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86 VETTE

  
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86 VETTE

 
padgett11 padgett11
New User | Posts: 3 | Joined: 09/13
Posted: 09/10/13
06:03 PM

New here...sold my 77 to get this 86.big mistake!! DASH LIGHTS flicker and the Idle surges, I know there are a few sensors but I have no idea where they are or what they look like.and I'm pretty sure I have to pull the cluster out to get it fixed.also the cruise don't work,thinking that has something to do with the digital DASH going out..can anybody out there share your wisdom..thanks,Richard  

waynep712222 waynep712222
Enthusiast | Posts: 251 | Joined: 03/13
Posted: 09/10/13
08:51 PM

that's ALL EASILY FIXED.

dash boards in these.. have issues with the interconnect pins and terminals between the layers of the circuit boards.. some broken solder joints also...

if the car has been parked for a while.. drive it.. the road bumps may solve the issue.. it has on others...

as for the surging idle..

click my user name.. there is another magazine called corvettefever..

i have posted a LOT of corvette C4 info there.. in the forums.. there is also vetteweb.. i have some stuff there also..

or i can start again here...

Scandatagm

you will want to print this chart i modified...

you will really NEED a scan tool and they are harder to find for these...

this 1986 model.. is 27 years old.. give or take...

there are going to be a few issues..

surging can be caused by several easily fixed issues...

vacuum leaks...

fuel pump pressure issues..  and don't sweat.. i can do a C4 fuel pump in under 30 minutes.. only needing to lay down twice to unhook and then rehook up the drain hose.. yes.. standing behind the car..  its all done thru the gas filler door area..  only issue.. you have to special order an AC DELCO #G1 gasket..  its the rectangular flange where the fuel pump sending unit bolts in..


idle surging can also.. and is likely on cars with over 100K miles.. as a worn throttle body shaft bore..  what....

engine off..  hold throttle open part way... see if the shaft wiggles in the bore like this.. (o )  ( o)   when it should be like this.. (o) nice and tight when slightly open..

what happens here is with the wear .. the throttle closes to fractions of a degree different each time the throttle is moved and closed..  where this screws up is the Throttle position sensor is on the passenger end of the shaft.. this causes the minimum Throttle position sensor voltage signal to vary slightly and it confuses the computer..   what.. yea.. the computer never knows when you actually have your foot off the gas pedal... so it does not revert to idle lean mixture programming..

these L98 engines should idle around 475 to 500 RPMS.. people turn up the idle speed screw to compensate for the wear and toss all the programmed abilities right out the windows...

incorrect temp thermostats.. must be a 192F...

engine coolant temp sensors in the front of the intake  that either have a broken wire/terminal in the pigtail.. or the sensor is bad.. pick up both for under 20 bucks at most parts stores as a KIT...  always a great thing to change..

air leaks from the air inlet duct... between the MAF sensor and the throttle body..

loose ground wires.. there is an issue.. they are scattered all over the place..

and they all need to be taken off .. wire brushed and reinstalled.. sorry.. too many issues have cropped up because of a faulty ground to not give you the heads up..

plan on a few hours in the engine bay.. and at least ONE hour under the car getting to the two drivers side transmission bell housing to engine block bolts/studs ground wires..

there is also a hidden one next to the battery tray.. and usually a distribution block/stud behind the battery..   i have images to help..

distributor timing issues.. can also cause issues.. still a fairly easy fix..

and you don't need to buy a new one.. only a hand full of parts ..


which area would you like to start at...

so i don't bombard you with info...

but i am likely to do so anyway..

a factory service manual would help.. they are available in print.. and sometimes on CD..  

padgett11 padgett11
New User | Posts: 3 | Joined: 09/13
Posted: 09/10/13
09:58 PM

WOW!! If I can't fix it from the info you just gave me then I'm the one that's not idling right.lol. thanks for all the info it's a great deal of help Grin  

padgett11 padgett11
New User | Posts: 3 | Joined: 09/13
Posted: 09/10/13
09:58 PM

Grin  

waynep712222 waynep712222
Enthusiast | Posts: 251 | Joined: 03/13
Posted: 09/12/13
12:23 AM

this is basic.. but accurate...

it really requires me to look at the live data stream from the computer to tell you actually what you need to adjust..

there are also issues with the fuel injectors.. that have been mostly fixed by going to a Bosch III injector out of late 90s moustanges 5.0 HO or something like that.

these have 4 small spray holes instead of a single.. and if you saw the side by side varible flow.. variable pressure test.. you would be running around looking for  set of them..  i have been buzy with stuff around my end of the computer.. so i have not had a lot of time to spend..
if you have questions do ask.. and if i don't reply as this is a buzy board.. drop me a private message by clicking on my name.. or post over at corvettefever forums.. i look thru there daily also...