Dobbo

Hi guys, ive an 07 RX-8 231ps that is an off road project that i intend to get working for the summer.

Ive had problems that a lot of the time came down to a bad battery. Ive replaced the battery and now the majority is okay. However, after revving the engine, it cannot seem to catch its idle, it falls bellow and stalls instead.

I read up a few things and found that the only thing i havent checked is the eccentric shaft sensor (ESS). Today i tried removing it to clean but is being an absolute pig to remove. Its the fully enclosed version.

Was wondering if anyone had any tips to remove it? And if there is anything else anyone can think of to stop the engine stalling?

CaymanRotary

First thing you need to check are engine codes. Did you get a code for the ESPS? If not, I wouldn't worry about it too much. If you have no engine codes, the next step is a compression test. This is to rule out any type of engine damage that could cause stalling at low RPM (Stalling at low RPM is generally a suspected compression loss issue). If compression checks out good, your next step is to ensure your ignition system is healthy (Coils, spark plugs, spark plug wires and starter). If those check out, you need to clean MAF and check for any vacuum leaks. This is pretty much my whole step by step process for diagnosing engine problems in this car. If its still not fixed after all this, we can look at other issues in the intake, baro sensor, fuel pressure and exhaust.

Loki

iTrader: (1)

This is after replacing the battery? Disconnect the battery. Wait 30s, reconnect it, start the car and let it idle. It just needs to relearn how to be a car.

Once it's fully warmed up, go for a drive. It might still stall, but give it a couple of drive cycles and it should be fine.

Any idea of engine condition?

Dobbo

Great advice! Thanks will get on it
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Dobbo

I let it idle for 15 mins and it was stalling. Cant drive it around as its off the road. Has no MOT or tax. As for engine condition im unsure, has done 40k miles and starts up from hot and cold fine now the battery is replaced.

Dobbo

Great advice! Thanks will get on it and see how it goes 😄

Dobbo

No engine codes.
Cant drive to get a rotary compression test completed so i used a piston compression tester and a converter/calculator and the front rotor is comes out at 5.61, 5.61, 5.61 and the rear rotor is 6.19, 6.19, 6.19.
Where would you recommend i go from here? To ignition or are these results bad?

I know i should get a real compression test but i cannot afford the tester or move the car to be tested.

Love_Hounds

Unfortunately, those results don't really tell anyone anything of value, to find the true compression you need a rotary specific compression tester as you already know. Don't waste money throwing parts at it that may fix it, save up and get the proper diagnostic tests performed.

CaymanRotary

Contrary to popular belief, your results on an ordinary compression tester may not 100% accurate but are actually close. Those numbers may be ok, it depends on what the cranking RPM was. Those numbers need to be adjusted to 250 RPM. If you can provide cranking speed and the elevation the test was done I can provide more accurate numbers for you. Ideally, you will want to use a rotary specific compression tester but if all you have is a piston tester I can work with that. If you already adjusted to 250RPM and accounted for elevation then yes, engine is definitely on it's way out unfortunately based on those numbers. IF those are your true numbers you have two options at this juncture:

1. Rebuild or install a rebuilt/remanufactured engine. Looking at anywhere from $4000 (if you DIY) to $7,000 (Done by mechanic).

2. Accept the loss now, sell the car as it sits and look for something in better condition. This is what I would personally recommend. These cars are cheap as chips in England. Make sure the car is compression tested before purchasing so you dont find yourself in this same nightmare again.

Love_Hounds

That's horseshit, but keep spreading it if you want.

CaymanRotary

I'll just agree to disagree but factually it is close. I've done compression tests with both testers. Difference is +- 0.3 bar max. Ideally should use a rotary compression tester but if a regular one all you got it's good enough to get a general idea of engine health. It is a lot more difficult to do however and requires 60 FPS video recorder, video editing software (which you can get for free), and a spreadsheet but its doable. I just use the same directions provided by Drivenbymadness on YouTube.

NotAPreppie

How many times can we compound measurement error?

CaymanRotary

The difference between getting a 6.3 Bar reading on a regular tester and, for the sake of argument, a 5.8 Bar on a rotary tester yields the same result. Engine is still an anchor regardless ^^.

Love_Hounds

Except it isn't close, with a rotary specific compression tester you get a reading for each rotor face and the RPM, which is what you need to know what is happening in the engine. With a piston tester you get numbers and with the use of extra equipment you list and time, you can estimate the values at best. If you want precise and accurate numbers, which is what you should use to determine the need to rebuild/replace, you need a real rotary compression tester.

CaymanRotary

RPM is easy to calculate with the extra effort. You can calculate cranking speed using the video editing software. As far as rotor face differences and accuracy I agree completely with your statement. A compression test with a regular tester is still better than nothing though.

NotAPreppie

How about the excess void space in the tube between the spark plug hole and the mechanical gauge. All of the calculations and charts assume a minimal void space since the electronic pressure transducer is threaded directly into the plug hole.

CaymanRotary

Yes, wont be totally accurate. Also, difficult to see the difference of the rotor faces. That being said testing this way will get you in the ballpark of a proper rotary tester. At least that's how it was when I tried it and compared vs my rotary compression tester.

Even if it's not completely accurate it's enough to know if you have low compression or not. if you have no access to a rotary tester, it's the next best thing is all I'm really saying.

edit: There is no Mazda dealer where I live and no one had the tester. That’s why I tested like this for so long.

andrewball2019

Removing the little valve in the compression tester and recording the meter will give you pulse compression. There is a calculator available to help calculate rpms, or you can log them using an obd2 reader. Using a standard compression tester to check a rotary motor out is only as accurate as the person doing the check. Much like using a dummy proof machine is only as accurate as the calibration/design of the machine. Like most arguments both sides here have their ups and downs. But neither of these methods is necessarily better than the other, they can both be very precise.

NotAPreppie

One is far less error prone and has much higher inherent precision and accuracy in the design than the other.

I'll let you guess which.