Lately I've been noticing an odd pulsating sound while accelerating, really only in 3rd and 4th gear. At first I thought it was some kind of tire noise, but the noise goes away as soon as I close the throttle.

It's not vibrating at all, and I don't really hear it in 1st, 2nd, or 5th. I mainly hear it through 3rd and 4th, throttle open, in the 2500-3500 rpm range.

The most recent work done on the car was back on Thanksgiving weekend. I replaced the heater core (pulled the dash), replaced the passenger side axle, and also replaced all coolant hoses on the entire engine and the oil cooler gasket, which involved removing my intake manifold, and replacing the original gasket with a new factory IM gasket.

Before that, I pulled my engine out last May to replace the clutch, front and rear main seals, timing belt, water pump, oil pan gasket, and various other gaskets, and put in fresh GM Synchromesh Friction Modified fluid (last fill of the same fluid had been in about 50K miles, and came out looking clean).

The car does not leak or lose any measurable amount of oil in 3K miles. No fluids of any kind are leaking that I can tell.

Could it be possible that it could be a slight vacuum leak around the intake manifold gasket? I tightened those bottom nuts as best I could when putting the IM back in, but with all the oil cooler hoses and that vacuum box on the P72 IM, getting to those bottom middle 2 nuts was difficult to say the least.

Car seems to idle rock solid at 750 rpm, so it doesn't seem like it would be any kind of vacuum leak. Anyone have an idea?

 

anyone?

 

anybody at all?

 

Thats what ive always said loud tires sound like "pulsating" so you get new **** tires ?

 

The noise stops when I close the throttle, and I really only hear it in 3rd and 4th gear. How could it be the tires?