Solution for intermittent no-start/no-run problem

[crossroads]

This was originally posted in the Oldsmobile Intrigue forum but was reposted here given the shared body style of the Lumina/Grand Prix/Intrigue/Century

You may find this reply to be rather long but you need not read the Details section unless you wish to follow the specific symtoms preceding the solution.

Vehicle: 1999 Oldsmobile Intrigue 3.5L

Issue: Vehicle will not start or may not run.

Solution: Faulty ignition switch. (Replace or disassemble and clean contacts)

Discovery: Ignition switch was removed from vehicle and disassembled. Start and run circuit contacts exhibited mild burning/smut build-up leading to intermittent high resistance or opening of start and run circuits. Contacts were cleaned and switch reassembled. Leads and connections to switch appeared to be in good condition. Issue has failed to reappear.

Details: Between April-August '03 vehicle began exhibiting with increasing frequency one of four conditions:

1) will not crank,
2) cranks w/o starting,
3) starts but will die immediately or run for short period (3-5 sec) then die,
4) starts and runs but will die w/o warning while vehicle is in motion.

Early on 1-3 would manifest only upon restarting warm. Toward the end, item 4 began to be observed regularly with 1-3 being seen for warm or cold starts.

An interesting observation was made but failed to be understood in the context of the observed problem. Normal behavior for the tachometer is to 'pop-up' indicating the current engine speed following a successful start and release of the key. When the tachometer failed to respond following start and return of the key, condition 3 was always observed.

OBD II system was interrogated using Auterra Diagnostic Module. It was important to note that OBD II never reported a stored code (at least none persisting longer than the next start, successful or not). Why was this? Consideration was made of each of the many devices dealing with engine maintainence. Nearly all of the on-board devices which might have been suspect, should they fail, would generate a code and upon failure OBD II would revert to default setting or seek the information via redundancy to allow continued operation as opposed total shutdown.

After a few wiring checks and some reflection it was considered that perhaps a code was not stored because the problem was not one which the vehicle considered to be a device failure. Turning off the vehicle is not an event that would generate a code (obviously) as it is considered normal operation but a bad ig switch contact would behave similarly thus resulting in a 'no-code' problem. This consideration led me to suspect a possible failure of the ignition switch or one of its leads/connections.

Hope this helps.

Mark

Personal plug: The author has held certifications in 7 of 8 ASE automotive specialties but subsequently 'traded' these for a B.S. and M.S. in Inorganic Chemistry. If anyone reading this is interested in employing a strong analytical thinker with a formidable mechanical and scientific aptitude please contact at: mbiscott(at)att(dot)net. Thanks.