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Hi all,
I had the DI wiring checked today, the LH 2.2 computer modified to 'understand' the 12V ignition pulse from the DI (stand alone '88 9K, #7585797 IIRC) rather than the negative coil pule it normally gets, the EPROM swapped from the broken custom programmed DI box to a 'new' box of the same #, and the whole shebang installed (very expensive at ~90 an hour, but I wanted it to be done with). Much to my dismay, a mile or so down the road it turned out not all is well.
The car will only drive properly when under load. If I keep the car close to or into turbo boost it drives very well. Cruising well into the athmospheric zone of the boost gauge causes heavy bucking and shuddering. Got home OK using the method of intermittently using half- two thirds throttle, then coast as traffic dictates. Where traffic cleared, it would cruise impressively well at 90-100 mph...
When stationary, it starts up OK, then settles into a low and very uneven idle, and revving it through the 1.5 - 3K RPM range will cause all kinds of stumbling, shuddering and spitting back into the exhaust.
Stupid thing is, when I disconnect the pressure sensor when stationary the engine stil runs unevenly, but the shudders and backfires are all but gone.
BUT measuring the input and output voltages (5V feed to the press. sender, output varying with load) they are perfect. 5V from the DI unit to pin 1, ~0.8V output on idle (-0.6 bar absolute pressure), 2V woth athmospheric pressure.
All spark plugs (new BCPR7ES-11s, put in today) show the same pattern: slight white coating, grey underneath. Turn the RRFPR way up and it will run -slightly better, plugs still look the same. Could it be that the Trent RRFPR has failed at the exact same time that I put the DI in? (Before, I sometimes and randomly got a slight hesitation). Otherwise, it sounds to me like the ignition timing is way retarded at idle and low loads.
How could that be possible, when the MAP sensor and DI computer interact perfectly according to the book, and the car seems to drive perfectly as long as you can stay around athmospheric or into boost? Would a misaligned crankshaft postion sensor and/or shutter wheel (for both, I see only one way it can be positioned) cause these symptoms?
I'm at my wit's end, frankly.
TIA,
Eric
posted by 213.116.17...
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