[Shotimes] Leaning out @ part throttle - opinions please

[James White]

Several years ago my '93MTX wasn't running well and wouldn't pass 
emissions.  Idle and WOT were OK, like yours.  Didn't have all that 
fancy equipment to see if it was lean or what, but it didn't set 
any codes.

Tried everything.  Swapped throttle body, MAF, TPS, etc.  Turned 
out to be the BARO sensor.  Got a new one for 40-45 at advanced auto.


regards, Jim White - greensho@crown.net



At Friday, 16 September 2005, "Timothy Tyner" <shospeedenterprises@hotmail.
com> wrote:

>Here is a brief history: When I first got the car running, my 90mm 
MAF was 
>wired backward. So the EEC was reding a full voltage at all times.
CE lights 
>on, MAF codes, etc, but the car ran decently enough, so that I drove 
it on a 
>140mile trip, and got 20mpg. Still, it was far from perfect, and 
I knew it 
>needed some changes. Well, once I datalogged it and saw my MAF values 
>(DOH!), I wired it up right and took it for a spin. WOT was AMAZING,
car was 
>very quick, all readings looked spot on and no CE lights, no codes.
>
>But for some reason, I could not drive the car part throttle. Try 
and cruise 
>for 5 seconds and my WB was looking like an oscilliscope (sp?), 
car would 
>lean out and try to die. Well, it seemed my old fix to a HEGO was 
no longer 
>working (wire had melted once, I rewired it, but it needed a new 
one). Well, 
>I had a new harness, wired it in, got two new HEGO's, and went to 
town. Now 
>the HEGO readings were where they should be. A full datalog showed 
my LAMBSE 
>and KAMRF values were what you would expect, all other values good 
as well, 
>but still the part throttle leaning out.
>
>This is what I know, MAF read correctly, TPS is new and reads correctly,
car 
>has the air/spark/fuel to make made power, and runs awesome once 
in WOT, but 
>awful in closed loop. This is what has been replaced with the last 
turbo 
>swap: turbo, BOV, WG, trans, halfshafts etc. All of those of course 
not 
>having an affect on my problem. BUT, I also removed the FMU, added 
the FPR 
>(and yes, fp checked out great), removed CC, and rerouted a number 
of vacuum 
>lines.
>
>So, cliff notes: WOT = great, part throttle = crap - car leans out 
and dies 
>within seconds. No CE lights, no codes. Idles good (though it take 
a while 
>for it to drop below 17:1, is this normal?), datalogs from Tweecer 
give no 
>evidence of a problem. My question to the forum, what is the problem? 
What 
>would only present itself @ part throttle, but let the car run amazing 
@ 
>WOT? I await your answers (and as always, a prize for the problem 
solver, 
>how does driving the turbo at Memphis for a few laps sound?).
>
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