Idle Surge- Need diagnostic opinions

[kpack5982]

I finished installing my 3g alternator last night and was looking forward to reaping the benefits but low and behold the idle wants to jump up from about 900 where it is set to like 1300-1400 and then back down again, even with the iac disconnected it does this. So I was thinking one of two things:

1) Since I have my battery mounted in the trunk, I should place a ground from the battery to the front of my car rather than just the ground I have to the framerail. Only problem is where does the battery ground to up front?

2) I have some other wiring electrical issue.

Any other ideas or suggestions?

 

[HISSIN50]

Did you knock any vac lines off?

Install an additional engine ground?

For grounding diagnostics, you might try using long jumper cables to see if it helps. If not, that might save you some time running cables the length of the car.

Jrichker will be in shortly I'm sure.

Good luck.

 

[kpack5982]

I already have a 4 gauge ground wire from the back of the engine to the firewall and another one running from a ground on the front driverside to a ground on the driverside engine.

I'll check for vac lines. None really in the areas I was working, but i'll take a gander, thanks.

 

[jrichker]

See "Help me create the Surging Idle Checklist" at http://forums.stangnet.com/showthread.php?t=698148
for help with your idle problems. The first two posts contain all the updates to the fixes. I continue to update it as more people post fixes or ask questions.

Rear mounted battery ground wiring. Follow this plan and you will have zero
ground problems.

One 1 gauge or 1/0 gauge wire from battery negative post to a clean shiny spot
on the chassis near the battery. Use a 5/16” bolt and bolt it down to make the
rear ground. Use a 1 gauge or 1/0 gauge wire from the rear ground bolt to a clean
shiny spot on the block.

One 4 gauge wire from the block where you connected the battery ground wire to
the chassis ground where the battery was mounted up front. Use a 5/16” bolt
and bolt down the 4 gauge engine to chassis ground, make sure that it the metal
around the bolt is clean & shiny. This is the alternator power ground.

The computer has a dedicated power ground wire with a cylindrical quick connect
(about 2 ½”long by 1” diameter. It comes out of the wiring harness near the
ignition coil & starter solenoid (or relay). Be sure to bolt it to the chassis ground
in the same place as you bolted the alternator power ground. This is an
absolute don’t overlook it item for EFI cars

Picture courtesy timewarped1972

Crimp or even better, solder the lugs on the all the wire. The local auto stereo
shop will have them if the auto parts store doesn't. Use some heat shrink tubing
to cover the lugs and make things look nice.