DTC P0139 - And rough idle
 

My car, inspite of all my maintenace, its running quite rough at idle and idling low. I got a random CEL yesterday which turned out to be the DTC for the rear O2 sensor, I have the RP cat, but I doubt that should be affecting the life of the narrow band sensor given it should run cooler than the stock cat.

Any chance the rear O2 sensor could affect the idle? I wouldn't think so, but i wanted to ask.

Probably not. That is just a collateral symptom. You are running rich.
Have you cleaned you MAF since you installed the RB intake?

EDIT - You are running the Int-X and you just now got a CEL ?!?
Since the MAF doesn't figure into the picture on the Int-X, I'd say you should play with your ignition timing and see if you can get the idle mix up to stoich if possible.

right now, the PCM is stock, so its not the int-x

cleaned MAF, TB and accordian hose two days ago. Plugs and coils are less than three weeks old.

I don't know if this was resolved but the service manual suggests several problems could be the cause of a PO139 code. Purge solenoid valve, loose sensor, low fuel pressure, AIR system, coolant leakage and PCM malfunction are just abbreviated listings.

Most rough idling issues are caused by plugs, carbon buildup on various engine parts, and/or dirty injectors. Since you have replaced plugs, I would try to clean out the injectors and combustion chambers with a really strong cleaner such a shock dose of FP60, BG44K, or Redline SI-1.

Does the BG44K really work? I may try it just to eliminate another variable in my own pursuits.

For a one-time cleanup, it is the strongest stuff out there, period. It cleans everything - injectors, combustion chambers, etc. When you use it, the exhaust actually smells different from the solvents and cleaning going on. Should only be used about every 7.5k to 15k miles.

Only downside is it is expensive at about $18 a can.

I may try that but my dealer just told me that my compression and vacuum are low and I am getting oil in my intake due to blow-by past the side seals. Looks like time for porting/polishing, rebuilding, and a new EMS so I can get to the next level of performance. I'll also march on to that 150 shot of nitrous I have been seeking.

Oil in your intake due to seal blow-by? Sounds like hogwash to me. Any oil blow-by would be burned in the combustion process.

Sometimes poor compression is not due to wear, but due to "stuck" side and apex seals (like stuck rings) from carbon, varnish, and/or sludge.

Before rebuilding, I would try something like Lube Control LC20 in the oil (not FP60) at a cleaning dose or possibly Auto-RX. These products are very good at cleaning engine internals (melting carbon, varnish, and sludge), freeing up the seals to let them do their jobs, restoring some compression. Your engine might not be worn out, but just dirty inside, causing the seals not to operate properly and causing the compression loss.

Worth a try IMO - a lot cheaper than a re-build.

Thx for the heads-up. I'll try that first and see what happens. If it doesn't work I'll just pull the engine and go full-tilt on it by summer.

I found a local spot that had the product so I'm going to give the BG 44K a shot. Swoope swears by the stuff and I think he drives the car even harder than I, and he felt it helps, so I'll be curious to see how it works.

Will it be ok to use it over a long trip while cruising? I'll burn a whole tank of gas over two days driving to the Alamo bowl, but I don't to make it less effective by just holding a certain rpm.

alright, BG is in, lets see what happens.

Using on a trip will work fine - I would occasionally try to rev it up to redline (on ramps) to get the treated fuel into your entire intake for cleaning.

DAM! I never knew that shit cost that much! :Eyecrazy:
I get that stuff free at work(personal use). :ylsuper:

Braggart!!

I've been driving the car hard before the trip, last night I redlined it in 3rd gear several times to get the stuff in all the injectors. If it wasn't raining today, I'd rag on it somemore.

Weird - my mechanic asked me if I had injector problems yesterday. I said nope, and why? He said that Mazda is chattering about them lately.

I got an oil change and my car started to idle rough. I'm thinking MAF and/or spark plugs, due to oil being spilled. I'm thinking the just wiped it up and did not say anything about it. Before I took it to the local gas station, my idle was fine.

I also used Gumout concentrated fuel system cleaner (can be used every 3,000 miles). It did not seem to solve the problem. But, its obviously going to take a little while for it to clean the fuel system and it can cause the idle to be a little rough too. my idle was already rough, prior to using Gumout fuel system cleaner. I also have Redline SI-1, but have not used it, as I used the Gumout.

I'm having the dealer check the MAF (cause they are not cheap to replace), spark plugs, etc... I want somebody to blame if something gets messed up or not fixed. If I clean the MAF, than I have nobody to blame, but me if it gets screwed up. If it does fix the problem, than I will clean it myself in the future.

If/When the problem is fixed, I will tell what worked for me.

Montgomery Mazda, aka OnLineMazdaParts.com, has MAF sensors for less than $140.

haven't heard anything about injector issues, since they are kinda a commodity product and not rx8 specific.

Anybody know of major retailers that might have the BG44K? I went to BG's website but they only list shops that perform the whole BG process. I want to run the BG through my engine and do the LC20 number on the oil. Then switch to mixing the FP in the fuel all the time. I am dying to get started because I am more and more thinking that Jax is right about carbon and varnish in my case. Oh yeah, I wanted to add that since I got the "emissions" reflash my idle had been a bit shaky and, more importantly, my off-idle transition during acceleration was jittery/shaky from 1,500-2,500 rpm's. I happened to do the e-shaft profile reset and it seems that the jitteriness is gone (for now) and my idle is much better and steady at 800 rpm's. Input anyone?

Unfortunately, major parts stores do not carry BG products - only authorized service shops and dealers. But, most of the shops that perform the full BG services will also sell the products separately. If you can't find one that will, contact the "distributor" for your area (find on the website) and call them for guidance.

check pm.

beers :beer:

I have a ton of BG service shops in my area so it shouldn't be too tough. Thanks you guys. BTW, after I reset my e-shaft profile(the idiot tech who did my comp. check didn't clear them before I got my car back) my car ran a little smoother and today it was about 50 degrees outside and it ran MUCH smoother and pulled hard to redline even in 5th gear. And that's with the factory cat in place. I just put my catless pipe back on to see how it runs tonight. Got some good weather and I don't want to pass it up. Sorry for the hijacking.....

also the new flash takes SEVERAL drive cycles to settle down... it really does..

beers :beer:

Do you think that two weeks ago, when I had the "emissions" reflash done, they were supposed to reset the e-shaft profile too?

one would hope.. but you know. if you want it done right...


beers :beer:

And I did...

Update, and then I am done here and the original author can have his thread back; after driving my car for most of the day I can say that it is running very well. It drives, shifts, and sounds as smooth and powerful as it ever has. Last night I put my catless midpipe back on and picked up the power that I normally would have expected. As a matter of fact, my car is back to being the beast it was back in August of 2004 and I now cannot wait to get back to my pursuit of a 150 h.p. shot of nitrous. A few simple things to tackle and I'll be back on track to those 11 second 1/4 mile times I have been aiming for. Consider this thread "unhijacked".

Interesting. I should really check the forums more often, I learn a lot from reading all of these posts.

Very glad to hear your car's back to normal, Charles. Do you still think you have a compression problem, or was it just a matter of resetting your e-shaft and PCM to get your performance back?

I'm thinking about taking mine in for the emissions recall, to get the latest flash, but just a little concerned after hearing about the oil in the intake and stuff after the flash. I know how to reset the PCM if the dealer doesn't do it, and I'm sure there's a thread out there that explains how to do the e-shaft, right?

Not trying to hijack the thread anymore.....:)

After conferring with MM about my compression values he and I both suspect the measurement process was done improperly, to some degree at least, which would have brought the numbers down. Most likely it was failure to warm the car up for at least 10 minutes prior to testing. That's one of the things I will be re-checking before continuing the nitrous project. As far as performance goes, what I can tell you, for sure, is that I had the 4206f reflash done and the car didn't run any better and maybe even became a little rougher. Once I had reset the e-shaft profile(that's the 20 brake pedal taps within 8 seconds deal and there is a thread about it) the engine started running much smoother and stronger. To have a poor e-shaft setting in the first place could be a possible cause of high rpm misfires and maybe poor cat performance because the PCM doesn't know exactly where the crank is. As for oil in the intake, that may be just a coincidence but I am keeping my eye on things and if it goes away that would be weird but certainly welcome. What should you do? I am not sure what to suggest, but only to ask which flash you are on now so as to be sure you are getting enough MOP oil in the first place, especially with nitrous use.

Ok, ran the BG-44K through the car, really had fun burning that tank of gas as I was hard on the car to make sure all the fuel injectors got some love. Its to early to tell if my idle is better, I’ll watch it this week and see how stable it is vs. before. The car pulls smooth and generally feels better, but that could be all in my head. As far as gas mileage goes
My trip home from San Antonio today was interesting, the first leg, which was 115mi, I got 25.11mpg doing 70 with no A/C. This was with a little premix and temps in the low 50’s.

The last 65 miles I decided to drop down to 65mph just for testing, as I have gotten almost 27mpg at 65mph once coming home in bad weather conditions. I ended up getting only 23.59mpg going slower! HTF does that work? This is actually the second time that has happened to me. I got about 24mpg with the A/C doing 70mph, and then tried testing the 65mph and also got about 23.5mpg.

(in case your wondering why I care about 65mph, its because the Mazmart 4.11 rear end would have you cruising at the same RPM doing 70mph as our cars do stock cruising at 65mph) - Note: I do not have this mod, but am pondering it.

Was it a fluke? Is 65mi not enough to test mileage? I feel good about the 25.11mpg number b/c I’ve gotten around that a couple of times, but why the hell would it get worse with less load?

Because the Renesis has differing efficiencies and A/F ratios depending on rpm's and lower is not always better. BTW, brillo, do you have an on-going discussion/thread regarding your 4.11 swap and the differences you have noticed with it?

I don't have the 4.11 yet, sorry for the confusion, although I am considering it.

the AFR's looked the same to me on my wideband, but it is possible there are spots in the power band that are more efficient than others.

i find that 68 to 72 is the sweet spot. the ac seems to be a 2mpg hit. brillo, after the cleaning i would reset the ecu..

beers :beer:

Peak torque (and, therefore, peak VE) is at 5500 RPM.
The best fuel economy for the engine (without respect to gearing) happens at that point.

Now, as far as how the PCM decides to inject fuel, there may be an over-rich condition there for EPA concerns.
With the Int-X, you can run the motor at 15:1 or so at that RPM and you will see maximum MPG.

IIRC, 5500 RPM in 6th is probably 70 MPH or so.

[QUOTE=

IIRC, 5500 RPM in 6th is probably 70 MPH or so.[/QUOTE]

not sure what you mean by this as 6th gear at 70mpg is a hair under 3400rpm

Yeah, I don't know. I've never had that speed-to-gear relationship going.
I go tach-to-gear and base it on sound.
Consequently, my speedo is often in triple digits...

So you are saying this was your problem all along ?
Have you run any cleaning products through the tank yet ?
Cheers
Brett

Heard this story from an ex rotary mechanic the other day . He says they used to get a lot of RX7s come in running poorly - low on power & generally rough .
What they did was put the car on a dyno & run it up to max revs under load . They would then pour a cleaner product (can't remember what it was) down the carb for about 2 minutes smoking out the whole neighbourhood in the process. Once complete the cars would be back to normal power - No engine rebuild required .

Sorry, I was a little confused about the terminology of what was actually being reset. Here's the official doc, in case anyone's interested:
http://www.finishlineperformance.com...30-05-1544.pdf

25MPG?? That sounds great. The best I have EVER seen was 23 on a tankfull. Lately I've been averaging 17-18, but that's mostly city driving with some high speed highway thrown in. What is the premix you're talking about?

Never mind. I found a sticky out there devoted to premixing 2 stroke oil with your fuel. It sounds very interesting and I don't want everyone to start posting about it here, since there's already a thread devoted to it. I may try it.

Was it "Seafoam"? Seafoam is poured directly into carbs or sucked into the combustion chamber via a vacuum line for cleaning - it is known for its HUGE smoke trails while cleaning.

I am not really sure what happened with my car, nor do I know if the e-shaft reset was the cure all along, but I am currently quite pleased with the way the car runs and performs and took it out Saturday night for a little fun. My current girlfriend has been my "co-pilot" for the past 6 months and she not only noticed the difference since the reset, but also became intimidated when I did a couple of full-throttle punches here and there. We also managed to get in a full "pass" on the way home and it was STRONG. She was speechless. Rather than get into it all here, I have decided to post my plans over on the "Direct-Port" thread.

Don't know - I'll ask the guy next time I see him .