Tapping noise in engine bay
Thread Starter
Heel & Toe
Joined: Aug 2019
Posts: 20
Likes: 0
Tapping noise in engine bay
Hey guys, so I have a 1994 Corvette LT1. I was driving next to a friend and decided to get on the acceleration a bit (I rarely do hard accelerations) and he said I shot out a bunch of black smoke from my left (driver’s side) exhaust pipe. I was shortly after that pulling into my drive way and noticed a tapping noise coming from what sounds like the engine. As my rpm’s raised it seemed like the tap got faster. I just found out my o2 sensor is bad and needs replacing, so I assume that’s where the black fumes came from during acceleration, but the tapping noise is a bit frightening.
I haven’t checked my oil level yet, going to do that in the morning, but just wondering what else you guys think it could be.
I haven’t checked my oil level yet, going to do that in the morning, but just wondering what else you guys think it could be.
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
Hard to say without hearing it. Check the oil level and color. The black exhaust was carbon. It's possible piece of carbon it stuck on piston and contacting head. Lifter is stuck from varnish. With a long screwdriver you could try to listen where noise is loudest. Towels or rags canbe used to block exhaust outlet. Blocking exhaust can aid in detecting exhaust leaks. Audio file(s) would be helpful.
Thread Starter
Heel & Toe
Joined: Aug 2019
Posts: 20
Likes: 0
Hard to say without hearing it. Check the oil level and color. The black exhaust was carbon. It's possible piece of carbon it stuck on piston and contacting head. Lifter is stuck from varnish. With a long screwdriver you could try to listen where noise is loudest. Towels or rags canbe used to block exhaust outlet. Blocking exhaust can aid in detecting exhaust leaks. Audio file(s) would be helpful.
Thanks for the feedback. Yesterday I checked my oil level and it looked fine, but the color was a brown color just a few days ago and is now completely black. I also started the car and there was no ticking noise but still black smoke when revving. Went to get a coffee and when starting my car after that there was a tick, drove to work and by the time I got there the tick was gone. I’ll try to get a video of the sound next time it does it.
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
Black oil isn't good, normally normally severely overheated or contaminated. I would suggest oil and filter change. Magnet probe drained oil see if anything sticks. If you could cut open filter see large solids are present.
Black smoke during regular driving would be a over rich condition, codes ? Montioring engine data : O2 sensors, integrator, and block learn. 1994 Corvette uses 16 pin OBD2 ALDL connector, because PCM is reflashed, engine is OBD1.
Black smoke during regular driving would be a over rich condition, codes ? Montioring engine data : O2 sensors, integrator, and block learn. 1994 Corvette uses 16 pin OBD2 ALDL connector, because PCM is reflashed, engine is OBD1.
Thread Starter
Heel & Toe
Joined: Aug 2019
Posts: 20
Likes: 0
Black oil isn't good, normally normally severely overheated or contaminated. I would suggest oil and filter change. Magnet probe drained oil see if anything sticks. If you could cut open filter see large solids are present.
Black smoke during regular driving would be a over rich condition, codes ? Montioring engine data : O2 sensors, integrator, and block learn. 1994 Corvette uses 16 pin OBD2 ALDL connector, because PCM is reflashed, engine is OBD1.
Black smoke during regular driving would be a over rich condition, codes ? Montioring engine data : O2 sensors, integrator, and block learn. 1994 Corvette uses 16 pin OBD2 ALDL connector, because PCM is reflashed, engine is OBD1.
I ran codes and I got both O2 sensors throwing codes. This morning got up early to check them out before I go to work and realized my cat converter is gone. Honestly had no idea someone took it out, it explains why my car says the O2 sensor is messed up.
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
The 2 Converters are close to manifolds not under center of car. I would be sure fuel pressure regulator isn't leaking fuel in to vacuum hose. Over rich will kill cat converters.
Instructor
Joined: Jun 2019
Posts: 105
Likes: 15
From: Portland, Oregon
Smell the oil to see if it's got fuel in it. Fuel in the oil will clean out carbon and turn the oil black. I had a Volvo years ago that ran around pig rich for months and the inside of the engine was spotless. Your fuel pressure regulator may have failed as Kevova pointed out. You could have leaky injectors. Revving the engine at a standstill shouldn't give black smoke. Hard acceleration can give a little smoke that should clear up quickly. This is the Italian tune up.
My '94 ticks slightly from a minor exhaust leak, but mine goes away when it warms up. Mechanical ticks are far easier to find with a mechanics stethoscope. An exhaust leak can be found with a piece of hose held to the ear.
My '94 ticks slightly from a minor exhaust leak, but mine goes away when it warms up. Mechanical ticks are far easier to find with a mechanics stethoscope. An exhaust leak can be found with a piece of hose held to the ear.
Thread Starter
Heel & Toe
Joined: Aug 2019
Posts: 20
Likes: 0
Smell the oil to see if it's got fuel in it. Fuel in the oil will clean out carbon and turn the oil black. I had a Volvo years ago that ran around pig rich for months and the inside of the engine was spotless. Your fuel pressure regulator may have failed as Kevova pointed out. You could have leaky injectors. Revving the engine at a standstill shouldn't give black smoke. Hard acceleration can give a little smoke that should clear up quickly. This is the Italian tune up.
My '94 ticks slightly from a minor exhaust leak, but mine goes away when it warms up. Mechanical ticks are far easier to find with a mechanics stethoscope. An exhaust leak can be found with a piece of hose held to the ear.
My '94 ticks slightly from a minor exhaust leak, but mine goes away when it warms up. Mechanical ticks are far easier to find with a mechanics stethoscope. An exhaust leak can be found with a piece of hose held to the ear.
I’ll have to look into that. I changed the fuel filter as soon as I got the car because it had never been changed and it showed, but I never looked at the injectors. After work I’ll try smelling the oil to see if I smell fuel. I had a suspicion of an exhaust leak and the guy who rebuilt my transmission confirmed it and fixed it, so maybe there’s another closer to the engine itself. I haven’t heard the ticking noise since yesterday afternoon so I’m hoping it stays gone. I do appreciate all the feedback!
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