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Maxing out stock MAF?

B

BadDecisions

New member
Hey guys.

I'm still having issues after my last dyno tune. I installed 42.5lb injectors, 3" exhaust and 1.9 RRs so that I could drop to a 3.0" pulley (I have all other supporting mods) - 2006 Grand Prix GT

Basically what happens is when I'm on the highway the car will go into "reduced engine power" as soon as it gets under load from a cruise (cruising at 55-60mph and then try to pass a slower car). It throws a P0068 code as well. You basically only have to get into the throttle 5-10% for it to trigger the issue. It's getting VERY irritating and gives a pretty unsafe feeling driving on the highway.

I've tried a different MAF, cleaned the throttle body, tried a different throttle position sensor, replaced the vac lines from MAP sensor to boost solenoid and tried just about everything before calling the tuner back (it's a pain to get the car to him)

I'm just wondering if with the mods I'm running if I'm maxing out the MAF table and causing the power loss issue. I have an LQ4 MAF that I can throw in but obviously there's a little work and a retune there.

Any ideas would be greatly appreciated. I'm done banging my head against the wall here and just wanna know if it's actually in the tune or not.

Thanks guys
 


i ran into this with 04+ and HPT

they have barely any tables mapped for 04+.

the same issue was corrected on my jalopy with changing the MAF max delta table via Tinytuner/DHP. its seeing to large of a change in maf value per calculation cycle, triggering a limp mode.

ziptie your BBV open and repeat the tests and without the sc pulling a large change in airflow it wont do it.

it always pissed me off that hpt mapped like 60 tables yet in Tiny i have over 400 tables
 
Thanks guys! Definitely going to give that a try today.

And to clarify a little bit, when the "reduced engine power" happens, throttle position seems to be about 30-35% and engine load around 80-85% according to my freeze frame.
 
So I tried the ziptie method and I'm still getting the same issue coming up.

The biggest issue is that it's intermittent so I'm not sure if the guy tuning it can actually get it to happen or not
 
These cars go into reduced engine power when the app sensors disagree.. there is a tsb for water intrusion into the wire harness leaving the inside of the car to go out to the engine bay .

Grab a scan tool and see what the accelerator pedal position sensors are reading.. app1 and app2 should read the same, if not the tac reduces engine power.. so very good chance your accelerator pedal sensor is bad or the wire leading to the engine compartment is messed up
 


Also with the scan tool make sure the 2 tps sensors agree, make sure the app sensors agree, make sure the app and TPS sensors agree. The pcm detects engine load using the map and mass air flow sensors, so graph your TPS, maf and map and make sure the graphs follow each other, also check the maf pid and see what's it's showing compared to what the map sensor shows.. I know for 8psi boost my comp g has between 220 to 240 grams per second going thru the maf. On idle you should see about 6psi on your map and about 5 to 7 grams per second thru your maf...

If you have a mechanical boost gauge connected to the vacuum\boost port on the supercharger compare it to the map sensor and see if the vacuum and boost match.. on most cars the map sensor is how load is calculated but on our gtp's the maf is used also. I don't know how is weighted toward which of the 2 sensors..

If your in Wisconsin I know I could connect my scan tool and take your car for a ride and tell you exactly what the issue is, but I will help you the best I can thru here... If your mods were the problem it wouldn't be at 30% throttle.

Also your boost control solenoid, is it still connected or is it bypassed? If you zip tied your bypass valve open and you still have this issue, then most likely the issue will be in the app, TPS, tac, maf, or map sensors or you have water intrusion on 1 of the app sensor wires...

Connect a scan tool and check what I told you to and let me know what you get
 
Grab a scan tool and graph the app sensors and TPS and make sure they agree.. three pcm detects engine load from the maf and map, so bad map, bad maf, bad app sensor wire, bad app bad tps or bad tac are really the only things that could cause your issue.. check those things via scan tool. I have more to post but this forum won't allow it so start there and if you still need help I have a few other things we can do to figure this out
 
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