Volkswagen: 1998 vw jetta gt, mass air flow sensor, throttle position sensor

Question
Dear John,
  I replaced the throttle body and mass air flow sensor. The car is running better but I still have the engine check light on. It comes on for about a week and then will shut off by itself for about a week. But, then it will come back on again. I was going to take it to the vw shop, but that morning the light went off and they said to keep driving because they would not get any codes and that the car had cleared itself. Of course, a couple days later, the engine light came on again. What could be going on? -------------------------
Followup To
Question -
My jetta has been having trouble idling and I got the codes after having the engine light checked. It showed some misfires on 1,3, & 4, something wrong with the idle air control valve and the throttle position sensor. I took it in to a shop and spent too much $ and still have the same problem. It also said that it was running rich, but I just an oxygen sensor replaced.
 On this year and model, is the IAC valve part of the throttle body and how can I get a part # for the throttle body for this year, make and model. It stalls at random and seems to run without incident if I take it real easy when I drive it. Sometimes, when I'm taking off from a stop, I will just get a loss of power from the engine, like it just shut off. Usually, I have this problem at 2000 rpm's or lower, but only intermitently.

Answer -
it sounds like you may have more than one fault. the cutting out is likeky to be throttle body related. you can not purchase parts seperately for this, just a new unit (alot of money). the other possibility is to remove the throttle body and clean out the main bore using thinners etc. you need to open the throttle flap and clean around the edges as this restricts the airflow and causes cutting out etc. as for the running flat, it may be the air mass meter at fault, which can also cause high co readings. this is due to the engine thinking it is getting more air in than it is. sorry for delay, moved house etc.

Answer
sadly witout knowing what the codes are, it is nearly impossible to say what the problem could be. it could be anything from a brake lightswitch to an engine sensor. you will need to get it code read when the light is on and then the fault will be revealed. sorry i cannot help at this point. john dempsey.