A little over a week ago (Sunday 9/10/2006), I had a mysterious engine malfunction: a major drop in power in the top-half of the rev range. The problem was first recognised durring the second day of a high performance driver education event (HPDE track day) in the 3rd (out of 4 sessions). However the symtoms have been persistent and consistent since that time.

The symptoms:

The loss is slight but just noticable (to me) arround 5k and progressively builds to a massive loss in power at 9k. To give an idea of how much loss I'm talking about, in 2nd gear WOT, there is barely enough power to accelerate the car: at 60 mph it takes a second or two to increase speed by 1 mph. With a slight uphill the engine doesn't make it all the way to the 9k redline: drag limited arround 63 mph in 2nd gear! There is conciderable more power at 5k then 9k (i.e. upshifting allows acceleration).

There is an abnormal high pitch pulsating noise at 1/2 throttle or more that starts arround 4k. It is loud enough to be clearly recognisable with windows open (first hear it on the track with helmet on). It kicks in at 3750 at WOT, higher rpm at less than WOT.

In addition to the overal power loss, there is an additional bog at ~6500 rpm. This bog is noticable at half throttle or more particularly in 1st gear. Engine power drops significantly (beyond the overall power loss) for <1 sec. The drop is enough that there is a noticable weight transfer due to reduction in acceleration, e.g. you get "thrown" forward in your seet for a brief moment (most noticable in 1st where acceleration effects are greatest).

Noticed that the symtoms are "less" pronounced soon after starting the car, but quickly approach "normal" severity as the car warms up.

The engine power feels normal to me at the low rev range idle - 4k. Other then the lack of power, strange noise, and bog, the engine runs smoothly and normaly. At the time of the fault there was no check engine light or pending code (used a scanner on the first day). Although, a week later I did get a seemingly unrelated check engine light (see below).


Investigation History / Additional Data:

The car is a 2004 RX-8 base 6-speed with <15k miles. Only modifications from stock are: brake pads, brake fluid, tires, and alignment. Just in case it is useful to know, alignement was adjusted at the track between first and second session (power probem showed up durring third session); camber bolts on all four corners were adjusted resulting in more negative camber (and more toe in as a side effect).

Gas was taken from same pump as day before. Filled up in morning with no issues first and second session. Also filled up two 5-gallon cas cans one of which was used by a turbo vehicle without problem.

Pulled airbox at track to inspect. Filter in good condition with no sign of blockages at entrance or exit of box.

Recall 4206F work was done on the Wensday after power loss manifested. Mazda service reported that neither cat nor engine needed to be replaced. New flash and new sparkplugs did not solve the power loss issue.

Research into the affected rev ranges has lead me to suspect the power loss issue is related to the SSV (Secondary Shutter Valve). The SSV is the part of the intake track that opens/closes the secondary ports of the renesis (one componens of the S-DAIS). From what I gather, the SSV should open at 3750 rpm at WOT (higher at less throttle). This rpm coresponds to the onset of the high pich pulsating noise that is one of the symtoms I noticed. The SSV is vacume actuated (via and electric valve), could the noise be some kind of vacume leak? In addition, since the secondary port opening normaly almost doubles the intake port area, if it didn't open the air flow through the engine would be dramaticaly reduced. This could easily explain the magnitude and general "shape" of the observed power loss.

Also at 6250 rpm at WOT the APV (Auxilerty Port Valve) should open up the tertiary ports. This rpm coresponds to the observed "bog" symtom. Does the ECU temporarily run rich here in order to compensate to disturbance in the airflow? What would happen if the secondary ports aren't open and the tertiary ports open (there would be a small increase in total port area but with strange timing)?

My visual inspection of the SSV didn't reveal any obvious problems. All vacume lines apeared to be connected correctly. I could open/close the SSV easily with my hand; the only resistance was a modest amount of spring loading. While free-reving the engine while parked I observed both the SSV and VDI open. Although I'm not sure at which rpms they opened, or what the correct ones should be at that relatively low load / throttle position. They both opened quite closely togeter in time SSV then VDI (the VDI normaly operates at 7250 rpm @ WOT), and then both closed VDI then SSV when throttle was closed and revs dropped.

The local Mazda service people had the vehicle last week for two days (Wensday & Thursday) for the 4206F recall (flash + plugs replaced), replacing a leaky taillight, and a starter recall. This didn't seem to have any effect on the power loss issue. I had the car back Friday, and on Saturday afternoon (a week afer the issue first started), I god a check engine light. I had the code scaned on Sunday morning: DTC P0455 = EVAP system leak detected (large leak). I dropped my car back at the Mazda service center Monday morning to continue working on the power loss issue and the new CEL. It is possible that the CEL is an unrelated issue (when it rains it pours ); the dealer has replaced the gas cap in order to correct it (I don't have the car back yet to confirm if this has solved the CEL). However, they don't seem to have made much headway on solving my power loss problem (its been two full days so far). Supposedly they have been in contact with corparate via the Mazda tech "hotline", and have been directed to replace the coil packs. Hopefully this will happen tomrrow (Wensday 9/20) if they get the parts in.

How likely are coil packs to be the problem? Wouldn't that be accompanied by ECU detectable issues like misfire? And wouldn't it be more of an issue only at the very top of the rpm band (7k+) or would it also affect as low as 5k?

I appreciate any ideas or suggestions anyone has with respect to this issue, and I will continue to post updates so that if anyone else has a similar issue they will have some clues.

Thanks,
David

 

David
Yep when it rains it does pour. Dont think this would be coil packs. If coils are bad it usually shows up in the higher rpms but it can show in the lower rpms also(no power until 4-5K) Besides like you say Mazda dealership should have picked up on that. Low miles on the car so I wouldnt think it would be the spark plug wires either. To do a home check on the coil packs just swap out the leading for the trailing and see if it makes any differance.
Check your maf also to see if it has any oil etc on it--it happens.
The high pitched noise sure would make one think of a vacumn leak somewhere--I would eliminate that 1st thing--rock solid eliminate.
A good A/F read would be helpful here also.
Last ----the cat is not clogged is it? Really want to check that. Did they pull the cat and visually check it or just take readings? Need a visual here to be sure.
Good luck chasing the gremlin--let us know what it was.
olddragger

 

One day more elapsed, still no solution. As expected replacing the ignition coils as recomended by the Mazda "hotline" didn't solve the problem. Apparently this was the last of a whole set of things they were checking. The dealer representative told me that the technition working on the car started looking for a vacume leak in the SSV control lines, and checked out the rest of the intake as well. Only then did they resort to trying the ignition coils.

As for the cat, I'm not sure if the inspection was visual or only by reading. I'll ask them when I talk to them again.

Apparently they are haveing some kind of "master technition" who supposedly has 30+ years of experience start working on it tomorrow. I guess that means I'm off the map of "problems" they've seen with the Renesis and into uncharted teratory. My hope of a small problem that they just didn't identify yet is starting to dwindle. Still got my fingers crossed tho.

 

were you premixing at the track???? have they done a compression test yet???

have you ever had any power loss problems on the street during long drives?

beers

 

dude - cat. My car had the SAME symptoms.

https://www.rx8club.com/showthread.p...&highlight=cat

 

coils would be down low.

don't ask me how i know.

 

Same thing happened to me. Turns out the second set of injectors weren't firing. There are two per rotor and apparently the second doesn't kick in until the higher RPM's or based on the throttle position. I'll have to look through my paperwork because it was fixed under warranty. If I recall, it may have been attributed to cats going bad and throwing o2 sensors off. I'll dig up my paperwork and see what the fix was. Coincidentally, it just started again 3 days ago so it's going back to the dealership tomorrow.

 

That is BS, and your dealer didn't do the recall correctly.

If you brought it in and complained about massive power loss FOR THE FIRST TIME then they should've road tested it. If it failed you were supposed to get a new engine. However, if you previously brought it in and it was already having this problem then according to the recall procedure they were supposed to give you a new engine right away without doing any testing.

Read the 19 page recall procedure and you'll see what I mean.

 

Make sure they have VISUALLY looked inside the cat. to make sure it is not plugged. DMP had his car in and out of the dealers for months because they kept saying the cat was fine but never inspected it. turns out the finally pulled it off and looked inside and found the cat element had come apart and plugged it up.

Make sure they do a visual inspection and show you what it looks like.

Here is his thread with his problems.
https://www.rx8club.com/series-i-trouble-shooting-95/saga-bad-cat-mazdas-inaction-110322/