I did a bit of searching, but my anxiety is getting the better of me. I haven't had a compression check, and right now I do not have the means for one.

So, my car was fine yesterday, and everyday since I've owned it. But tonight, after work, I decided to drive it and noticed some weird characteristics and lack of power. Here's my description of the symptoms: It only happens at half or more throttle, and its very noticeable at a higher gear below 5k rpm. The engine will vibrate (its audible and you can feel it in the steering wheel), rpm and speed increase way slower than usual. It backfires more than usual (those beautiful pops between gears or when letting off the throttle). No check engine light.

I felt this on my way to run errands, which turned into an short evening of driving around town and feeling my car. On hills (uphill from a stop), it will have this same power loss. But if the RPM is high, it will pull fine (I redlined 3rd, 4th, and almost 5th on the highway and it felt fine, but backfired between every gear. Usually it'd just backfire on one of them.) Once I was done, I turned the car off in the driveway and waited 10 seconds before cranking it back up. It took like 4 seconds, but it was still able to hot start.

Relevant upgrades:
BHR Ignition (Bought new with plugs. Installed early January)
Cobb Accessport, tuned by mazda maniac
RacingBeat non resonated test pipe
All recalls done

Is there something I should monitor with accessport to help?
Could it just be a sensor (Like MAF) that needs cleaning?

I haven't actually done anything under the hood to check on this issue yet cause its cold and rainy.

 

Check out your long term fuel trims and MAF rate.

There are three distinct zones with separate trims based on MAF rate. < 8 g/s, 8-20 g/s (I think), and >20 g/s (again, I think). I wonder if you've got an issue with the MAF that's making it think more air is getting in than expected.

You can try cleaning your MAF (use MAF or electronics cleaner, nothing else!!!) and see if it goes away.

 

That's what I was thinking too. I can't wait for tomorrow so I can start working on it. My one friend with an FC says it might be the dynamic variable intake getting stuck due to carbon buildup, which would require replacing the manifold according to him. Does that sound right (not too familiar with the mechanics of this car yet). So far, my to do list is to pull the manifold and clean everything. I don't want to even drive it to monitor anything right now.

Also he said that a compression tester from harbor freight would work if I pulled a stem from it. Anyone hear of of this method before?

 

It's possible but it wouldn't explain the unburned fuel in the popping in the exhaust. And you don't necessarily have to replace the entire LIM if one of the valves is stuck. That's what the dealer tells you but you may be able to remove it and get the offending valve to move with a good soak in carb or throttlebody cleaner.

Pulling the LIM is non-trivial but do-able. You have to put the car up on stands, support the engine, remove the engine mount brackets and shift the engine as far to the driver side as possible. That should give you just barely enough space to work with to get the LIM out.

Using a piston engine compression gauge will make you think you have valid information but you won't. You need to know how fast the engine is spinning and to catch the peaks of each compression stroke. I suppose if you rigged up a high-speed video camera with a stopwatch next to the gauge you could work out the math but it's far from ideal.

Talk to the guy at Rotarycompressiontester.com (site vendor). He was thinking about a rental service a while back so that might be an option for you.

First thing to do is pull the MAF sensor and clean it. Then, clean pull the ESS and clean that, too. Then, reset the ESS profile (twenty-brake-stomp) and the fuel trims (disconnect the battery for a while). After this, start the car and let it warm up. Check your fuel trims after the coolant temp has reached 170°F. LTFT should be zero. STFT should be around 5g/s at idle. After a few driving cycles, the LTFT should move a little bit. Anything below +/- 8% is NBD.

 

What is NBD

 

No Big Deal.

 

I clean the MAF and ESS but nothing changed. Data monitor looked good according to the numbers you referenced. I think I will pull the upper manifold and check out the air valve tomorrow. And if that proves to be good, the only other thing I could think of right now would be a compression check. I think I will buy a tester once I get paid.

This is just so weird. The idle is fine, and acceleration up to about half throttle is fine. And there is no weird vibration or anything unless i'm on the pedal at about 50% throttle or more.

 

If you can, monitor the throttle position. Maybe you've got a bad pedal or throttlebody.

 

The pedal reads 0 to 99%. The throttle body reads 4 to 67%. It actually opens all the way though.

 

Well, this problem is smarter than me because I got nothing.

 

As I recall 67% is the normal maximum for the throttle body. It'll never go to 100%. It's not that it's not fully open, just the sensor has more range that the throttle body (this plays into the throttle body calibration the car has to do on startup/shutdown).

Is it full throttle that causes the issue or some rpm range? Like you crawl up into the 7k rpm range, does it go smoothly?

It sounds like beyond a certain calculated load it's dumping fuel, so I would suspect the secondary injectors. Have they been messed with at all?

 

I have not done anything with the fuel system at all, except the recall back in November.

Got the upper manifold off. Intake runners are super clean along with that valve. But there is hella sludge in the oil filler. It's not on the dipstick and not in the coolant. I'm about to drain the oil to see. Isn't there some seal inside the engine that could go bad and cause coolant to mix into it? Which would require a rebuild

 

Not particulary, the risky coolant seals are between the combustion chamber and coolant passages. You *could* blow the outer water seal and leak into the oil, but that wouldn't be my first guess. Plus you would be missing coolant and have an apparent excess of oil.

Sludge in the oil neck is not uncommon, it's just condensed oil fumes.

I know you've gone over this already, but it would be good if you could post actual data from STFT, LTFT, airflow, AFR and ignition timing while the car is doing this thing.

Maybe get a passenger who can take screenshots while you drive, or log the data to a file.

 

So I think I found the issue. Clogged injectors from running 2 stroke that's not tcw3. I already pulled them out. Gonna try to drop them off Monday locally to get cleaned and tested.

 

How did you determine this? I feel the issue was too much fuel, not not enough.

Also TCW3 is not what you want. Go JASO FC/FD

 

hi Check out your long term fuel trims and MAF rate.

 

If premix clogged your injectors, I'll eat my hat. They may have gotten clogged but it wasn't premix that did it.

 

I'm just good a jumping to conclusions lol. The injectors weren't too bad. The little filters inside were dirty, but they flowed well. Got them cleaned and everything and they picked up about 2% efficiency. Gonna start getting it back together this evening. Anything else I should check while the upper intake manifold is off?

 

did this fix your problem, i have something similar, mine started perfectly fine on last week thursday, come friday mornign and it start not wanna start within the first few cranks, i cleaned my ssv and swaped my coils but im afraid of doing the compression test becuase well.... the car behaves and drivers perfect. the coils were BAD all burnt i strongly believe that i have a clogged cat. so ...... im gutting that sucker tonight. hopefuly we both get our cars back to good running shapes

 

A good cat is worth many dollars, maybe actually diagnose it before destroying it?

 

youre right, i'll go get it plugged in before i trash it

 

Nope. My car is still acting a fool. I even checked my fuel sock, which looked immaculate (probably thanks to the recall).

I did a compression test with a regular tester with the valve removed. Rear rotor bumped 95 to 100 psi on all 3 faces. Front rotor was bumping between the 100 to 105 on all 3. And it cranks around 170 30pm according to data monitor. (I might order the real tester this weekend).

So yea, still at a loss. Probably gonna drive it around this weekend with a stock tune and hope for a check engine light to point me in the right direction.

 

Generally I'd say this is a clogged cat but assuming when you said test pipe that means you are catless.

Have you checked all of your coils, plugs and wires with an HEI tester? Even new coils/wires can sometimes crap out:

https://www.rx8club.com/series-i-do-...-wires-222641/


Other than that, what is your LTFT at idle when hot? What is your AFR at WOT when this issue is happening?

After cleaning ESS did you do the 20-brake stomp reset and pull the battery for 20mins to reset fuel trims?

 

i went autozone and it pulled up these codes p0300, p0443, p0037, p0302 and p0171 good thing i didnt cut the cat

 

Did not do the HEI test for the spark. But its not misfiring. I will do it next weekend if what I do today doesn't fix it.

The LTFT at hot idle is 0. The AFR at WOT is 14.2 Tries its best to stay at 14, ranges from 13.8 to 14.8, but usually steady around 14.2.

After cleaning the ESS, i did the 20 brake stomp and the oil cooler needles jumped up and went down.

Now, I thought I had the SSV out, but that was the VDI. Gonna pull the SSV today. (This intake has so much going on).