Ok from my understanding the IAT is part of the MAF, correct?

I understand "heat soak", but maybe not fully.... After driving home in heavy traffic I plugged my scan tool in and was checking some stuff out, I saw my IAT was reading 140-150*f, that sounds really high, is it?
The car was just idling for about 20min or so after I got home, I had the hood open too. Outside air temp was right below 90*f. The intake tube sure didn't feel like it was at 150*f either.

Next issue, about a month ago I had gotten a compression test done by Mazda, the tech said the numbers were good, but 2 of my coils (1&4) were out of spec. Odd, since they had less the 2k miles on them. I decided instead of buying more shitty coils I would save up for the BHR ones.(Still saving up btw ) At the time of the test, the car was running GREAT and I mean it. MPG went up, idle was smoother, I was happy... Fast forward to this past week, now I'm not so happy. The idle has gotten really shitty, and for some reason it "idle hunts" after I fill up with gas (1.5k-800rpms, Kind of like my FCs use to do warming up) for about a mile or 2, then it acts normal, also there is a SEVERE lack of power in the higher rpms (+5krpms) when it's doing this. After a few miles it returns to it's normal happy self. My scan gauge shows misfire counts but I have yet to fully understand it.....
It reads....
Cyl.1-
EWMA Misfire Count
-Measured - 4
-Min - 0
-Max- 65535
(Press Down arrow) Still Cyl.1
Misfire Count Last Counts
-Measured - 3
-Min- 0
-Max- 65535
-System- OK

Moving to Cyl.2
EWMA Misfire Count
-Measured- 13
-Min- 0
-Max- 65535
(Press Down Arrow) Still Cyl.2
Misfire Count Last Count
-Measured- 56
-Min- 0
-Max- 65535
-System- OK

I assume the above means one or both of my coils for the rear rotor is crapping out? Anyone care to break that down to simple english? Should I just use some of the money I have saved now and buy 2 coils and replace 1&4? This all seems odd since my MPG are still going up, so I'm totally lost on this....

Next question, Coolant Temps... Okay so my coolant looks like its in real shitty condition (I got new coolant and flush sitting in the trunk, waiting for a day off), I'm more concerned about what normal operating temps are. (So I can also compare old coolant temps vs. new coolant temps) While driving around in moving traffic, the coolant is anywhere from 185*f-215*f, in stop and go traffic it somehow manages to stay at a constant 212*f (I don't drive it hard in heavy traffic). Is all this considered "safe", "normal"? The highest I've seen it go was like 222*f when I was really pushing the engine. And it took maybe a minute for it to drop to 212*f when I stopped driving like a dick.

The cars history, (to the best of my/Mazda's knowledge )
-93* chevron fuel with premix. 6oz per fill-up from the 1/4 mark.
-3rd engine, about 47k on it.
-Compression tested 3/16/11 - OK
-Oil was changed at 300mile intervals 4 times when I first got it, I was attempting to get all the old black oil out, worked too. Every time I switched to a heavier weight. Started at 5w-20, slowly moved up to 10w-40. About 1.5k miles on this oil, had to add 1/3 a quart of oil last week to get it back near the full line.
-Coils(OEM)/Wires(MSD)/Plugs(NGK) changed about 3-4k miles ago
-Tranny fluid changed
-Seafoamed twice, and 1 treatment of Mazda's "Zoom-Zoom" cleaner done by the dealer.
-Stock
-Cat is on its way out, rattles, straight pipe to replace with soon.

Thanks for all the replies,
-Shawn

 

Your high rev issue is caused by your failing cat, it does slightly affect idle. You might wanna try cleaning your maf sensor and throttle body.

Your coolant temperature is similar to mine with similar ambient temperature.

 

180*F for coolant temp is the MINIMUM for norm op temp. People easily get into the 200*F+ range without issue.

Have you checked your MAF/IAT sensor? May need a good cleaning. With your description of "idle hunting", it sounds like both can be dirty.
Or maybe the CAT, like yiksing mentioned.

 

Yea, I've cleaned the maf And throttle body the last time I seafoamed aswell sorry forgot to list that.

 

Its time to gut the cat.

 

I was thinking about trying what someone posted about, they only gutted the back half (keeps the CEL light off). Sorry don't recall who said it, but what do I got to loose right? The cat is defiantly rattling. If I get no improvements I'll beat the whole thing out I guess.

But I'm still lost on the "car running worse, but better mpg" part..... My driving habits are pretty much the same week after week. And I'm pretty sure a clogged cat would cause worse mpgs.

 

Well, I got a lot of crap done today... On my way to my parents home to work on the car I left the scanner plugged in.

Cruising @ 80mph Coolant Temp was 190-195*f, Outside Air Temp - 80

I flushed the coolant and refiled with 40ish%Coolant and 60ish%Distilled water, also added a bottle of water wetter.

Changed battery terminals.

I looked at the cat, and it looks like I'm fucked.... I could undo the cat on the manifold side if I wanted to, but the rest of the pipe seems to be welded all the way to the muffler . Looks like I will have to bring it to a muffler shop now.

On the way home I was checking the scan gauge out again and cruising @ 80mph my coolant was at 182*f, Air temp - 90*f, IAT read 127*f So I'm happy with that result. Still wondering about that IAT sensor...

Checked the misfire count, Cyl-1 = 3, Cyl-2 = 36, so it seems I still have a problem here....

MPG have gone to **** due to excessive idling times this tank.

-Shawn

 

The stock RX8 exhaust does come apart right about where the rear wheels are with two shoulder bolts. If you don't have those you might want to start looking at exhaust options beyond just the straight pipe. If you can get the cat to drop, which I don't think you will be able to do, you could inspect the front of your cat to see if it is failing/failed.

 

I might have missed it then, I recall a cross member blocking a small portion of my view of the pipe. I will reinspect it Tuesday.

And my MPGs continue to rise.... 17.6 this tank..... So confusing..... I know I did a lot of hwy driving but I also had the car idling for over 2 hours on this tank..... Not to mention while on the hwy I was doing +80mph..... Also the ECU was reset.

 

what are youre fuel trims?
coolant temps over 220F is firting with problems.
Engines will ALWAYS have some misfires--no blinking CEL--correct?
Your cat, if bad, will probably have the damage in the front brick not the rear one.
IAT's on the oem intake are high. Even racing Beats with their ca scoop will see 10-20degrees above ambient.
But at the same time you will not see a great improvement in street performance by converting to a true cai. You would see a little, but hardly enough to tell.
rather than buying the coils, I would invest 1st in something that will get your coolant fans turned on earlier---90degree weather is coming and once it gets over 95F it really hurts.

 

-Not sure what fuel trims are, sorry. The car is stock. The scanner says I'm always in Closed loop, it only goes to open loop when I'm engine braking.

-Since yesterday I haven't seen Coolant temps go above 205*f, but today will be the real test when I go to work.

-No CEL, no pending codes.

-I had a fellow 8 owner confirm it was the cat rattling, he stated he had the same noises and a few months later replaced it with a mid pipe and has been trouble free since (minus a CEL light for it).

-I also noticed its about 30*f off even when I go for the first crank of the day (IAT will read like 115, when its 80 outside). Time to replace it? It's got 92k on it.

-Not looking for a CAI, from what Ive been reading they are just good for making sounds.

-Would you recommend buying something like this?

http://cgi.ebay.com/ebaymotors/ws/eB...%3AMEWAX%3AVRI

Seller claims it turns the fans on around 180*f.

Thanks
-Shawn

 

For the misfires, can you clear out the history for the misfires, and then switch the coils from the rear rotor with those for the front ones?

If the misfires follow the coils, then you know they are the issue.
If the misfires stay with the rotor, then its something else.

BC.

 

well I think you will get a cel if you bypass the ecm fan control? But I am not sure.
I like the one that flex a lite makes--its variable, you can set it your self (hi and low settings) recognizes a/c and has a cool down feature.

 

I don't think it bypasses it. It just turns the relays on at 180. The ecu should still be able to turn the relays on for the a/c or whatever else it deems necessary to do so. I guess we will find out cause I bought it when I woke up.

 

Small update:
The fan kit has come in and is installed!
BHR ignition kit is ordered!

Even after my coolant flush I would see temps from 203-213, fans came on at 212 and turned off at 203.

With the fan kit I have not seen the temp go over 190, most of the time it floats between 181-186. Very happy with this result. If feel a lot more confident about taking on the summer months down here. I would recommend this to anyone in the southern region.
Btw the ecu can still control the fans. They come on with the a/c no matter the temp. This was a 1 beer job, very easy took maybe 10mins to install. The only downside I can see is it might wear the fans out sooner.

Will update again once BHR kit is in and installed.

-Shawn

 

Hey Shawn any updates?

 

Lets see...

Coolant hasn't gone above 205*f (to my knowledge) since installing the kit. Although now that I know how it works, I would just wire a switch to turn the fans on when I want and save the cash. But it has been working flawlessly since I installed it. On the Hwy I stay at 181-183* still. In heavy traffic with a/c (summer temps) 190-205*. No real complaints.

Never got around to changing the maf/IAT. Still will always read a little higher.

The car still "idle hunts" after a fill-up, but I just learned to accept it.

The cat blew itself out.

I love the BHR kit, no issues at all.

My current LTFT (I know what that is now!) is 5.5%, seems ok.

About once a month I still get a random hard start. Takes about 4-5secs to start rather than the normal 1-2sec.

Recent drive to the sticks netted a 21mpg avg.

Now also burning a healthier amount of oil after cleaning my lines and nozzles, and manipulating the vacuum line to the nozzles.

So it seems the engine is doing fine.


Fix my dsc/tcs light and get a free cookie!

-Shawn

 

We could get together to compare. U could try my maf
It's brand new. I'm having a problem also, maybe we could troublešhoot that also?

 

Yea man, sounds good. I'm free Monday and Tuesday coming up.

What kind of problems are you having?

-Shawn

 

I just got I Missouri today, I'll be back around the 11 of jan maybe then? Just idle issues mainly.

 

Sure man, just hit me up on a pm when you get back in. Happy New Years!

-Shawn