LAST ISSUE: Not building boost, cutting out at 4K rpms.

M

Metallic36

Member
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2003 Mazda6 3.0L Speed Yellow
My car is at the shop still, just one small issue remaining. This issue happened when I had the car stock (with stock turbo), with the Unichip, and now with the mods I have (and the GT28RS). It isn't building boost, and when you push the gas, it seems to cut out at 4000 rpms and bucks.

The tests have been done:

It is getting enough fuel, 440 cc injectors and the stock ones still have the same result.

The wastegate actuator, turbo, wastegate, etc. is all working correctly and has been tested.

The MAF is putting out the correct amount of voltage.

They did a test that shows the spark on each cylinder, and two of the cylinders showed a higher scale than the other two.

They are thinking it's something in the ignition, making it cut out somehow.. anyone have thoughts? The ECU has been reflashed, that was before I bought the car.

We ran it with just the stock ECU, and with the AFC. It does run better with the AFC, but still wants to cut out unless you ease it into the throttle, then once you get past that cutout mark it goes into boost fine. It's just getting it there.
 
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I think you may have a boost leak, after the turbo. Have you relocated the MAF? If so then it would not cut out with a boost leak.
 
Yes, MAF has been relocated. This happened even before the MAF was relocated (and I've switched MAFs for the heck of it).. at higher boost, and even just trying to get into boost.. I'm now wondering if it's the ECU kicking in that "safety" thing with the boost, where that MAF voltage is going to the max, then causing it to cut out.

We took it for a road test today.. with the SS AFC installed. With just the stock ECU, it would cut out pretty bad.. with the AFC it jerks some but not as bad as it did before (this is with the 440 injector map), but it seems like you have to gradually ease into throttle to get boost without it jerking. We got it up to 11 psi, then did another where it seemed to stay at 5 psi, then jumped immediately up to 10 psi and then it went into boost better. It seems like there's a thin line to cross just getting into boost.
 
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That sounds like a bad wastegate actuator. I'd get full boost and then a few minutes later I couldn't get 1-2psi no matter how hard or high I'd rev it.
 
it can be one of the coils is going bad or a wire..... if u punch it does the car start to sputter..... cuz my car did the same thing and if u easy in and go past the spot where it sputter then give it gas it will build boost my car did that because one of my coils went bad and if its not that u need one step colder plugs how much boost r u running
 
They have pressure tested the WGA.. or however they test it, and it's been fine. They did that before and after the WGA was on the car. It's done the same thing with two sets of MSP coil packs, two different sets of wires, and now I have the 1.8L conversion on there and it's still doing the same.

I did some reading, and it seems that around 4K rpms, the stock ECU goes into open loop. I'm sort of thinking it's maxing out the MAF voltage somehow when it does this, then causing the hesistation.
 
I spoke to the guys at DSM about my problem with start up. They say clear your stock ecu so the long and short terms are 0. Then tune the car. Maybe try that first. The SS adjustments are very exact. So make changes by 0.1
 
a bit of a shot in the dark but have you ever checked the primary o2 sensor to make sure it was sending back the proper readings?

beyond that its a boost leak from IM gasket, TB gasket, etc...(since you said you had it when it was stock). if its not that maybe swap the ECU...
 
If the car isnt going into boost at all, sounds like it would either be a wastegate issue, or a boost controller issue. Maybe you need to run an external wastegate
 
Deatschwerks said:
If the car isnt going into boost at all, sounds like it would either be a wastegate issue, or a boost controller issue. Maybe you need to run an external wastegate
Click to expand...
it is boosting, but only when she eases into it.... sounds like fuel cut... I'd check for leaks first... and if you can drive it with a volt meter on the maf... I'd try datalogging the MAF and O2 voltages.... see if anything gets out of range.
 
WB? Sounds like too much fuel!!!! I bet your afrs are way rich when your first getting into boost which is like reverse fuel cut. It hits a wall becuase it can't burn the fuel in the cylinder. Try hotter plugs and see if that helps if so it's too much fuel!!!
 
i would most certainly suspect your intake manifold for a leak.its very comon for these cars and would cause exactly the problem you are getting.i would check there first.you could have a leak anywhere but that would be my best educated guess.if you have access to a smoke machine smoke out your vacume lines and see where its leaking from.if you dont then use brake clean/carb cleaner or something to spray around the manifold and see if its idle changes...if it does you know theres a leak..im sure you already know but just in case you dont do it when the cars cold...wouldnt want to torch the poor car...unless of course its upsetting you enuf to do so lol
 
Thanks for that info.. it's definitely possible. It's at the shop now still so I'll tell them about that idea too. The O2 sensors are working like they should be, the wastegate actuator is working perfectly, and the shop has a scope to test different things with also, along with a laptop & diagnostic programs to show graphs of just about everything they need to look at.

That idea of the intake manifold is a good one though.. since that last shop did change the gasket and may not have tightened everything.. they sure messed up on a lot of other things.
 
If you try to get it to start boosting, keeping your foot on the gas, right at 4K which is where the boost kicks in, it will jerk and fall on its ass. If you ease into it and get it past that point, it will grab you and go! Yesterday we eased into it and it reached 11 psi and was swerving itself on the road because of the power behind it.. so it can definitely get up and go, it's just trying to get it to do it without falling on its ass at 4K.

Deatschwerks said:
oh i thought she meant she wasnt building boost at all
Click to expand...
 
It could be a cracked pipe or messed up seal on you intercooler hose, of course if it were that it would die after boost like when you let off the gas after 4 grand.
 
I did the FMIC myself, so everything is fine there. I'm thinking it may be the EBC, as we didn't set it on a particular boost before it's been driven (didn't have the manual with me). Would that cause it?

It doesn't die at all, pulls SUPER hard when it does go into boost and after it is fine. It's just that moment around 4K where it falls on it's face.

Can anyone give me some info on the open/closed loop stuff? And perhaps if anyone knows about that "safety" thing (hesitation) that the ECU does for boost too, for when it goes over the stock amount.

matt12046 said:
It could be a cracked pipe or messed up seal on you intercooler hose, of course if it were that it would die after boost like when you let off the gas after 4 grand.
Click to expand...
 
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