Pontiac Repair: 99 monte carlo problem, torque converter clutch, mass air flow sensor

Question
QUESTION: when i am driving at cruising speeds(55-65) i will notice the car will jerk for maybe 2 or 3 seconds at a time. It may be a small jerk or a very noticable jerk. I drive 32 miles to work and it usually happens only once or twice. there is one spot in particular that seems to make it jerk, it is at the bottom of a big hill(3/4mi) were speed limits drop from 60 to 45. here lately i am noticeing a rattling coming from  underneath when my rpms are on the way up and pass 2000 rpms. I was thinking that maybe the jerking was from a bad sensor or something air related but the rattling makes me think it may be transmission related. 3.1 ltr auto w/od. any ideas what this may be?

ANSWER: Hi Shane:

well this can be either an engine or transmission problem. The car is going to have to driven with a scan tool an look at a few things in the transmission possably an issue with the torque converter clutch cutting in and out ior an issue with the pressure control valve in the transmsision cauising a harsh down shift frpm 4'th to 3'rd gear or apply of the TCC. with the engine you could have an issue with the fuel trim and the car is running lean causing a lean burn issue and it causes a "chuggle" feel that can be caused by a bad sensor say a Mass air flow sensor or even injectors that are dirty.. The rattle noise could be a loose catalist inside the catalitic converter in the exhaust and that in turn could be cauing an exhaust restriction and the end result would be a running problem.... I would start by going to one of the big box auto parts stores and have the car scanned for codes and see if any are stored. may of the stores will scan your car for codes for free with the hopes that you go to them for the parts you may need.. Good luck :0


---------- FOLLOW-UP ----------

QUESTION: I did take it to advanced auto and had it scanned. None of the problems were transmission related. They were all emession problems. One of them was a catalyst something or another but I did have a new catalitic converter and mass air flow sensor installed about 18 months ago. I did put on a new pcv valve and have driven it about 100 miles with no jerking but i still got the rattling. Im thing the jerking is emission related and the rattling is something different. What do you think?

Answer
You could be right. The rattle can still be the converter especially if you have an aftermarket on on the car the catalist could be loose in the converter and a lot of times aftermarket ones are "fits all" and they are not correct for the car they are usually too small thus the cheaper price then the factory ones and they will cause codes to set. good luck :)