Urgent help with loss of Power when hot on my RX8.
 

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.

What year is the car?
Mileage?

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

Get a compression test performed.

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.

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.

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.

Hi,

Please check the compression test results on the images below

Attachment 221593

Attachment 221594

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

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.

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?

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.

+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..

He said he replaced the cat.

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

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

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

So are the O2 sensors showing it running very rich? What are your fuel trims like?

I was just pointed to this thread, and I see there are a few calls for me previously.

The original compression test sheet is acceptable, if not exactly normal. Ignore the 17 and 30 psi references, and look at the 200 and count the lines. the thicker line next to the 17 and the 30 is the 8th line from the bottom/top, also known as the 'middle' line. If we assume that the 200psi at the top line is accurate, then there is no way that the 17 and the 30 would be at the same point on the chart to, just doesn't make sense. However, if we assume that those numbers aren't important to the scale, and use the middle line as '100psi', then those results (one peak for each face in sequence, you can see the front rotor face with the problem as the lower peak for every 3 peak.

The PSI numbers are then about 96/97/90psi for the front rotor, and 100/98/97 for the rear rotor (rough numbers eyeballing an average, assuming every horizontal line is 12.5psi, which is 1/8th of 100)

The Rear rotor also shows what I think is the time, of 0.167 seconds per vertical line. Assuming that is true, the math looks like the RPM of the test was about 239rpm. A really rough eyeball guess, but it looks like just about 1 peak every 1.5 vertical lines.

So that means that the compression conversion would be something just about like:
Front: 7.1/7.1/6.7
Rear: 7.3/7.2/7.1
@ 250rpm
at sea level

Again, REALLY rough. If my guess on RPM is too high, then the numbers are better. If my guess on RPM is low, then the numbers are even worse. If the test wasn't done at sea level, then the numbers get even better.

So the engine isn't stellar, and one face may very well be failing, but there hasn't been a SINGLE reference about hard hot starts, so I am inclined to think that my number guesses are lower than they actually are.


Fernando, I would take a good hard long look at your fuel pump. Hook up a fuel pressure gauge and go for a drive. See if the fuel pressure starts falling off when you start seeing power problems. The factory fuel pump can start failing as early as about 50,000 miles, with 60,000 miles being a fairly common occurance (right about 100,000kms). Most last longer, but failing then is still seen quite frequently. When they do tend to fail, "about 20 minutes" of driving is exceedingly common for when they start to cut out on a given drive.


A drop in fuel pressure from the fuel pump overheating could be generating a lean running condition which will sap power by itself, and ECU trying to correct it will continue making the situtation worse.

Hi MikeTyson8MyKids,

I don't know. These were replaced is all I know. But what outputs they are giving to the ECU I am not sure. I guess it does require some ECU monitoring and maybe my mechanic doesn't have the results for this.

Anyway car is moving to a Mazda dealer and I will request them to check this.

Hi RIWWP,

Thank you very much for your feedback.

As far as I understood, it seems that one of the rotors has definitely a problem. To be sure of this I want to repeat the compression test from another Mazda dealer and ask them to provide the results on the correct form.

The car has indeed hot start problems but from what i read this was due to the poor starter motor. When hot I just have to keep the key on the ignition few more seconds before the car is started.

I will ask the Mazda mechanic to check the fuel pump following your input and check the result.

Let us know how it goes. :)

I like the idea of getting the CAT out of the way.

It seems your mechanic is talking about the oxygen sensor. The one in the CAT just checks to see if the CAT is bad. The one further forward is how the ECU monitors the engine. If that one is bad, most bets are off.

With all the work, has the battery been disconnected for any period of time to reset the ECU. Or, 20 brake stomp it? That many changes, without the ECU reset, will leave the computer trying to figure out what is going on after it stabilized on something. This could result in a lot of fuel going through the engine, as it was rich to just keep alive before.

My thoughts? CAT, if that test worked out, and fuel pump. Mine ran a heck of a lot better with a new one.

Best I got right now.

I seem to have a similar problem. My car will get me to and from work just fine (I live about 5 miles away), but I am nervous to drive anywhere outside of town. My typical symptoms start with the coolant light coming on but not staying on (My coolant level is fine. I check it nearly every time I drive just to make sure). I then get a huge loss of power. The car will have a hard time doing 60 MPH in 6th gear. I've noticed that the problem seems to be more persistent in hot weather. Shortly after the loss of power several lights on my right instrument cluster will illuminate (I believe its the battery, oil, and one other light in that area) and the car will die. My oil level is fine. Took the car to Mazda and they had a "rotary specialist" work on it. The mechanically self admittedly has never seen the inside of a rotary engine.

I will try and figure out a way to post the diagnostics report. The mechanic said that I would need a new engine because the apex seals. The report said loss of vacuum on both rotors with the voltage dropping as the engine heated up.

Is this similar to the problem you have?
Does anyone have any input?

Here is the report.

I do not suspect an engine problem.

Every single symptom you just mentioned has one thing in common: voltage drop.

I have never heard of an engine failure causing dash cluster lights to come on at the same time, but they do come on with voltage problems. Voltage problems could also be reducing fuel flow, affecting AFR signals, affecting ignition coil output, etc...

For somewhere less than $6,000, I recommend that you clean your battery terminals, battery clamps, and all grounding points first, and see what that gets you. Grounding problems are a common cause of voltage drops, dash lights, etc...

The next step is to test the alternator, to see if you aren't actually charging it well, so while driving, you are powering everything off the battery, until it finally drops voltage too low to sustain everything, and systems start shutting down.