xXxKillDogxXx

Hi everybody,

So recently I bought everything i needed to turbo my MX5, that includes ECU, Engine, Turbo the lot its even mapped and this engine has been running the same map for the past few years so everything should run perfect... But it does not.

Originally it would idle really bad, fluctuating a lot and also the AFR would read 17s even 18s and sometimes go off the guage, so we started looking for air leaks and found one right where the first silicone pipe connects to the turbo and this was fixed.

However the problem is still persisting just not as bad, it seems the idle is higher than it was before which was around 900rpm and now it sits about 1100RPM and fluctuates still but not as bad but I still have really lean AFR readings.

The AFR readings will go rich if i quickly apply the throttle and then go back lean, however if i slowly apply the throttle they will stay consistently lean.

So i did a little more digging and tryed to find some more leaks and noticed when i sprayed engine degreaser on one of the pipes the engine RPMs would rise and the AFR readings would read around 13-14.8...

So i switched over some clamps and still the same problem does this sound like a air leak to you guys?

Also i have attached a quick datalog file I dont know if it will be any use?

EDIT: IF i disconnect the IAT sensor it will run at about 10-13 on the ARF gauge and of course cause its so rich it hesistates when you hit boost.

Alejo_NIN

iTrader: (2)

ok, why are you going into boost when you cna't even idle correctly? no-no

have you checked your IAC valve? it may be open hence why RPMs are so high at idle.

load a base map for your car after saving the updated one and see if that makes the car idle better.
you didn't state this, but are you running the WB to the ECU or are you using stock O2 to feed the eCU?

18psi

iTrader: (76)

boost leak test

xXxKillDogxXx

I had to drive it back from the garage so i had the IAT disconnected which made it run rich and its kinda hard not to hit boost haha.

I havnt checked the IAC no, what would be the best way to check it?

And im using a AEM UGO WB and gauge all going to the ECU and everything.

Would that make it run this lean though

Girz0r

iTrader: (1)

Boost leak would be rich I believe, On boost + Leak = less air in = more fuel on WB read out

I had a knock off greddy bov with an o-ring seal on my turbo kit when purchased, car ran like crap, would run rich and die coming up to lights/stops.

With no adjustments to the map, the bov replacement was a night/day difference

I would check for vac leaks, due to the high idle. It could be pulling in air that isn't being seen through the ecu so you see high AFR all around.

thenuge26

iTrader: (2)

Do you run the AFM/MAF still? If you're running speed density I'm not sure why a boost leak would change your AFRs.

Check for pre-O2 sensor exhaust leaks while you're at it.

Alejo_NIN

iTrader: (2)

you could have a leak at the exh manifold which is drawing in fresh air and making you run lean, worst case scenario is one injector not firing...are you sure all inj are firing?
this will cause a LEAN condition but no detonation because there is no gas at all.

xXxKillDogxXx

Well when i rev the engine quickly is will get rich readings if I rev it slow the AFR will read lean just like it does at idle.

I suppose I could have a exhaust leak I'll see if I can find anything in a bit.

As for MAF I have removed that and replaced it with a IAT and map sensor.

The car is so close to running perfect just this little issue

thenuge26

iTrader: (2)

Yeah since you're running speed density, vacuum leaks affect much less than if you were still running with the MAF. My money is on an exhaust leak of some kind throwing off your O2 readings.

As for revving slowly vs quickly, when you rev quickly you're probably getting accel enrichments as your TPSDOT is hitting the threshold and adding fuel vs revving slowly and not stabbing the gas.

Miater

What ECU are you using?

What injectors are you using?

What does "mapped" mean?

xXxKillDogxXx

I'm running a megasquirt 1 with ev14 550cc injectors and the car has been fully mapped it was all taken from MX5 dans old car who runs universal inter coolers.

The car was running fine before swapping everything over to my shell so and it should be a straight swap since I have the full setup nothing has changed.

Thanks for all help btw guys it's greatly appreciated!

xXxKillDogxXx

Okay so found a leak on the manifold looks like the gasket is not sealing properly would this cause the symptoms I'm having ?

18psi

iTrader: (76)

yes. and its warped. proper mating surfaces don't need gaskets

xXxKillDogxXx

Okay well I'll get a new gasket on order and see if that corrects the issue, how exactly can you say its warped when it could be a bad gasket?

Btw the manifold is a Corksport Cast manifold, so its not exactly a **** manifold by any means so i would hope its not warped... But the gasket is not a decent one by any means.

Girz0r

iTrader: (1)

^This

Possibly, is there any trace of carbon coming out the leak? My Begi heat shield had a nice black streak of build-up from months of rich/bad tune. The local shop who touched it last did a poor quality job, I now question if my turbo was ever serviced.

xXxKillDogxXx

Yeah there is carbon streaks and I let the car cool and sprayed so liquid on the gasket and it may as well sprayed it back at me so there is a leak for sure.

Could this cause a surging idle ?

Girz0r

iTrader: (1)

Not sure,

The only thing I can think of is if the manifold is leaking, not all air/fuel mix is hitting your o2 sensors and based off of that. Your ecu could be trying to 'fix' itself from being too rich if it's not seeing enough air. The mixture could be off and your ECU could be confused & unhappy

I would check for vac leaks after the manifold is fixed if you're still having idle surge issues.

xXxKillDogxXx

Could i possibly disconnect the Wideband and see if that changes anything?

Girz0r

iTrader: (1)

If the WB is hooked into your megasquirt I wouldn't. I'd try fixing the manifold leak first, check for vac leaks 2nd if still high/surge idle.

xXxKillDogxXx

Okay well I have ordered a new gasket, some vacuum hose and some heat sheilding which should be here in the next few days, from what we have checked there is no more leaks in the piping just the exhaust leak now, as the car no longer sounds like its strugling to idle like it was before with the air leak its smooth but just surging a bit between 1000-1100rpm and the obvious lean AFR.

So hopefully the new gasket solves the issue.

Also if I have the manifold leak that means the car will have more boost once its fixed so should be a interesting test drive once its all fixed...