It’s been a while. Today I replaced the knock sensor. It was difficult to remove with the tools I had. I rounded off a bit the hex, so I had to order a better wrench for the job.
Replacing the knock sensor didn’t fix my problem at all. I also went back to Densos. 
I took the EGR valve off and tried to probe the ports but I couldn’t get anywhere. Not sure if there is a way to snake a wire inside like those plumbing snakes you get in hardware stores.
Since this thread began a question has hung in the air…Compression… What is the compression?
A theory was postulated by @Tester by his rec to try Seafoam for carbon deposits. You tried it… yet we never knew cyl pressures. Not before, not after… and not now. We need to know…because if Mr. Testers hunch about excess carbon was correct… (and it is a correct working theory, without question) we still don’t have the data, yet we have moved on as if we proved something. Nothing was proved there I’m sorry to say. SO…
I ask for a compression test. What are your cylinder pressures in each cyl? If we knew the cyl pressures…we could at least rule out one thing for certain…then move to the next thing.
A comp test compared to what you’ve already been thru is nothing.
Since the spark plugs have to come out to do a compression test, that’s a good time to install new plugs too.
It’s been a while. I thought it was a good idea to report back in case anybody needs this.
I don’t have much time now to work my car, so I decided to pay a shop to find out why my engine is pinging. Yes it is still pinging, though they told me it is still okay to drive. Results came back positive for the overall health of the vehicle.
The shop did a compression test and checked the fuel trims and all are numbers are good. Smog numbers are also excellent. They noticed I installed a new knock sensor (I had a knock sensor code), new plugs (colder plug) and wires, new fuel filter (with regulator inside). Injectors are good. My car doesn’t overheat and I already replaced the thermostat and serviced the cooling system myself.
The problem seems that there is excessive carbon in the EGR port that runs to the intake manifold. I know that the intake manifold is also full of carbon everywhere. Visible through the throttle body.
They told me that it is a common problem with Saturns. I did try to clean the port myself before, blow out as much carbon as I could but didn’t do much. However, I couldn’t get into the intake port through the EGR opening with a cable and a drill that time so maybe that’s it.
They told me the fix ($650) would be to remove the intake manifold to clean all the excess carbon. What do you guys think? How does a shop clean the intake manifold? Is there a way to prevent more carbon to form inside the intake manifold and the EGR passages?
Carbon deposits can indeed form hot spots inside the engine and result in some of the gasoline igniting before it is supposed to. The EGR valve routes exhaust gasses back to the intake manifold, so that’s an obvious place carbon deposits could form. I think if I had this problem and thought it was carbon deposits I’d replace the EGR valve (and verify the new one opens when it should (i.e. during acceleration and higher speeds), and when opened manually at idle it stalls the engine). During the valve replacement I’d clean the EGR engine passages the best I could and see if that solves it. If not I’d ask the shop if there’s a chemical treatment that would help remove carbon deposits, especially from the combustion chamber and the valve surfaces inside the combustion chamber. Also double check the valve clearances are in spec, especially the exhaust valves.
So you would replace the EGR valve? What do you mean by “when opened manually at idle it stalls the engine”?
If it’s easy to do, I’d remove it and inspect the passages and verify the pintle opens with applied vacuum at least. An EGR valve that doesn’t open when it should can be a direct cause of pinging. The way I do a basic test of an installed EGR valve is to apply vacuum to it using a hand-held vacuum pump when the engine is warm-idling The vacuum should make it open and allow exhaust gasses to flow into the intake manifold, and that should either stall the engine outright or at least make it stumble badly. If it does that means the EGR valve remains capable of opening. One caveat: This test has been effective for my diy’er use on all my vehicles; but the newest among them is 27 years old, so it might work on other, especially more modern, vehicles.
Hello George, I don’t think I can test the valve using a vacuum pump. The EGR controlled electronically. Is there another way to test it? Or maybe I should just replace it if it’s cheap.
Ok. If the EGR valve uses an electric actuator then there’s probably two options: (1) cross your fingers and replace the valve and hope it solves the problem, or (2) take the car to an experienced shop for a diagnosis.
I don’t see how pinging would be caused by carbon in the intake manifold. It’s the carbon in the combustion chamber that causes it. Does it stop if you use premium?
Using premium gas doesn’t help. It pings in the city but not in the freeway. I can do full throttle, no problem.