I have a 305 TPI in my car '89 Camaro. It is running off a 1227165 ECM, a ARAD 4868 PROM (350 chip, according to here), and 1985 19lb/hr injectors. The problem is that the car runs lean throughout the operating range (Granted, this datalog is only @ idle w/some rev, and the car not moving. But, I have done other logs that have indicated the lean condition throughout operating range). BLM's pegged to 160 almost constantly. Today, I tried disconnecting the FPR vaccum line (to up the fuel pressure). I have attached a TunerPro RT datalog. Here's what went on during the log: 1. Sample #0~340: Idle, not quite fully warmed up (enters closed loop @ sample #190ish), vaccum hose to fuel pressure regulator disconnected, fuel pressure reading 46.5psi, (vac. gauge in place of FPR line, reading about 19ish in/vac). BLM=150 INT=128 RPM=725-750 TEMP=120-130 SPARK ADV (total)=10.9 INJ BASE PULSE WIDTH=2.58-2.73 2. Sample #340~500: Hold revs to about 1375, vaccum hose to FPR still disconnected. BLM=149 INT=134 (at start of rev.) 128 (at end of rev) RPM=1375 TEMP=132-138 SPARK ADV=21.8-23.2 INJ BASE PULSE WIDTH=2.30-2.33 3. Sample #500~570: Idle again, same as #1. BLM=150 INT=126 RPM=750 TEMP=139-140 SPARK ADV=12-12.6 INJ BASE PULSE WIDTH=2.40-2.50 4. Sample #570~1000: Idle, hooked vac. line back up to FPR, fuel pressure reading 37.5PSI. BLM=160 INT=134 RPM=725 worked its way to 675 TEMP=142-154 SPARK ADV=works up to 15.82 INJ BASE PULSE WIDTH=2.55-2.61 5. Sample #1000~1265: Idle, unhooked vac. line from FPR again, (vac. gauge read 18 in/vac) BLM=153 INT=123-128 RPM=675 TEMP=154-161 SPARK ADV=15.82 (completely steady) INJ BASE PULSE WIDTH=2.25-2.35 6. Sample #1265~end: Idle, hooked vac. line back up to FPR again, same as #4. BLM=160 INT=133 RPM=675 TEMP=161-166 SPARK ADV=15.82 (again, completely steady) INJ BASE PULSE WIDTH=2.38-2.45 So, there it is... I guess the point to all this is: Will running a 305 with 19lb/hr injectors with a 350 chip cause this lean condition, or is there something else going on? I was searching around and found this. Which seems to indicate that there should be no problem with my setup... And it makes sense; if you have 350 injectors and PROM running a 305, it will be rich, but if you use 305 injectors, the difference in flowrate is proportionate to the difference in engine size...

Well 350 prom on a 305 isnt the best idea, you need to get the injector constant right, in a 350 prom you got 22.02 inj. constant. and in a 305 you got 19.48 inj. constant.

So that will make you lean. You need to get that fixed, also the spark advance is difference between 305 and 350.

Why do you have an 350 prom on a 305 ?

The ECM thinks its 22 lbs injectors in your car and takes away fuel to compensate for the 305 fuelling needs. So unless you fix your injector constant in the prom you will run lean = not good, to lean overtime will melt pistons..

tpiparts.net burns and sells proms, contact them and get the prom fixed

Heh, well it's definatly not my doing... So, when I bought the car I ran the VIN, it came out as L98. I asked the sellers what engine was in the car, they said 350. And, so I assumed that there might be a 350 in the car and bought it. Later on, it started doing the blue smoke on startup thing, so I figured I'll get a valve job, and maybe guides done while I've got it taken apart to do the seals... Sooo, I go to the machine shop, pull out these "350" heads and the machinist looks at me and says "You know these aren't 350 heads, right?" I didn't want to waste my money on a vavle job on some 305 heads, so I went home and measured the bore of the block to make sure. And, sure enough that is when I found out someone had swapped in a 305. Eventually, I ran the scanner on it and found it to be way lean. And, after a couple years of tinkering with minor stuff I was more and more convinced that everything was in good working order, so why should it be lean... Then I got the idea to check if maybe when they swapped the engine that they just left the old computer and PROM. And, upon finding that to be true, I figured that it must be the main if not sole source of the lean condition... But, then I wasn't sure, so I posted this up...

Getting a new chip is going to be a temporary solution anyway (for the Camaro, at least)... I'm going to solve all my current problems (and make myself some new ones...), by dropping in the 'ol 6.0L LSx. But, I kind of wanted to reslove the lean condition so the TPI can move over to the El Camino...

And, thanks for turning me to TPIParts.net, I didn't kow they did programming. They appear to do it cheaper than other places I've looked, too. Now, I just gotta see if I can get my dad to pay for part of it (the El Camino is his).