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Discussion Starter #1
About 3 weeks ago my Elantra stalled while I was sitting idle in a drive-thru -- it kind of revved a little bit before cutting the engine off. The car started right back up after it happened and ran a little rough the rest of the day.

I figured it was time for some new plugs (hadn't replaced them since I bought the car used a couple of years ago at 98k miles, it has 120k now). I put some new plugs in and changed out the air filter and had an oil change and the engine was running smoother than the day I got it.

A few days later I go to start the car in the morning and it started up alright but the RPMs went straight to 2k before falling to the usual 1k after a minute or two and thought that was strange since it's usually gone to about 1200-1500 for only a few seconds on a cold start before falling to just under 1000. I then started noticing the engine would shake a bit and kind of bog down when I had the AC on and would idle perfectly fine and smooth if I turned the AC off.

The engine stalled again last week while I was parked with the AC on except this time it took slightly longer to start back up and it started pretty rough BUT even though the engine was on and I could rev it the RPM gauge stayed at 0 and wouldn't move.

I figured it was an issue with the AC compressor (i've been driving with the AC off just in case) until today when I pulled into a parking spot and the engine just cut off for no apparent reason -- all electronics still bright and working. The car started back up faster than usual and every time I got to a red light it felt like it was on the verge of stalling again unless I held the RPM at about 1k. So now I'm thinking it's not AC related.

Anyone have any experience with this? The car runs perfectly smooth otherwise -- no hesitation when I accelerate and no stalling or bogging while I'm driving (knock on wood). Hoping it's a quick/cheap fix -- I cursed myself by saying something like "my car will have issues now" because I JUST bought my first house and money is tight :rolleyes:

I should also note that I've had issues in the past where the car won't let me turn it off and the shifter won't move into park/the car will try to start but won't turn over (just makes a chugging kind of sound) and I have to release the shift lock button to shift into park/drive -- this has happened maybe 3 or 4 times since I got the car and hasn't happened since the dealership replaced some kind of washer that was causing a clicking noise when changing gears. Could this new issue be caused by the new washer that was put in?

SUMMARY:
Stalling in idle
- Changed spark plugs
- Changed air filter
- Changed oil/filter
- Tested battery/checked fuses
- Tried the ECM reset

Sorry for the long post. I like details.
 

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We starting to crank position sensor fail on the UD/MD Elantra 1.8 NU engine system..

Plugs wont stall

Air filter wont stall, maintanance item

Fuses,, once a fuse go open circuit,, it dont fix itself back to closed circuit

Tried reset ECM,,, what we do there ?? Did we not scan it first to see if maybe PCM detect fault in any particular input-output circuit that may have set DTC to PCM memory.. depending on what you did, you might have lost diagnostic info,, and now you going to have to wait for a couple stalls in order to see if anythong logged,, though you free to scan Willy-Nilly in hopes of finding something to guide you to what circuit may have fault
 

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I would get a obdii bluetooth reader, get an app on your phone and try to read error codes coming from the car. You'll need to wait until the next stall before you can get some information on it. If its an intermittent problem (doesn't show error codes via obdii), having the obdii reader plugged in may log that temporary error. Sometimes there is an error code, but it won't register any lights on the car so give that a shot first before replacing a lot of other items in the car.

Another thing to check is the mass airflow sensor right after the engine air filter. The connector may be loose but the sensor itself maybe dirty. I haven't heard about this problem on elantra, but my old car had that sensor moved (cold air intake) and a loose wire to the mass airflow sensor caused my car to stall when it was raining or humid outside. Cleaned up the wire and connected it better and the car ran fine after.
 

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First since there's no code, it's usually ECU related. I attached a pic of engine wiring, focus on these 2 ground wires or any others similar, they work as negative ECU terminals. Clean and tighten them back.

Another part you need to check is purge valve. This electrical controlled valve can be worn out and cause rough idle, hard to start, running rough, and it's cheap to get a new OEM
 

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Another thing to check is the mass airflow sensor right after the engine air filter. The connector may be loose but the sensor itself maybe dirty. I haven't heard about this problem on elantra,
1.8 NU in the UD/MD Elantra does not have a MAF,,,, we use MAP on this engine
 

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First since there's no code, it's usually ECU related. I attached a pic of engine wiring, focus on these 2 ground wires or any others similar, they work as negative ECU terminals. Clean and tighten them back.

Another part you need to check is purge valve. This electrical controlled valve can be worn out and cause rough idle, hard to start, running rough, and it's cheap to get a new OEM
Purge,,, I would expect rough run after refuel for couple minute until HC vapor cleared from canister and draw fresh air,, or a 0441 incorrect purge flow with tank pressure sensor seeing activity when PCM knows we not commanding purge..
 

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Purge,,, I would expect rough run after refuel for couple minute until HC vapor cleared from canister and draw fresh air,, or a 0441 incorrect purge flow with tank pressure sensor seeing activity when PCM knows we not commanding purge..
Well that did happen on my car. Idling from 700-900 rpm at stop sign, delay in shift. Tried clean with throttle body cleaner, no difference. Then replaced with new OEM and fixed. Driving and shifting smoothly. Never seen any code. I can't explain this
 

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Discussion Starter #8
I'm going to check for codes later today.

One thing I have not tried yet is taking a look at the throttle body to see if it's gunked up. Probably wouldn't hurt to take it out and give a cleaning anyway. Anything special to watch out for when removing/cleaning?
 

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UPDATE

Went through all the fuses again and checked for any that were blown or reading low and they all checked out ok.

Cleaned out the throttle body and the car started up like it should with no hesitation or rough idle. Turned the AC on full and the RPMs stayed around 900 and didn't drop. Revved the engine a few times to see if there was any hesitation and didn't have any!

Drove the car all the way home and to the store with the AC still on full blast and didn't have any issues while driving or in idle at a light or while I was parked.

I picked up a scanner and got 4 codes -- P301, P302, P303 and P304.. Could these have just been from cleaning the throttle body since the car sputtered a little bit right after the cleaning?

I'm not calling this 100% fixed just yet since I assumed it was fixed after the spark plug change and it stalled again a few days later, but so far it seems to be idling just fine after the cleaning.
 

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Discussion Starter #10
First since there's no code, it's usually ECU related. I attached a pic of engine wiring, focus on these 2 ground wires or any others similar, they work as negative ECU terminals. Clean and tighten them back.

Another part you need to check is purge valve. This electrical controlled valve can be worn out and cause rough idle, hard to start, running rough, and it's cheap to get a new OEM
The car stalled again at lunch just now. Plugged in my scanner and got these from the live reading. I don't know how to read these, but here is what I had


DTC_CNT: 0

FUELSYS1: CL

FUELSYS2: --

LOAD_PCT(%): 41.2

ECT(C*): 91

SHRTFT1(%): 0.0

LONGFT1(%): -2.3

MAP(kPa): 39.0

RPM: 679

VSS(km/h): 0

SPARKADV(*): 4.0

IAT(C*): 66

TP(%): 12.5



OS2LOC B1S12--B2S----



02B1S2(V): 0.690

SHRTFTB1S2(%): 99.2



OBDSUP OBDII



RUNTM(SEC): 560

MIL_DIST(Km): 0

EVAP_PCT(%): 14.9

FLI(%): 37.3

WARM_UPS: 8

CLR_DIST(Km): 187

EVAP_VP(pa) -57.00

BARO(kPa): 96

EQ_RAT11: 0.981

02S11(mA): -0.082

CATEMP11(C*): 365.4

CATEMP12(C*): 292.4

VPWR(V): 13.866

LOAD_ABS(%): 23.9

EQ_RAT: 0.999

TP_R(%): 3.5

AAT(C*): 20

TP_B(%): 12.2

APP_D(%): 14.9

APP_E(%): 14.9

TAC_PCT(%): 3.9

MIL_TIME: 0 HRS 0MIN

CLR_TIME: 5HRS 22MIN

STSO2FT1(%): 0.00

LGSO2FT1(%): 5.5
 

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My crank position sensor failed months ago. One symptom it exhibited was sometimes the engine would start but the tach showed zero RPM.
 

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Discussion Starter #12
Well, it's been a few days and the problem has come back.

The good news is that my car now has a new PCV valve that needed changing anyway, new spark plugs, new oil/filter, clean throttle body, new air filter and a new gas cap because the old one had a broken seal.

Just got done replacing the PCV valve just in case that was the issue and it's something that is cheap and easy to fix and I noticed a hissing sound coming from the engine bay that sounds a lot like a vacuum leak somewhere!

Next stop is to find where the hissing is coming from and if that doesn't do it I'll just take it in and spend some money...
 

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My crank position sensor failed months ago. One symptom it exhibited was sometimes the engine would start but the tach showed zero RPM.
The zero RPM only happened that one time and I think it was because I somehow got it to start (very rough and not very long) while it was stuck in neutral with the shift lock engaged. Haven't seen it since.
 

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UPDATE

Went through all the fuses again and checked for any that were blown or reading low and they all checked out ok.

Cleaned out the throttle body and the car started up like it should with no hesitation or rough idle. Turned the AC on full and the RPMs stayed around 900 and didn't drop. Revved the engine a few times to see if there was any hesitation and didn't have any!

Drove the car all the way home and to the store with the AC still on full blast and didn't have any issues while driving or in idle at a light or while I was parked.

I picked up a scanner and got 4 codes -- P301, P302, P303 and P304.. Could these have just been from cleaning the throttle body since the car sputtered a little bit right after the cleaning?

I'm not calling this 100% fixed just yet since I assumed it was fixed after the spark plug change and it stalled again a few days later, but so far it seems to be idling just fine after the cleaning.

TB cleaning is probably all it needed. Clear the misfire codes and drive it. Let us know what you get.
 

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I would get a obdii bluetooth reader, get an app on your phone and try to read error codes coming from the car. You'll need to wait until the next stall before you can get some information on it. If its an intermittent problem (doesn't show error codes via obdii), having the obdii reader plugged in may log that temporary error. Sometimes there is an error code, but it won't register any lights on the car so give that a shot first before replacing a lot of other items in the car.

Another thing to check is the mass airflow sensor right after the engine air filter. The connector may be loose but the sensor itself maybe dirty. I haven't heard about this problem on elantra, but my old car had that sensor moved (cold air intake) and a loose wire to the mass airflow sensor caused my car to stall when it was raining or humid outside. Cleaned up the wire and connected it better and the car ran fine after.

If the CEL comes on it stores a code. If not, it doesn't. Code readers are a far cry from a scan tool. To know better what is going on he'll want live data. Looking at engine RPM and idle control is a place to start.
 

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First since there's no code, it's usually ECU related. I attached a pic of engine wiring, focus on these 2 ground wires or any others similar, they work as negative ECU terminals. Clean and tighten them back.

Another part you need to check is purge valve. This electrical controlled valve can be worn out and cause rough idle, hard to start, running rough, and it's cheap to get a new OEM

There are many things that will not set a code and have ZERO to do with the ECU. Bad grounds of the ECU causes many problems, some of which set codes.
The purge valve when stuck open will cause a rich condition and should be properly tested. Don't just throw parts at it. This is one of those things you would do well to have a scan tool. You can monitors the trims and a decent scanner will allow you to command the vent and purge valves which help locate the problem.
 

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Well, it's been a few days and the problem has come back.

The good news is that my car now has a new PCV valve that needed changing anyway, new spark plugs, new oil/filter, clean throttle body, new air filter and a new gas cap because the old one had a broken seal.

Just got done replacing the PCV valve just in case that was the issue and it's something that is cheap and easy to fix and I noticed a hissing sound coming from the engine bay that sounds a lot like a vacuum leak somewhere!

Next stop is to find where the hissing is coming from and if that doesn't do it I'll just take it in and spend some money...

How did you clean the TB? Remove it? If so, did you use a new gasket? How about the IAC, did you mess with it?
 

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I had stalling issues with my daughter's 2012 Elantra limited, which for a while did not throw a code. It was the camshaft position sensor. $12 on Amazon, delivered the next day, and Installs in about a minute right on top of the engine. When it did finally throw a code IT DID NOT ILLUMINATE THE CHECK ENGINE LIGHT.
Cheers.
 

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The car stalled again at lunch just now. Plugged in my scanner and got these from the live reading. I don't know how to read these, but here is what I had


DTC_CNT: 0

FUELSYS1: CL

FUELSYS2: --

LOAD_PCT(%): 41.2

ECT(C*): 91

SHRTFT1(%): 0.0

LONGFT1(%): -2.3

MAP(kPa): 39.0

RPM: 679

VSS(km/h): 0

SPARKADV(*): 4.0

IAT(C*): 66

TP(%): 12.5



OS2LOC B1S12--B2S----



02B1S2(V): 0.690

SHRTFTB1S2(%): 99.2



OBDSUP OBDII



RUNTM(SEC): 560

MIL_DIST(Km): 0

EVAP_PCT(%): 14.9

FLI(%): 37.3

WARM_UPS: 8

CLR_DIST(Km): 187

EVAP_VP(pa) -57.00

BARO(kPa): 96

EQ_RAT11: 0.981

02S11(mA): -0.082

CATEMP11(C*): 365.4

CATEMP12(C*): 292.4

VPWR(V): 13.866

LOAD_ABS(%): 23.9

EQ_RAT: 0.999

TP_R(%): 3.5

AAT(C*): 20

TP_B(%): 12.2

APP_D(%): 14.9

APP_E(%): 14.9

TAC_PCT(%): 3.9

MIL_TIME: 0 HRS 0MIN

CLR_TIME: 5HRS 22MIN

STSO2FT1(%): 0.00

LGSO2FT1(%): 5.5
Did you ever get this fixed? My car is doing same and I have replaced all the same parts and more.
 
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