Car shakes under throttle. What could be the cause?

[ghodge]

I'm trying to troubleshoot a shaking/trembling that takes place when I apply throttle. It only happens under throttle and generally gets worse the more throttle I give it. As soon as I let off the throttle, the shaking goes away regardless of what speed I'm coasting at that point. The car has recently had an alignment but that hasn't resolved the issue. I plan on getting my wheels balanced to see if that helps but wouldn't I have shaking whether or not I was on the throttle?

I need to preface everything with the following in case it helps in the line of troubleshooting. Last year I was driving the car with my JB4 installed using map 2 for 93 gas and map 3 for an E30 blend. I ran into a situation on the freeway where I gave the car a lot of throttle and the car started shaking and the power was breaking up. There was no check engine light and it felt like the car was in limp mode that would not clear until I turned off the ignition. I was able to repeat this again and once again there was no check engine light. I pulled the the Densos that were gapped to .024 and all of the plugs had the electrodes worn down to the nubs in about a year and a half of driving. I replaced the plugs with the HKS M45IL gapped to .022 and that seemed to resolve the issue. Late 2022 I removed the JB4 because I get free oil changes with my dealership and took the car in. Fast forward to about two months ago, I start getting vibration, with no check engine lights. I reinstalled the JB4 and it pulled no codes. I have since replaced all the coil packs and pulled all the plugs for examination. Everything is still gapped to .022. I still get the vibration so I'm looking elsewhere.

Is there anything in the driveline that needs to be looked at? Could wheels out of balance cause vibration only under acceleration? I'm trying to figure this out before handing it over to the dealership.

Thanks,

George

 

[Snowwhite]

i'd have the driveshaft and related joints checked.

 

[Herb_Remington]

Hasn't happened on my Stinger, but I have had bad coil packs on my Volkswagen cause trembling or stuttering of the motor under power (basically misfires) without causing a check engine light. I see that you have changed yours, but my issue persisted through coil pack changes. I kept using AutoZone or cheap rock auto packs. Eventually bought OEM and the issue went away. Thought it worth mentioning.

 

[ghodge]

Thanks Snowwhite for that pointer. That’s definitely going on the list.

Herb,

I replaced the coilpacks with the updated OEM coil packs with no change.

George

 

[Snowwhite]

Are you running any intake mods? K&n filters or similar?

 

[ghodge]

Are you running any intake mods? K&n filters or similar?

I’m running AEM filters inside the stock boxes along with snorkels.

 

[Snowwhite]

are those dry or oiled filters?

 

[ghodge]

I am using the dry filters. I’ll take a look in the airboxes tomorrow when I have daylight.

I forgot to mention that another thing I did was jack up the front wheels and check for play in the noon/6 oclock and 3/9 oclock positions but things were solid.

George

 

[rpoffen]

Thanks Snowwhite for that pointer. That’s definitely going on the list.

Herb,

I replaced the coilpacks with the updated OEM coil packs with no change.

George

Yeah, I second checking the driveshafts and where they bolt to the diffs. Another poster in another thread on this forum said his front driveshaft at the front diff, the flange bolts had elongated. I imagine they may have been loose for some time.
Hope its not a common problem.

 

[ghodge]

I hope so too. We’ll see what I (or the dealership) see.

Thanks,

George

 

[Rodtheviking]

Rear flex coupling, check that.

Pretty sure its part number 491303M000

 

[ghodge]

Thanks guys! I hope this is it.

 

[ghodge]

Updatish:

I haven't put the time in yet to clear enough room to jack the car up and get under it. I did pull the AWD fuse and the shake went away. I have an appointment with the dealership Nov 2 (thank you Kia/Hyundai for making a lot of your cars easy to damage and steal). How likely is it that have Ark GT-F springs installed a couple of years ago may be the underlying cause for the shake under throttle? My thought is that it probably isn't an issue with axles or bearings but still possibly a coupler up front or "clutch pack" in the AWD case up front?

Thanks,

George

 

[Snowwhite]

If disconnecting the front diff electronically makes the shake disappear, then it has to be something with the drivetrain. Springs wouldn’t cause that.

 

[ghodge]

My concern was that the procedure for replacing the springs might be indicted. I think I remember some folks having the axles pop out slightly when trying to drop the front suspension to get the struts in/out.

 

[Snowwhite]

Good point. But if it didn’t shake for two years it’s not the springs.

 

[ghodge]

Agreed. I just hope the dealership doesn’t try to blame the issue on suspension mods.

 

[ghodge]

I finally got the car into the dealership today. The tech indicated that the transfer case will need to be replaced under warranty. We'll see how that goes.

 

[DoctorStiches]

Im having similar issues and also have the ark f springs installed. Had axles checked and there were no issues . They said they couldnt replicate it (i believe the dealer didnt atcually accelerate hard enough)

 

[NS_Stinger]

I finally got the car into the dealership today. The tech indicated that the transfer case will need to be replaced under warranty. We'll see how that goes.

Happy to see they figured it out. Let us know if the invoice shows the cost on that repair, Im AWD and curious what it would cost out of warranty.