2007 GS430 intermittant problem when driving at around 30/40mph. sounds like driving over a cattle grid for approx 2/3 seconds. cannot simulate problem with accelarator or brake.

Remove your rear rotor check emergency brake shoes

this could be because of the fuel pump not functioning properly.

My son is a master technician. He said it sounds more like the heater core to him. Does it have any smell to it, like antifreeze. I would definitely get a second opinion.

Bent valves- my 96 civic had that too. it's a manufacturing fault. Have you mechanic do a leak down test.

could be your wheel bearins juck car up an check for movement or rumbleing sound

Sounds like a turbo bearing problem. They start off intermittent or at specific RPM's, then get worse with time.

i have a grand cherokee jeep 3.1 dsl, year 2000, lhd, on 3 occassions now i have been driving and then car shudders as if you were driving over a cattle grid ..after i stop the car and then drive away its fine and i suppose approx between each time its done it i mut have driven about 2,000 to 2,500km .....

it also seems very sensitive to road surface , sometimes when driving over a slight pitted surface the steering wheel seems very jumpy ,

there are no problems at high speed etc

i have had the tyres tested ,tracking done

also

my wife has a grand cherokee 4ltr auto 1998 , when she is driving sometimes i jolts as if it has fule starvation or misfired , drives fine seesm to do it most after we have been driving for 10-15mins , if your on a long journey it will do it every 1min or so , we have had checked for plugs, timing etc etc ..could it be a sensor ?

cheers

paul holley ( spain)

Bad amplifier

If you got debris on the wheel speed sensor, that would cause this. Wipe off the sensor and tone wheels and then drive it and see if it goes off

Could be a little thing's, security system issue, fuel issue or a EGR or Throttle senser issue.