Wierd stutter/stumble, no power and now cel.

[Dewayne Waldron]

Ok, a few weeks ago my car started stumbling or stuttering as you hit the gas. The more throttle the more it would bog. It almost seems as if it would get worse as the turbo kicked in and not only that but the turbo was much louder and seemed to start spooling alot sooner. So I done a boost leak test . Fixed a few small leaks and still the same. At first it only happened under load, now it does it when I just free rev the engine. A couple days ago it finally threw a code 12 meaning Mass air sensor is troubled, or open or short ciruit or improper contact in the air intake temperature circuit, or finally the ecu is troubled. My logger at that point showed 0 hz from the mas. I then installed 3 different MAS's all with the same end result . Then I unplugged the MAS harness and the car still ran the exact same with no change. So now I'm thinking ECU, but my ECU was rebuilt less than a year ago. If it is the ECU what would have caused this? Can someone please help shed some light on something I could be overlooking or help me understand this a little better? I need my car back. Thanks in advance.

 

[steve]

Have you checked the SAFC wiring? Does it also show 0 MAF HZ?

 

[Dewayne Waldron]

Yes, I have checked all wiring and the safc shows the same.

 

[steve]

If the SAFC also shows zero then you have a problem with either the MAF or the wiring.
The MAF actually puts out something like 3 HZ when it's on so that the ECU can tell if it's connected. The ECU normalizes this to zero when it reports MAF HZ but you'll see it on the SAFC.

 

[Dewayne Waldron]

Yep. turned out to be a loose wire just before the mas that was causing the 0hz and cel. It takes me forever to get it started. Idles and revs fine now. Still bogs and has no power under load. It seems to be alright until about 2k or so. I can have it floored and it struggles to get anywhere. If I go uphill it will die. The engine is only a month old. new fuel pump, filter, plugs, wires, coil pack. It almost seems like the more the turbo spools the less power I have.. The temp gauge started to rise a little yesterday after letting it warm up for 20 minutes and attempting to go a block away.

 

[steve]

I'm glad you found the MAF problem. Now you can move on to solving the rest.
I'm assuming you have a datalogger since you were able to read the codes and could look at the MAF HZ count from the ECU. You'll need to spend some time logging to see what else is going on.

Make sure the base timing is correct at 5*BTDC, that the engine is firing all on 4 cylinders, and look to see if your knocking.

 

[Dewayne Waldron]

Both the logger and safc show a substantial amount of knock even when I'm free revving the engine. Don't know why. The timing is dead on and the engine runs fine. No missing or anything of that nature.

 

[steve]

That explains it running like a dog. When the ECU sees knock it starts pulling timing.
How old is the sensor?

The SAFC is useless when it come to reading knock, I don't even connect the wire. What's important is what the ECU knock count is and it measures differently than the ECU does.

 

[Dewayne Waldron]

I'd say the knock sensor might be 2 years old. I always thought that if the black shit in the sensor leacked out then it was bad. This one still looks brand new.

 

[steve]

That's why I asked.

 

[Dewayne Waldron]

So, what else could be causing this?

 

[steve]

What do your fuel trims look like?

I wouldn't be surprised if you still have multiple problems. You say it's hard to start. You're getting knock, had your ECU worked on by somebody (making it still an unknown), and you had some wiring problems. I don't want to just point you to phantom knock because that might not be the only thing going on.

 

[Dewayne Waldron]

The Fuel trims are dead set at 100%, though I do have to make negative adjustments on the safc on the low side in order to be at 100%, and this is with stock injectors, wally 190, stock fuel pressure regulator and unhacked 1g mas.

 

[steve]

Exactly 100%? That's really hard to do and usually an indication that they aren't being updated or that the backup power isn't working.

 

[Dewayne Waldron]

It usually fluctuates between 97% and 101% .

 

[TeclipseFTW]

I am having a very similar problem. I believe my issue is in the beginning stages though because it only happens some of the time... when i watch my logger I get knock like hell but the engine only has 4k miles on it.... I havent even pushed it to redline.... but when I take off sometimes the engine just slowly bogs and the boost goes through the roof. no boost leaks and no cel. also with my it seems worse when the boost increases... My maf is moded and original. I wish i could figure this out! my car performs like a minivan with the air conditioning on full blast... sigh. any more advice?

also sometimes my car turns over forever before it starts. and it has died occasionally while driving. (not bc i killed it. )

at startup in the summer my car is fine bc of warm weather. but in the winter when the lifters are loud as hell, it runs like shit.

Any help would be so appreciated!

found this: I have horrible lifter tick which could be the issue : http://www.dsmtuners.com/forums/newbie-forum/183922-car-building-boost-but-no-power.html

read that.