Cadillac Repair: 1989 Deville erratic running engine, cadillac dealer, independent garage

Question
  My 89 Deville with 115000 miles ran perfectly until recently when it randomly began to "cut out".  I took it to an independent garage recommended by AAA. The garage verified there was problem, but during trubleshooting, the problem went away.  Their partial diagnosis "...checked distibutor wire connection, all seemed good, after reassembly, miss was gone -- may have been loose connection..."  The vehicle ran great for four days before the problem resurfaced.
  This time I took the vehicle to a cadillac dealer.  They experienced the same T/S problems - problem did not occur on diag machine but did during road tests.  They replaced plugs, plug wires (major tuneup except distributor which they said was ok). Problem still there.  Replaced the ignition switch and apparently problem cleared.  I picked up vehicle and on the way home, the problem came back.  When starting the vehicle the last two mornings, the engine raced and sputtered for about 15 seconds - I think I smelled fuel while and after this occured.  I have chatted with the cadillac ggarage - they don't know what else to do.  Hoping you can provide me and them with a lead.      thanks

Answer
Hi Jack, An engine needs spark, fuel and compression to run. Since it will restart after awhile that should eliminate compression. Now you will need to test for spark and fuel. Driveing with a fuel gage hooked up and when the engine dies noting the pressure will tell if it might be fuel related. Also monitoring the ECM data while driving might give some insight as to the cause. Intermittant problems are the hardest to fix as you are now aware. I am kinda surprised that the Caddy dealer thought a major tune-up would cure this type problem. If the main driveability/master tech. didn't get this job I can see why those parts were replaced. If the parts didn't need replaceing due to time/mileage or the engine didn't run better after replacement then I would ask for a reimbursement...some or all of the tune-up price...because it didn't fix the problem. The first shop you went to could be onto the trouble spot because I have replaced the wireing harnesses inside distributors because of an open connection but they were on '90 and newer. One that comes to mind is a '91 SDV where it didn't want to start cold intermittantly. So here I am in the middle of an Illinois winter outside testing things when it didn't start and found the problem to be the wireing harness inside the dist.after about 4 hours of sitting. Other things that could cause this are the distributor/ignition module, ECM/computor, or a loose dirty negative battery ground cable near the starter or ECM grounds by the battery or horns. There was a bulletin published around '93 that describes how to test this. If the engine won't start or misses when it wants to the grounds need to removed, cleaned and reinstalled even though they look good. Doing a voltage drop test with the headlights on, blower on high and the rear defroster on can show if the grounds need cleaning. Tapping on the side of the ECM with several fingers can cause an ECM to make the engine die when running due to bad soldier joints. If hit with hammers or other objects too hard you can damage an otherwise good ECM. The dist. modules usually fail when hot and after cooling down will work again. The same can be said for any circuit board componant so just replaceing the module first might or might not be a good idea. If the engine never dies but runs rough then checking the fuel injectors for leaks, shorting and that they all drop the same amount of pressure when tested. A fuel regulator that is just starting to leak past the diaphram will act like this after sitting for 3 or more hours. Removing the vacuum hose from the regulator will show if it is leaking while running. The dealer also has a tech assist hotline that is available to them that can give more things to test. Sometimes however the service manager is the only person that is allowed to talk to them which is a mistake because things get lost in the translation between the tech, service manager and assist hotline helper. Too bad you weren't near Rockford as I might be able to personally look at the car if you are still having problems. Hope this helps. Bill