Cam & crank sensors

[mclasser]

2018 Elantra w/ 55k miles.

I decided to replace all three of these sensors in an effort to fix a hard start / extended crank this car's had since it was essentially new. It happens so intermittently and sporadically that I didn't bother pursuing it when under warranty since Hyundai dealers don't do anything unless the CEL is on.

What happens:

When frequently stopping & starting the car hot, like when running errands around town, it extended cranks (~4 seconds) before starting.

When cold starting in the morning, it extended cranks and starts hard. The idle gets really lumpy and the exhaust has a strong smell of gas. I know a little gas smell when cold is normal but this is excessive. After a minute or so, everything smooths out. Again, all this happens very sporadically. It can be fine for a month and then it randomly acts up. And the CEL is never triggered.

Over time, I've replaced the battery, plugs, coils, air filter and ran fuel system cleaner. I've read about the cam & crank sensors on these cars having funky failures with similar symptoms so I've fired the parts cannon and now installed OEM Mando sensors.

Will monitor things but hopefully, this is a permanent fix .

 

[DemoFly]

This kind of problem is solved with a scan tool. If it ran and didn't throw a CEL or limp mode it's not the cam and crank. Likely not a vacuum leak from a randomly sticking EGR or Purge because those are easily caught by a CEL.

But the car doesn't know weather or altitude so it usually assumes air metering and ECT are known goods and will instead throw a CEL later for misfire or rich/lean. I'd bet its MAF/MAP or coolant temp sensor based on symptoms.

 

[ls1mike]

Yeah that does not sound like a cam/crank sensor to me. I'm with Demo, sounds like a MAF or MAP to me.

 

[michaelluscher]

My armchair opinion is more of a fuel system issue

Weak pump, mild vapor locking

Have you tried cleaning the MAF with MAF cleaner?

 

[ls1mike]

A good mechanic with the proper scan tools should be able to figure that one out without making the parts cannon ready in respects.

 

[Soft Cars]

When cold starting in the morning, it extended cranks and starts hard. The idle gets really lumpy and the exhaust has a strong smell of gas. I know a little gas smell when cold is normal but this is excessive.

That sounds to me like the computer doesn't know what the air/coolant temperature is or is being told the wrong temperature.

 

[Chris142]

You are describing what to me sounds like a fuel problem. Not sure why you would replace those sensors Instead. Those sensors generally work or they don't.


Sounds like the valve that keeps gas in the fuel line is letting it bleed down instead. A way to test this is to turn the key on but don't start it 2-3x then try to start it.

 

[ls1mike]

You are describing what to me sounds like a fuel problem. Not sure why you would replace those sensors Instead. Those sensors generally work or they don't.


Sounds like the valve that keeps gas in the fuel line is letting it bleed down instead. A way to test this is to turn the key on but don't start it 2-3x then try to start it.

Like the check valve? I had that fail on one of my cars. So it took the extra time to prime it.

 

[14Accent]

Sticking canister purge valve - just a thought.