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Jim Grant's Tech Tips
90
Chevy Beretta, Stalling Problems
Q: I bought (with a lot
of his money, too) my 17 year old son a '90 Chevy Beretta. It's great
looking and I had it checked out by my mechanic. About 1 week after he
had it , it started to stall out periodically. This happens when he first
starts it and begins to drive. He can only go 10mph and then it will stall.
If he pulls over and shuts it off and restarts it, it's fine. Neither
the dealer nor my mechanic can find anything. They put in a new ignition
module and coil pack (whatever they are) and checked the grounds and the
wires. One mentioned the computer being replaced. I'm frustrated and thinking
about asking for my money back, if that would even work, but my son just
wants it fixed...Sally.
A: We've
seen some strange computer problems with vehicles of your type. The difficulty
is in proving that the computer is the problem\cause. The procedure we
use to identify a problematic computer is about as odd as the problem
itself. The vehicle's computer is removed from its hiding place in the
dash and the electrical connectors are inspected. Then with the engine
running the computer gets a slap. If the engine shutters or stalls then
the computer has a problem. If the engine doesn't act up, the computer
is left hanging by its electrical harness and a hair dryer is positioned
to blow hot air on the computer. Heat helps to aggravate computer type
problems. In the meantime, a computer scan tool and PC is connected to
the computer's diagnostic connector. With the engine running the PC is
commanded to download the data from the vehicle's computer. Once again
the computer is slapped and the electrical connectors are wiggled. Then
the data recorded from the vehicle's computer is reviewed. Because the
vehicle is just idling in the shop bay there should be no sudden changes
in the recorded data. Example; one problem computer was thinking that
the vehicle was going from 0 to over 200 mph in the shop bay in two seconds.
A replacement computer corrected that vehicle's problem. Diagnosis of
difficult computer related problems is not a 15 minutes job. Careful diagnosis
by a qualified technician should pin down the cause to your stalling problem.
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