Mr2 maf mod rough starting

[Rallyeluke]

Hi

I did the maf mod yesterday on my facelift 2003 mr2

I have a genuine corky maf riser and yellow 2zz injectors.
It is now all fitted up and the vehicle gets better and better every time I drive it but the vehicle cranks without starting initially and then you turn the key again and it will start and for a split second it will misfire, after that she is perfect.

Any suggestions what may be causing this? Initially I fought a dodgy injector or fuel leak, no leak is present from the rail that I can see.

Any advice is greatly appreciated 🙏  Thankyou Lucas

[Petrus]

Unfortunately that is a downside.

Mine took rather a while to relearn.
Then it started ok when cold and véry reluctantly when hot unless I pressed the pedal a bit during starting.

After I changed the pcv valve for a new one things have improved to almost normal.
My take on that is that the MAF sensing less flow makes the starting more critical.

[Bugster_MR2]

I've ran my MAF mod for 5 years+. No such problems with mine.

Try disconnecting your battery overnight and let the ECU reset? What is the state of your air filter and spark plugs?

[Petrus]

I've ran my MAF mod for 5 years+. No such problems with mine.

Try disconnecting your battery overnight and let the ECU reset? What is the state of your air filter and spark plugs?

I you disconnect it, it will reset and it will need to relearn.
He can always do that after a few rides.

[Beachbum957]

We have run the MAF mod on 2 different MR2 with no issues.  However, it is entirely possible to damage the injector seals or use the wrong seals when changing injectors.  That will certainly cause problems from a fuel leak to a small air leak

[Cap]

Mine is MAF Mod serial Number 1.. No such issues.. Daily Driver.. Cold frosty morning starts, with no throttle input I just turn the key and it Starts. Same when it's hot..

The only 'Issue', is the annoying throttle 'Tip Out Fuel Cut' at 3K RPM..

I wonder if it's somehow a Debris issue from when the fuel system was opened..

I'd like to see a Fuel Pressure Gauge installed, to see if your up to fuel pressure when you are having starting difficulties.

It's a reversible MOD..  Change it back to see if it clears up.. If it Does, then it's Likely an issue with the Injectors..

Cap

[jvanzyl]

I had that issue - it's down to your O2 sensors beginning to age. As they get older they cannot adjust as quickly thus the extended cranking. You will only need to replace the pre-cat ones. I would also consider replacing the PCV valve as per petrus's comment.