Oils Aloha
Oil pressure gauge needle goes back & forth.?
As I was driving I heard a loud wacking noise, like someone threw something at my car. I noticed that my oil gauge needle was going back & forth when I speed up & slow down, Theres no oil leak, she starts up & all, but the gauge still acts the same. Worried it will break down. It's a 1996 Chevy S10 PU Truck. Aloha
I had a 2k Jeep with a 4.0L 6 cylinder in it. The Oil Pressure gauge was acting like what you are describing. When the RPMs came up so would the oil pressure. Conversely when I came to a stop my oil pressure dropped to ZERO. My engine was NOT knocking, ticking, smoking or running rough at all. Checked and changed oil several times.
We ended up replacing the Oil Sending Unit twice. (This would normally fix the problem according to every mechanic and service person we spoke with. So CHECK THE SENDING UNIT/OIL SENSOR FIRST. It's cheap and easy and normally right on the side of the block)
We wanted to keep from replacing the gauge, as it was the hardest thing to get to, and on most newer vehicles you end up having to replace the entire gauge assembly. On mine we ended up replacing the head, turns out it was cracked, and checking oil pressure with a mechanical gauge. The pressure was fine. We traced it all the way back to the wiring harness going up to the gauge where it had melted a little, and when it got hot it would begin doing this. We taped up the wiring and it was perfect.
One more thing to keep in mind. If it was a loud noise like something hit the bottom of your truck... Check the oil pan to make sure it was not dented up against the oil pump. This could have an adverse effect as well, yet would not be too difficult to fix by taking off the pan and flattening it back out.
Sorry about the length... I just know what a pain this was to track down on mine so I thought I would give as much detail as possible.
Boedie
TX