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Stumping all the 3800 guys...

None that I've been able to get in contact with.
Nobody seems to reply even though I'm willing to pay whatever for their help.

I just don't get it. I don't understand why it's showing so high on one ECM but not the other.
 


what year maf you running? they change with the years, 97-98 is one part# 99-00 is another. if your running a 01 maf with a 99 tune, that could be the issue right there.
 
I have the OEM '99 MAF in it, I even put in another MAF from an unknown year (At the very least it was a 98/99), with no change at all.
 
I'm seeing pretty much your same numbers, posted about it before with no luck. Mostly my speculation but another test you can do is add E85. If the trims trend back closer to 0 you know at least the injectors/O2 etc are seeing the change.

This week I added about 25 percent E85. Should have been enough for the PCM to start adding fuel. Nope trims still hitting negative double digits. So I have a new O2 going on this weekend.
 
truth be told it sounds like a crappy stock factory tune. my 98 is at -10.3 at idle right now. used to hit -15 a lot too. im just starting to re tune it now.

last engine i had i tuned it i got the litft's down to -3.0 at idle and cruising around, and locked in at -0.8 wot, close enough to 0.0
 


that are the f/t's doing wot? both long and short? both with any luck are at 0.0

do the short term trims read 0.0 at idle? or bounce around 0.0
 
Short term is around 0.0 to -1.3, -2.3, -3's ect.
LTFT is 0.0, or -3.1 Riiiiiiiight up until I touch the gas. Then it's -7.0+ at idle.

At WOT it comes way down to close to 0.0, it's just driving around, and idling which hurts the most.
 
it needs to be tuned.


post a tuner wanted thread for the north east. if no one responds and you want to drive to NJ ill try to fix it up for ya.
 
Do you run a MAF screen? Choppy air flow over the maf will skew readings.

What brand o2 sensor, if something like a bosch they tend to suck. Delco/denso are the only things I'd ever run.
 


Deleting egr takes a little timing out of cruise. What's the tire size and how healthy is the trans? Ultimately your going to need to get a log from the car to see what it's doing, realtime is not very easy to diagnose or compare.
 
What thermostat are you running? If it's a 160, a drilled 180, or a stuck open thermostat your car will not warm up normally and will get bad gas mileage
 


MAP vacuum should be anywhere from -19 to -20 if you are reading it in in/hgs.

Then once it's over 0, that turns to PSI because it's a 2 bar map.

Some hand held scanner can't read those numbers right, your broken aeroforce can.
 
A Genisys scantool should be able to right? I mean.. it's a couple hundred dollar scanner.
If so, it's reading the same as the Actron does.

So I know that's low...
 
You say the front O2 is acting normally. Does it switch high/low nice and fast almost right from startup?

Are you sure the vacuum is showing at 17-20 psi and only 10 inHg? 10 psi = about 17-20 inHG. I think that's posted backwards though, worth checking I'd say.

Things that can cause fuelling to be off this drastically are maf, O2, stuck injectors and tune. Let's say your tune isn't the issue. Unplug the MAF and see how your O2's go after say 20-50 miles. Don't abuse it, because you'll be running off tables. But drive it. That will rule out maf.

O2, there's so little to go wrong that if it's blipping, it's good. In my experience..often this is an o2 that isn't moving enough.

Lastly.. send your tune to my username at gmail.com. I'll compare it to a couple of things and let's see if that's not the issue.
 
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