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, Mon, 30 Oct 2023 18:31:34
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Hi Reed,
The issue you noted are likely one dramatic over fueling issue.
1 is suspect is a split rubber vacuum boot in the full manifold vacuum line from top of intake plenum, 5" behind the throttle body. there is a 2 ft white plastic tube that has 2- 2" long rubber connect tubes at either end. IF split in this line, ( air leak) EFI thinks throttle manifold vacuum is telling computer that the engine is at full throttle. Location MAP sensor: the manifold pressure sensor sits atop the left under bonnet inner fender, aluminum barrel shape, elect connection with 4 wires ( all of them white wires ) and black cover cap on one end.
Again, this input from Manifold pressure sensor value leading to the bosche FI ECM is the main mixture BIGGEST influence on engine mixture. if vacuum leak here in that connecting vacuum hose, idle is terrible and plugs do foul.
more fuel tests:
next, in boot remove fuel filter and back plow it or replace it ( same as VW TYpwe III)
to make sure EFI basics are dialed in: easy and basic next check fuel line pressure:To power pump, carefully take a jumper wire w alligator clips , affix one end to Marshall alternator B+ 6mm threads, and then at fuse box, remove cover and connect B+ in other end alligator to fuel pump fuse ( look at label for fuse number ) (#8?) pump you will hear running in trunk.
test fuel rail PSI expect 28-30 PSI, where to connect 0-60 PSI fuel gauge? disconnect rubber fuel line where it enters the fuel injector pipe. entry for fuel is at one end or other. so connecting gauge with a "T" connection ( 8mm or 5/16" barb sized ) to test fuel rail pressure. jumper electrical from alt top fuse to run pressure test.
The fuel pressure regulator is in the middle of fuel inj rail and the exit for gas from the regulator is the bled off fuel pressure path for excess gas return to gas tank.
For overall fuel pump health, take needle nose pliers and pinch return hose briefly ( hose that is below regulator ) good pump is 45-50 psi.
If pressure is above 28-30, lets say 40 or 50 psi, check for a restriction in the return line to tank. LPHV air connection to take off gas cap FIRST!! then lightly blow some air 1-2 seconds only in return hose below f regulator having assistant listen for air bubbles in tank filler w gas cap off.
If pressure 32psi and needs to be lowered , the fuel regulator has a 13 mm lock nut on top and when loosened, the 10mm center screw can be screwed in to increase pressure, and if above 32 psi, screw center threads out ( up )
finally idle on EFI is key to set up throttle and throttle switch.
1. remove air cleaner, carb cleaner on rag, clean throttle plate bore and brass throttle disc.
2. slacken throttle cable 1/4"
3. on throttle housing: there is a stop locknut and little throttle stop phillips screw. loosed locknut 2 turns. ALSO loosen throttle switch ( 2) screws so that throttle sw is free to move. "to an fro"
4. screw up phillips till actual throttle flap in throttle housing closes fully ( visual w air cleaner still off
5. then screw down phillips till you see throttle disc just move ( life away from fully closed) FROM that pint w phillips, screw screw down 270 degrees ( 3/4 turn) this is "mechanical air only" baseline air: Tighten 8mm little throttle stop lock nut. Note: 3/4 from closed throttle disc ISset up for ALL saabs efi need till 1994! and 9000's
6.now w key on, AND w eng NOT running, move throttle forward till one "click " is heard. lightly turn in 2 throttle sw screws, TEST by opening throttle slowly and listening for 20 clicks as you open to full open throttle disc. The let throttle disc return ( NO CLICK in return travel, YET one click when disc then hist full closed ( mech air flap setting ) may need to tweek adjustment few times.
to get some idea of injector open duration in miliseconds.. just a basic hand held Volt meter ( digital fluke ) with pos and neg probes inserted in one injector backside under wire boot ( injector still plugged in. will give idea of amount of fuel injected. works great on LH cars too.
idle warn is .3V ast Idle Idle cols is .6 V > 40F, flipping throttle open briefly you will see 1-2 V
VW trained 1971 and 1972 including EFI and Saab dealer tech 1977 onwards where servicing 99 pre 1975 car EFI issues were common.
May this information fix your 99 driveability and fowling and idle problems Don
posted by 174.19.117...
, Mon, 30 Oct 2023 18:31:34
, Fri, 3 Nov 2023 15:24:03, Sat, 4 Nov 2023 06:30:46
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