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This is a long shot...but...Is the MAF oem? There are A LOT of fake/counterfeit maf's out there. They look totally authentic at first glance but do not work properly.
Pull up the rubber boot covering connections on MAF. You will be testing the pin furthest away from you when standing behind the car. Use the grounding lug of the fuel filter that is near by for ground.
With car off but ignition in position 2 you should get between .9 and 1.1 volts.
Then start the car and get it warmed up and test voltage again. Now you should get 1.2 to 1.5 volts.
I've been having a similar issue since I had the engine out for fittings and did injectors/tune/lwfw/turbo piping at the same time. I recently got P0491/P0492 codes but indy said they found no leaks and everything was good. I think I might try billet DVs next to replace the 710Ns but from everything I'm reading it does seem to be some kind of vacuum leak; as with your car it seems to run just fine at WOT, its the cold start and partial throttle on initial tip in from vacuum that makes it hesitate.
I've been having a similar issue since I had the engine out for fittings and did injectors/tune/lwfw/turbo piping at the same time. I recently got P0491/P0492 codes but indy said they found no leaks and everything was good. I think I might try billet DVs next to replace the 710Ns but from everything I'm reading it does seem to be some kind of vacuum leak; as with your car it seems to run just fine at WOT, its the cold start and partial throttle on initial tip in from vacuum that makes it hesitate.
Sounds like similar issues... Are you getting constant up and down surging when you are at constant speeds like with the cruise control on the highway?
I'm wondering if I have something wrong with the secondary air injection? Cold start ups are awful for the first 45 seconds or so, the idle goes up and down rapidly for about 20 seconds or so, then it idles perfectly. Maybe the SAI is letting /sending air in the system when it's not supposed to, leaning it out and causing the DME to make adjustments with the air fuel? My data logs show that constant adjustments are being made for some reason.
Anyways, if I ever find a solution, I will let you know what the fix was.
Sounds like similar issues... Are you getting constant up and down surging when you are at constant speeds like with the cruise control on the highway?
I'm wondering if I have something wrong with the secondary air injection? Cold start ups are awful for the first 45 seconds or so, the idle goes up and down rapidly for about 20 seconds or so, then it idles perfectly. Maybe the SAI is letting /sending air in the system when it's not supposed to, leaning it out and causing the DME to make adjustments with the air fuel? My data logs show that constant adjustments are being made for some reason.
Anyways, if I ever find a solution, I will let you know what the fix was.
I've never used cruse control before but it would make sense since that's probably the easiest way to make frequent small throttle adjustments. I have no way to log unfortunately, are you using durametric?
I am having issues with the car ONLY when driving passively typically bellow 3k rpm's. The car runs incredibly well at WOT. The data logs are very good at WOT.
When driving around town or on the highway below 3k rpm, the car is constantly making corrections causing an "up and down" sensation & lots of hesitation. The car cuts out every time after reapplying throttle after coasting in gear. The gets utterly confused when doing low RPM roll ons. I am getting no codes whatsoever. Cold starts are bad as well...starts up fine but goes really bad as soon as the SAI kicks in about 5 seconds after initial start up. About 30-45 seconds after start up, and I believe as soon as the SAI shuts off, it idles perfectly. The data logs show that the car is making constant adjustments for some reason.
I've done countless boost leak lest test...no leaks + I don't think it's a boost leak issue anyways as am making incredible power & boost at full throttle + the data logs at WOT are great.
One of the "ideas" has been that perhaps there is a vacuum leak as my issues are when I am not boosting. Maybe a faulty check valve? Faulty EGR vacuum solenoid? Faulty secondary air injection check valve? (I've ordered all of the above solenoids and check valves and will be replacing those soon.)
I thought I might have a bad ECU so I sent it out to have it checked out and to make sure it was working correctly. They cleared it out and returned to OEM specs.
Unfortunately, I am on the east coast and my tuner is on the west coast. For the record he has been great but is limited with what he can do not to mention that the issue is not with his tune as it has been done many times on other cars.
This has been going on for nearly 3 month and I've about had it...Hoping someone out there experienced this and can help.
If I were you id replace all the check valves and vacuum lines u can get ur hands on 996T are getting old mate plastic gets brittle and rubber get hard with age and it doesnt cost much if you can do yourself.
Then tighten every clamp and zip tie every vacuum line you can find and do another Boost Leak test Following Markskis instructions on here.
Oh and the rubber boot that attaches the OEM airbox to the intake manifold can split plus the hose clamps there often come loose and if they have and u have a leak there u would get the symptoms you describe.
these cars really play up with the slightest leak anywhere.
If I were you id replace all the check valves and vacuum lines u can get ur hands on 996T are getting old mate plastic gets brittle and rubber get hard with age and it doesnt cost much if you can do yourself.
Then tighten every clamp and zip tie every vacuum line you can find and do another Boost Leak test Following Markskis instructions on here.
Oh and the rubber boot that attaches the OEM airbox to the intake manifold can split plus the hose clamps there often come loose and if they have and u have a leak there u would get the symptoms you describe.
these cars really play up with the slightest leak anywhere.
