Fernando Lopes

Hi All,

I hope you are able to help me so I can feedback to my mechanic. Recently I have notice that my RX8 has very low power after some kms driving it. Seems that the problem appears when the car gets hot.

My mechanic looked into the car and said several parts needed to be replaced. So I have replaced:
- Catalytic converter (previous was completely destroyed)
- Ignition Coil Leads
- Spark Pugs
- Ignition Coils

Unfortunately, the problem remain after changing all the parts. The mechanic also says that the car temperature and catalytic converter is way hotter than the temperature marked on the temperature gauge. I have been searching the forum for possible causes and I see it might be related to MAF. How to be sure of this?

Can you please advice on the next steps to try to find what is wrong with the car. Please if more info is needed let me know I will describe as best as I can.

Please help.

wcs

iTrader: (2)

What year is the car?
Mileage?

You've addressed all but one of the usual suspects.
Compression.

Get a compression test performed.

Fernando Lopes

The car is from 2004 with around 105000KM.

A compression test has been performed on a Mazda dealer and their feedback is that the compression is not bad but is lower than a new engine. They have said that there is one rotor performing worst. However they have told me the compression is around 80% comparing to a new engine.

blckninja

iTrader: (1)

Good thing you got the test, bad thing you didn't get the numbers.

Call them back and ask for the specific numbers for the compression test. What they said means nothing.

Fernando Lopes

They provided me kind of graphic document. I believe some numbers are written there. I will uploaded to get your feedback.

Thanks for the help so far.

Fernando Lopes

Hi,

Please check the compression test results on the images below

Williard

iTrader: (18)

Bump this, RIWWP..Calling RIWWP, this guy needs help. never seen this sheet.

Fernando Lopes

Hi,

Any help guys? My mechanic keeps trying to find the source of the problem. He suspects it might be related to the sensor on the catalytic converter. He says that there is no error message on the ECU but the believes it is giving bad readings when the car starts heating.

How to be sure of this? Somekind a test he can do to he sensor? He found out a sensor from another Mazda to try to test it out and see how the car behaves later today.

logalinipoo

Those sheets show 30 and 17 psi and both of those pressures are extremely low. Im surprised you can even get it to start if that is true.

What exactly is the car doing? How fast will it drive?

Fernando Lopes

Main problem of the car is that when hot (after driving for 15-20 min), it starts to lose power/torque. Is become extremely hard for the car to rev high. It feels the car is making a lot of effort on the engine.

Car has no starting problems when cold. Always at first. When hot it does take some more seconds to start.

Stange that you say that. The mechanic after checking the compression commented that it was not that bad. It was not new but still good.

Khurram

+1 Williard1 We have never seen a compression sheet like the one above.

RIWWP would be your best bet, but he seems to be missing for last few days i hope he is doing fine.

Drive your car for 20 mins at night, and then pull up and look underneath the car to see if your CAT is glowing red.. if it is, than thats your answer..

Aston177

He said he replaced the cat.

Fernando Lopes

I did replace the CAT. My mechanic does say that it heats too much. What would the normal operating temperature for the cat?

Aston177

Depends on how you drive. Cruising would be around 1100F. Could go up to 1600F when you're flooring it.

blckninja

iTrader: (1)

What the graph is showing is the psi of each rotor face. Where it spikes is the individual face of the rotor. This is probably the raw data that the mechanics can receive, but never show it because it's a graph, not a specific number.

What i'm incredibly concerned about is the psi rating, there is no way the car would be working on 30 psi front rotor and 17 psi rear. Either the test was done incorrectly or he measured it in an incorrecting format.

What i'm thinking happend is that he did the test incorrectly. When you do the compression test on a rotary, you can't take off all the spark plugs at the same time as people do with a tradition piston engine. If your mechanic doesn't know how to do the compression test, you should get a different mechanic. Here is what the dealer should have given you, each rotor face for front and rear rotor, and a specified cranking speed:

Rotor 1: 7.5, 7.6, 7.5
Rotor 2: 7.2, 7.3, 7.3
250 RPM

Fernando Lopes

The strange thing is that the compression test was performed by a rotary specialist LOL so he should be aware of the correct way to do it.

Anyhow my current mechanic says the engine is fine. Otherwise for the forst 15 minutes there will no power also. I am waiting for the o2 Sensor results.

blckninja

iTrader: (1)

Even though he says it's fine I would still pressure him to give you the actual results of the test, it just seems a little weird that he's not giving you the numbers that you're supposed to have.

hoosier1104

iTrader: (2)

For the cat, did you buy OEM or aftermarket? I bought aftermarket and it burnt up in 6 months. There is a reason why the OEM cat is $1500 US.

If you do not have inspections, which I am guessing you do, go catless. Problem solved and one failure point taken out of the equation. You have several options if you go this route. A simple search on the site for 'catless mid pipe' should yield some results.

Fernando Lopes

Good news at least. Seems the issue is with the O2 sensors not working properly. My mechanic did fit some used sensors from other Mazda and the car works just fine for 2 hours. Now he will replace them for then new ones and finally hope that everything is finished.

Fernando Lopes

Here I am again Seems that a new set of sensors did not fix the issue. It still looses some power after around 20 minutes.

So any clues what still might be causing this?

Something related to the temperature control on the car? Could this potentially trigger something on the ECU to cut power, somekind of safe mechanism. My mechanic insists that the car goes extremely hot.

He will look into the temperature controls, radiator, etc.

Fernando Lopes

Hey guys,

I am loosing the hop at this moment. Seems that mechanics have no clue on what is going on with the car. Also Mazda dealers on my area say there are no mechanics with enough experience for my car since only few were sold.

So seems to me that I will rely only on what I can find on the internet hoping to have a light on the problem.

Fernando Lopes

So going through the list of possible causes:

chokes as revs increase

• O2 sensor failure (too rich) REPLACEMENT DONE
• MAF failure TO BE CHECKED
• MAF disconnected TO BE CHECKED
• e-shaft sensor fouled TO BE CHECKED
• accessory belt fraying

high end power loss (jerky and stumbling)

• Ignition failure SPARK PLUGS, IGNITION WIRES and IGNITION COILS REPLACED
• fuel pressure loss TO BE CHECKED
• e-shaft sensor fouled

high end power loss (smooth)

• Catalytic converter clog REPLACED
• air filter clog CHECKED OK

low end power loss (stumbles)

• Ignition failure
• front O2 sensor failure

revs slowly but smoothly

• O2 sensor failure (too lean) REPLACED
• catalytic converter clog REPLACED
• air filter clog CHECKED OK

sudden power drop at a specific rpm
NOT THE CASE HERE

• Intake valving actuation problem

trouble getting to redline

• Ignition failure REPLACED
• front O2 sensor failure REPLACED
• catalytic converter clog REPLACED
• air filter clog CHECKED OK
• e-shaft sensor fouled
• fuel pressure loss
• MAF failure

Will have to look how to check the MAF sensor and fuel pressure. As far as I know there are no error coed coming from the ECU or whatsoever. Will look into information on how to check these things.

MikeTyson8MyKids

iTrader: (1)

You really need a compression test done, get the results, and post them. The compression test above was not done correctly. There is no way your engine would start with results posted from that test.

People are trying to help you.

Fernando Lopes

Yes that is the next step. I will go the Mazda dealer and ask for the compression test with the correct output values.

I will let you know of the result.

Fernando Lopes

Again I have some more news on my car. So here it goes:

• My mechanic checked cooling system and everything seems OK.
• He did a final test to debug the power issue, of removing the original exhaust and let the car run till hot.
• He noticed that the fuel is not being completely burnt by the engine
• Fuel is then coming out after the catalytic converter and a dummy exhaust with the new temperature sensor.
• Temperature of catalytic convrter and exhaust goes extremely hot.
• He also did a manual compression test by using a manometer I believe and the compression level is good (more than 7).
• What is the reason for the excess of fuel? He believes is something on the engine but he claims I should take the car to a rotary specialist to open the engine.

So I am looking for an opinion now for you? Is it possible that could be something not engine related maybe injection system? What do you suggest me to do?

At this moment the engine is one of the few things on the car that was not checked. A lot of money was already spent on the car and for sure that if I did not want to keep the car, I would not have done it.

I am evaluating taking the car to the rotary specialist but this is so far away from my place that I would only take it there on a last possible measure.