98 Silhouette power loss/rough idle

Hi all, new member, hoping someone can help. I have a 98 Olds Silhouette (First and possibly last GM product:banghead:) that has recently lost power, started rough idle and general poor performance. I have received the following trouble codes -- P0171 System to lean / Bank 1, P0300 Random Multiple Cylinder Misfire Detected, P0446 Evaporative Emission Control System Vent Control Circuit, and P0453 Evaporative Emission Control System Pressure Sensor High Input. I bought the van used and ran fine first couple of months, then...., you guessed it, head gasket went, I replaced it and it ran fine until one day it just stopped running. I got underneath the van and smacked the fuel tank around the fuel pump and the fuel pump started working again. Replaced the fuel pump and it ran fine for a couple of months and then this problem started. It started having a rough idle, poor power (especially uphill) and under heavy acceleration. It acts as if the Cat. Converter is clogged, so I punched out the converter and no improvement. I so far have replaced the O2 sensor, mass air flow sensor, throttle position sensor, cam shaft sensor. I have had the coils and ignition control module tested. They tested fine but still have had trouble so I replaced the coil packs and ignition control module today without improvement. A friend of mine has a garage and tested the fuel injectors by shutting them down independently and all injectors tested ok. He called a GM garage and they were less than forthcoming...you know....bring it in.....$$$$$ So anyhow, sorry about the short novel but I am at a loss. Anybody with any help and/or suggestions would be greatly appreciated!

Thanks,

Scott

you don't mention changing fuel filter..... there is a little sensor on the throttlebody that i have had to clean before it is above the tps carbon gets in this sensor aand once you clean it out runs alot better i also had a vacumn leak under the black metal that covers the pvc line there is a rubber grommlet under it i ran like **** until i put a new grommlet in

rockwood84....thanks for the quick reply, I did change the fuel filter, I forgot about that as it was like the very first thing I did in a long list.....anyhow, that did not help, you mention a sensor above the tps (I assume this is throttle position sensor), did you simply clean the contacts or do you remove the sensor and clean the sensor itself? I am not quite sure where you mean in regards to the black metal that covers the pvc line. Do you mean the line that runs into a rubber hose (for lack of a better description) near the Ignition Control Module / Coil Packs? Is this the hard black plastic line?

Thanks,

Scott

rockwood84....thanks for the quick reply, I did change the fuel filter, I forgot about that as it was like the very first thing I did in a long list.....anyhow, that did not help, you mention a sensor above the tps (I assume this is throttle position sensor), did you simply clean the contacts or do you remove the sensor and clean the sensor itself? I am not quite sure where you mean in regards to the black metal that covers the pvc line. Do you mean the line that runs into a rubber hose (for lack of a better description) near the Ignition Control Module / Coil Packs? Is this the hard black plastic line?

Thanks,

Scott i think it is iac just take it out and clean it off and clean up in the hole mine had gunk in it . the line goes from the pvc back to back valve cover it changes size after the "t" that goes in top of throttlebody the "t" is under the black metal lip i guess the lip is to hold the "t" in but there is a seal
there you will have to take the throttlebody off and the black plate. when you get it apart you will see what i was talking about. the line that goes back to the sensor by coilpacks on mine goes to the fuel line with green cap on it. let me know what you find