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Discussion Starter · #1 ·
Hello guys, ive been having a problem with a rough idle on my 2013 3.8 gt and have been yet to source the problem. It throws no codes and almost seems to smooth out when the ac is on but when off the car has a shake/stutter. Ive tried new spark plugs, MAF sensors, iat sensors, cleaned the throttle body, as well as checked for any exhaust leaks and as far as my vaccum gauge shows i have no vaccum leak. Any ideas or suggestions?
 

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Discussion Starter · #2 ·
Additionally, the car is full bolt on custom tuned on 93 oct by alpha speed and was previously on a canned tune with less mods but still had the same problem to a lesser extent. I will try to post a video with showing the stutter.
 

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Discussion Starter · #4 ·
check valve timing
Thanks, ill have my mechanic take a look. I noticed via dash command my engine timing is constantly jumping around, could that be a sign the valve timing is the problem or is it normal for engine timing to vary a few degrees (jumping between +6 and +10 ). I noticed when driving at a constant speed the valve timing almost never changes and holds its value.
 

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I'd rather do it myself
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If the timing is really jumping around at idle that is because the ECU uses timing to control the idle speed and is having problems.

On my 2L when this happened it was a dirty throttle body. And it finally set a code.
 

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While the engine is running, disconnect an injector. reconnect, if how the engine does change. Repeat with the next injector, and so on.
You want to find the cylinder that does not change when you disconnect the injector.
This will narrow your scope of where to look.

if it changes on all of them, then it's either valve timing, and/or something with the ecu.

Also take each spark plug coil out (Actually disconnecting the harness and THEN pulling them out. Mark them first, of which cylinder each coil came out of)
Check the silicone boot at the end for cracks. Also since they are out at this point, check to see if there is a spring in there (sometimes they fall out)

Boots - flex/squeeze them. Cracks will be hard to see unless you do this. Also look for white dust, usually a sign that it's been arcing through the boot.
Coils - check for obvious burn/melting marks. Never seen it on a hyundai, but it's common on fords... you never know.

FYI, checking these won't tell you if a coil is bad. It's just the obvious signs of one. Boots can be bought and replaced at any auto parts store.

if you identified which cylinder is the problem child, put in a different coil into that cylinder, start the engine, then do the injector thing, just on the problem cylinder.
if idle changes, then it's the coil. If it doesn't the injector.
 
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