Ok.. been at it for over five days.. on cold start..idle smooth for maybe 10 seconds...then rough...shuts down...p0040 code(swapped o2 sensors)-not the case....will at least stay on with maf unplugged..soon as i plug in-DEAD!... checked everything from plugs/coilpacks/variocam solenoids, vacuum leaks, and the MAF is new... will get misfire codes as well ... ANY HELP OR IDEAS WOULD BE TRULY WELCOME!!!!

 

What mods does the car have and how long have they been on there for? Did this problem start out of nowhere, or did something happen and then the problem started?Other than swapping the O2 sensors and unplugging the MAF, what other troubleshooting steps have you tried? Any other codes than the P0040? Do you have access to software to log the car?

 

Reads like a bad Maf. I don't care if it's new they can fail at anytime. Or you picked up the wrong Maf...

 

does sound like a bad maf...although 3rd straight new bosch one.. i did remove the y-pipe and another forum member mentioned to check the n75 valve??? teflon_jones...it all started when i removed the y-pipe to tighten a air leak i found.. i've check and double checked, but everything looks good and routed properly.. if i let it run, i will get misfire codes.. and seems like bank 2 shuts down.. any insight on why both banks would run with the maf unplugged... ?
thanks again guys..

 

Both banks run when the MAF is disconnected because the MAF is bad. When you disconnect the MAF and the symptom goes away that's a pretty good sign the MAF is bad or at fault. Or the connector...

Or if all 3 new MAFs have been the same part number they are the wrong MAF. Or you bought MAFs from some place that's selling 2nds or worse. Or the wiring harness connector is bad.

As long as the engine is not acting up with the MAF disconnected check for air leaks, and other things, just to be sure that there is not something else going on. Wouldn't want you to buy yet another MAF when there is something else wrong.

 

Back up... Unplugging the maf does a few things. Open loop and closed loop. The car will cold start in open loop until the O2's heat up then it will go closed loop and use the maf for fueling inputs. I would smoke the intake system. When you unplug the maf the ecu will use the primary O2's for fueling inputs. the secondary will confirm the cats are working. If you only get misfires on one bank check that your injectors are working right. The right clips are on them. I think the coil and injector wires are bundled so you can see them easy. The injector clip is is the same clips for a lot of things.. the cam soleniods.. n75 and n75 looking valves. Also you can look at the O2 values to see whats going on. hope this helps.

 

thanks again... smoked the intake again.. found minor leak at oil cap(hoping this was gonna "seal the deal"(gotta find some humor in this!) ... but no luck there either).. tomorrows endeavors will be the n75 valve...n75 valve is right by the secondary air pump right? A bit confused as I've heard both the "change over valve" and the "cycle valve" called the same thing... cam solenoids are good after testing...

 

N75 is right under the wye pipe to t/b connector on passenger side. hose comes off the wye right by the coupler.

 

I left all those valves plugged in when I ran the stock ecu, to keep the cel's away.. car still ran no problem.

 

think that would cause overboost...? i just got this one and I was normally hitting 1-1.2 psi... did have pss9 coilovers,baileys DV's.. Missing secondary air pump..(which i reinstalled) so perhaps previous owner modded a bit.. not sure if it would affect anything. so you think the n75 could cause my issues?? i was messing with that area when checking secondary injection lines..

 

I think you a durametric cable. lol

 

Just ordered one today after hours of "diagnosing" ha! so much easier with the proper equip... appreciate your input

 

When you start the car cold it should be in warm up enrichment and should be looking at the MAF sensor for fuel mixture ie open loop. Once warm up enrichment is done the car reverts back to looking at the O2s ie closed loop. The car should not have transitioned to closed loop after 10 seconds on cold start. So if the car is shutting down after10 seconds even on the first start of the day, then the MAF thing is most likely only a symptom of another issue. I know this probably seems silly, but have you done a throttle body alignment? This can be done via Durametric or by turning the key to the on position without starting and leaving for a minute or more and cycling off. I would suggest disconnecting the battery for 15 minutes or more then do the throttle body alignment after. This is to reset all of the ECU fuel trim learned adaptations. If this issue remains you will need to monitor throttle plate angle, MAF G/S, injector duty cycles and O2 readings from a cold start and see what is happening. I would suspect either the throttle plate is slamming closed or you are loosing fuel pressure. The other thing I would suspect would be maybe a lean condition caused by one of the purge valves not closing once the SAI pump shuts off? Just grasping on this one. Not really sure what this would really do.