Up & down idle 88 Duke when warm

[Fierofool]

In our investigation of the Evap Canister operation, I found that both ports of the evap canister are attached to the intake and throttle body.  If one of the lines between is cracked or if the canister purge valve is defective, this could result in a vacuum leak to the intake system. 

I don't know if the 88 Duke has a canister, but you might try disconnecting and plugging the two lines that go to the throttle body and intake to see if the idle calms down.  Just a WAG. 

[TopNotch]

The 88 duke does have a canister.

[Donster]

In our investigation of the Evap Canister operation, I found that both ports of the evap canister are attached to the intake and throttle body.  If one of the lines between is cracked or if the canister purge valve is defective, this could result in a vacuum leak to the intake system. 

I don't know if the 88 Duke has a canister, but you might try disconnecting and plugging the two lines that go to the throttle body and intake to see if the idle calms down.  Just a WAG. 

The vacuum lines to the canister were one of the first things I replaced. Also found out that the PO had a brainfart and swapped/reversed them. Can happen, as original lines were hard plastic and different sizes, but the ones he used were rubber/flexible and would fit on either connection. In cases like this, it is great to have an 88 Helms. 

Thnx!

[Donster]

The problem is back, worse than before! 

[GTRS Fiero]

Caught an infection from the Merc's.  O2 sensor still unplugged?  Plug it in, and see what happens.

[Donster]

Same, except, now the CES light doesn't come on anymore.

BTW: New pod with circuit membrane arrived, all instruments working again, just need to place the fuel gauge needle again. It shows sooooo full, there should be 30 gallons of fuel in it. LOL

[GTRS Fiero]

12 gallons uses about 1/3 of the gauge, so 30 gallons would be slightly below empty.

[Donster]

So today I replaced bot ignition coils and hooked the O2 sensor back up, runs nice, no stuttering, no hunting, no Check Wallet Light.    Didn't run her real hot, but did get her to a good operating temp. So far, so good.......now if I just could get the fuel gauge to work (different thread)........ 

[Donster]

Ran the car real hot today on a long trip, with a lot of stop 'n go, hunting idle is back! 
The ONLY part I have yet to replace is the fuel pump, although the fuel pressure seems to be OK, but at high temps, the pump may be functioning intermittently.
Very discouraged at the moment.

[GTRS Fiero]

My original coil packs and ICM were some aftermarket brand.  There were issues.  They were replaced, and the issues persisted.  Now running on an AC Delco set, and things are good.  You didn't get a cheap set of coil packs, did you?

[Donster]

AC Delco
I did notice that the heat shield was missing on the ICM when I replaced the coils. It seems to be impossible to get, so I made one myself from coke cans (made mine 3 layers).

[GTRS Fiero]

Did you replace the ICM, or just the coil packs?

[TopNotch]

AC Delco
I did notice that the heat shield was missing on the ICM when I replaced the coils. It seems to be impossible to get, so I made one myself from coke cans (made mine 3 layers).

If you're talking about the flat metal piece between the ICM and the coils, it needs to be made of steel. It is a magnetic shield. If you have hardware stores over there that sell galvanized sheet metal, get some and make your shield out of two layers of that.

[Donster]

So what negative affects could the missing shield cause? Hunting idle perhaps?

[TopNotch]

So what negative affects could the missing shield cause? Hunting idle perhaps?

According to The Ogre, a missing shield can cause code 42. I'm not sure what else, and I don't think I'll try running mine without it.