Pontiac Repair: 97 Sunfire RPM Surge and Steering Question, 1997 pontiac sunfire, pontiac sunfire

Question
I'm glad you are still around - I haven't needed you for awhile now - you've been helpful with a couple of questions last year. 1997 Pontiac Sunfire 2.4L Auto. Check engine code shows EVAP minor leak - car has been "smoked" for leaks - none found - code I think is 442. Gas lines are less than 2yrs old - filler tube replaced - gas tank seems fine. No odors or leaks seen. What I think is related (I hope) is the car now is surging a bit in rpms at nearly all speeds - jumps briefly up about 400 rpms for about 5 seconds before dropping back - speed does not change. 2nd question - my mechanic thought this was in my head (smile) - starting from a cold stop when I first turn the wheel I could swear I heard a subtle "thump" from a dead center turn of the wheel - driving down the road I could not hear this. After the mechanic laughed - now I can actually feel this "thump" in the steering wheel turning from dead center after a cold start and the car will sometimes make this noise turning a corner from a dead stop at a stop sign. I swear this car is giving me an early warning about some kind of steering problem- yet it drives just fine down the road - no steering play - no tire wear - no play at the tire--- any ideas? Or is my mechanic right in laughing? The thump is always at dead center on the steering wheel. Thanks again for your help and thanks again for your help long ago.

Answer
Hi Bob:

well first off the steering. it can be a steering shaft thunmping but it would do it off center and at any positon. It could be out of the steering gear it's self or one of the strut mount binding up. If you live in the rust belt Like I do I would suspect a strut bearing issue It' not in the steeering wheel pewr say but the binding is felt through the steering and you may feel it in the wheel.
No as for th p0442 Yes that is a small leak and they are hard to find a smoke test is the best way to check it. If there are NO leaks in the system that can be found then it could be somehtin like a tank pressure sensor that is faulty Not all that likely but you never know. On these engines 2.4 I have seen the front plastic line going from the purge solenoid to the metal line on the body crack and break. If it's just cracked it could be you issue And at rest it may not leak but as the engine is torqued up the crack opens up and it causes a leak and possably you sure issue also causing a vacuum leak. As for the surge I would have the throttle body and Idle control motor cleaned up they carbon up and cause all kinds of idle issues.
Good luck :)