope... or at least a decent multimeter and low amp clamp. And a hand held scan tool that can read live data from global OBD2.
    – Ben
    Commented Jul 13, 2016 at 0:52
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    It sounds much more like a classic idle air control problem than a fuel delivery issue. Your IAC I beleive is controlled by a motor that is pulsed, and these can noticably buzz with the key on, engine off.
    – SteveRacer
    Commented Jul 13, 2016 at 4:18
  • @Ben Not questioning, just curious and trying to understand better. What are the effects of moving the throttle plate by hand?
    – cdunn
    Commented Jul 13, 2016 at 16:45
  • @cdunn It's like moving a IACV by hand you can break the motor. If you need to open the plate do a key on engine off and have someone hold the throttle pedal down or use a scan tool to actuate the motor.
    – Ben
    Commented Jul 13, 2016 at 16:54
  • @Ben I didn't know that, thank you. I will do that if it comes up. So far only moved the throttle while engine was running
    – cdunn
    Commented Jul 13, 2016 at 16:56

1 Answer 1

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It sounds like the car is unable to maintain sufficient pressure in the fuel rail.

Have a look at this answer for more details on potential causes for hot start problems.

It is usually a good strategy to confirm suspicions through measurements and/or diagnostic tests, many of which can actually be performed by an average DIY-er. As you saw with the MAP sensor, the diagnostic codes report symptoms, not necessarily root causes. The alternative to diagnosis (what i affectionately like to call parts roulette) can get expensive and frustrating.

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