19# to 42# injectors...car running bad

[thomas2323]

Hello everyone, I put new Bosch 42# injectors in my 95 Z28. It has a brand new block and is a 383. (Everything under the hood is new) I just changed from the 19# to the 42# injectors because it was running too lean. I even had the Walbro fuel pump already changed. The car ran fine after he finished putting them on and I had to drive about 30 miles to get home. Now when I start the car it idles around 500 (it used to be around 1000) and now I have white smoke coming from the exhaust. I did contact the place where they are going to dyno and tune it but I can't bring it there until Tuesday. When I add gas to the car it really sounds bad now. Should I just leave it in the garage until I can get it tuned or will me driving it around mess it up even more?

[95Z]

You shouldn't drive it at all unless its been tuned for the injectors that are in it. It will run pig rich and washout the rings and contaminate your oil.

FWIW stock injectors are 24 lbs an hour at 3 bar, not 19.

[Mystery Bird]

I wouldn't even start it again going to that large of an injector without tuning for it. You are just pouring raw gas down the cylinders, that is why it's running to bad.

[guppymech]

White smoke is antifreeze. If it's really cold where you live the white smoke could just be water vapor. Rich is black smoke and blubbery. What was the duty cycle you were running on the smaller injectors?

[Racy Roadmaster]

Dont start it any more until you reprogram the PCM, it would also be a good idea to change the oil and filter so as to remove any gas that went
thru the rings. Now I am not trying to berate you, but that is an extreamly
bad error to make.I dont know what if anything you had replaced in your motor,but there is a good bet you damaged your piston rings,now that dosent mean you must install new ones ,but those fuel washed rings will
probably never seal properly. Always make small incremental
changes to a motor. Never make large outlandish types of changes,the person who has been guiding you with this build should have made better
recomendations. Sorry to have to tell you this. ed

[95 Firehawk]

Put the old injectors back in and change the oil.

Those 42lb'ers are good for well over 500 hp, I hope you have more supporting mods besides just having a 383 or you'll need to get smaller injectors anyway.


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[Dynamic396]

Yeah, I agree with Firehawk here. While you can make the 42's work, they're REALLY overkill for your setup. You'll end up with extremely small duty cycles at/near idle with injectors that large, which can be made to work, but unless you need the fuel at WOT that 42's provide, it will just be an unnecessary tuning nightmare.

In either case, no...don't be running the car until you get it sorted out. When you first start it, you're in open loop and it will just lay there and blubber. If it goes into closed loop, your INT and BLM's will help by going full lean, but going from 24's to 42's will be way too much for your PCM to compensate for. You'll just kill your cat by running it that way...