Odd idle and only starts on second attempt

I have a 1988 etc 3.9efi fitted to my 90, first problem is a irratic idle.

I have changed all sensors, check air gap, set timing to 8 degrees as it sounded better at that setting, set base idle correctly but it still idles slightly irratic from 750 up to 1020 can anyone shed any light? I have also fitted a brand new TPS and set that to bang on middle tolerances. The only way I can make it tickover perfectly is by adjusting the slack in the throttle cable near the butterfly to just grab the revs and it will tick over purrrrrfectly.

Second problem is, the truck always started fine and as of a day ago it will start, tick over for a couple seconds then die, crank it again and will run perfectly for as long as I want it to until I shut it off, I have a RRC in tank high pressure fuel pump fitted. Can anyone help on either.

Thanks

Bade idle?

cooltide said:

Bade idle?

Click to expand...

Sorry I meant base idle

Kernow90 said:

I have a 1988 etc 3.9efi fitted to my 90, first problem is a irratic idle.

I have changed all sensors, check air gap, set timing to 8 degrees as it sounded better at that setting, set base idle correctly but it still idles slightly irratic from 750 up to 1020 can anyone shed any light? I have also fitted a brand new TPS and set that to bang on middle tolerances. The only way I can make it tickover perfectly is by adjusting the slack in the throttle cable near the butterfly to just grab the revs and it will tick over purrrrrfectly.

Second problem is, the truck always started fine and as of a day ago it will start, tick over for a couple seconds then die, crank it again and will run perfectly for as long as I want it to until I shut it off, I have a RRC in tank high pressure fuel pump fitted. Can anyone help on either.

Thanks

Click to expand...

Not sure you'll have a 3.9 if it is a 1988 motor? Anyway, if it is a 3.9 on standard hotwire injection my thoughts would be:

1: Remove plenum, clean inside. Clean the ram housing too. Then check and set the throttle disc. Remove and clean the stepper motor, make sure there is no air leak from the stepper - the gasket normally falls apart. Reassemble with a smear of rtv silicone, works fine.
2: Sounds suspiciously like an inlet air leak. Check for split, perished or damaged hoses.

HTH

As kev says
Does sound like idle too low / air leak affecting setting