So I have a 1997 Sunfire with the LD9 and it seems to have a rod knock. Now I have owned this car for a LONG time and I can identify a rod knock when I hear one bu this is different. Ive went through two engines in this car and both were knocking ones. The reason I am not completely sure this is a rod knock is because it only knocks about 2800-3100 rpm and then goes away. There is no loss of power either and it doesnt fall on its face like my last engine did. I have been driving it like this everyday for the past three weeks and it hasnt gotten louder or lost power. The oil isnt mettalic either which baffles me. I deliver pizzas everyday and put close to 150 miles on the car a day. Everyday the car sees close to 5000 at least every delivery. Motor was freshly rebuilt with new bearings and such and the crank and rods were all miked and were well in spec. Only mods are a "Slappy Cam Swap" (running two inake cams). I was curious if anyone had this issue before and also shouldnt the engine had threw the rod by now, or at least be knocking so loud it was noticeable? Maybe I have the invincible 2.4, or just lucky lol
Wrist Pin maybe?
I have seen a lot of knocking 2.4's. Only two of them sounded exactly the same. These motors can really throw you off when it comes to noises.
I have never had one loose power when it did have a rod knock either.
FU Tuning
I'm thinking it the wrist pin. I'm not worried about it too much because I already purchased a back up engine.
I had one that had a knock and it would barely get going and even build power. But I was just curious what your opinions were cause I heard valve train noise is also common at those rpms
I had a very similar "knock" for almost two years (and 25k miles), it sounded like a tick from 1500 - 2200 rpm. I originially thought it was in the head, but after a lifter exploded and i replaced the entire valve-train, the tick persisted. Finally the tick turned in to a knock, and i replaced the block with the one i have now. On tear down i found i had spun cyl 3 rod bearing.
Z24Sunfire wrote:I'm thinking it the wrist pin. I'm not worried about it too much because I already purchased a back up engine.
I had one that had a knock and it would barely get going and even build power. But I was just curious what your opinions were cause I heard valve train noise is also common at those rpms
A broken wrist pin will not make much noise when under a load, such as accelerating or steady state load. It will make what sounds like a rod knock when decelerating or when there is a unloaded state. Hope this helps.
Dennis
From experience with other gm engines, I sort of doubt the lack of no drop in power if it is the engine. Gm knock sensors are over sensitive where I am betting if it is the engine in that rpm range or the whole rpm range it is pulling a butt load of timing out of it. Though how about a vid of the noise would help more then guessing, along with just a suggestion is to cut the filter open and see what it looks like.
I've never had a drop in noticeable power in any of my motors before they failed..... until damage was done (such as spinning bearings, exploding lifters, bending valves, etc) ... with a bent valve and exploded lifter, my motor still ran, however i cut it off, parked it, and built the head i have on the car now
Edited 1 time(s). Last edited Friday, November 23, 2012 5:03 PM
2fast4u88 wrote:From experience with other gm engines, I sort of doubt the lack of no drop in power if it is the engine. Gm knock sensors are over sensitive where I am betting if it is the engine in that rpm range or the whole rpm range it is pulling a butt load of timing out of it. Though how about a vid of the noise would help more then guessing, along with just a suggestion is to cut the filter open and see what it looks like.
I understand what your saying and it makes sense. From my experience tuning this motors they have alot of knock/false knock even bone stock, and pull timing but still run strong. My guess would be (never had the chance to datalog a car with a real knock) it is not picking uip anymore than it already has, was, is (unless the car has been tuned and knock retard was fixed from stock).
My ex wife had a 96 Grand Am SE with a LD9. at 129k it was making a noise at light load, like cruising. At idle it sounded fine, you could go WOT no noise. I took it to a few shops no one could pin point it for sure, some thought wrist pin. Her Dad who was a mechanic did not think it was a rod bearing either. We drove the car for a month like this and I would still push the car hard.
Finally we replaced the timing chain guides (per GM), no change. We dropped the oil pan no metal in the oil, opened the filter no metal in it. From the little we could see around the balance shaft assembly saw no signs. Finally I said screw it will pulled the motor. Once apart it had a bad bearing. Crank was polished and good, replaced all bearings, gaskets, oil pump, water pump, clutch, valve job, etc.. and it was good to go.
My point is these motors will throw a curve ball in regards to sound.
FU Tuning
Addicted to meth wrote:2fast4u88 wrote:From experience with other gm engines, I sort of doubt the lack of no drop in power if it is the engine. Gm knock sensors are over sensitive where I am betting if it is the engine in that rpm range or the whole rpm range it is pulling a butt load of timing out of it. Though how about a vid of the noise would help more then guessing, along with just a suggestion is to cut the filter open and see what it looks like.
I understand what your saying and it makes sense. From my experience tuning this motors they have alot of knock/false knock even bone stock, and pull timing but still run strong. My guess would be (never had the chance to datalog a car with a real knock) it is not picking uip anymore than it already has, was, is (unless the car has been tuned and knock retard was fixed from stock).
My ex wife had a 96 Grand Am SE with a LD9. at 129k it was making a noise at light load, like cruising. At idle it sounded fine, you could go WOT no noise. I took it to a few shops no one could pin point it for sure, some thought wrist pin. Her Dad who was a mechanic did not think it was a rod bearing either. We drove the car for a month like this and I would still push the car hard.
Finally we replaced the timing chain guides (per GM), no change. We dropped the oil pan no metal in the oil, opened the filter no metal in it. From the little we could see around the balance shaft assembly saw no signs. Finally I said screw it will pulled the motor. Once apart it had a bad bearing. Crank was polished and good, replaced all bearings, gaskets, oil pump, water pump, clutch, valve job, etc.. and it was good to go.
My point is these motors will throw a curve ball in regards to sound.
Yeah this one is just strange. My buddy and I already pulled it once and took it apart and the bearing had spun but caused absolutely no damage to the crank or rod. so we miked it and found them both to be in spec so we threw in a new set of bearings and it persisted so i just got to the point of saying eff it lmao. I still run the hellout of it waiting for it to blow up. getting another engine tomorrow so we'll see if i have any luck finding a good replacement
