95lexus000

I hope that somebody here can help me with my Lexus.

My 1995 SC400 recently developed an odd sound. It is a knock that occurs only when the car is in drive, at rest with full brake on. As the RPM is raised to about 800-850 with full brake on, this sound goes away. The knock is not heard while idling in park or neutral, or while driving, even under load conditions. It is not very loud (the surrounding area must be quiet to hear this), although it is definitely present. I have also noticed that if the AC is on, the knock does not occur (the rpms are higher).

Another thing, the knock is not consistent...its rhythm is something like 5 knocks in a row then a few in a row, etc. In other words, the pause in between each knock is not always the same.

Please let me know if anybody here has any idea of what might be wrong with my car.

btw...One last thing, a few days ago I removed one of my cats, the resonators, and I replaced the stock mufflers with magnaflows. Could this be what has caused the problem??? I think maybe because there is definitely less back pressure now.

Thanks!!!

willhickey

iTrader: (1)

does the oil pressure light ever come on? (the teacup one in the tachometer housing)

jadu

iTrader: (42)

check the timing?

95lexus000

I haven't noticed the oil pressure light coming on at any time. I guess I can check the timing too...I have a mechanic coming today to assess the sound, and I may run the car by another mechanic tomorrow. I just hope there is nothing critically wrong with my car. Since the sound only occurs at very low rpms, maybe it is just the sound the engine makes just before it stalls??

Anybody else ever experienced this sound?

Anybody else have any idea of what might be wrong with my car?

Thanks so much!!

1JZPWRD

iTrader: (59)

Bring it to me tomorrow! We will figure it out. We will check the TPS, and try to increase the rpm's.

RyanV

iTrader: (9)

May be the power steering pump, if you can reach it place a screwdriver on the housing and listen to it like a stethoscope.

What does the oil on the dipstick look like? Put it up to the sun, it should not have a shimmer to the oil, which would be bearing material.

It's not your mufflers..

95lexus000

Thanks for all of the replies!

The more I look into it, the more docile I think the problem may be. I get the impression that the problem is that my car idles too low when it is warmed up and the ac is off. I think maybe that when the idle is so low, that the oil pressure gets low and so the engine makes the sound it is making. My car actually just stalled. It runs great throughout the rpm range when driving, I think I need to increase the idle speed

Thanks again for all of the help