[AT] Check the grounds

[David Bruce]

Given my experience with my 2001 Malibu I can believe the events.

My situation started with an occasional total loss of electrical.  First 
check ended up with a new ignition module.  Next time the car would not 
start I brought the shop owner and his code reader home with me to check 
- of course the car started then.  He kept the car a week to try to 
duplicate the problem and could not.  After the first rollback ride the 
though was the anti-theft module was throwing the fault - this seemed 
plausible because you could follow the procedure to reset the anti-theft 
module and sometimes restore electrical.  After the second the problem 
was finally diagnosed - a bad connection to one of the fuse boxes 
creating an intermittent electrical fault.  Apparently the fault finally 
went from intermittent to constant.

When it comes to dealing with the computer module controlled stuff I am 
far from versed and have relied on the particular shop with excellent 
results other than this vexing case.

David
NW NC


charliehill wrote:
> David I have a good story about that.  I have an 89 GMC that I bought new 
> and have now put out to pasture.  When it was maybe 7 years old or so it 
> started to miss and buck when the cruise control was on.  I tried for some 
> time to find the problem and couldn't so I stopped using the cruise control. 
> Well in time it started to do the same thing without the cruise control.  I 
> still couldn't find the problem so I put a Jacobs ignition system on it. 
> That solved the problem for a while as well but after a time, probably 2 
> years from the start of the problem it started to run ragged again.  It 
> eventually got to the point that it was barely drivable.
> 
> Then I started looking very hard for the problem.  As you probably know 89 
> was in the beginning years of computer controlled stuff and was the OBD I 
> system which is much less involved than OBD II.   I bought aftermarket 
> manuals and started checking every sensor, voltage and ground I could find. 
> I never could find a problem.  I finally worked my way to the cruise control 
> system (where the problem began) but the aftermarket manuals didn't have any 
> cruise control information in them.  I was at a stopping point.  So, I went 
> to a small local dealer about 15 miles away.  I knew those guys and knew 
> that they had good mechanics.
> 
> When I went there I told the mechanic all that I had done and asked if he 
> had the specs for the cruise control system.  He said yeah had them in his 
> factory manual BUT he wanted to look for the problem his self.    We talked 
> about it and I understood why he wanted to retrace my steps.  He went to 
> work but he allowed me to go in the shop with him.  (that's why I chose that 
> shop).
> I stayed out of the way and let him work.  He checked everything I had 
> checked and finally decided it was the ignition module so he replaced it. 
> The problem didn't go away so, to his credit, he took that part back off and 
> put it back in on his shelf.  Finally after an hour or so he got around to 
> checking the cruise control.  He took his volt meter and checked the 
> resistance between one of the lugs in the cruise control wiring harness and 
> the stud on the thremostat housing where a ground wire was attached.  He 
> looked at me and kind of said Hmmmmm.  Then he took his 9/16 wrench and 
> tightened that stud.  We drove it down the road and the problem was gone. 
> The stud was double nutted on the ground wire and that was tight but the 
> stud was about 1/4 turn loose in the intake.  Since that stud goes into the 
> water jacket some coolant had seeped up around the threads and it wasn't 
> reading the right resistance.  Problem solved.  I realized after the fact 
> that I had changed the thermostat just before the problem started a couple 
> of years before.   That ground wire is kind of short and it's hard to get 
> the stud tight and the double nut tight on the ground wire without twisting 
> the stud a bit and that's what happened.
> 
> As Farmer says,  check the grounds.  It blew the mechanics mind and I know 
> it probably doesn't make any sense to some of those reading this but I swear 
> to you it's fact.
> 
> Charlie