[Gmecm] Tracker TBI

[dgilbert78 at juno.com]

Hello: two things come to mind, but possibly not your problem. Poor accel
off Idle could be delayed vacuum to MAP. By this i mean the ported vacuum
to the MAP sensor has become plugged to the point that is no more than a
pin hole, this will delay vacuum to the MAP and cause stumble when
acclerator pedal is advanced. Another thing also comes to mind, weak
spark, Weak spark will drive you absolutely nuts. Get one of those
adjustable el cheapo spark energy testers and see what the output is.
Good luck, hope that helps
Darryl..
On Mon, 11 Dec 2006 17:55:32 -0800 (PST) Cowen <captain_krill at yahoo.com>
writes:
> Hello all, I have a mystery, with a Pontiac Asuna
> Sunrunner (Chevy Tracker).  It started quite abruptly
> in August....
> 
> My wife has the 1.6l TBI engine, and it fails
> emissions with only high CO.  Looking at the graphs of
> emissions over time, it spikes super high every time
> the tester accelerates during the road test - then
> it's fine  all other times.  That seems to indicate
> running rich on Accel.
> 
> I also noticed last week we had a day down to -11
> Celsius, and when I started it, it was so rich it ran
> on 3 cylinders for 10 seconds - then it went to four,
> as normal.  I'm guessing it was very rich in open
> loop, then when the HO2S warmed up, it was fine.
> 
> It also has a mild "bog" coming off idle - just like
> when it spikes the CO on acceleration in the emissions
> test.
> 
> Finally, mileage is down from around 30 MPG to around
> 20 MPG.
> 
> So, that's what's wrong.  Seems to be running rich!!
> 
> My mom has the same car, year and even color!  So I've
> switched known good parts from hers.  Hers still runs
> great, my wife's doesn't.  Here's what I've done:
> 
> New Plugs.
> Cleaned air filter.
> Cleaner EGR.
> Set the valves.
> All engine compartment grounds have been sanded clean,
> Nev-R-Sezed, reassembled.
> 
> Swapped the following from mom's good runner:
> -cap, wires, rotor
> -HO2 sensor
> -TPS
> -MAP
> 
> 
> I also inspected the O-Rings on the injector(it was
> immaculate), set the timing, the TB is very clean
> inside, the compression is good and even, the coolant
> level is up (those cars are very sensitive to that
> we've found), can't find any vacuum leaks, PCV is
> clean and sealing, charcoal cannister is clean and
> dry.  I watched the fuel spray from the injector with
> a strobe light - looked even and misty.  No dribbles
> when I shut off the engine.  Vacuum line to the
> pressure regulator is clear and solid.
> 
> So, I'm guessing it's rich in open loop.  What can
> cause that to happen suddenly, in a totally stock
> vehicle with no messing around??  Thanks for any
> guesses!
> 
> Duncan
> 
> 
>  
>
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