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90 tracker hesitates when accelerating
#4
when cold, the EFI is super rich already (maybe 10:1 AFR) (like a CARB choke) (the ECT shows hot and ECU enters hot running air mix mode)

when hot: THE EFI in closed loop (@14.7:1 AFR) and you hit the throttle hard, (this is huge air added fast) AFR = air fuel ratio.
the air flow is instant, and a huge air slug (hits the intake valves) and the result is a temporary bog . a gross hesitation. (TPS dead)

Enter the TPS:
the TPS senses this fast change (throttle angle) (virtually instantly) and causes the ECU to go to enrich mode , until such time, as the MAP senses this new air flow caused by driver, correcting this bad air/fuel mix.

This works just like the High-speed Accelerator pump on old Carb's and for exactly the same reasons. (that funny device that squirts, even key off.)
on carbs, the air is faster than the fuel (jets) (air is faster than viscous gasoline)
on EFI the AIR is faster than the MAP. (MAF in 16v) (or your right foot is faster than any MAP) can be... (move R.foot slower, see it work ok?)

This comment assumes good fuel pressure 30PSI, and ECU has good inputs .
Are the advancing weights working in the old funky dizzy?, (mech. monster)? they rust and fail just like all cars did ,back when.
Is the dizzy advancing correctly (full RPM advance) with a timing light attached? 18deg. on weights. alone.
8 static, +15 with weights, to about 23deg.? and the vacuum part works too, for 5 more degrees? (and the diaphram in the vac, adv. is not leaking?)
is the vacuum advance working ?

VR gap. open dizzy. see magnetic, coil (figure 1, id 5/6)
http://www.fixkick.com/IGN_timing/89-timing.html

The Vacuum advance, can be tested separately , pull hose and attach any hand vacuum pump to it it and check leak down first. (zero for 1min) and
then pump it and see the effect on advance, if no effect at all its DEAD.

for sure spark is first, it must advance correctly or the fuel will not be burned fully.
http://www.fixkick.com
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Messages In This Thread
90 tracker hesitates when accelerating - by bcbud - 12-03-2013, 02:27 AM
RE: 90 tracker hesitates when accelerating - by fixkick - 12-05-2013, 11:06 PM

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