1981 Bad computer?
Thread Starter
4th Gear
Joined: Aug 2010
Posts: 4
Likes: 0
1981 Bad computer?
1981 305 auto. During idle and full throttle everything is fine. But while cruising or accelerating at around mid-throttle (normal throttle), the 'check engine' light will flash, the tach will dip momentarily and return back, and the car hick-ups. I think it might be a problem with the 'computer'. And I think the computer is behind the driver seat next to the battery. Am I right? Any help would be appreciated.
Racer
Joined: Nov 2009
Posts: 289
Likes: 0
From: Franksville Wisconsin
Either computer problem as simple as a connection or with tach dipping could be faulty distributor. Beware I had a rebuilt distributor go out in 20 min. Could be carb problem like I also had sticking mixture solinoid. Best thing to do is eliminate what its not. The factory manuals give testing procedures for each of the comonents. The computerized carb models are simple but complex at the same time. Its hard to find someone who can fix them. Good luck
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
It's more than likely a sensor problem...mass airflow sensor, temp sensor, throttle position sensor, etc. When the computer goes 'whacko', nothing works right. You need to get [or read] the info on that system in the Chevrolet Chassis Service Manual. There are detailed checks and trouble shooting strategies there to find such problems.
Pro
Joined: Apr 2008
Posts: 596
Likes: 6
From: Irving Texas
I have an 81 and agree.......its probably carb related. Think about it, the computer has no moving parts, nothing to wear out........the carb (an electronic carb at that) has a million parts that could go out due to wear. Any carb works well during open throttle...it takes a good carb to go from idle to part throttle with no hiccups.
I've eliminated my computer completely and went back to the good ol Edelbrock 600 carb.
My suggestion: take a whole can of carb cleaner to the carb (engine off). work the choke mechanism and throttle linkages open and closed several times while spraying.
I've eliminated my computer completely and went back to the good ol Edelbrock 600 carb.
My suggestion: take a whole can of carb cleaner to the carb (engine off). work the choke mechanism and throttle linkages open and closed several times while spraying.
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Race Director
Joined: Jul 2004
Posts: 12,686
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From: Scottsdale Arizona
-Turn the ignition off
-Pull the ashtray out. Underneath you'll find the ALDL connector (six slots in the plug, I think)
-Two of the slots on one end have a smaller divider between them. Put a paperclip, staple, alligator clip or anything electrically conductive from one to the other.
-Switch the ignition to the "on" position but don't start the engine.
-You should hear some clicks coming from the solenoid on the carb. Ignore these for now.
-The "Check Engine" light will begin flashing.
-Count the flashes and write them down. Each set of flashes will have a pause between them and the next set. The codes are two digit and each two digit code is repeated before going on to the next set.
Post the codes and we'll go from there.
Incidentally, I'm betting on the Oxygen sensor but I also think 7T1 has a good shot with the MAF sensor too.
Last edited by CA-Legal-Vette; Aug 29, 2010 at 01:42 PM.
Race Director
Joined: Jul 2004
Posts: 12,686
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From: Scottsdale Arizona
Instructor
Joined: Jun 2010
Posts: 130
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From: Summerville SC
