running rich on cold start... ?

[lifeiskaos]

i recently put in 19lb pro cleaned and flowtested injectors, and an m30 afm with a modified stock airbox. it ran pretty well before the afm, with just injectors, just a little trouble starting. now with the afm, it runs WAY too rich on cold start. it idles really low, at about 400 rpms, and the whole car bounces and if i give it any gas it will stall. eventually it will start to warm up and it will backfire a little, and it starts to run normally. the whole process takes about two minutes, then as long as its warm, it runs great. great throttle response, nice idle at about 800 rpms. needless to say, the engine light is on (1222) the whole time. i've tried doing research, i tried driving like crazy for several days in hopes that my ECU would adjust, but i've had no luck. i believe my options are either a bad o2 sensor, a bad ECU, or an excuse to buy a markd chip. any advice will be greatly appreciated. i'd like to take care of this asap

[mrsleeve]

Its is supposed to run rich on start up when cold (in old school terms Choked) and when cold the O2 sensor is not even supposed to be working as it has not reached operating temp to go in to closed loop. The comp just runs things off a set fuel an timing maps till operating temp is reached.

That said you may have other issues as it should not be idleing low it should be up around 1200 or so. I would venture to guess the M30 AFM is you trouble, try going back to the stock 1 an see if that clears up the issue. Or find a know good M30 AFM and do the same. or look into the ICV, If neither 1 of thoes is it you have bigger fish. fry

[lifeiskaos]

i already replaced the ICV and the throttle switch under the tb. yeah, i'll try using my old afm. thanks so much for your response. with the old afm though, wouldnt it get less air and run even more rich?

[mrsleeve]

It would not make a big difference at idle. You dont see any upgrade of the bigger bore in AFM till high RPM. If the standard M20 AFM is working properly it will idle fine.

[lifeiskaos]

same problem with the m20 afm... any other ideas?

[lifeiskaos]

help

[DaveSmed]

If you have access to one, try an eta fuel pressure regulator for a little while. The change may take some time to notice.

[lifeiskaos]

why? just curious. would you trust one from a scrap yard?

[DaveSmed]

Why certainly. 19lb injectors are a bit on the big side for a stock engine, and with no other mods done (I don't know your particular setup) or some light bolt ons, they can be a bit much for the DME to cope with. However, the extra capacity is nice in the upper RPM band, and the fact that they aren't 20 year old injectors with god only knows how many miles on them.

So, the i motors use a 3bar FPR. ETAs use a 2.5bar. By dropping fuel pressure across the board (by that I mean load x rpm) it might bring the mixture back to where the DME has an idea what it's doing, and can adjust accordingly.

I would absolutely trust a used one, worst it can do is leak internally (provided you used a fresh Oring like your supposed to) and make you run rich. If there's fuel in the vacuum line after you run it or it even smells like fuel in that vacuum line, it's junk.


Figure for what they cost at the junkyard, I thought it would be worth a shot. Might even get rid of that code too if your lucky.

[lifeiskaos]

and would you keep it? or let the car adjust and use the i one later?

[DaveSmed]

Up to you, if you put it on, drive for a week and it's running awesome, I wouldn't touch it. If it doesn't help or makes it worse, i'd take it back off. Wait a week though and see.

[lifeiskaos]

sounds good. thanks so much. since the idle isnt completely smooth, i think ill check for any kind of vacuum leaks while im at it. the boot's new but you never know

[DaveSmed]

Sure couldn't hurt. Wouldn't expect it to be your running rich problem though, as a vacuum leak would let in air that the computer didn't "see" resulting in more air than the computer is injecting fuel for- a lean mixture.

[lifeiskaos]

yeah im just running out of ideas here. after replacing the ICV, throttle switch thing under the TB, intake boot, brittle vacuum hose, i was getting close to going back to stock... but i will definitely try the ETA fpr. its a great idea, thanks.

[nando]

there's this thing called a "Ferrari tune up": go drive the @$^%@^ out of your car, forcing the ECU to adjust the PW. I never figured out why so many people had trouble with larger injectors, mine always ran fine after the first startup and shakedown.

I wouldn't bother with the M30 afm though - not worth the hassle in the least.