Mark_ZZ3

I recently upgraded to 24lb injectors on my mildly modified 350. Surprizingly it runs great, fuel mileage is BETTER than my old injectors, and apart from a rougher idle, it is fine.

I've always had a slight rough idle with my setup (most likely due to the cam and heads), although it seems a bit more with the 24 lb injectors.

Can anyone describe how their car idled? Did it just shake while in gear? Did it stall? Did it smell horribly rich? etc.

I've checked my BLM's and they are in the 130 range in special mode (10K resistor). IT does not smell rich when idling, but if you drive it back and forth in the driveway it smells rich. Perhaps the ECM can compensate at idle, but not just off idle.

My old 165 ECM does not seem to output any data while in normal mode, both my snap on scanner and diacom will not capture any data unless in the 10K resistor mode. So I can't say what's going on while driving.

I'm just looking for people's experiences with 24lb injectors on a stock prom TPI.

Mark.
PS. I know all the benefits of programming PROMs. So no need to go off on that tangent please.

rezinn

The ecm can't compensate well because it knows that it's rich, but it doesn't know what size guns it's using to fix the problem. So it's always going to be off. I'd expect a rough idle at the very least, as well as a huge off idle stumble. You should be getting 20mpg highway easily, if not you may as well spend the money on a prom because it's going to pay for itself.

I don't know what special mode you're talking about.. but if you're getting scrambled data or no data on your scanner you may want to check for your coil or wires arcing. By the way, nothing short of an LT4 HOT cam or more should really affect your idle much if running properly. Sorry if I didn't exactly address your idle concern.

Viprklr

iTrader: (5)

My 24's on the stock prom ran smooth. No problems. Programming just brought my mileage up.
The 165 ECM needs the 10K resistor if you're going to take a look/see at what it's seeing. The 730 does not need the resistor.

formul8!!

I have had 24# injectors for about 65,000 out of 91,000 miles. Mostly on the stock PROM. It does smell a little rich at idle, but idles fine. It has never been a "smooth" idle, but hey- it's a muscle car!

I do agree that a custom chip is necessary due to the injector sizing. Granted, a 2lb difference is not huge- but if you want big gains by tuning alone, it is important.

Mark_ZZ3

Thanks for the replies thus far.

Mark.