New To Me MS3 Needs Smog p0301

Hello everyone this is kind of an introductory post and also a cry for help. Im the new owner of a kind of rescued 2008 Mazdaspeed 3. I really need some help because this thing needs just a little love to get back on the road. I need to get it smogged asap (DMV giving me 30 days smog exemption) then will get it fine tuned to run at its best.

Its been sitting a while but seemed to be running well at first. Its been modded by owner #1, I got it from owner #2 and he wasnt able to offer too much info on it. From what I gather the car has these mods:

Greddy Turbo
FMIC (dont know the brand)
3 port boost
JBR Racing 3.5" intake
HPFP
Cobb AP with freektune
Had an ungodly full catless CNT exhaust, but car came with factory DP so I put that back on and now its much bearable to drive.


It seems I will need to get another protune to make sure all the sensors are on and smog ready and account for the new exhaust. When i try to run a cobb OTS tune just to see if it will run, the car immediately starts and shuts off, I presume this is due to the intake requiring custom tune?

My main problem right now is a misfire code p0301. It seems to run fine when i clear the code but it always returns after driving a little. Im not pushing the car very much when I drive.
Ive moved the coil- code remained- so replaced spark plug with NGK iridium gapped to .028. Not sure if means anything, but ignition coils all have .177 ohm reading(decimal placement could be wrong)

Im not a pro at all when it comes to these modded cars. Ive tried to do as much reading on this I could find and it seems that Im left with 2 possibilities. I either need to do a compression test or pull the intake and check the injector. Would the compression test still be accurate if an injector seal is bad? Comp. test would reveal whether that particular cylinder is low but wouldn't tell me why its leaking (i.e pistong rings vs injector seals).

Sounds like I need to cough up the $175 or so for a set of corksport injector seals? These seem to be the only other option aside from buying weak OEM seals at $50 each??

Given the time table with the DMV Im scrambling to get this resolved. Am I on the right track with this? I dont mind spending money to get it right but dont want to guess and throw parts at a modded car like this. Thanks in advance for anyone that can help!

 

1.) Changing parts without retuning is not a good idea.
2.) Good luck with registering a modded car in LA, unless you know a guy.
3.) Compression and leak down tests (they are different) would be a good place to start figuring things out.
4.) Dont throw money at a problem until you know its an actual problem.

 

Sounds like you already know what you need to do to chase the issue. Don't swap parts unless it's just to fix the seals. You're also tuned for a catless system so slapping on a stock downpipe is going to cause some issues for you and your tune. You pretty much have a zero % chance of getting that car past emissions in the modded form so you may want to pick up a stock intake at least.. I'm not sure how much smog folks care about intercooler piping.

- You're correct the car turns off with the cobb ots tune b/c the car is tuned for a 3.5" intake not the stock diameter, which is what the cobb intakes are.
- Pull the intake manifold and look at your injectors. Do they show signs of leaking? Excessive soot? If so, that may be a good indication you need to replace your seals. CS seals are a great choice and really with them available, there's no need to waste money on stock seals. You could also try swapping injectors around and see if the cyl 1 injector is trash while you're replacing the seals.
- If you do a compression test and your seals are total garbage, it could show up and your leak down test would confirm it.

 

Thank you both for the info. If I do a compression or leak down test first, would a (potentially) faulty injector seal throw off the accuracy of the tests? I know theres a compression problem with that cylinder, but I was not sure that the compression or leak down test would tell me if it was injector related or piston ring related.

Regarding the injector seals. The factory set looks like it includes extra seals like an o ring and flat gasket that go on the fuel rail side of the injector. The cobb kit just looks like bullet casings that slide on from the nozzle side. Are these extra seals that come with the factory set typically needed when using the COBB kit? I dont have any fuel leaks so I am I safe presume the fuel rail side seal is still good (and can be reused)?

 

If you do a compression test and your cyl 1 is lower than the rest, then you can pull the intake manifold and take a look. I wouldn't pull the injectors until you have a replacement set of seals. It's easier to check the injectors for an issue than it is to check the pistons. Hopefully injector seals are all you have to worry about.

Corksport injector seals are just the injector-to-block seal. If you need new o-rings for the rail-to-injector side, see here:
https://mazdaspeeds.org/index.php?t...ing-rock-auto-fuel-injector-rebuild-kit.7407/

The rule of thumb is if your orings are still round, you should be fine. If they're flattened, you should probably replace them. Then again 32 bucks for new orings isn't bad and is good insurance.

 

Update:

I replaced seals with CS seals and new upper seals/o rings as well as new intake manifold/TB gaskets.

The car seems to be running much better than before, I gave it some spirited driving and it pulled very nicely in all gears. I drove for about 35 mins (mix of street and hwy) and everything seemed fine. When I got home I let the car idle for a few mins and the cylinder 1 misfire RETURNED!!! Grrr

Im about to do a compression test as folks have suggested, but Im skeptical its the source of my problems because the car seems to run great under load. Only if left to idle will the code return and stick around until I clear.

At this point if the compression test doesnt reveal any problems, is my next step to replace the injector? Is it possible that there would be a fault with the injector at idle only - no issues during acceleration? As a quick fix Im going to run a bottle of the best injector cleaner I can get my hands on and run it concentrated on like a 1/4 tank of gas and see if that helps. The misfire is MUCH less noticeable now, so Im guessing I might have a partially clogged injector that atomizes properly at high pressure but fails to do so at idle/low pressure.

I should have had the injectors professionally cleaned/tested before putting it all back together, but regretfully due to time constraints I had to forego that step and now fully regret it.

 

Should've switched injector around to see if the misfire followed the suspect injector. ez pz troubleshooting for injectors. At least by the end of this, you'll be pretty proficient at pulling injectors.

 

Injectors probably looked nasty. Hopefully you cleaned em up some too.