Scotty, I've tried everything I can think of but can't seem to resolve an issue. It's on a 2013 Hyundai Elantra GLS, 1.8L, automatic with 137K miles. My daughter was driving and came to a red light. Upon stopping the engine stalled. First time that's ever happened. It restarted without a problem and she drove to a safe place. I swapped her cars and began working on it at home. The vehicle has no codes and seems to run fine except when idling in gear - it's rough. Rough enough to make the vehicle shake/vibrate (vehicle had new OEM motor mounts and tranny mount installed six months ago). Idle rpm in gear seems too low (640-660).
I installed a new air filter, removed and thoroughly cleaned the throttle body, sprayed a can of intake valve cleaner into the intake, replaced the spark plugs with double iridium plugs, checked for vacuum leaks by spraying carb cleaner at all vac line connection points and added two bottles of chevron fuel injector cleaner to the tank and took it for a high rpm ride (Italian tune up). None of these efforts made a difference. Performance was fine on the drive but the shaky idle is not going away.
I'm at a loss.
Thanks in advance!
Did you already scan for any stored trouble codes?
what about your fuel pump/filter and MAF sensor?
Scanned, but zero codes.
Fuel pump/filter seems fine (that's based on no issues with fuel flow at high rpms). I'm assuming if the pump were not working correctly or the fuel filter was dirty/clogged that it wouldn't deliver enough fuel at the higher rpms? I'm trying to think logically.
The MAP sensor was cleaned.
Scanned for codes - none. MAP sensor is fine and fuel pump/filter were fine. Took Scotty's advice and just kept driving it until it finally threw a code. P0335 - bad crankshaft position sensor. Replaced with OEM and everything is back to normal. Thanks InThrustWeTrust and komodoris -- appreciate your assistance!
Idle rpm in gear seems too low (640-660)
According to specs I found online, the rpm seems to be within range
With A/C off: In neutral and parking: 640 ± 100 / in the D-range: 640 ± 100
With A/C on, In neutral and parking: 680 ± 100 / in the D-range: 680 ± 100
Rough enough to make the vehicle shake/vibrate
This requires quite a bit of troubleshooting.
According to a repair manual,
DIAGNOSTINC PROCEDURE:
1. Check the fuel pressure
2. Check the Injector
3. Check the long term fuel trim and short term fuel trim
4. Check the idle speed control circuit (Check DTC)
5. Inspect and test the Throttle Body
6. Check the ECT sensor and circuit (Check DTC)
OTHER CAUSES CAN INCLUDE:
1. Low compression
2. Intake air leaks
3. Contaminated fuel
4. Weak ignition spark
The non-official non-repair manual procedure would be:
First of all, as with any car, the first thing you want to do is to check the engine oil - the Hyundai NU engine is known for having the exhaust manifold integrated catalyst convertor create ceramic dust that gets into the engine and cases damage to the cylinder walls, is the engine oil clean?
Is the air filter clean?
Scan the car for codes with a basic OBD2 scanner, does it have any codes (including 'permanent' and 'history')
Put your key in position II (without turning on the engine), connect an OBDII scanner, and go to live data - what is the MAP (Manifold Absolute Pressure) reading? (it should be around 14 psi when the engine is NOT running)
Does it act the same with the AC on or OFF?
Turn on the car, check how it idles within gear when the 'fuel system' shows "OP" or "Open Loop" as opposed to idling in gear when "CL" or "Closed Loop" - is there any difference?
Same for misfire counters, there's a counter for each cylinder that shows how many misfires were detected on in within a certain period (often a few seconds until it resets) is there any cylinder on which that counter goes up occasionally at idle in gear?
When warm, take you engine to 2k-3k rpm in Neutral, does the MAF read the approximate size of the engine? (1.5 - 2.5L)
Although this is a big of a stretch, while not moving select D, move the shifter to M and push it to +, the number 2 should show up on the gauge cluster - does it still idle poorly?
When the car goes to 'closed loop', in live data, what are the upstream and downstream O2 sensors showing?
The upstream should oscillate, while the downstream should be stable.
Do the AIM and ACTUAL measurements for CVVT (valve timing) match within a degree?
This is also a good time to read the fuel trims, fuel rate, fuel pressure, ignition advance, desired rpm, etc.
Although this is not a "real" solution but it often works:
These issues are often caused by the ECU setting the idle too low, you can try to reset it so that the car will attempt to learn the correct idle, this is done by disconnecting the battery, waiting for a bit, and connecting it back.
After letting it try and set the correct idle on its own, if it doesn't set it correctly - turn off A/C, lights, put it in Neutral and rev it up to a bit 4k rpm at a stable throttle opening for at least 45 seconds. This often can resolve these kinds of issues.
But when we don't know what lead the ECU to set the idle too low, this issue may reoccur.
If issue persists, it's time to replace the fuel filter.
And from there it's some more troubleshooting before replacing expensive parts - like a compression test, these NU engines love loosing compression right at about 125k-150k miles due to scuffed cylinders...
Thanks Dan!
I'll have to find someone with a more in-depth scanner and give it a go. I tried disconnecting the battery and reconnecting later, but it didn't work. Tried the high rpm for 45 seconds... no go. Followed the instructions in the TSB on the NHTSA site... still shakes and vibrates. 🙁
It's being fiesty.
Thanks for all the above advice Dan. Tried them all, but nothing worked. Scotty said to just drive it until it throws a code, which I did and it did. Turns out it was a bad crankshaft position sensor. Replaced with OEM and now all is good! It's back to a super smooth idle and no more stalling. Thanks again!
Either pressure clean or replace the fuel injectors after verifying fuel pressure. Putting $13 bottles of so called fuel injector cleaners in your gas tank does little more than contribute to somebody else's house payment.
Thanks Doc. Gotta get the pressure czeched.
It won't happen again!
Thanks for the advice Doc. Turns out it was a faulty crankshaft position sensor. Replaced with an OEM and it's back to smooth sailing and no more stalling!
Well, if it's really stumbling around at idle, it will trip a code d eventually. You might just wait for the code. But since it's stalled out entirely when you came to stop, you might try my video. Make your car run better with little spray cleaner.
Thanks Scotty! I may just have to do that.
You were right! It threw a code a couple days ago. P0335 - Crankshaft position sensor. Replaced with an OEM and it's back to running smoothly without issues. Thank you very many!
I'll have to find someone with a more in-depth scanner and give it a go
No need for a fancy scan tool - all of these procedures are for a regular cheap OBD2 scanner.
Also, when looking through data, check that the IAT (intake air temperature) is within the realms of reality, I've seen that cause cars run really poorly but that's rare.
Followed the instructions in the TSB on the NHTSA site
Have you verified that it is moving correctly?
with the car off and the key in position II, Press on the gas pedal and see if it opens up...
Thinking about it, I think the Elantra 1.8 was equipped with a VCMA - small flaps in the intake that can close to create "increased tumble flow" and in theory this can malfunction (jam / the control arm can become loose / it can snap internally) - can you verify that it's moving the shaft it's connected to? or is it just spinning freely?
This might require taking off the intake manifold but it's quite easy.
This is the location of the VCMA that actuates the VCM - you probably do not need to replace it.
But please if nothing else helps, I think you should try to verify that the ECU can move the internal flaps.
After you check the readings, by the sounds of things you'll need to perform a fuel pressure test:
This helps check if the pump is in working order, if the fuel filter is not clogged up, if there's a leaky injector and the condition of the Fuel Pressure Regulator.
Preparing for the test:
(Under the hood) disconnect the battery.
(In the interior) Remove the rear cushion and disconnect the fuel pump electrical connection.
(Under the hood) Connect a fuel pressure gauge install between the fuel feed tube and the delivery pipe.
(In the interior) Connect the fuel pump electrical connection and reconnect the battery.
The test procedure:
Start the engine and look at the gauge and measure the pressure at idle (write it down)
(According to online sources, the pressure should be in between 46.9-52.6 psi)
Turn off the engine and 4-5 minutes - then write down the fuel pressure reading.
If the fuel pressure has dropped (this would be an issue) has it dropped fast or slowly?
(you can repeat this process multiple times to verify that the readings are correct)
Cleaning up after the test:
(Under the hood) disconnect the battery.
(in the interior) disconnect the fuel pump electrical connection
(under the hood) remove the fuel pressure gauge and reconnect the fuel feed tube to the delivery pipe.
(in the interior) Connect the fuel pump electrical connection and reconnect the battery
If the results of this test are that the fuel pump works correctly, the next thing is to perform a compression test and if that checks out just installing new injectors.
Also, are you sure that the fuel is good?
Thanks again Dan! Really appreciate your assistance on this issue. My daughters so glad it's reliable again. 🙂