Hello, I need a sanity check with this PROM burning stuff. I did some basic adjustments to make sure everything works and I seem to have the process down pretty good. Next I started trying to lean out my new combonation and can't get it done. Here is what I have:

'87 IROC, 383, 6-speed
Canfield heads
Xtreem energy cam 224/230 with 4 degrees advance and 114 LSA
P+P Edelbrock lower, AS&M LTR, stock throttle body
SVO 24 pound injectors, AFPR backed all the way down reading 50 psi
165 MAF computer with $32B code programming with PPII and Tunercat.

Here's the problem(s): It's a new motor and it's running rich which I expected but the idle varies from near dying (400 rpm) to about 1200 rpm. After some tuning I've got that better and it stays running on it's own after a little warm up. Next, I adjusted the injector constant to 26 and it was still rich. I adjusted it again to 28 and it's still rich. How far can I really take the injector constant without problems? Next is the timing issue, it only runs without backfiring with the brown wire disconnected and even then it backfires under load. I've tried cutting timing in the chip and still get the backfire but I'm not showing any knock counts.

I've been out of cars and into bikes for a couple of years so maybe I'm missing something obvious and mechanical but it doesn't seem so. I had a small vacuum leak and fixed that but it didn't help. I've tried setting the base timing everywhere with no results. The only code I get is for the timing wire being disconnected. I've read some other people with this cam running off of the stock 350 chip and I don't see how.

Any help would be appreciated.

 

Is it rich just in one place, like idle or is it rich at all times (ie idle, cruise, part throttle & WOT)?

 

In open loop it idled at 138 blm / 128 int
At part throttle it would settle into 128/128

Then it went into closed loop and the reading went to 006??/117 and I shut it down. I haven't made any WOT attempts since I can't get the backfiring out yet.

 

The open loop numbers mean nothing, disregard them.

I saw this in your previous post AFPR backed all the way down reading 50 psi
You are saying your regulator is backed out as far as it will go and you are still getting 50 PSI out of it? That isn't good. If you have your old stock regulator you may want to put it in and see what happens.

 

Thanks Morley, the AFPR crossed my mind as a problem. I made some headway last night with the injector constant set to 30 and repaired a couple of small vacuum leaks. I suspect that I still have some leaks cause I was only getting 10 inches of vacuum at idle. I actually got a stable idle last night at 750 rpm and the blms were in the 138 range. At part throttle they would settle in between 126 and 130 with the int hanging at 128. I didn't get a chance to drive it though.

 

Yeah 10" of vacuum probably wasn't enough to operate the regulator and all.

 

we still dont undrstand the purpose of the fpr ?

 

sure, do you know how it functions? No vacuum, full pressure to injectors, means they can't open and close properly.

 

I was under the impression that as engine vacuum dropped, the fuel pressure increased and therefore more fuel was delivered during each injector pulse. I don't think it has anything to do with the injectors opening and closing properly.

 

With too much pressure the injectors have a harder time opening as they have to over come the pressure in the rails.

 

its has to due with pressure diferential across the injector at atmosphere an injector flows 24pph into the atmosphere. at 45 psi in a 10 vacum the same injector now flows 28pph. its a way to keep flow canstant at various pressure differentials across the injector.

 

I have the same problem, not to add to yours but I'm trying to find some results as well, I have a 350 with vortec heads and tpi with a hot cam and my vette is running very rich with a stock 350 chip.....I have black and bluish white smoke you can smell the raw fuel coming out of the exaust ...I've tried everything but getting a new programed chip...if anyone thinks that the programed chip will help or reduce the richness please enlighten me because I'm about to give it up...i beleive two weeks is enogh of trying to fix this problem...HELP!!!!!!

 

I would definetaly make sure the FPR is adjusted within specs for the injectors. If you have too much fuel pressure the injectors will flow more than the ecm can compensate for resulting in an extremely rich mixture no matter what you do.

I had the problem when I turned up my fpr a little too high. No mater what it was pooring smoke and raw fuel out the exhaust, only thing that helped was WOT where it could burn the extra fuel.

 

I agree with the f.p. need being corrected. I also found
Funstick's 32/32b tuning in the stickies to be very informative
to what you are trying to accomplish. Well worth reading and plenty of info.

 

If you have access to a Wide Band O2 sensor, use it.

I was running blms of 108 and eng idled cappy. Thought for sure I was rich.

The wide band told me I was lean.

Had to relocate my factory O2 sensor to make it work right with my combo. (also switched to a heated O2 sensor since I moved it a couple of feet down the Y-pipe).
Apparently, the factory O2 sensor was getting hit with unburned fuel that slipped past the exhaust valve and that was triggering a false rich signal.

I'm running 24 lb/hr LT1 injs. Had to set Inj constant to 28 to get 128's at cruise.

 

Thanks for the replys. I like the info about relocating the O2 sensor. Mine was definately rich by the plugs and the tailpipe though. Adjusting my injector constant to 30 and the idle to 750 rpm seemed to help a lot. I got rid of the black smoke from the tailpipes and my BLMs went to 136 at idle and 128 at part throttle. Idle was much improved and actually settled in at 750. As for the FP, I may have to buy another regulator because I haven't been able to get under 50 psi with no vacuum since installing the Walbro fuel pump.