I own a 2001 Hyundai Elantra, bought used about a year ago. About 8
months ago I noticed that about every 20 startups the RPM would surge to
just under 3,000 RPM for just a second or so when I started the car.
Then about 4 months ago the car developed a low-idle condition when
warm, idling at about 500 RPM or so, just enough to make some vibration
when idling at an intersection. No acceleration or stalling issues were
present and the car otherwise continued to operate just fine. I used two
tanks worth gas with fuel injector cleaner in each, plus throttle body
cleaner, and gradually the low idle issue when away.
About the time the low idle issue was resolved, however, the car began
experiencing an RPM surge to just under 3,000 RPM for 3-4 seconds
whenever I would let the clutch out as I was stopping the car. It does
the RPM surge whether one is in 3rd, 2nd or 1st gear when the clutch is
released, and the condition kicks in after about 1km of driving on the
first trip of the day (on a warm day), and thereafter is evident on
subsequent trips each day of the car has not cooled off significantly.
The problem seems to be worsening such that when I let up on the gas
when in motion and let out the clutch, the RPMs tend to stay at 2,000+
briefly and then the RPM's settle down slowly, or the surge occurs as I
stop, and then the RPM's settle quickly to around 2,000 RPM and then
more slowly to normal idle. Once in a while the idle just stays at
around 2,000 RPM. If I engage the clutch and move forward a bit in 1st
gear, this usually settles the RPM down. And I can end the surge by
getting under way in 1st gear as well. But the surge as I said will end
on its own but not immediately.
I wonder if anyone has any ideas on what the issue could be. I have
sprayed the throttle linkage, clutch and brake cables under the engine
hood and in the area of the pedals with WD40 in case it is a stuck
cable, but no luck.
About 8 weeks ago I changed the spark plugs and put new platinum plugs
in. At that time the plugs showed no evidence that would suggested any
problem with any of the cylinders. This was when the low idle issue was
present and the plug change did not help the low idle issue.
I am wondering as well whether I should remove the sensors in the
throttle body and clean them, perhaps they clogged after the throttle
body cleaner was applied. Is this a possibility?
Many thanks for any suggestions that may be offered as what this problem
London, Ontario, Canada