86 Start problems

[tcolyer]

I have a high mileage daily driver with an occassional no start issue: Usually happens when car has sat all day. It starts then dies immediately, it will do this for several times. If I stop and leave it alone, come back about an hour it starts right up. I have replaced: injectors, fuel pump, fuel pick up sock, relay, fuel filter. The tank has been replaced with new GM so it is clean. I removed the Superchip last night and now the car starts well but will not Idle. It never seems to do this unless I don't have all the tools with me to do a good diagnosis, fuel pressure and power. But I can hear the pump run.

The problem may happen once a week to once every 3 - 6 months. No pattern I can find.

Any help would be appreciated.

 

[jmccloud]

Intermittent no start

I observed your Corvette's symptoms on a '91 Regal. Slowly got worse. After it totally crapped, a new ECM (or PCM, depending on the year) brought the car back to life. The FSM cautioned to assure that the ground was well made (PCM to ground). Further, when it was acting up, trying to read codes (paper clip technique) did not result in the 'service engine' light illuminating nor cause the cooling fans to run. When 'things worked' the fans ran and the light came on when the paper clip was applied with the key in the 'run' position (engine not running). Also, they came on during diagnostics with the new PCM.
Good luck and hope this helps.

 

[tcolyer]

Could this be related to VATS? tell me if I'm wrong on an 86 the VATS only controls the starter? It does not turn off the injector pulse or the fuel pump? I am not sure that is why I am asking.

 

[jmccloud]

No start

Vats prevents the starter from cranking, along with fuel inhibit.
If your Corvette cranks, it ain't Vats.

 

[keremarsan]

Hi,

Please check the İddle air control valve , just below the throttle body,
if it is not working properly, you don't have iddle control.

On my 88 , the throttle position sensor also must be 0,54 Volt +- 0,07 , I think the 86 has the same ,

there is 3 cable going into TPS ( thr.pos sens ) Check the Voltage between I think the last 2 ,

How to check iddle air control valve :

when your car is cold, the idle is controlled by this valve : if you RPM is not between 900 - 1100 when it is cold , it can be faulty

after some minutes, valve closes and idle speed must be 700 RPM controled by ECM

How to adjust the iddle:

1) turn the key on , but not start the car
2) wait for 1 min and disconnect the idle control valve connection
3) when you start the car ( İACV not connected ) , the engine spped must be 500 RPM ( even if the engine is cold ) in N , 400 - 450 RPM in D

If not, the throttle body screw ( on driver side of the throttle body ) must be adjusted to obtain these engine speed.

Now , adjust the TPS , there is 2 torx screw , loose them , turn down or up way the TPS connection to obtain 0,54 V on the voltmeter.

Now you can attache the IACV connection . If IACV is good, the car must start great and idle must be OK

Think also the clean the throttle body , open the up side by torx screw, you can see some times it is soo dirty , clean it , clean also the butterfly of the TB: