87 2.5L ISA and Idle issues

[billyjp2]

My 1987 2.5L had a long crank/ hard start issue over the winter. Only when the weather was cold and the engine itself was cold. I replaced the ISA with a new unit from Rock Auto.

 

This solved the starting issue, but immediately I was plagued with a high idle. I tried a different new ISA with same results. All vacuum lines look to be in good condition. 

 

Any suggestions?

[eaglescout526]

I gotta think on this one. Have you ever seen any of the ISA's move?

 

Edit: there is an ISA adjustment procedure that has to be done when installing a new ISA. How far out is the bolt on the ISA plunger?

[billyjp2]

39 minutes ago, eaglescout526 said:

I gotta think on this one. Have you ever seen any of the ISA's move?

 

Edit: there is an ISA adjustment procedure that has to be done when installing a new ISA. How far out is the bolt on the ISA plunger?

 

At the moment, not very far out at all. I've never seen it move, but on startup the idle is relatively low, it builds up as the engine warms.

 

I've seen the adjustment procedure alluded to in Google searches, but the links I've clicked are dead.

[eaglescout526]

Alrighty. I’m out and about at the moment but here’s a quick summary of it. You need to connect a tach to two pins on the diag port D2, don’t remember which right now and with the ISA disconnected the idle will be high and loud. You screw the bolt counter clockwise or clockwise until the tach reads 3500 RPM

Edited May 10, 2020 by eaglescout526

[billyjp2]

I'll get my hands on a tech in the next day or so. Thank you.

[eaglescout526]

22 minutes ago, billyjp2 said:

I'll get my hands on a tech in the next day or so. Thank you.

Meant tach, autocorrection from being on the phone. Once you get the tach I can tell you which pins on the diagnostic port the tach goes to.

[billyjp2]

On 5/10/2020 at 6:25 PM, eaglescout526 said:

Meant tach, autocorrection from being on the phone. Once you get the tach I can tell you which pins on the diagnostic port the tach goes to.

Tach came in, were you able to find any details? 

 

 

[eaglescout526]

So to connect the tach, do you know the diagnostic ports on the pass fender? Covered by yellow covers?

 

connect the tach wires to D1_(positive)1 and D1_3(negative). Once the tach is correctly wired in and reading the RPM, the truck will need to be at operating temp for best results.

 

Once at temp stop the engine. Unplug the ISA as it should be fully extended after engine shut down. You will need some ear muffs for this as the engine screams. Watching your tach you will adjust the bolt on the ISA by the throttle plate. 

 

If I remember correctly, counter clock wise raises the idle and clock wise lowers it. Once at 3500 rpm + or - 200 you can shut off the engine and plug the ISA back in and then start it again to see if the idle has come down.

[benjy_26]

5 hours ago, eaglescout526 said:

So to connect the tach, do you know the diagnostic ports on the pass fender? Covered by yellow covers?

 

connect the tach wires to D1_(positive)1 and D1_3(negative). Once the tach is correctly wired in and reading the RPM, the truck will need to be at operating temp for best results.

 

Once at temp stop the engine. Unplug the ISA as it should be fully extended after engine shut down. You will need some ear muffs for this as the engine screams. Watching your tach you will adjust the bolt on the ISA by the throttle plate. 

 

If I remember correctly, counter clock wise raises the idle and clock wise lowers it. Once at 3500 rpm + or - 200 you can shut off the engine and plug the ISA back in and then start it again to see if the idle has come down.

I've been messing with my idle as well. I was about to adjust my ISA motor, but my engine didn't rev up to 3k when I unplugged the motor. 😐

[eaglescout526]

25 minutes ago, benjy_26 said:

I've been messing with my idle as well. I was about to adjust my ISA motor, but my engine didn't rev up to 3k when I unplugged the motor. 😐

How low is your idle? Mine sits between 900-1000 warm and AC on. So it probably would be best to have the AC off with the adjustment now that I think about it if both of your guy's trucks are equipped. 

[Warren Mohler]

1 hour ago, benjy_26 said:

I've been messing with my idle as well. I was about to adjust my ISA motor, but my engine didn't rev up to 3k when I unplugged the motor. 😐

Run engine till warm, shut off, motor should extend at key off then unplug and start engine adj. plunger bolt to 3500 RPM

[benjy_26]

Thanks for the responses, guys. My truck doesn't have an AC, BUT, it did have a very stiff throttle spring. While monkeying around, I took off the spring and, like magic, my idle motor worked. My idle sits right below 1k and I don't have to depress the pedal anymore to get it started. 

[eaglescout526]

31 minutes ago, benjy_26 said:

BUT, it did have a very stiff throttle spring.

Sounds like the TB needs a bit of lubing. But glad its all normal.

[benjy_26]

14 hours ago, eaglescout526 said:

Sounds like the TB needs a bit of lubing. But glad its all normal.

Where would I lube? 

 

Would white lithium grease work?

[eaglescout526]

White lithium grease will work. I would just spray it on the big throttle spring where the throttle plate is.

[benjy_26]

Nice. Thanks!