need opinions on knocking sound at low rpm after A4 shifts to second.
04-11-2007, 06:38 PM
#1
need opinions on knocking sound at low rpm after A4 shifts to second. Car is 100% stock except for a PTB I just installed with 40K on the clock. Last night I installed the PTB, replaced a bad check valve, and changed the oil with mobile 1 0w40 and delco filter. I filled the filter up with oil before installing it. Oil pressure is 40 at warm idle and goes up to 55-60 under throttle.
After doing all that I took it out and it ran great. Drove it pretty hard and got in a race with a thunderbird twice from about 70 to 130 on the highway and it ran better than it ever has. Noticeable improvement with the PTB. After all that I was happy as can be and then driving down my street on the way home I had the window down and radio off and I noticed a considerably loud knock right after the car hits second gear under light throttle, it also does it a little bit right after it shifts to 3rd, but not near as bad. Any ideas what I screwed up or what to look for?
No noise at idle or when revving it and it runs very strong.
It does sound like there may be a small vacuum leak but I couldn't pinpoint anything. Also, the one side of the check valve that conects to the hose from the air pump was smaller than the one I replaced but I clamped the hose down as best as I could and it doesn't seem like it is leaking there. The guy at the parts store assured me it was the right one for my car.
Could a vacuum leak cause something like that? Could I have knocked a plug wire loose and still get that kind of performance? Wrong check valve?
After doing all that I took it out and it ran great. Drove it pretty hard and got in a race with a thunderbird twice from about 70 to 130 on the highway and it ran better than it ever has. Noticeable improvement with the PTB. After all that I was happy as can be and then driving down my street on the way home I had the window down and radio off and I noticed a considerably loud knock right after the car hits second gear under light throttle, it also does it a little bit right after it shifts to 3rd, but not near as bad. Any ideas what I screwed up or what to look for?
No noise at idle or when revving it and it runs very strong.
It does sound like there may be a small vacuum leak but I couldn't pinpoint anything. Also, the one side of the check valve that conects to the hose from the air pump was smaller than the one I replaced but I clamped the hose down as best as I could and it doesn't seem like it is leaking there. The guy at the parts store assured me it was the right one for my car.
Could a vacuum leak cause something like that? Could I have knocked a plug wire loose and still get that kind of performance? Wrong check valve?
Last edited by Spink; 04-11-2007 at 07:08 PM.
04-12-2007, 05:36 PM
#3
Now it's getting worse. It's sounding more like massive valve chatter at low RPM and also when I rev it in neutral and then let off the gas it chatters real bad as the RPM's are coming down. It never used to do this. I'd post a video if I knew how to do that stuff.
