Help Please...intermittent CEL, stalling, & surge

Hi guys, I'm having a problem with my 99 996 (tiptronic) that I'm unable to resolve without assistance. The most noticeable symptom is surging when I'm driving on the freeway and maintaining a continuous speed. It feels like a slight misfire; however, it is not noticeable during acceleration or deceleration. It does not show on the tachometer. The car idles smooth. My car also occasionally stalls at idle (possibly related to abrupt stops), In addition, it displays a check engine light about once every couple weeks. The check engine light goes away after a day or two. I had the car smogged two months ago. It had four stored fault codes. They were P1123, P1125, P1128, and P1130. The fault codes are for "Oxygen sensing Adaptation Area 1&2 (all cylinders) both rich & lean thresholds" The diagnostic procedures for these fault codes involve testing the fuel system. They are way above my head and require specialized tools. Has anybody experienced similar problems? I would love to fix the problem myself.....if I could figure out what it is. I have previously cleaned my MAF thinking that it was fouled by the filter oil in my EVO CAI. Should I try replacing my MAF or my O2 sensors? Or....Should I admit defeat and take it to the dealer. I would appreciate any advice.

WHAT KIND OF DIAGNOSTIC EQUIPMENT DO YOU HAVE ACCES TO?

Brad, thanks for your response. I have a volt meter and a vacuum gage. I can borrow a fault code reader.

what kind of scan tool do you have acces too. you need to look at the actual real timen values for the fuel trim if its rich you prbaly need a maf sensor if its lean you have a vacum leak you could even have both issues i have fixed many a vacum leak and then had it go way way rich due to a bad maf

Hey there. I don't know about the fault codes, but the stalling symptoms definately sound like a MAF sensor problem. My belief is that the aftemarket intakes are not kind to the pre-2002 sensors. I also believe (for various reasons), that the MAF sensor problems with the earlier cars are not always due to oil contamination, but rather the fact that the flow is not "laminar" as with the stock set-up, but is more turbulent due to the shape of the aftermarket filter and the location of the MAF sensor in relation to the filter (I think the later MAF's "smooth out" the flow by having a bit more turns and "piping" before the air reaches the element). As for the surging symptom, well, I don't want to alarm you, but your description of the car "surging" really made me cringe when I saw it, especially when you said your car was a tip. I have a tip, and I had this odd surging, and spent a lot of time and money with the very best tech's available trying to figure it out. However, my surging was visible on the tach, and was accompanied by "hard" shifts, especially after prolonged periods of stop and go driving. I literally tried everything (the tip unit is very robust, but is very senstivie to things like low ATF, mismatched tires, or tires that have unequal tire pressures). In my case, it was none of these things, but we did find my fluid low, and the chances are it had been like that for some time. The recommendation was eventually made to try a new tranny, and this cured my problem. The good thing was that I located a nice used unit from Silverstar recycling for 2700 without a core exchange, so the cost, although not fun, was not the end of the world. The good thing for you is that you have some codes. I never had a single code, even though every tech that drove my car agreed that something was SERIOUSLY amiss. More than likely your sypmptoms are not tranny-related, but the coincidence was enough for me to at least mention what happened to me. If you want to chat about how my car was acting, I'll happily send you a p.m. with my contact info so you can pick my brain (I actually contacted a few rennlisters myself who described surging in tip's, and so I feel like a bit of an authority on this topic). Good luck. Scott.

If you don't have access to a code reader go to advance have them check the codes then clear and drive the car till another appears then have it checked, most of the time you only have one fault the others are a result of the first in most cases. I'm also leaning toward the maf prob. because of the surge and stall as formerly stated

Thanks guys for the advice. I really appreciate the assistance. Brad, I have access to a couple different scan tools from a friend's shop and the fleet department where I work. I don't know what type they are. The codes that I posted came off the machine that was used to smog the car. Scott, I see that you are new here also....welcome aboard! Thanks for taking the time to help me. (I got your e-mail, I'll call you this weekend). Sorry to hear about your adventure with the tiptronic. I just had mine serviced by the dealer and they gave it a clean bill of health. I've bought three cars from Silverstar Recycling, they're a pleasure to do business with. 2fas4u, thanks for the advice on the codes. It's comforting all of you agree that it is most likely the MAF. At this point, I'm leaning toward just replacing the MAF to see if that cures the problem. Brad, Scott, & 2fas4u, guys like yourselves are the reason that I joined this site. Thanks again for taking the time to help me.

get some actual fuel trim values (if you have acces to a piwis or pst2 those numbers are best) and i will see if i can point you in a direction. frrm your description. you may have a big air leak, check the oil fill tube and the cap. then get under the car on the drivers side on the back of the engine there is a rubber accordian connecting the seperator to the engine, check for leaks and touch it ot see ifs ripped. Also check that the air cleaner is fit properly and tight and the maf is propery installed i nthe right direction

Brad, I'm not sure what type of fault code readers I have access to. I apologize for sounding ignorant, but all that I know about them is that they are hand held and I believe they are both made by Snapon. I don't know if they can read fuel trim values...I don't even know what fuel trim values are. When I had the engine apart, I replaced all of the rubber and plastic parts. The oil fill tube and cap still appear to be fine. I had an independant shop replace the oil seperator about six months ago. They did it without removing the engine...the dealer told me it was not possible to do on a tiptronic. I had my car at the dealership about three weeks ago for some suspension work. A tire store jacked the car improperly and caused $1,500 in damage. Fortunately, my insurance covered it. I had the dealer check the oil seperator to make sure it was done properly. They said it looked great. The hose connecting the air cleaner elbow to the throttle body is a piece of crap. I need to order the correct one from EVO. It may be causing turbulence between the mass air meter and the throttle body. I have cleaned the mass air meter a couple times hoping that it was the cause of the problem. It is installed correctly. The car idles, accelerates, and decelerates flawlessly. I'm still leaning toward the MAF sensor being the problem. I really appreciate your assistance with this problem. If you can explain the additional diagnostic information (fuel trim values), I will be glad to try and get it. Thanks again.

Brad, there is one more thing that might be the cause of the problem. The CAI that I have on the car is the first generation model from EVO. I bought it used on e-bay. It came off a six speed car. Evo told me that the only difference is a vacuum nipple on the elbow. They said it connects to a vacuum line coming off the transmission. I did not have any unused vacuum lines when I reassembled the engine. The dealer did not know what line EVO was referring to. They also did not locate any improperly installed vacuum lines. Any ideas? Thanks again. If anyone else has any suggestions, I would appreciate them.

fuel trim (or adaptaion numbers if your using a porsceh scan tool) I had thought you had accesss to a porscehscanner as your fault codes read like the porsceh tool not durametric or snappy scaner faults. Fuel trim though is the engines adjustment in the fuel/air mixture trying to keep the engine running optimaly. There should be a line to the drivers side of the throttle body that runs into the air cleaner box, odd that you dont have it? I need to look at one and see where the other end goes, but tip cars are the only ones that have it

Brad, thanks again for your time and input. I talked to (Arizona) Scott yesterday on the phone. He also has an early 99 tip. He told me that his car does not have a vacuum line coming off the air box elbow. He said his dad's 02 tip 996 does have the vacuum line coming off the elbow. I'm guessing that the non e-gas tip cars do not have that vacuum line. He also had his MAF sensor go bad due to and aftermarket CAI. I'm going to order one and hope that resolves my problem.