[SOLVED] No Acceleration Under Load

benesis

benesis

Greenie N00B Member
Year/Make/Model: 2008 Mazdaspeed 3
Mileage: 109K
Location: San Francisco
Concern: No Power under load
DTC's: P0300 Multiple Random Cylinder Misfire
Modifications: Air Intake, Coilover.
ECU/Tuning Software: Don't know
Tuner:
Is the concern intermittent? No, it's always there
Can you duplicate the concern?
Recent Repairs: Replaced turbo, replaced catalytic converter.
Correction:

HI Gentlemen...and Ladies;

New to the forum and a new Mazdaspeed 3 owner. Proud owner of the car I've always wanted, but so far it has been painful...MAZDASLOW!
The car starts and idles fine but has no power passed 2500 rpm like it's in limp mode. It drives fine on a flat surface as long as the rpm doesn't go over 2500, if I go over it sounds like it's running on 3 cylinders. It does not climb a small hill in second gear, it has to be in first, kept below 3000rpm and it goes slowly. No power under load. It has thrown the P0300 code and CEL is blinking.
Before I bought it, it had been sitting for 2 years and the catalytic converter was stolen. The seller said the car ran fine before the converter got stolen. Replaced the catalytic converter. I also noticed the turbo was leaking oil, and had a crack, replaced the turbo as well.
Replaced the spark plugs
Replaced the coils
Removed cleaned and tested the fuel Injectors
I noticed the high-pressure fuel pump was only at 400 to 800.
Replaced the high-pressure fuel pump and it now goes to 1600
Checked the low-pressure fuel pump, replaced the fuel filter, and inspected the inside of the tank.
Cleaned the carbon off the air intake and the intake valves
Swapped the Mass Airflow Sensor.
Compression test 180 wet and warm and all 4 and 145 cold and dry
Leak down test was good too.
What else it could be? What defective sensor on that engine could make the car operate like that?
I'm ripping my hair out and starting to be depressed about it.
Reading on this very forum a thread with similar symptoms, it turned out to be a bad ECU. What are the likelihood? Does the first gen MS3 have ECU issues?
Thanks
 
What are the spark plugs gapped at?

Have you done a boost leak test?
 
To add to what EB said, how old are the spark plugs and what plugs are you running?

What do your STFT and LTFT look like?
 
Thanks guys,
I'm running NGK Iridium LTR6IX, gapped at 0.032", they are brand new out of the box.
I have not done a boost leak test, will look into it.
For the STFT it all over the place since I got the car. First it was at
-2.3 iddle,
-7.8 at 2000 rpm,
-10 at 3000 rpm
After cleaning the injectors
It went to
7 at idle
8.6 at 2000 rpm
5.5 at 3000 rpm
I have to run it again and get an average.
When i got the car, The LTFT was at
14, now it's at 0.
I have Forscan and the Bleu Driver.
 
I would tighten up that spark plug gap for starters. Also to clarify are you running the one step colder NGK 6510 plug?

Per the FSM

Spark plug gap Standard: 0.60-0.80 mm {0.024-0.031 in} New spark plug (reference): 0.60-0.70 mm {0.024-0.027 in}

I use this tool to adjust the gap on new plugs. There are some videos on YouTube as well on how to adjust the gap on iridium plugs.

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So you saying your LTFT were at plus 14 when you first got the car? Seems like there is a leak somewhere past the MAF and the ECU is dumping fuel to compensate.

As EB mentioned I would perform a boost leak test or smoke test and try and find a leak.

Does FORSCAN show any developing DTCs?

Edit: I noticed you said you swapped the MAF, what brand MAF did you put in the car?
 
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The spark plugs I'm running are the NGK Iridium LTR6IX (94374) gapped at 0.032". NGK recommends them on their website for the Mazdaspeed, I don't think they are the issue.
As for the MAF sensor, the car came with a genuine Mazda one. I swapped with a cheap one to troubleshoot, no change, so I swapped back to the Mazda MAF sensor and ruled out that it was not the problem.
I will run a boost leak and get more STFT numbers. I'm not too familiar with Forscan, will play with it some more to find DTC.
 
If those are step colder plugs and they recommend them for speeds then NGK is no longer a trustworthy company
 
Easter Bunny said:
If those are step colder plugs and they recommend them for speeds then NGK is no longer a trustworthy company
Click to expand...
Nah they're heat range 6 same as as 6509 or 3787, so probably fine just not ones we typically see used on the platform. 3787 is where I saw multiple years of the speed years listed for fitment so I'd say that's one that they actually reccomend
 
I ran 3787 plugs for the entire life of my OEM motor without issue.

OP even if you don't think the plugs are the issue you def should fix that gap it's low hanging fruit and could contribute to other issues.

I had all kinds of fun this summer with my car trying to troubleshoot a bunch of things. It's all resolved now but one of my issues was spark blowout.

My plugs had worn to a point where my gaps were around .031 and it made a BIG difference putting in new ones gapped at .025.

It didn't solve all my problems but there was a noticeable improvement. I had other things to deal with as well but that's another story.

These motors can be finicky and things that don't seem like a big deal can make a big difference.
 
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Sure, I'll close the gap to 0.026 for now and eventually replace them with NGK LTR6IX-11 (6509). Can the plugs I have make the engine run that bad? Probably not, but I'll get to it.
On the report ECU loss of communication is probably because I disconnected the ECU.
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Attachments

https://mazdaspeeds.org/index.php?t...ode-on-acceleration.15105/page-18#post-106342

Was reading on the forum and came across this thread with quinda the same issues and turned out to be the ECU.
I took a look at my ECU tonight and MAMAMIA! found some corrosion on it. The pictures are a little blurry, sorry, but you can clearly see it.
In your guys' experience, can that cause the no power under load conditions?
 

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Yup I asked about the positive 14 LTFT initially, OP as was mentioned you need to find your leak AND fix your plugs.

That corrosion on the ECU board does look less than ideal but in all honesty I've never looked inside mine. Moisture and corrosion on a circuit board is typically a bad thing. Is it the cause of your issue? Maybe yes, maybe no....

I can tell you for sure a LTFT of positive 14 to 20 is BAD and will cause drivability issues. I would address the easy/cheaper stuff first before going through possible replacement of the ECU.

If I were you I would look up some YouTube videos on smoke testing and boost leak testing if you are unfamiliar.

I have this smoke machine and like it for $120.
AutoLine Pro Automotive Smoke Machine Leak Detector EVAP Vacuum Diagnostic Tester | Shop Series https://a.co/d/4xlBbff

I initially built my own and it was just ok but this one is just easier to use as long as you have an air source.
 
Hi Gentlemen,

Thank you for all your suggestions. I performed a boost leak test. Went to Home Depot and bought a 2.75" wide PVC cap, screwed in an air-quick disconnect, and used my blow-down tester and a soapy water spray bottle, it was fun :-) No leaks found, intake, turbo, and manifold are sound.
As I said earlier, I suspected the ECU since I found corrosion inside it on the electronic components and because I read the thread on this very forum. https://mazdaspeeds.org/index.php?t...ode-on-acceleration.15105/page-18#post-106342
Well, for $250 I bought a used ECU from eBay that came with the key and the ignition lock. The idea was to replace the ECU and the lock and with the provided chipped key, no need for a locksmith to come over and charge me to WAZZOOOOOO. Replaced it all and...no start! The dashboard red light blinking (with the little key on it) like the ECU doesn't recognize the chipped key. Well a little research later and I found out the chip has also to be recognized by the Body Control Unit. That is in the footwell on the passenger side, it's part of the anti-theft system.
Then I came across this YouTube video from a nice man from Australia.

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Turns out you can use Forscan to program the keys, you just need to have 2 of them.
To make a long story short, the program is done, and the car finally starts and runs like a dream with that used ECU. STFT is at 4%. It was that damn ECU all along and it makes sense since the previous owner had the car in the driveway for 2 years, in the rain, humidity, and California sunshine.
Today was my first time driving a Mazdaspeed. That thing is fast.
 

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