Deep resonance between 1000 - 2000 rpm

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milehi

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loveland colorado
I have a very nice 05 Hyundai xg350 purchased 3months ago which I thought has a bad motor mount. Mech. gave a clean bill of health on the mounts on an inspection when I had the front tires balanced.
I have a resonance that starts a 1000 rpm in neutral through 2000 rpms, most pronounced at 1500 rpm either going up or coming down in rpm.
Car starts and runs fine,passed emissions, the coils had been replaced in the last 8000 miles, has champion iridium spark plugs, no codes and 115,000 miles. well cared for by previous owner, new trans and torqe converter 8000 miles ago.
Any Ideals what is causing this resonance???
 
Flex pipe looked clean (no rust here in Colorado you know) did not notice any problem and Firestone Mech. gave the exhaust a clean bill of health ??? Thanks for the response. milehi
 
Update, "MAYBE", its more of a flutter than a resonance. I don't hear well but can at least feel it through the steering wheel. Does this open up and new ideals?
 
I have a 2001 XG300 with 85000. I'm the original owner. Had a similar issue years back. It felt like a "shudder" of aprox. 1-2 seconds. Is it repeatable with regularity? Car in motion or running in neutral with the parking brake engaged?
 
GEZ said:
I have a 2001 XG300 with 85000. I'm the original owner. Had a similar issue years back. It felt like a "shudder" of aprox. 1-2 seconds. Is it repeatable with regularity? Car in motion or running in neutral with the parking brake engaged?
Click to expand...
This is to bring everybody up to date, just had the intake manifold pulled and new gaskets on top side with new spark plugs. The lower intake manifold has plastic runners in it and they are loose. Held in place by some kind of unavailable plugs which has worn grives in the aluminum. ( New one goes for $500).
Still have same shudder as before but more power, looking to replace same with used unit, will advise how this works.
 
milehi said:
This is to bring everybody up to date, just had the intake manifold pulled and new gaskets on top side with new spark plugs. The lower intake manifold has plastic runners in it and they are loose. Held in place by some kind of unavailable plugs which has worn grives in the aluminum. ( New one goes for $500).
Still have same shudder as before but more power, looking to replace same with used unit, will advise how this works.
Click to expand...
CORRECTION---THATS THE UPPER INTAKE MANIFOLD, SORRY ABOUT THAT!!!
 
milehi said:
CORRECTION---THATS THE UPPER INTAKE MANIFOLD, SORRY ABOUT THAT!!!
Click to expand...
Well, the plastic intake runners were the problem, acquired another intake manifold from a 75,000 mile car, It had the same loose runners just not as bad as mine. we removed the runner, cleaned them up and bedded them into a nice bed of epoxy, tight as a drum. Problem solved.
 
milehi said:
I have a very nice 05 Hyundai xg350 purchased 3months ago which I thought has a bad motor mount. Mech. gave a clean bill of health on the mounts on an inspection when I had the front tires balanced.
I have a resonance that starts a 1000 rpm in neutral through 2000 rpms, most pronounced at 1500 rpm either going up or coming down in rpm.
Car starts and runs fine,passed emissions, the coils had been replaced in the last 8000 miles, has champion iridium spark plugs, no codes and 115,000 miles. well cared for by previous owner, new trans and torqe converter 8000 miles ago.
Any Ideals what is causing this resonance???
Click to expand...
avisitor said:
Thanks for the update.
Am sure it will help another person.
Click to expand...
 
Been away for a bit and found this thread in my email. Maybe I'm missing something, but it sounds to me like two separate issues: one with the car in motion AND Xmission loaded, the other being engine related with no load on the torq drive regardless of the torq converter or xmission.

I have learned a lot since my original post of shudder or resonance that is "felt" thru the steering and/or body. I cannot address the upper intake manifold other than to say the interface seal to the block IS a source of Inefficient spark firing form engine oil seeping past and collecting in the spark plug tube. This provides an electrical leak path to ground leading to rough firing. Bringing the engine to temp just makes the firing system more efficient. It does not solve the problem. On my XG 300,the spec torque value was 5-8 ft.lbs. Thought that a might low and bumped it to 10-12. Oil seepage stopped. Go figure. Also the coil packs can look and measure proper resistance when cold. Try removing the air plenum cover and run the car in TOTAL darkness. You may find a small blue arc between the coil winding and the iron housing. If so, replace all three.

Don't bother with a transmission flush as the Dealer doesn't really flush anything; it just drains the pan and some small amt in the lines. A flush is possible, but it takes special equipment that recirculates and filters the fluid thru a pressurized closed system. Ask First. I won't even get into the solenoid pack, but if you know what your doing, it ain't Rocket Science: I know cause I used to be one back in the day.

Rough or intermittent shifting that produces a vibration or 'late/reluctant' shifting, was in my case, eventually traced to a transmission over speed pickup coil. 1 hour for access and 2 minutes to R&R. $70.00.

Hopes this helps somebody. It's a journey! Enjoy the ride...
 
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