FireCode

iTrader: (1)

This has me worried a little I changed the oil today in my 95 SC400, put 5 litres or 5.28quarts. Took it out shortly after to fill up on gas. It is about a 30 minute roundtrip. Get back to the house and I have the windows down and no A/C. As Im slowly pulling up the drive and into the garage, I hear a knock 1,2,3,4,1,2,3,4 knock knock knock, Sounds like you are taking your knuckle and knocking it on a wooden table at a quick pace. It's not a really fast knock, just a methodical knock at low(below 1,000) rpms that is pronounced.. With the car in park or nuetral, nothing noticeable. I took it out for a quick spin right after I heard the noise to see if I could hear it on the road as I accelerated, nope, sound was not there. No lag in performance. I did put it in drive andheld my foot on the brake, reving it up to 1k rpm the sound gets faster but not louder. Over 1k rpm, the sound is drowned out. With A/C on, you can't hear the knock

Oil on the dipstick shows right in the middle of low and full. Did I starve it of oil? 5 quarts is what it calls for. Bad gas? Chevron 93 octane. The sound def. seems to be coming from the top. I did get a slight stutter the other day so I am about to change the cap/rotor/coils/plugs and wires.

Any thoughts guys? It is entirely possible this sound could have been present for some time because I don't drive without my A/C on, its texas in the summer.

It sounds very similar to this BMW minus the airy exhuast sound...just the knockhttp://www.youtube.com/watch?v=M70r6WC_9Dw

1sxyrxy

might just be un lucky. what oil did you use?

FireCode

iTrader: (1)

Castrol GTX 5W-30

I officically have no clue what it is..took it for another quick spin...I can powerbrake it to 1500rpm and hear nothing. You only hear this knock at low idle to about 800rpm with it in drive or reverse. As soon as the AC comes on when it is in drive, the sound goes away. I really don't think it could be engine knock by these symptoms but what do I know. I can sit there in nuetral and rev it to 4k and hear nothing except a great sounding engine

turbodremz

iTrader: (18)

Try a heavier oil. 10w-30

imDementeD

iTrader: (7)

rod knock would increase with rpm's.

Vintage91

Likely piston slap, not rod knock. Piston slap would be more evident at low rpms like you're describing. You can try a heavier oil like turbodremz mentioned. It may soften the harshness of the sound.

FireCode

iTrader: (1)

I will try it soon. Listen to this though...I go out there this morning and start it on a cold engine....Nothing zilch. no sound.

turbodremz

iTrader: (18)

After listening to the video again, that doesn't sound like rod knock, also like mentioned it would be RPM dependent. Now I'm not too familiar with BMW engines, but if piston slap is an issues with them, rip it out and replace it with a 2JZ..cause I have experienced piston slap, but it was with an r/c car nitro engine which uses a ringless piston, not to mention it was a cheap one

Honestly, and I know this probably isnt it cause it seemed to idle smoothly, it sounded like a spark plug was missing. Did you happen to put your hand on the engine at all to see if you could feel vibrations that were in sync with the knocking?

Drive the car, get it hot, check the oil level and see if it does it again.

FireCode

iTrader: (1)

drove to church this morning. Car was its normal running self. the 1uz ran fine no noises. I get to church and leave it in drive and turn the ac off, 3-4 seconds later, the knock sound was there at 600 rpms. Turned ac back on...nothing, sound goes away. I think it may be a plug issue. Like I had stated, there was a stutter and hesitation when acclerating a couple of days ago. I have parts being shipped in right now to do the ignition tune up. I'm hoping it is just a firing issue at low rpms.

I just felt for vibrations. It is coming from the passenger side of the engine whatever it is. It just sounds like someone is lightly tapping there knuckle on a wooden table.So weird though becuase you only feel it with ac off and in drive.

good2go

iTrader: (6)

You do realize that your rpm's go up when you kick in the ac, right?

That could be what's making the sound go away, and not necessarily anything to do with ac.

FireCode

iTrader: (1)

Absolutely. That was my point in saying it is only when the ac is off hence very low rpms. Although, why would once it hits 1000k rpm, the sound goes bye bye

Maybe I will get brave enough and stand it front of it with the ac on and in drive with the parking brake on to see if I can still feel the knock. SO far, I have only done it with no ac. I just don't trust the parking brake haha

1sxyrxy

cracked flexplate?

FireCode

iTrader: (1)

Interesting theory. I did do one semi hard pull(enough to break the tires loose in 1st) up to about 40mph right before I got home last night. Wouldn't that be a *****, crack the flex plate 2 seconds from my house.

Although the more I listen to vids, it really doesn't seem, like a flex plate...no chatter.

joeazy187

iTrader: (1)

change the oil to a thicker oil. when you started the car in the morning it didnt knock because cold oil is thicker and once the car warmed up so did the oil, hopefully thats all it is good luck.

FireCode

iTrader: (1)

Thanks guys. I will change the oil. The car runs perfectly other than this weird knock sound at idle (you cant even hear it in traffic) like someome is taking a rubber strip similar to a belt, spinning it around in circles and having the tail end of it repeatedly hit a wooden table.