Hyundai Genesis Forum banner

1 - 15 of 15 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter #1
Hey everyone, new to this forum and have a question about one problem I've been having. I have a 3.8 with 98k, since I got it I have been dealing with a rough idle.

I have replaced plugs, checked all the plug gaps. Checked for vacuum leaks. Intake filter is clean, no intake leaks(that I can find). It never stalls and the tach doesn't have any noticeable fluctuation but when sitting still for more than a couple seconds at idle it will start getting rough, and shakes a little bit. Don't think it's misfiring.

Don't know what else to try, I thought it was something I just had to live with until I test drove another bk1 3.8 and noticed that car idles perfectly. Now again I'm chasing this problem. Appreciate any input! Sorry for the long post.
 

·
Premium Member
Joined
·
14,833 Posts
Hey everyone, new to this forum and have a question about one problem I've been having. I have a 3.8 with 98k, since I got it I have been dealing with a rough idle.

I have replaced plugs, checked all the plug gaps. Checked for vacuum leaks. Intake filter is clean, no intake leaks(that I can find). It never stalls and the tach doesn't have any noticeable fluctuation but when sitting still for more than a couple seconds at idle it will start getting rough, and shakes a little bit. Don't think it's misfiring.

Don't know what else to try, I thought it was something I just had to live with until I test drove another bk1 3.8 and noticed that car idles perfectly. Now again I'm chasing this problem. Appreciate any input! Sorry for the long post.
Check your valve timing
 

·
Premium Member
Joined
·
14,833 Posts
Appreciate the response. The engine runs great and doesn't hesitate at all coming from idle so I wouldn't think timing would be a problem.
Valve timing.

And engine needs 3 things to run; spark, air, and fuel.

If you check one system completely, then you would have to check the others.

Common things to check.

Fuel:
check fuel pressure
Check injectors

The way to check injectors is unplug and plug back in each injector, one at a time, until the engine idle doesn't change. This doesn't mean that the injector is bad, but tells you which cylinder is the problem. You can do the same with the spark coils.

Spark:
The obvious
Also check coil boots for any cracks
I doubt it's anything to do with spark, because normally, it would get worse higher in the rpms.

Air:
Check/clean the MAF sensor
check filter
check valve timing.

Why did I say that in the first place? Because you've state that it has 98k miles on it. When was the valve timing checked?
timing chains wear out. When they do, valve timing will be off and eventually break valves, then you're going to have to pay for a head rebuild, if you're lucky.
The engine has a variable cam gear, that is oil pressure driven. It's not going to start adjusting until the oil pressure is up and the solenoid opens. That happens when it's cruising.

Whether you check it or not, is up to you, but I'm sure plenty of other people on here wished they checked it, before there engines turned into paper weights.
 

·
2012 Gen. 3.8 Track w/ZF
Joined
·
716 Posts
My 2012 3.8 idled pretty rough till the dealer found the left engine mount (hydraulic) was collapsed. They replaced it under warranty, and no more rough idle.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #6
My 2012 3.8 idled pretty rough till the dealer found the left engine mount (hydraulic) was collapsed. They replaced it under warranty, and no more rough idle.
I tightened up my engine leash the other day because it had loosened up a little, and the idle got noticeably better. Still rough but not as much vibration so I'll check the engine mounts as that would make sense. As for checking the timing, I'll get the timing cover off eventually. Maybe order a timing belt kit as they seem to be fairly cheap.
 

·
The whistles go WOO! WOO!
Joined
·
829 Posts
When checking the intake, did you check/clean the throttle body? Mine gets pretty gunked up every couple years and needs to be cleaned.

When mine's dirty, it doesn't idle quite right, and eventually will throw codes while driving if it gets bad enough.
 

·
The whistles go WOO! WOO!
Joined
·
829 Posts
Valve timing.

When was the valve timing checked?
timing chains wear out. When they do, valve timing will be off and eventually break valves, then you're going to have to pay for a head rebuild, if you're lucky.
The engine has a variable cam gear, that is oil pressure driven. It's not going to start adjusting until the oil pressure is up and the solenoid opens. That happens when it's cruising.

Whether you check it or not, is up to you, but I'm sure plenty of other people on here wished they checked it, before there engines turned into paper weights.
Noob question I guess, but how does one check the valve timing? I'll check the service manual when I think of it, but I know the forum often has better methods :)
 

·
In Charge of Snacks
Joined
·
2,055 Posts
Noob question I guess, but how does one check the valve timing? I'll check the service manual when I think of it, but I know the forum often has better methods :)
It's pretty involved on a hydraulic-tensioned chain-driven timing engine. Ideally you'd pull the front clip, remove the engine's front dress, remove the front cover/timing cover and inspect the chains, cam sprockets, crank sprocket, chain guides, and tensioners for proper alignment and operation. You'd also need to remove the intake and ignition system to pull the valve covers and get a look at the timing marks in their proper orientation. And if you want to go full elbow deep, you could inspect each lifter bucket for proper lash under the cam lobes with a feeler gauge.

I think the shop manual specifies removing only the intake, ignition, and valve covers to be able to check to see if all the cam sprocket timing marks align with the appropriate links on both timing chains, and the crank pulley timing mark. This wouldn't tell you if the entire timing system was in good health, but it would tell you if it's all in the right place.
 

·
Registered
Joined
·
784 Posts
After reading all the replies, and in light of 98K I say do some preventative maintenance. Remove your LPFP in the tank, clean the filter sock and replace or upgrade your LPFP. At your mileage it cant hurt, and its real cheap.

Then after doing that run about 3 full tanks with big bottles of techron.

I agree if it was timing it wouldnt just effect idle. Vac leaks would be the primary culprit but you have insisted you've checked that.

We are left with fueling, heck yyou might just try the techron first, but cars that age suffer low pressure fuel pump issues all the time.
 

·
In Charge of Snacks
Joined
·
2,055 Posts
After reading all the replies, and in light of 98K I say do some preventative maintenance. Remove your LPFP in the tank, clean the filter sock and replace or upgrade your LPFP. At your mileage it cant hurt, and its real cheap.

Then after doing that run about 3 full tanks with big bottles of techron.

I agree if it was timing it wouldnt just effect idle. Vac leaks would be the primary culprit but you have insisted you've checked that.

We are left with fueling, heck yyou might just try the techron first, but cars that age suffer low pressure fuel pump issues all the time.
OP hasn't specified, but I think he has a BK1.

"...I thought it was something I just had to live with until I test drove another bk1 3.8... "

In that case, he only has the 1 in-tank fuel pump. I agree with you, it's probably a sneaky vac leak somewhere. I've got one I can't find and have nearly identical sounding symptoms...
 

·
2012 Gen. 3.8 Track w/ZF
Joined
·
716 Posts
He stated in the OP that he test drove another BK 1 and found it vibration free. I'm still thinking the motor mounts. Mine did not vibrate when moving and also quit when revving the engine up to about 1000 rpm. Only shook at idle.


Also did you check for any engine codes? Might also be a cam position sensor. If the timing was off it could also require a tweak of the ECU by the dealer.

Also we do not have timing belts. We have chains. Another thing, does it vibrate with the AC on? Mine catches a bit of vibration when the AC is on and the motor is idling. Turn it off and it's vibration free.
 

·
Registered
Joined
·
784 Posts
OP hasn't specified, but I think he has a BK1.

"...I thought it was something I just had to live with until I test drove another bk1 3.8... "

In that case, he only has the 1 in-tank fuel pump. I agree with you, it's probably a sneaky vac leak somewhere. I've got one I can't find and have nearly identical sounding symptoms...
Yeah, with him it still wouldnt be a loss to replace the pump at his mileage, and clean out that fuel filter element.
Even if it doesnt fix it its just good maintenance.
 

·
In Charge of Snacks
Joined
·
2,055 Posts
I am the king of fixing what ain't broken. LOL, as far as the fuel pump and sender go, though, I don't see where changing them before they outright die could do any harm.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #15
Hey everyone, first thanks for all the input. Anyway, yes mine is a bk1. I have checked for codes and nothing. Turning the AC on does make it vibrates a little more, but nothing crazy, and it still does it when it's off. I did valve cover gaskets a little while back and cleaned the throttle body then so I think that's good. I suppose I will go ahead and clean that filter on the pump and if they aren't super expensive probably drop a new one in there, like someone said it won't hurt. Also I'll try that techron stuff.

As of now I've checked the engine mounts and they look ok. I'll update you guys when I change the pump and see if that helps.
 
1 - 15 of 15 Posts
Top