clean88coupe

Hey! I got this vibration running thru the stick and going nuts trying to figure it out. I have done as much as I can...wondering if someone got some good advice. The vibration come on only between 1400-1600RPMs then goes away and comes back at 2500RPMS and get worse with higher RPM. Idle is good. This is what I have done myself to try get rid of this problem with no luck.
+ set the TPS to .89
+ new plugs, cap, TFI module, wires
+ fuel filter
+ cleaned Mass Air, IAC, EGR
+ Fuel system cleaner added to gas
+ ran scanner got codes. KOEO 11 1 11 1
KOER 41,91

The vibration does not vary. At idle, driving, with clutch in and out. I was on the highway and turn the engine off to coast and the vibration went away. Turn it back on and the vibration is back. Anyone with some good info???

clean88coupe

BTW the car was running just fine one day and the next started this problom. Work I have done on the car is larger Mass air, 70mm throttle body, 24lb injectors, 165 AFR heads, Edelbrock manifolds, electric fan, headers, off-road X-pipe, Steeda #18 cam, if this helps...

AdderMk2

does the vibration happen at those given RPM's in every gear?

calfroper_06

vibration suck azz uh!!! just got had my motor rebuild cause of one, check all your mounts, motor mounts, trans mount??? Like adder said does it happen in every gear at those rpms, and also does it do it in the driveway in neutral, try it this way with clutch in and also clutch out

OneGearhead

could be the harmonic balancer going bad maybe?? the rubber insert starting to deteriorate....

clean88coupe

yes it happens in every gear. We put on a new vibration dampaner no luck. Checked the motor mounts and tranny mounts, all good. Clutch in or out no difference.

AdderMk2

you have clearly eliminated the drivetrain as the source of the vibration. So now focus on the engine itself.

You replaced the Harmonic Balancer on the front of the crank?
Have you tried taking your serpentine belt off to eliminate the myriad of rotating accessories on the front of the engine? (dont leave it running to long or you will overheat)

clean88coupe

the motor has +180k miles on it. Also got a knock at low rmps under load(only when I step on it or put in lower grade gas). Got the timing set at 11 degrees

clean88coupe

Yes, i did try running without the serpetine belt and no luck. Same result

clean88coupe

Vibrations freaking suck. Can't drive over 2300RPMS. Might as well be driving a 4 cylinder. Missing my torque. Maybe I need a new block. Never did a compression test. Bad block?