HELP: Missing power under 5k rpm!?!?!?
 

I've had this problem for about three weeks now. Under 5k rpm my car is lacking about half its normal power. After 5k rpm it still feels strong. When taking off from a stop, or accelerating under 5k, the engine sounds like it's being flooded; however, it starts and idles perfectly fine.

Here is the interesting part: when the car is cold. It feels very strong from idle all the way to redline. After the car warms up I loose most of my down low power.

The only engine mods I have are RB intake+duct and RB exhaust. Both mods have been installed for over 2 years without any issues. The car has 57k miles on it.

I tried the normal fixes. I installed new plugs. Checked all the fluids. Cleaned the air filter. I even completely reset the computer.

Help?

loss of power when warm seems to usually be bad cat, or bad engine. Hopefully it's not the engine.

Did you replace the coils? That'd be my first thing to replace.

The coils and cat are original.

My first guess was the coils as well. I looked at the bottom of them about a year ago and they didn't look that bad. Only a little white. I took it to the dealer the next day and they said it wasn't enough to warrant a replacement.

If it was the cat, shouldn't I have power down low and none at the top?

you can't tell if the coils are good by looking on the bottom. Replace the coils as your first step. They tend to last 12-40k miles usually, so you're overdue IMO. I usually change them once a year just to avoid having issues.

When the BHR coils come out, I can stop that cycle.

the items listed will actually be worse at high rpm than low, and then this doesn't explain why they're fine when the car is cold

I love this forum ...

How about MAF sensor cleaning? Maybe debris on the E-shaft sensor? SSV stuck open? Bad fuel pump resistor?

When I cleaned the air filter I noticed that my intake screen was badly ripped. After replacing it with a new one, the car did seem to run a little better. It could have just been my imagination though.

The new screen probably DID help as the MAF sensor is notoriously sensitive to turbulence.

Do you think my MAF sensor is dirty? What could I clean it with if it is?

Maybe it got air filter oil on it?

Some people like to use MAF cleaner from a spray can. I just use a little rubbing alcohol on a Q-Tip. Try checking each individual wire as it runs into the connector and take a look at the connector interface on the sensor, too.

Find a mountain road go up hill in a high gear, see what happens.

Stalls or no power = CAT

It hasn't stalled once but i'll try that.

I just got some rubbing alcohol and i'm going to clean it. What exactly am I cleaning?

wait wait wait. What !

STOP. Dont FREAKING touch anything on the MAF !

Go buy a can of MAF cleaner, its in a spray can and it cost like 4 bucks, spray clean it, dont touch anything on it. remember to clean the inside too. Search for DIY

dont cry if u mess it up by touching them, that thing is like a 100 something bux item.

Does this help?

https://www.rx8club.com/series-i-tech-garage-22/define-dirty-149934/

Well, I took it out and cleaned it with rubbing alcohol and they blew it with the air compressor. After reinstalling it the car idled rough for about 30 seconds and them evened out. It now runs like before.

The problem still exist.

Jackson, relax. I have cleaned my MAF sensor countless times and it works fine. The part that shouldn't be "touched" is shrouded. If one doesn't handle the sensor like a gorilla it'll be fine. Blowing air on it, however, probably isn't good. Then again, he didn't touch it did he?

Any other ideas?

Yeah, I'm missing power under 5k too...I think it might be this weird engine I see under my hood.

Couldn't resist:lol:

In my first 8 when this type thing happened to me, when I stopped and shut off the car it sound like a small pump was running, and ended up I had the compression loss issue, and that car had 17K on it, but I hope that this isn't the case for you. Have you tried what Razz1 suggested?

I did try it. It didn't stall; however, variables such as speed, incline, and gear all affect it. So his method, while a good preliminary test, doesn't definitively tell me anything.

I'm working on attaining a compression tester from a friend. I need to do some searching to see what the compression should be and how to test it. That is unless anyone knows off hand.

A normal compression gauge will not work; there are three areas for compression on each rotor...
You need a compression gauge without a "stop" so the needle can move back down after the compression stroke, watch and compare the high points on each rotor as the engine is turned over.
You may want to get a Mazda dealer to test the compression, but that is like pulling teeth, they don't want you to possibly prove you need a motor.

crap... I didn't know that.

I wonder if I can rent one.

I've seen a few people on these forums talk about running perfect when the engine is cold but lack of power due to bad compression when warm - that was how it was diagnosed by the dealer multiple times.

Happens because when the engine is cold you have a good seal, but when it gets warm the metals expand (like any engine) but a failing seal will not adjust to the expansion to create a good seal.. leading to this.

I didn't think it would stall but I thought that you would have to start revving really high to get any power. That's how I really knew mine went bad. I had nothing until I started to go into higher RPMs.

Yup, exactly how my first one was. I really hope that this isn't the case for you. I would def get a compression test done. At least that would rule out the main engine parts, and if it has lost compression, warranty? Isn't there a local RX shop near you? I'm sure one of them would have a tester suitable for rotaries. I know Mazdatrix sells two testers, one from Mazda, expensive, and the other from some other company, less expensive but still not cheap. Just a thought.

Remove the valve core from the tester so the needle bounces as the compression strokes pass by. Note where the needle stops each time and determine the numerical value later. Make sure to disconnect the e-shaft sensor, first, and remember using an analogue gauge is only a general idea of the compression values. Don't forget to crank the engine at WOT.

question: Will this get worse as I put more miles on the car? How soon until it's obvious there is a problem?

If I took it to Mazda right now, in typical dealer fashion, they would say that it's running fine. I have 57k miles behind the wheel of that car and I know it's not running correctly.

Would this apply to me?

http://www.finishlineperformance.com...14-08-1924.pdf

It could, everytime I have taken my car in and mentioned a TSB they haven't charged me anything for looking at it. You could try that route. Alot of the TSBs you have to actually "complain" or the TSB might say verify customer concern, etc. about the problem or mention the TSB otherwise the dealer won't know there is an issue. Unless it is a big saftey concern.

Worse comes to worse, have them check it out and bring a copy of the TSB. Sorry I can't be of more help.

If you have been driving her for that many miles then it is obviously a problem, cause you know your car better than anyone else. If it is the compression it will only get worse. Do you pre-mix? Cause that TSB concerns carbon and apex seals supposedly from not enough lube.

I've never run pre-mix.

Rodger: that WOULD apply to you.
Do you have a good relationship with your dealership? If so, see if you can get the tech to ride in the car with you. (or even just the service advisor) If they can see it first hand, you might be in luck

All the dealers hate me. Long Beach Mazda wouldn't even given my a loaner car when they replaced my motor mounts.

stop being such an asshole! ;)
any dealerships near you that you haven't been to recently?

Jedi, you know I can't be anything less than an asshole.

The closest dealer to me is 30 miles. (Long Beach Mazda, they wouldn't give me a loaner last time)

Browning and Galpin are next at about 40 miles.

Browning hates me and Galpin is in the valley.....

Try Huntington Beach Mazda, they have the same owner as Tustin.

soooooo far

If they don't help you out start calling Mazda. I had to do that when my first 8 went down. I bitched enough, that and my situation wasn't good at the time, and got them to ship the car after the engine was replaced to Ohio from NM. I let them have it too! I don't have the time or luxury to put up with stuff like that.

Well, the first thing I'm going to do is check the compression. I'll be doing that monday afternoon. Once I know that my motor is bad, I'll have more courage when dealing with the stealer.

What is spec for our motors?

That I don't know for sure off the top of my head, but I know it's here in the forum somewhere.

why not be nice to them for a change? maybe if they see that you're genuinely worried about your car, and not just coming in to be rude to them, they'll be more apt to help you out. also, you have your warranty. even if you're being a dick, they shouldn't deprive you of proper service.

tustin mazda tries to milk you for your money and some of the guys there are just incompetent. not sure if that goes for huntington, but with the same owner, i wouldn't be surprised. if you're gonna go to any dealer, get the rates from various ones and then choose which one you want to take your car to. go in with a good attitude and you'll get good service ;)

Who said I'm not nice to them? No offense, but you've never dealt with dealers before.

yeah i would try the compression test at mazda sounds like a failing apex seal of somesort like someone above said when the motor warms up the seal does not expand like it should causing a "leak" from one side of one of the rotors to another!!!

So I should do the compression check when the motor is warm....

RR, you should not only do it when it is warm, you should also make sure your oil isn;t overdue for a change. Clean oil, clean air filter, and good compression tester.

RR I saw this thread from rotarygod and is just a thought.

https://www.rx8club.com/series-i-tech-garage-22/rotary-compression-tester-149967/

I change my oil every 3500 miles +/- 500. Air filter was cleaned about a month ago. I normally clean it every 5-6 months.

I saw that the other day. It's very nice but I couldn't drop $300+ on a compression tester I will probably only use once in my life.

I got a hold of a basic compression tester. I'm going to hold down the release button while I have some one crank the motor. It should give me a general idea.

How big of a compression difference am I looking for between a good chamber and a bad one? I assume that there will be two bad and one good per rotor if I do have a compression leak? (each apex seal holds for two rotor faces)

I can't seem to find the compression spec of our motor.

MSB-16 Re-Flash.