Slightly new development with this issue(I'd just never connected the dots before), but the issue goes away if the car is completely heat soaked. Like on an hour or longer drive. It does not matter if I allow the EGT to cool down from easy driving or make it super hot, the problem is fixed after a long drive, but comes back once cool. The IAT and ECT both stay normal, so it's not an internal heat issue.

What else could be positively affected by heat?

 

Valves loosening is literally all i can think of... very strange. I wouldn't of thought it'd take an hour to do though. For my issue I phoned a specialist and they suggested the gears in the engine might be seizing, could that be a possibilty for you as well? After a long drive everythings heated up equally and expanded to a more free turning degree? Wouldn't explain why you run rich though.

 

By valves loosening, do you mean the intake valves, such as the SSV becoming unstuck?

 

Since you mention heat soak, have you thought of the coolant temp sensor? maybe it is malfunctioning and sending the PCM a bad reading, making the PCM think that the engine is still cold. I'm not sure if we have 1 or 2 sensors, most cars have two, one for the ECU and one for the gauge, but since ours is just a dummy gauge, it may only be one.

Edit: After searching we only have the one in the thermostat housing.

I intermittently have the same problem, but haven't been bother enough to really care

 

Yeah, a sensor would make sense, but I have the ability to pull data from every sensor the ECU is looking at and everything stays normal during the episodes, so it makes me think that a sensor couldn't be the culprit.

I'm borrowing a rotary compression tester after the new year and will post up results once that gets done although I'm positive it isn't a compression issue.

 

hmm.. ok I wasn't sure if you were monitoring temp as well. It was just an idea since the temp sensor is known to cause some weird issues with the PCM

 

It's all good, that's why I believe it's something non-internal that is being affected by the heat, which really narrows things down.

We swapped batteries with a friend who had a new one and checked voltages and charging capacity and both my battery and alternator seem to be fine, it could be an ignition grounding issue although I doubt it. Next step is to swap ECUs and do the compression test.

Next question, are ECUs VIN-linked or can I just swap one out of another 8 and have it work? The donor is an '05 and mine is an '04.

 

It's been a while, I've been busy with other projects, but it's time to jump back on this train.

My issue has been getting steadily worse since the beginning, it no longer is hit or miss and is always there, and the power loss is more severe(my friends FB can outrun me without even trying).

So I replaced the front O2 sensor, just to make sure that the AFRs I'm logging are correct and rule out another option.

Quick list of everything tried to date:

Walbro 255L fuel pump
Checked coils
Checked plugs
No cat
New front O2 sensor
No rear O2 sensor in car(bung plugged)
MAF swapped with known working car
SSV cleaned/checked
All solenoids tested
All vacuum lines tested
Fuel injectors correctly seated
No abnormal oil consumption


So here is a WOT pull through 1st and 2nd:


As you can see my MAF is maxing out at around 200g/sec, which demonstrates the fact that power loss is definitely occurring, and the AFR is definitely wayyyy richer than it should be.

At idle my LTFT sits at +1.8% and the STFT bounces between ±2% which seems quite normal to me.

The fact that my MAF at idle is between 4.2g/sec and 4.8g/sec looks to me to be low, which could suggest a vacuum leak, but my MAF isn't calibrated and I have no clue how much to read into that. Can someone chime in on that please?

 

Sorry, no idea about the MAF readings...I'm pulling 0.5lb/min=~3.7g/s according to my MAF.

If your injectors are all correctly connected....what about a failing/clogged fuel injector/injector wiring issue? The fact that yours seems to be going rich at a certain point seems like maybe it's adding more fuel to compensate for a failing secondary, which is what mine was doing when my rear secondary was unplugged.

That also fits in with the fact that it was intermittent in the beginning, as the injector was failing. Does it run okay at lower rpms? Mine didn't loose power until about 5k. It felt like my power was coming back about 6.5-7k but really it wasn't. It just felt like it because some power did, and I didn't know how it was supposed to feel since it had always done it

 

My injector wiring has never been unplugged so they should still be correct. I went ahead and bought a new secondary injector, it's sitting on my desk. I think I'm going to strip it down this Sunday and see if I can find an injector that is bad.

My issue is that beyond resistance testing them, I can't do much to diagnose which one is bad if any are.

 

worked on a mazda 3 recently; and I had a similar issue like yours where the intake piping had a hole in it past the MAF.
The engine was recieving more air than the MAF was reading.
possibility?
Also i read somewhere on here that around the rpm range where your losing power is a good sign that the engine is going south.

 

Not really much you can do, short of replacing all of the secondaries. Which one are you going to replace, and how much was it?

 

Seems like he would be having low rpm issues as well though. Plus it's been compression tested.

 

Yeah, compression SHOULD display a lot of other issues besides just the one I'm having.

And I'm going to take a multimeter to all of the injectors and see if one is out of line with the rest, if so I will replace that one, if not, they'll all go back in and I'll try to figure out another thing to try. I picked up a remanufactured Denso for $39 including core charge.

 

That's pretty cheap...you could always just replace all of the secondaries, though I don't really like throwing money at problems. Seems like if the current measures ok, then there isn't really a way to tell besides replacement. I just put new plugs in because my old ones were SCARY. That rogue fuel injector caused it..it hurt to have to replace plugs with barely 10k on them

 

Very true. If I get in there and they all present good characteristics then replacing all might be an option, but I'm holding off on that.

For future reference, you can get them that cheap from rockauto.com.

 

Good to know. I hope you get it straightened out, I sure know what you're dealing with.

 

So I have been doing more thinking, and I have spent a lot of time trying to track down a vacuum leak as that would be one possible cause of this mess. I have had no luck so far but I feel like the way the symptoms are, it would only be present when everything is actuated and the entire vacuum system is in play. Before doing the injectors tomorrow I think I'm going to put it on stands, take the rear wheels off, and slowly get it up to ~7500rpm in first gear and set the cruise, then do a quick leak hunt and see if any of the VDI/SSV/VFAD is presenting a leak.

Also, I'm having trouble deciding if a leaking injector could cause all of this nonsense, since I'm going rich, not lean, I doubt it is a failed injector, but if it were a secondary that were leaking it could 'pool' in the intake runner prior to the valve allowing intake charge through it and once it does open cause a spike in combustible fuel. I just don't know if this would allow me to have a leaking injector without any idle/low rpm issues.... Thoughts?

 

Has me stumped too . What seems to be happening is that the opening of the APV is having a clearing effect for whatever is going on .
Suggest you do logs from now on in 3rd gear from a low rpm vs rowing through the gears . This will show a clearer picture of the timing of events.
How about trying a run in 3rd gear from low rpm as is then another with apv disconnected . Might just give us a clue as to what is happening.

 

I typically was doing 2nd gear pulls from about 2k rpm but for some reason the log didn't save the last time I did it, along with the cruise log and the idle log.

I'll try and get a clean one, there aren't too many places around here that I can do a 3rd gear pull without attracting too much attention though.

The APV having a clearing effect is kind of what I was getting at with the whole leaking injector thing, like if enough gas is pooling in the runners and then getting flushed into the combustion chamber when the APV opens. But part of me says that's a load of bull crap because I'd still be getting excess fuel at idle, right? I have positive fuel trims at idle which wouldn't match up with that.

 

oh well , try without apv in 2nd then . I think it would be helpful to overlay the two runs and use rpm as the x-axis if you can .

 

By that you mean just unplug it so it can't actuate?

I was planning on taking the motor off while I'm messing with things tomorrow and seeing if it seems stuck or if the gear is in the correct position. Could I try it with it both stuck closed and stuck open if I take the motor off and just rotate it myself?

 

Yeah - just unplug it . To get it in the open position you can have the plug almost off then get someone to turn the ignition off . When you hear the first whirr for the motor - pull out the plug . The first whirr is apv open the second whirr is apv closed.

 

Sounds good. It's pouring down rain but I'll try to pull it when I'm leaving work if it slacks up, will post up results when I get it off.

 

I tested it with and without the APV stuck open last night and with it closed it had a smooth power curve but was lacking power everywhere, with it stuck open it ran like poo under 5k but had plenty of top end(where I have been lacking since this whole thing started).

After figuring that I should look at the two injectors that feed the runners the APV uses we tore down and swapped the new injector for one of them, put it back together, no luck. Tore it down again and swapped back in the other injector and put the new one in place of the other possible injector and... SUCCESS!

It would appear that was the issue as I am staying about 12.0:1 AFR all the way until 8k rpm now and flowing a max of 220 g/sec which still isn't amazing but way better than the 180 g/sec I was flowing yesterday. Hopefully the top end will improve as the fueling tables relearn of the next few days.

Now to figure out how to stop the ticking coming from the SSV actuator arm...