Arrrrrrrrgh! Intermittent dead 90q ignition (long)

[Mihnea Cotet]

Nathan,


As you still have the fuel pump running, I'd suggest you try to find a
junkyard distributor and swap the whole thing.... The Hall sensor can go
bad and if it's a transistor (I think so); it could close the circuit when
hot.... Try to find a known good used one and try it before swapping the
ignition switch...

HTH,

Mihnea


At 09:55 9/08/2002 -0500, nde264 at lulu.it.northwestern.edu wrote:
>I've been having intermittent ignition problems with my 89 90q with 214000
>miles for over a month now.
>
>The symptoms/problem are as follows.  While driving the car, or more
>correctly,
>while running the car it will sometimes just lose ignition, as if someone had
>just turned off the key.  The tach drops to zero.  Sometimes, while driving,
>with the engine still turning, the car will just buck and spring back to life.
>This is accompanied by the tach needle bouncing.  When I do lose the car
>entirely, it will usually restart after 5 or so minutes of sitting.  The car
>will run very well, like nothing ever happened, for about 10 minutes and die
>again.  I believe that I have isolated this to the ignition system as the fuel
>pump does run immediately, autocheck flashes OK, etc. when turning the key off
>and back to the run position before trying to restart.  I just get NO spark.
>
>In the past month, I have replaced the distributor/hall sensor and ignition
>control computer with units sourced from Chris Semple.  Neither of these fixed
>the problem.  I looked through the schematic in the bentley with an
>electrician
>friend, and he told me to get what is referred to as the ignition booster in
>the bentley.  I bought a NEW ignition coil/module from pap-parts, and the car
>drove fine from Dayton to Chicago and drove fine for most of this week as
>well.
>
>I thought that this was a thermal issue as it usually happened after the car
>had been running for a while.  Well, yesterday, it happened while pulling out
>of a parking lot in which the car had sat for 3 hours.  It was still light
>outside, so I swapped out the new ignition coil/module for the old one, still
>no start.  I returned to the newer coil and then swapped for the old ignition
>computer, still no start.  I try both old computer and coil, no start.  At
>this
>point, I can smell gas coming from my exhaust.
>
>I pull a spark plug and set it on the valve cover, no spark when turning the
>engine.  I pull the coil->distributor wire, set it on the strut tower
>brace, no
>spark.  I then run the tests listed on pages 28-130-1 through 28-170-2 in the
>Bentley manual.  Everything tests fine.  The diode test on the hall sensor
>(28-160-1, first test) provided what looked to be a constantly on LED, but
>maybe the pulses were too quick for me to resolve (starter turning engine
>circa
>300 rpm, 5 revolutions/second, therefore either 12.5 or 25 pulses/second)?  Is
>my hall sensor fried and consistently closed circuit when hot (as it is
>effectively a transistor)?
>
>After an hour and twenty minutes of tinkering and testing, I am thoroughly
>disgusted and decide to wrap it up and call a friend for a ride home.  I slam
>the hood, try one more time, and as unburnt fuel fumes pour from the exhaust,
>it miraculously starts.  Drives beautifully for 10 minutes and stalls again.
>It's dark out now, and I sit in the car for 5 minutes, starts, drives home.
>
>I did not drive my car to work today, as I am afraid of it.
>
>Am I missing something?  Where else should I look?  Is it possible that the
>keyed ignition switch is failing, though it still performs all other functions
>it should?
>
>I'm debating wrapping up this 90q and getting another vehicle if I can't
>diagnose/fix this easily/cheaply.  I love my car, and would hate to see it go,
>but the rage is setting in.
>
>TIA,
>
>Nathan Engelbert
>89 90q