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: