Who Can Answer This?

[LaDyInReD]

ok... I have 95 240sx automatic and I've been having this problem where the car vibrates (or shudders) at 1800rpms. It doesn't do it all the time but 90% of the time I'm driving it happens.. I was worried it would be the transmission ( which I just recently replaced), but when I brought it to the dealer they said my rear tires were "out of round" and I needed to replace them. What the hell does "out of round" mean?! Cuz when I asked them, they couldn't really desribe it. I brought my car back to the place I bought my tires ( by the way they are practically brand new only 4,000 miles on them!), they checked it out and said that the tires have nothing to do with the problem. And even they couldn't tell me what "out of round" means!!

Has anyone else experienced this problem with their 240? Because it seems like nobody knows what's wrong with my car! I need your help!

Thanks

[GEO]

Means you need a tire rotation and alignment.

[LaDyInReD]

Thanks... so would that be what's causing the vibration at the certain rpm? cuz i still don't know the root of the problem-- dealer says its the tires, tire shop says it's not....

[IvoryJ30t]

if its rpm related, its definately not the tires.

i would say check the motor mounts. they could be loose/cracked/ect.also check the transmission mounts while your at it.

i would say the vibration your experiencing is the motor resonating at that RPM/frequency.

[Nismo_Freak]

Thanks... so would that be what's causing the vibration at the certain rpm? cuz i still don't know the root of the problem-- dealer says its the tires, tire shop says it's not....

An out of round tire vibrates usually above 50 mph and eventually goes away.

[LaDyInReD]

if its rpm related, its definately not the tires.

i would say check the motor mounts. they could be loose/cracked/ect.also check the transmission mounts while your at it.

i would say the vibration your experiencing is the motor resonating at that RPM/frequency.

Thanks, i'll definitely look into that...

--> Someone also suggested that it might be the air intake sensor.. it might be caused by the sensor being dirty? Would cleaning it help? What do you think?

[nightwalker]

have you cleaned you IACV lately?

[TachyonS14]

Oh LadyInRed, I've had a vibration with my 240 for over 6 months. I've done about everything possible. My vibration really comes on at 2krpms. I think I've narrowed my search down to a fuel problem. But just yesterday, I tested my fuel pressure and It was fine... The search goes on.

A good way to check for is to see if the vibration occurs while idling. Because if the car vibrates when its not moving, how could it be the tires or alignment :-p ?

Here's what I've done to combat my problem and yet no success: I've gotten new spark plugs, plug wires, O2 sensor, cap and rotor, air filter, fuel filter, cleaned the throttle plate (which was very dirty btw) all new motor mounts (left, right, and transmission), I also ran Seafoam through the gas tank, crank case, and brake booster line, checked timming