87 TPI computer and wiring harness (with MAF) running a moderately modified engine using a custom-burned chip (not burned by me).

O2 indicates lean at idle and all part throttle conditions: 200-500mv range, never even a blip into the 700-800 range.

Actually IS running lean (verified the old-fashioned way: looking at plugs and exhaust soot color)

Block learns are all maxed-out at 160. That means it's trying to make it richer, right? 160 APPEARS to be the maximum value in this field- could somebody confirm this, please? ALL BLOCK LEARNS ARE 160, not jsut a few.

Cells (what get's modified by the block learn): these appear to be related EXCLUSIVELY to throttle position. Idle = 0. Part throttle is 1 through XX before it goes into WOT (fuel enrichment?) mode cells. Right? Wrong?

Also, please give me your input on this hypothesis: Either the chip is burned wrong or the injectors are much smaller than what we (opr the programming) believes them to be.

ALL SIMPLE STUFF HAS BEEN TRIED ALREADY, so don't ask about fuel pressure becuase it's right (50 PSI), vacuum leaks (none), no trouble codes (except an intermittent lean O2 code which tipped us off to the problem in the first place), no exhaust leaks, replaced O2 sensor, replaced MANY bad ignition parts recently, replaced ECM recently for a bad ground (swaping in the custom chip, obviously), etc, etc. It runs acceptably.

Yeah? No? Have I missed anything (don't think so)? Just want to run it past before shelling out big bucks for a new chip and/or bigger injectors. Thanks in advance.

 

Ahhhh, so you're planning on burning your own proms now, right?
But you said something about shelling out $ for a new chip???
Is it going closed loop? Whats the inj. constant set at and what size are the inj. now? You really can buy what you need to burn your own for less that what you'd pay for a "custom" chip-lots of info available here then............
I got into this after learning the hard way.......yes it's well worth it!!!

 

Not my car, not my money. I only work with what other people are willing to do with their money and cars and go from there. I'm not personally burning a prom, but that would be a good way to go, I admit. A new custom burned chip would be about $200 and might not be any better.

The injectors are SUPPOSED to be 30lb SVO units. The fuel injector constant is set to 32 lbs (to account for the slight difference in the way Ford rates their injectors).

 

You are DEFINITELY running far too lean. Are you getting any SES 02 Lean codes? The two things you mentioned are defintiely possibilities. The other possibilities are 1) the O2 sensor is not working properly (is it heated by any chance? Some heated seem to have problems) and 2) the actual "burn" was not quite done right, possibly because the erase was not long enough. I've actually done this myself initially when I used eproms instead of Flash Proms.

 

Problem solved!

Turned out to be injectors that were not what they were supposed to be. 24# is just not the same as 32# by a long shot. And they were NOT the 30# SVO injectors they were supposed to be. Word to the wise: NEVER EVER buy injectors from a private party off of ebay! Owner finally admitted he cheaped out and took a chance buying a set from a private party off e-bay in an effort to save money. Not a great way to save money, in my opinion- buying them twice.

Just to tidy up a few loose ends here......

Yes, it did experience an intermittent O2 lean code, especially when idling for a while. It seemed leanest at idle, buy only by a tiny little bit versus the rest of the fuel curve. Just enough to throw a code at idle sometimes. Had it not done this we might never have even gone looking for a problem we didn'ty know existed!

The O2 was converted over to a 3 wire O2 several months ago. We tried replacing the O2 as one of the first attempts to fix the problem. We even switched brands of O2 just in case there were problems with a certain brand not "liking" the setup. Made no difference. Switching back to an UNheated O2 also made no difference. Readings were pretty much the same no matter what so we went back to the original heated O2 sensor.