3.1 engine ignition(?) problem

[ifixalot]

Just a reminder, the injectors from a 92 Buick 3.3 liter are the same as yours. I checked on the Autozone
website. Over here, those cars are plentiful in the junk yard and the injectors are easy to pull.
Maybe you can find one over there.
I thought i had an extra or two in my toolbox but I can't find them.

[michi]

plentiful of them? I will find more berettas than 3.3 buicks in the junkyard here, lol. But i have to drive 200km one way to get to a junkyard that has berettas and probably will cost more than a new one, lol. so i will be better off buy a new injector or get a set of used ones... i am not sure yet but i think i just order a new one and get it in 5days, swap it in and drive it till another one fails, lol.

Anyways, just ordered a new injector. I am so sick of people that wanted to sell me injectors here in europe... one guy from a american car forum want to sell me old used injectors for $250... holy crap, i can get new delphi injectors for that. Also found two other people on ebay that part out berettas... the one guy wants with big big money too and the other one dont even got time to get them out of the motor... wow, lol.

Thanks for all your help. I hope my engine runs better with the new injector and hope the problem is solved.

[Money pit Beretta]

Delphi is the way to go. They are an upgrade from the stockers. My old injectors would have been the cost of shipping. I'd feel better knowing that you have the Delphi over my 3100's.

[michi]

Yes i heard good things about delphi. I just wonder, would you mix 3100 and 3.1 injectors? I dont think that would be good cause theyre arent the same, right? Also i cant wait to drive the beretta again... my bmw 330d bores me to hell right now, lol!

[themixer]

It should work fine with a mix of them, they just all have to work

[3X00-Modified]

No you cannot mix them 3100 and 3.1... The flow rate has to all match. Old and new for the same engine yes he can mix them.

[themixer]

Sorry I was wrong thought it wouldn't make a difference !

[3X00-Modified]

The ECU calculates how long to pulse the injector based off of the flow rate constant entered in the ECU.. That's considered the base tune. It will then auto learn and adjust if the real world conditions don't match perfectly, hence the fuel trims and use of the O2 sensor for verification of the proper mixture. Now say you take one injector and swap it out for a larger one now that one injector over flowing in comparison to the others and that will skew the O2 readings. The ECU will then try to make a global adjustment to how long all of the injectors pulse and rest of your cylinders may run lean in comparison to another... This is why people spend so much money cleaning and flow balancing injectors, to ensure each and every cylinder is delivered the same amount of fuel. It will do the same thing on an SFI engine as well.

The O2 reads an average of the engine yes... but you don't want your average derived from say a cylinder running at 10:1 a/f and another running at 18:1...

In the end even matching Old and new injectors of the same "flow rate" is risky since you don't know unless tested how much they old ones flow vs the new one... It's worth having them checked if possible then you will know if the engine is balanced and won't lean out a cylinder.

[michi]

Hey guys, my problem is finally fixed. I swapped in 6 new delphi injectors and just passed emissions test, even waaay better than the last years. It runs good BUT when the engine is cold its stuttering a little bit when im in gear and give it a 1/4 or 2/4 trottle... when i do WOT it doesnt stutter. And also when the engine warmed up it runs just fine, no problems at all.
I also have to do a idle relearn again and do some oil change and stuff but this stuttering is kinda annoying.

Any suggestions what could cause this stuttering when cold?

[Asylum]

Forget the idle re-learn. It will do that on it's own as you drive.

[Rettax3]

If the injectors are oversized at all, it will get too much fuel (causing stutter) until the O2 sensor is warm enough for the ECU to go closed-loop mode. Once it is warm, the ECU reads that sensor, and can pull (or 'trim') fuel from it. If you retro-fit a heated o2 sensor in, and wire-in a power-source for it, it will heat in much less time, and should go closed-loop sooner. Some of the Quad people have done that with good success, I have read.

[ifixalot]

It's nice that you let us know the new injectors made the improvement. I wondered about that.

In your previous attempts to fix the engine, did you replace the TPS and the FPR?
I don't think your car has a MAP and MAF?
In my experience, a bog is caused by a lean condition brought about by the sudden gulp of air
as you open the throttle. The TPS and FPR and a MAP (and MAF if you have them), are there
to richen the mixture with the opening of the throttle. The oxygen sensor only trims the mixture.

This problem may just go away as the engine re-learns it's settings with the new injectors.
I think the computer needs to learn the engine settings based off running warm. It will then it
calculate cold settings based off that experience.

[michi]

FPR is a new one installed, also swapped in another IAC that i had laying around and i just disconnected the batterie yesterday to do a idle relearn but i just drove it home and to work today... the main thing i thought was if the ecm does a little relearn with all these new parts (sensors&injectors) installed. It idles even better now but still stuttering when cold. It will do that for about 2-3 miles or so, then no problems at all. Havent swapped the TPS yet, i think i have a used one in my garage that i could try. Also put in a new O2 sensor along with the new injectors some days ago.

[themixer]

sadly i have had similar issues even with brand new 02 sensors if you have a scan tool make sure the output of the sensor is within range .

[Money pit Beretta]

Glad to hear the injectors fixed the main problem. You should get a little better MPG's with those too.