Ruff idle and sometimes stalling

[Ziad Joumaa]

I have an 08 Mazda S3 that was brought to me by a friend of a friend. The story is old engine went and they paid a shop to put a be one. Now it’s been running ruff ever since with a strong gas smell/rich smell. It was later taken to a reputable tuner who smoke tested it replaced a bov that was also jb welded back in. Comp tested and re mapped via cobb. He came to the conclusion it might need injectors but hed need to send them out to be sure. Owner didnt feel like spending that much more.

Something concerning me is the shop put jb weld on the top of the spill valve/relief for whatever reason. It holds 900-1000 psi of fuel pressure at 700-850 rpm idle which seems too high to me. AFR’s sit at 14.7-15ish which is acceptable to me but doesn't explain smell.

Things I've done:
Removed injectors for inspection and they seemed fine, gave them a back yard cleaning wth a ultra sonic cleaner reinstalled with no change. I know im suppose to do seals and i cringed re-installing but i couldnt justify telling him to spend X $ for a maybe.

Replaced Plugs because they were gapped to .16-.18 which seemed very tight to me and regapped new ones to around .27, car idled better and stopped throwing a miss fire code, yes i think 2 were fouled.

Smoked test again as well as a coolant pressure test thinking someone might of missed a vac leak or turbo seals were going because the intake/throttle body section was disgusting.

Removed MAP and tried running but it starts and dies immediately or wont even run. Seems odd to me every car ive done this with will run somewhat but if it has no reading it’s basically not running.

Conclusion:
Im very focused on the hpfp section now because of the abnormally high reading at idle even though during accel it does go up to 1400-1500ish psi but it will not go lower then 900. Also the jb weld thing has a story that no one knows. Im pretty capable but I wanna be more confident before i start throwing more money at it because it will get pricey fast.

Mod list: some sorta dp, maybe a cat back, cai, aftermarket bov, Cobb piggy back,

Let me know if any more information is needed, appreciate everyones time.

 

[Mosbey]

Hey I had the same issue and I messed with injectors, fuel pump, and fuel press tx and fuel press relief valve and no joy! The fix was when I realized some injectors were not squirting (no change when coil removed and dry plugs) hence high HPFP press way too high all the time. Then I replaced the fuel injector drive module ,it was obvious when replacing that it was damaged from corrosion and the split line opened up . Once module was replaced idle was normal at 420 or so and solid on. Check where the steel bracket attaches way too close to the aluminum module bottom plate .This creates dissimilar metal corrosion and the aluminum swells and causes module split line leaks and eventual failure .Mosbey

 

[Awafrican]

Please tell you mean .0.27" plug gap otherwise it'll run log dogshit, if you do mean .027" why do people feel it's okay to omit the zero? It makes a very big difference. Is "around" Jesus spec is .026-.028" don't be going with "around" it's not hard to land it right on .027" if you wanted middle.

Should run without MAF not MAP afaik.

What size intake / brand ( MAF housing), wondering, if MAF cal is off as I can tell you as a fellow Canadian there are no tuners that I would let tune my car in Canada, the only one I'd consider is stratified in BC if it was lex personally. Was it tuned by this tuner or just a Cobb ots map? I presume by Cobb piggyback you mean accesport? (Which is not a biggy back device). That tuner sounds sketch JB welding stuff on, what is the idle set at it could need an idle bump.

Hpfp presume during accel is fine, if you're wot it should be above 1600psi... Normal acceleration numbers you've given, but idle number seems could be high but not of concern. As for injector seals there's no need to pay money for OEM seals you can get the GB remanufacturing kit from rock auto
https://www.rockauto.com/en/catalog...1447278,fuel+&+air,fuel+injector+o-ring,13679

Why did the shop that did the engine swap think it's okay to give it over like this? I wonder if there is a loose ground / connection somewhere

 

[Ziad Joumaa]

Appreciate everyone getting back to me, as for the first reply i went ahead and bypassed the resistor box and had zero change. This might tell me something. Im reading on here guys are getting .8-.9 ohms and im at .4 at room temp. This is telling me im out of spec.

Yes i meant 26 mils not 1/4”+ my bad , im a millwright too that actively machines i think its because i say 27thou not .027”. The intake is a cobb pos thats jammed so hard against the battery tray. The previous mechanic not tuner that delivered the car like this is the biggest idiot and has no integrity with his work. The tuner was a guy from edmonton Alberta and i know hes done some of these cars. Cobb maf housing but will not run with it unplugged. It will only start then immediately die. It has a cobb tune stage 1 (i assumed it had to be plugged in to work might be a suby thing?). Also idle adjustment is currently set off so i assume whatever factory is. Id be happy to go through the grounds on this car ive had lots of experience with bad grounds but i didnt notice anything first look without having a diagram with me. Appreciate the link for seals and when i drove it i saw it hit 1500ish max. As much as i trust your experience I havnt found an example yet where someone idle fuel pressure is 900-1000 i even messaged guys on marketplace to check and they all said 500-600. Im gonna throw a fuel pump resistor box thing but continue to look for whatever anyone suggests.

Let me know if you guys need any more info, pictures etc

 

[Awafrican]

Yeah idle fuel pressure is high, perhaps spill valve sticking? Nah Cobb access Port doesn't have to be connected to run, I'd try stage 0 while trying to diagnose things. Good news is that's a stock sized.maf housing also chatting to one tuner the Cobb TIP actually flows the best of all the stock sized ones out there but yeah it can be a little tight, especially if it's not fully seated on the turbo...

If you're un familiar here is a great thread on how to clean the hpfp and by proxy the spill valve
https://mazdaspeeds.org/index.php?t...nd-spill-valve-michael-rey-facebook-kit.8069/

If you're looking at the hpfp there is a ground near it that seems to be the cause of a lot of issues


Other issues that I've seen caused are due to non-oem cool pack

@Enki remind me / us please what's the cause of car dying when MAF unplugged

 

[Ziad Joumaa]

I never wanted to be that guy that found a fix and never updated the forum. First, I would like to say thank you for everyone's help and advice. I have learned a lot about these engines since January.

My biggest problem was I could not find parts for this car at all in any junkyard (I wanted to go with junkyard parts because I was taking educated guesses on a lot of stuff here). I eventually learned very recently that the cx7 is essentially the same motor with a different turbo and I was able to find a lot of cx7 parts and that's when I started working on the car again. I went ahead and replaced the injector resistor pack and the Jb welded spill valve. I also checked the grounds back in February and made sure everything else from the swap was acceptably done. After replacing those parts I immediately noticed I am finally seeing proper hpfp pressure at or around idle (resting at lows 5's - mid 600's). Now the vehicle still had a very minor stutter/misfire but it would not kill itself like it did so I know I was on the right track. I went into more diag at this point knowing I was close. The first thing I thought of is if I disconnected the maf to see if it would act the same as before (readings I was getting were 5-6 g/s at 850ish rpm at full temp). The car settled itself out the ran as it should. I went out to a local junkyard got an oem mazda 3 maf from a na car threw it in and also reflashed the car to the "stage zero" option using the cobb tuner, just to eliminate everything. Started the car and it was back to normal. Let it warm up to temp went for a spirited drive came back and now I'm seeing readings of the maf at 3-4 g/s and the same idle speed. Also, put the tune that it had back on it and again it's been good since (3 days). Very unimpressed that the tunner could not see what I see given the nature of his job, I'm gonna assume he didn't wanna get into it.

Safe to say I will never own one of these given the problems I've seen but it definitely was worth the drive and now I know why they are popular and also very fun.

 

[Awafrican]

Glad you got it sorted, sounds partially like neglected maintenance. Out of curiosity who tuned it?

 

[Ziad Joumaa]

Glad you got it sorted, sounds partially like neglected maintenance. Out of curiosity who tuned it?

looks like there is a cobb stage 1-2-3 then there is 3 tunes under the name stratified (loud crackle, no crackle and something else) but just to be clear he was not the one that we gave to try to diagnose after the engine replacement. I didn't know it had it till 2 days ago.

 

[Awafrican]

dam crackle tunes, poor stratified has fallen I remember when the choice was freektune or stratified (when lex was tuning). Stage 0 should be your simulated stock map, cobb ots maps drive worse than stock though. If the owner wants a fun tune to drive on that reliable and safe go with freektune even Justins OTS+ map drive really well, is reliable and will make more power. having a non oem downpipe will increase the exhaust notes, I get burbles and pops anyway without tuning for it and cooking valves.