MSP Stumble, and the Mazdaspeed Tantrum

[f1yen]

Hello Folks,

The Speed has a nasty stumble/misfire while in boost. But to my demise, it is not consistent to time/temp, only that it is more noticeable while in boost. (can feel it slightly at zero psi sometimes)

For example, accelerating in 2nd gear, starts to stumble when boost sets in. I can rev the gear out, and stumble the entire way, shift, and it MAY keep stumbling, or sometimes it will disappear... and the car will accelerate smooth as normal.
This "stumble" that I refer to feels like a misfiring cylinder...

Ignition:
New plugs (4 months ago)(even gapped to .025"), New wires (4 mo ago), new Coils (1 day ago).
Used a spark checker to and showed about an inch arc in the air...

Fuel:
The Wideband does not show anything too crazy when this is happening, Hunting for 14.7 before 4200rpm and then dips down to 9.8 - 10.2 after entering open loop.
Thought an injector could have been clogged...Lucas injector cleaner had not effect
Also performed a "leak" test on the injectors, and they did not leak at all in 2 minutes.
Injectors were traded with a spare set, and no resolution there.


TODAY: I got myself an ELM 327, and I think I finally have all the tools I need to chase this problem down. Checked my MAf and trims... hopefully you guys can help me here:

Idle seems a bit rough... but maintains about 705rpm (spec 650 - 750)
@ Idle:
STFT bounces around -.8 to .8 % (spec -10 to 10%)
LTFT moves a bit around -2.3% (spec -5 to 5%)
MAF 2.2 gm/sec (spec1 1.6 to 2.2g/s or spec2 1.6 - 2.5g/s)
Spark advance: bouncing up and down 10 - 12deg (spec 6-18 degrees)
Load : 19.6 to 20.4% (spec1 13 - 20% or spec2 13-18%)

@ 2500 rpm
STFT bounces around zero ish
LTFT - 7.8 % (spec ? )
MAF 7.8 to 8.1 g/s (spec1 5.1 to 6.5g/s or spec2 6.2 to 7.4g/s)
Spark advance: 23deg (spec ?)
Load : 14% (spec1 11 to 17% or spec2 12.5 to 17%)

Notes: I found 2 specs in the Mazda manual I have, both for manual trans.... idk what those Mazda engineers are doing.

Notes: trying to get the motor to 2500rpm was actually difficult.... the rpms waver, (up and down 100 rpm or so) and If I am very slowly rising the rpms, as I just pass 2000 rpm, it rockets to 3100 rpm, then taking a little less gas would overshoot again lower than 2000, and so forth.... I guess it seemed really odd to me, took me a while to get to that rpm??? Can anyone else just try this? I will take a video if needed, maybe it has to do with the problem...


It looks obvious that the MAF has taken a crap, but would this really give me a chugging stumbling feeling?
I have the MAF relocated to the cold pipe... would this effect my readings?/can someone else share their trims with the cold pipe setup of the MAF


Thanks guys!

 

[f1yen]

Does anyone at least know if the MAF readings look okay for a cold pipe setup? Or should I order a MAF now?

 

[CHIQLES]

here are my stats

 

[CHIQLES]

heres my idle its a little low but runs good

 

[f1yen]

Thanks CHIQLES, are these with a non-relocated MAF?

 

[CHIQLES]

yes but I have supper short piping so relocated or not signals should be the same. My idle was a little low due to i had reved it and it dipped a little. I have a feeling everyones having coil problems..

 

[Stiki]

i also have the studdering during boost, sounds like running lean.

i changed my map sensor today and its alittle better but still there..

changed plugs and wires yesturday.

replaced all vacuum lines and cleaned throttle body and all my piping.

no exhaust leak and no codes except for heater control valve which has nothing to do with this problem.

f1yen, have you had your ecu reflashed?

debating if i shud get mine flashed and see if that might fix it.

 

[f1yen]

Don't think it will be my coils, just replaced em 3 days ago. And I have 2 other sets to swap around and They all work about the same...

Stiki, I had it flashed.... I had a problem with the car, seeing boost, in low rpms, and being slower than with no boost, at which point I would try to throttle myself under 0psi untill around 3500rpm , then punch it, got the reflash, and It drove night and day better.... I never had stumbling like this back then.... It was just way too slooooow if I got into boost with too low rpms

My wideband is jumpin all around, can somone with a wideband add their $0.02 with this???
Its an Innovate MTX-L, and I just re-calibrated it last week.

Freeway driving : http://www.youtube.com/watch?v=YFCvi5RgMPo
Idle : http://www.youtube.com/watch?v=D3u7hscYuKU
Normal Idle : http://www.youtube.com/watch?v=lZSh9G2Iniw

Lately I saw the "normal" idle once, and the car was driving "well" at the time....so I took the video of it.

 

[f1yen]

I also checked my ignition advance vs RPM in neutral.

This might explain why I was having such a hard time arriving at 2500 rpm.. because its retarded below 2000 and advanced above 3000 and a very large slope between them.

I am assuming the 2 curves at the bottom is the ecu "trying" to advance the timing, but being bumped back down again.

Soooo If anyone has access to that fancy Torque app like me, (or If your local to MKE I could hook up mine as well, in exchange for some beers!) maybe I could see if this is normal or not.

 

[Stiki]

Don't think it will be my coils, just replaced em 3 days ago. And I have 2 other sets to swap around and They all work about the same...

Stiki, I had it flashed.... I had a problem with the car, seeing boost, in low rpms, and being slower than with no boost, at which point I would try to throttle myself under 0psi untill around 3500rpm , then punch it, got the reflash, and It drove night and day better.... I never had stumbling like this back then.... It was just way too slooooow if I got into boost with too low rpms

My wideband is jumpin all around, can somone with a wideband add their $0.02 with this???
Its an Innovate MTX-L, and I just re-calibrated it last week.

Freeway driving : http://www.youtube.com/watch?v=YFCvi5RgMPo
Idle : http://www.youtube.com/watch?v=D3u7hscYuKU
Normal Idle : http://www.youtube.com/watch?v=lZSh9G2Iniw

Lately I saw the "normal" idle once, and the car was driving "well" at the time....so I took the video of it.

what you described sounds like my car a week ago..i could peak boost at 3grand..but i could never WoT without my engine stalling..didnt think the reflash would fix that..now it just studders anytime i hit above 3 psi..yesturday while test driving, everything was fine then BAM!..i couldnt hold idle..rpms were going up and down like nutts..reset my map sensor in a parking lot and drives better but still studdering above 3psi..

i had 5 check engine codes one day, and then 1 the next..a friend told me a hairline crack in the ecu could be doing all of this?..anyone know?

 

[Stiki]

btw, i just looked up the torque app..i think i need to get that

 

[Dr0]

So far I'm really surprised at the success ive had all I did when my car was hesitating is

Install ssafc (supermap)
And switch to a COPPER plug at .30

Its weird bc the plugs made a bigger difference to the hesitation

 

[CHIQLES]

I think the reason I dont have many issues is my plugs as well. I know people think there a gimick but they work at least if you install them right..

 

[f1yen]

Really, the pulstar ones?

Sounds like bunk to me, anyone else have pulstar?

I guess I am a bit confused what is happening with this "stumble".... I mean, what is really going on? If it is not firing, then it will feel very sluggish, and should be dumping plenty of O2 into the exhaust for me to catch high numbers on the Wideband...

If the gap is small enough for the spark to jump, (considering compression and added atmosphere (boost)) then I dont see why different spark plugs would make much of a difference at all....

 

[Preferio]

I use standard NGKs. I personally don't believe the the Pulstar E2s are worth it. I change my plugs every 15k miles because of the hell I put them through. 15+psi on built engine and (when it's driving) it sees that many times a day. Just curious as to why you gapped the plugs at .025 instead of, say, .029... And have you removed them and attempted to go with a larger gap closer to that? If not, try it, though I'd expect your issue would be higher in the RPM range if that were the case, but I believe it's worth a try if you haven't done so.

At idle (650-750) you should see a MAF value of 1.6-2.5g/s at 13-18% load. At 2,500rpm you should see 6.2-7.4g/s at a calculated load of 12.5-17%.

 

[BOOSTR]

Some highly modified and boosted early MSP people started running the tighter gaps. I always use NGK copper plugs and gap them at .029, right in the middle of the factory gap specs. I change mine even more frequently since they only cost $8.56 for all four plugs.

 

[CHIQLES]

heres my graph

 

[CHIQLES]

I only got one dip maybe graph you rpm versus throttle pos?

 

[CHIQLES]

 

[f1yen]

I gapped to .025 when I noticed the issue, was at .030 and wanted to MAKE sure... lol It was the next size on the gauge (steel wire style).

hmmm Crap CHIQLES, your graph is all over... ha. Did you try going super slow from idle? Just go up real slow, then stop logging and the graph should look cleaner. I think you might also have the 2 step in there.. but it looks like your still more advanced than me as you are just below 0 advance.

I started to blog my graphs, you can look at them there, it has load vs advance in there.