My 99 Saturn sc2 has always run like a old champion until recently. If I put any load on the engine the power cuts out feels like a misfire without any noise. I gave it new plugs and wires, cleaned the throttle body, new fuel filter, and a new purge solenoid. Nothing has help it still bogges down when giving it any gas. I can slowly idle up to speed but can't get above 50, and if I put in neutral and give it gas it won't get above 4k rpms and it jumps (usually down). It is a manual 5 speed. Tried a seafoam to clean the injectors. It fires up every time and never stalls. Any help would be great. Just started out of the blue 2 weeks ago, no codes, one time I was able to downshift and it went away until I started it again, but that is the last time it helped. If I give it to much gas the whole cars jumps around and feels like it will break something. Also cleaned the map and EGR valve. The car idles well, there is definitely an exhaust leak, but that is not new. If I slowly accelerate it will get there, but if there is any type of hill I will just slow down and the RPMs drop like a missfire (no pop), If go from a stop up a small hill I can't get above 25 MPH. There are no error codes.

 

Sounds reminiscent of a clogged cat converter. If so, the car is probably shaking because it can't get the exhaust through the system and is creating back pressure that impedes proper operation of the engine.

I believe your vehicle also has a pre-cat on the exhaust manifold. I wouldn't expect that one to be clogged but anything's possible. Monitor the front and rear O2 sensor signals to see if your cat is actually doing anything. Usually it will throw codes if it's not. However it can still partially function when partially clogged.

Have you looked at the fuel trims? This will give you an idea of whether it is an air fuel mixture issue or not (see below)
--------
Less likely = do not run out and throw parts at the car

The ects + connector? Fuel mix is d dependent on coolant temperature. A problem with this sensor will cause the PCM to command an improper mix, usually too rich. These typically cause the engine to bog down around 2K RPM under acceleration, but your situation sounds much worse than that which is why I say less likely

Same general deal with the front O2 sensor. The feedback from it strongly contributes to the air fuel mix. But I don't know that I've seen a dohc completely bogged down from a bad front 02. Then again anything's possible.

 

I have been thinking along the same lines, the only way I know of to check the cat is to unplug the o2 sensor in the front and see if that helps the engine not bog down. I ordered a reader that will give me live data and will continue to baby it until I have that. It is my only work vehicle right now, luckily it is only a 2 mile drive at 25-30 MPH.

 

Do these cars still have a fuel filter? Lots of catalytic converters get replace for plugged fuel filters. Yes, do remove the first O2 sensor and see if it runs better.

 

All the S-series have fuel filters with the 98 and up having the filter incorporated with the pressure regulator.

 

Yes, I changed the fuel filter, it made no changes, I also disconnected one at a time to see if any of the following was an issue, no change in the loss of power, TPS, MAP, coolant Temp, front O2, I am going to remove the O2 once I find my socket in the garage tonight, to see if the cat is clogged.

 

My first thought was cat con, but I'm NOT a mechanic.

 

Remember that it can be the honeycomb of the cat blocking the exit of the converter, but that stuff can also get blown all the way to the back. The dohc has a resonator so it could get into there or all the way back to the muffler. Tapping on the components with the vehicle not running might help locate the junk if this is indeed the problem. If not. Ignore this post

 

My stepdaughter had a 96 SL2 and the precat broke up with the honeycomb turning sideways which blocked the exhaust flow. It made it barely drivable.

 

Well then, scratch my earlier comment of not expecting that to happen in the pre cat.