86VX1

86 corvette runs perfect, other than this little issue.

heres what i have done so far.

just fyi., i have two 86 cars. the silver bullet corvette auto runs perfect with out issues.

the 86 red devil corvette manual is the one with the fan idling issue. the car runs perfect other than this problem. it has plenty of power, idles steady. fan comes on at 229 and turns off at 218 average. not service engine soon light, no trouble codes.

if i remove the fan relay and apply direct power to the black wire,(which goes directly to the fan) it will not want to idle and die, regardless of the temperature. if i hold the throttle open slightly it will stay on. If i let it warm up to 229, and reconnect everything, it will do the same thing when the fan comes on.


i have replaced the following,
new idle air control
set the tps to .54
set base timing

i have switched the following from my 86 silver bullet corvette.
switch mafs
switch fans
switch maf burn of relays
switch alternators

cleaned the body to battery ground
cleaned the fan body to ground
cleaned the engine to battery ground. and also added another body to battery ground.

i have had both alternators checked and both have checked out good.
i have a yellow optima deep cycle battery, new.

PatternDayTrader

I would start by making sure the ground circuit for the fan motor is good. It sounds like the fan motor turning "on" is interfering with the ground of another component or components, and so the ecm cannot properly control the idle speed. I would start by checking the fan motor ground circuit.

PatternDayTrader

Using a volt meter, start the engine and turn everything "on" including the fan, then test for voltage on the ground wire for the fan motor, while its running. You have to back probe the connector while its connected and everything is turned on. It should be zero or maybe a few hundredths of a volt (almost zero).

86VX1

Ok. I will re check the fan ground tomorrow.

86VX1

i have found the problem. just some background. this red devil corvette was taken to five shops in the local bakersfield area including the dealer. the dealer had it for about a month and could not find the problem. i bought the car super cheap because the owner hated the car by this time. it only took me about 8 months to finally figure out wat was wrong with this vet.

after looking at all the fuse able links and testing to ensure that they actually worked, the car sat for a while again. so this weekend my kids encouraged me to get back on the red vet and see if could figure it out. in the process of switching batteries, i decided to switch to old school baterty terminals because it was sick of switching batteries and bolting on adapter terminal side posts.
low and behold on accident, once i replaced the side post terminals, the car stayed on when the fan kicked in.

hope this helps some one out.