I have a 2002 SSEi with 130000 miles. I have changed plugs, wires, coils, pcv, air filter, cabin filter, fuel filter and used a tank of 91 octane with a boost and injector cleaner. I noticed a month or so that when I was accelerating up a grade on the interstate; that I heard some spark knocking and felt a loss of power. That is when I started replacing parts and it has gotten worse. There are no codes and the O2 sensors seem to be working properly. I have some graphs of what the car is doing and the thing that stands out to me the most in the timing advance. At idle the advance is high and when accelerating and under higher RPMs the timing advance decreases. I have done a fuel pressure check and it reads 40 psi with ignition on, engine not started and 44 psi when engine started and idle.

I am thinking that I will replace the fuel pressure regulator next, but I am really worried about the timing, anybody with any experience in this problem?
I appreciate any and all advice.

It'* a little tough to say exactly what is going on. Your fuel pressure is about 5psi lower than it should be and while that is common on the 00+'* it'* also bad.

When you say you tried a tank of 91 octane, I'm confused because you car requres a minumum of 91 octane. Anything less and damage and/or defaulting to the low octane tables can occur.

My fist suggestion would be get the highest grade fuel you can and run that for a couple tanks. Try and stay off the wide open throttle if possible. The computer takes a hundred+ miles and a few start cycles to learn the fuel is a better quality. Also try changing the FPR to see if you can bring the fuel pressure up

While doing thiese things look for any signs of noise, such as loose brackets/items on the engine, exhaust leaks, any chattering in the motor etc.

What you think about a bad cat Bill? Could be plugged.

I appreciate the responses.
I have been running 89 octane for quite some time, but with no ill effects; (til now), so I will keep the 91, should I do more injector cleaners? Also, I don't hear any noises that would lead to believe that I have anything loose or broken in the way of mounts or brackets, everything seems as normal.

I do notice that I have, what seems to sound like lifter noise at startup and it goes away. There is no smoke what so ever out of the exhaust. Another thing, when I am accelerating from a stop or very slow, the car is jittery about moving and I hear like a sucking sound in the driver'* side of the engine compartment. It sounds like that from inside.

On the note of a plugged Cat; I checked the vacuum at the intake, from what I remember when I done it; the testing procedures to indicate a plugged exhaust system, indicated that it wasn't. But, I can't remember what the numbers were, I can retest on Saturday and post those numbers. I also, am going to try and test the back pressure at the O2 sensor on Saturday too. That should tell me for sure if the Cat is plugged.

That sucking sound is the intake. A supercharger pulls a lot of air in. Check the air filter. You can try doing a seafoam clean. You can get that at most auto parts stores. Suck about 1/3 can in to a smaller vacuum line near the throttle body, then shut the engine off. Pour there remaining 2/3 can in the fuel tank. After about a half hour start the engine. It will smoke like crazy and run rough, so you will have to give it some gas to keep it running. I've seen this do wonders for cars. You will need to change the oil after you do this.

Besides maybe doing the seafoam I wouldn't suggest anymore cleaners or octane boosters.

Noise on startup isn't normal from these motors, if possible please try and get a sound clip/vid of it this weekend for us. Hopefully running the 89 didn't chip a piston.

Run the better fuel, do the back pressure tests and FPR, etc and see if things improve. If not, we'll keep on digging further.

I replaced FPR and done the sea foam. No difference made. I can rev with the throttle under hood and at near WOT there is the knock or grind or slap noise, I can't really pin it down. I did notice when I was putting the sea foam in through the vacum, that the smoke that you mentioned was coming out of the exhaust but also from the engine compartment, near the EGR. Could there be a leak, restricted flow or the EGR is leaking?

I made a clip of the engine noise, but how do I upload it to the forum? I saw the allowed files are all pics.

Thanks again for the help, I will be trying to get the back pressure done today.

A cracked EGR tube has crept up here a few times. It exactly the same as any other vacuum leak. Spray carb cleaner around the EGR and tube.

To put a video here you will need to upload that to a place like photobucket and then link to it.

Thanks, I put it on Youtube. I will check out the EGR and tube.

YouTube - 2002 Bonneville SSEi Engine Rev

Ahh, tell me. does it sound like this?



Take off the supercharger belt and try this.


Sounds like a worn coupler to me. Easy fix, should be $50 or less and a bit of yoru time. Less if you can find a used coupler.

https://www.gmforum.com/t279064/