Surging, 2004 Hyundai Elantra

[Rodolfo]

Hi to all,
My car is a 2004 Elantra GLS/GT 2.0 I4 engine with CVVT. AUTOMATIC TRANSMISSION
car comes with Traction control
no trip computer.
VIN number.
KMHDN46D04U716010.

Long story short. I had an OCV stuck, got so bad I needed a new head. after this the car was rough idling, surging, had CEL of 341 (CamPosition) bad gas millage(13~15mpg).
Noticed that Spark plug #4 was full of dry soot( carbon fouling).
using a scanner and the Torque app. noticed that the reading of the TPS would fluctuate while I was stopped and breaking.

after doing a lot of diagnostics. found that debris from the stuck OCV got into the new OCV that was installed. cleaned it. after this no more codes.
but still had surging issues specially when I break, or i’m stopped at a light etc. some times the surging would be immediately followed by stalling, I was able to make stall while Idling, by manipulating the throttle .

Also gas millage improved but still bad (about 16~17 mpg)

For the spark plug swapped injectors problem remains I till get #4 dirty (carbon fouling) saprk plugs used where NGK platnum.
I did the vacuum leak test according to the video.
So before I tart buying and swapping sensors any help will be appreciated
thank you !

Topic

[college man]

Try this procedure for the crank sensor. I’m surprised the computer is not picking up a
misfire? Does the engine light flash at all? seeing its one cylinder #4 and you swapped
injectors with no change. Before we get crazy with compression tests. Check spark to that #4 with a spark tester. If spark is
not good this would cause a rich condition which would cause carbon fouling to the plug.

http://www.justanswer.com/hyundai/6ngpn-hyundai-elantra-gls-2004-hyundai-elantra-stalls-short.html

http://www.ericthecarguy.com/faq/solving-automotive-no-start-problems?start=3#NoSpark

[Rodolfo]

Hi

No there are no codes, not even when it stalls. have not been able to get my hands on a spark tester all I did was pull the spark wire out while the car was running to hear the spark. I know this does not replace using the spark tester.

After the post the car did a really weird thing. after driving to work (about 10 miles) I parked and went to work after about 4~5 hours I went to drive out to lunch. and the car started rev up and down from 700 to 1500 rpm I looked at the scanner data and noticed the TPS value going up and down with the RPM.
So I disconned the TPS and it stop
tuned off the car re-connected the TPS
started the car and now the RPM wet all the way 3K RPM!!
Again I disconnected the TPS again after it seemed to get better I had a bunch of codes because I had been disconecting the TPS and IAC.
So i decided to clear the codes. as soon as the Check Engine light went off the RPMs jumped to 3k again so I just shut it off
when I went to go home some hours later no issues???????
except for wat I already mentioned in the original post.

So any way searchhin for the cause

[Author]

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