Stevie Ray

For background, refer to the original thread here:
https://www.rx8club.com/series-i-trouble-shooting-95/reduced-power-more-noise-after-highway-driving-211214/

Sorry for the long post but good analysis needs good data. So...

Took my RX to the dealer immediately after a 2 hour highway stretch and made him drive it. BINGO. It misbehaved perfectly.

The dealer did the decarboning procedure called for by the “lack of power TSB. Invoice (0$) said the SSV and APV checks showed them working OK. Car had somewhat more power and was quieter with a power increase at 3K as opposed to 4-5K RPMs as it was before the decarboning. In the week after the decarboning, (all city driving) I got a CEL of P2004 (Auxiliary Port Valve stuck open on 2 CCM) but it disappeared. I later got a pending code of 2004 that also disappeared. I have gotten two pending codes for misfires (front rotor misfire, P0301) that later disappeared. The dealer saw the misfire codes but dismissed them as a persistent problem.

Performance after extended highway driving is somewhat better, but still had diminished power both on and off highway. Flooring it at 75MPH still results in very little or no acceleration and no noticeably different sounds.

I installed the OBD-2 toy…er…tool and gathered a LOT of data in the form of a time sequence photos of the gauge as I drove on a 2 hour trip and back. I still need to put the data in a spreadsheet and look for trends.

Most notably the CAT temp stays at 1550-1650 degrees while driving and a faint glow can be seen from around the O2 sensor when it’s dark.

At this point, I’m suspecting confusing diagnosis due to multiple problems. I suspect the fuel pump and weak ignition coils as the main issues. BHR’s website notes fuel pump issues that are identical to the symptoms I’m experiencing. I’m also suspicious of the CAT. RacingBeat says the CAT temp should not go above 1652. Mine goes slightly above that and comes down quickly when I back off. No clear indications of CAT clogging but I wonder.

Any and all advice and thoughts are welcome!

Mazurfer

Will answer more later with my thoughts, but EVERYTHING you said about your CAT temps are right in line with what I see. Not sure about the glow, but your numbers mirror mine very closely and we are in the same area, so we are driving at roughly the same outside temps and conditions.
I have seen that data from racing beat and have always wondered how accurate that statement really is.

Stevie Ray

I noticed my CAT temps were above 1700 today in the warmer weather.

Mazurfer

Okay, I've been wanting to start a thread about this EGT for a while, so look for one shortly.
As I said before, I saw that max temp on the RB site as well and was questioning it.

Example: It's now 7:10 am and I just got to work. After what I will call a warm-up of a mile or two, I held 3k rpm's in 4th gear at right about 42mph for quite sometime and my CAT temp was 1540-1550. Letting it return to idle it would drop back into the 1340 range, which is about what I normally see at idle. Then about 10 miles later, I do my WOT run taking it very near or at redline in 2nd and 3rd gear on an uphill climb getting to roughly 82mph. During this run, I saw very close to your 1700. After that redline in 3rd, I shift to 6th(usually) and continue the rest of the drive(50mph or so in sixth) and the temps dropped back to roughly 1550 once again.

Mazurfer

"I have gotten two pending codes for misfires (front rotor misfire, P0301) that later disappeared. The dealer saw the misfire codes but dismissed them as a persistent problem."

I never did like this statement that was made by them. Misfires are misfires and either a sign of weak coils(most likely), bad plugs, and in some cases wires. I have had my car since December of 05 and have NEVER had a misfire(flashing CEL or code thrown). True, I'm not on stock coils and haven't been for a very long time, but I really do think you should go after these coils. If you have a weak one(evidence by misfire), then as you drive for long distances and it really gets warm, it can only get worse. This can lead to all kinds of other issues and eventually can lead to serious type issues.

WingleBeast

cat, cat, cat.

had same issue, and it got to the point where i couldn't drive above 25mph. get a midpipe and coils before you mess with the fuel system. a clogged cat can cause spikes in fuel delivery that mirror a faulty pump (Charles and i discussed this a few months ago) An easy way to tell is to look at your short term fuel trims, if it spikes rich, your cat is most likely toast, if it spikes lean, it may be a pump issue.

Mazurfer

^..............don't think you can make this leap for him yet until he gets rid of the supposed mis-fires, but I could be wrong.

I'm still making that thread I spoke of because I am wondering if a clogged CAT or the beginnings of one would show up in EGT's? His EGT's and mine are about the same, and I have no issues what-so-ever.


I started the thread I intended to start on EGT's................... https://www.rx8club.com/showthread.p...34#post3897834

WingleBeast

my cat melted and it dragged the coils down with it. I mean instantly. I drove 100 miles to atlanta fine, then 20 miles into the trip back home my power is gone, cat is glowing, and my car is literally bucking at full throttle because my AFR is trying to correct itself from the massive rich dumps of the misfires. It seems like a fuel problem, or even a coil issue; but the real problem is your cat is at least 30% blocked off and the increased pressure is killing your coils and causing misfires. Now I could be wrong, but honestly this is the most preferred problem as it is the cheapest. Just pull the front of your cat down and look inside. dont go replacing tons of stuff when it could be a $300 midpipe away from being fixed. Some people get new engines and just have the same problem cause the dealer never looking inside the cat.

MazdaManiac

iTrader: (3)

A glowing CAT is a dead CAT.

Stevie Ray

The only glow I can detect on the CAT is coming from around the O2 sensor. When you say glowing, do you mean the body of the CAT?

Stevie Ray

I looked for the 1652 number too. Didn't find it. I know I didn't dream it!

Stevie Ray

Here's some data from my recent highway trip, averaged over two 1.5 hour trips on the same day.

Ambient temp 60 - 64 deg F. Avg speed 77 mph, Avg Cat Temp 1642 deg F, Avg RPM 3943.

FLYN8

I agree with this, I had a power issue years ago in an Alpha Romeo; I disconnected the cat at the front side and looked inside. I could see deformation of the honeycomb. Not sure of the relevance to today's cat. but it seems worthwhile checking.

Here's the link to my similar engine issue:

https://www.rx8club.com/showthread.p...=1#post3955740

HiFlite999

iTrader: (2)

Yeah. The heat shield itself generally won't glow.

swoope

iTrader: (5)

what are you getting the cat temp from? how many miles on the car..

does it happen after a long cruise? ~1.5hrs?

beers

Stevie Ray

60K miles on the car. Cat temps are in the 1670 range on 80 degree days in normal suburb driving. Cat tems didn't change after replacing ignition coils, wires and plugs. Restored the low end power I was missing and restored the normal exhaust sound. Much higher power overall. Have not had it on the highway after the new ignition parts.

I still suspect the fuel pump.

stickyRice

Any news on this?

I'm having your same symptoms on my '04 110k. I've changed the plugs and coils (not wires), and the problem got slightly worse. My situation is different in that it doesn't take two hours to manifest, more like 10 minutes.

As for cats: My cat died a year and a half ago, so the dealer gutted it for me (they wouldn't warranty fix it because apparently I ran over something that deformed it.. meh). Anyway, this problem of ours does seem in many ways like a cat problem, but in my case it certainly is not.

My fear here is that I'm dealing with a blown engine, but I don't want to take it to Mazda because I don't trust any of them... I guess I just had such an awful experience with the cat, that I don't want to fuss with them any more -- and nothing is warranty covered, anyway.

Let me know about your fuel pump hypothesis.

DeViLbOi

iTrader: (1)

The dealer can't legally gut your cat for you...heck...nobody can remove an emissions device like that legally for street purposes.

FLYN8

Question is: is this the original engine? If it is, I would say your apex seals are shot. The older cars have a different type of seal and when mine failed at 37000 miles and 7 years old they swapped the engine no charge.

FLYN8

And one cat.

stickyRice

It's true that no one can legally gut the cat, but they did. It was under 80k and they told me I'd have to come up with $1400, so I told them to button it up and forget about it. I know it's gutted because I took it apart and saw it for myself. It's the only noble thing they did for me.

As far as I know, it is the original engine. How many thousands of dollars would I be looking at for a rebuild, do you think?

jamesog

I'm having the same problems as the op. Decreased power while driving on the highway and such. Coils were replaced about 2 months ago along with plugs. I decided to check my cat last weekend and it was perfectly fine. No noticeable problems with the honeycomb pattern unless there's something I'm visibly missing. Not really sure what the problem is and don't want to take it to a dealer just to pay them to diagnose it. If anyone has any solutions let me know. I might try the carbon cleaning and see if that helps.

FLYN8

https://www.rx8club.com/showthread.p...=1#post3955740

Having the dealer check will be worth it, as they replaced my engine at 71/2 years old, no cost.

jamesog

Thanks, yeah that might be my only option. I've heard of fuel pumps going bad and exhibiting problems like mine. Anyone else have any information on this being the case?