Up & down idle 88 Duke when warm

[GTRS Fiero]

Yep, that's me.  I'll sit here in my easy chair, provide links and make suggestions, and let you turn the wrench and get your hands dirty.  I probably won't lend a hand on your Fiero in 2019, either.   

I used to have a Firehawk that I bought used at 109K miles.  The car ran very well, but while things were apart in front (routine used car maintenance), I decided to change the plugs.  Anyone who has done this will know that you have to either drop the engine or remove a fender to access some plugs.  Anyway, I found that it still had the factory plugs, which still looked good.  Since I had them out, I replaced them, unfortunately with platinum plugs.

I'm not sure that age is a problem for the plugs.  I am curious how your plugs looked, when you pulled them.

[Raydar]

...
Again, does anyone have experience with blocking out the EGR on an 88 L4? I can have a cover-plate and gasket made within minutes and permanently plug the hoses.
Thanks

\D

I was thinking about deleting mine but, like the V6, there are some timing (and I thing fueling) parameters that are changed to account for the EGR. (I have the software, and found those changes.) Deleting the EGR without a reprogram would likely make it ping, at best.
I didn't bother with mine. Didn't seem worth the trouble.

[Donster]

...
Again, does anyone have experience with blocking out the EGR on an 88 L4? I can have a cover-plate and gasket made within minutes and permanently plug the hoses.
Thanks

\D

I was thinking about deleting mine but, like the V6, there are some timing (and I thing fueling) parameters that are changed to account for the EGR. (I have the software, and found those changes.) Deleting the EGR without a reprogram would likely make it ping, at best.
I didn't bother with mine. Didn't seem worth the trouble.

I thought on the 88 Duke, the EGR doesn't run over the ECM, hence no software changes needed? Some on PFF said the older Dukes started knocking, but the majority reported no negative behavior. Mine isn't knocking, but I will replace it with new EGR anyways.

\D

[GTRS Fiero]

There are no electrical connections to the EGR, but there should be to the EGR solenoid.  I'm just guessing on the duke.  I think the ECU allows for the EGR, which should be an intake thing.

[Fierofool]

There isn't an EGR solenoid on the Duke. 

[GTRS Fiero]

Then it is controlled by the ECU.

[TopNotch]

As stated previously, the EGR on the duke is controlled by vacuum and back pressure. The vacuum comes directly from the intake, and is not controlled by anything. No electronics involved.

[Donster]

IAC & TPS replaced today (as they are identical to the 88/89 Opel Astra), idle is still hunting.
Vacuum lines are all good.......but wait........sprayed starter fluid around the throttle body, and low and behold, the up & down idle went away! Turns out the gasket for the throttle body is leaking/sucking air!
Problem is, I can't find this gasket anywhere. Has anybody had to replace this in the past? Can't ID it in the P22 either. :-(

\D

[GTRS Fiero]

Does it look like this FelPro?  From autopartswarehouse?




Felpro 60764 Throttle Body Gasket - Direct Fit, Sold Individually
Part Number: 60764

[Fierofool]

Looking at a complete rebuild gasket kit, that gasket is included.  There is also a similar gasket that has no gasket material between the two larger holes.  It's otherwise identical.  The image doesn't tell where any of the gaskets fit. 

[Raydar]

...
I thought on the 88 Duke, the EGR doesn't run over the ECM, hence no software changes needed? Some on PFF said the older Dukes started knocking, but the majority reported no negative behavior. Mine isn't knocking, but I will replace it with new EGR anyways.

\D

The ECM doesn't control or monitor the EGR, as the V6 does, but it does assume it's there, and operational.
My first 88 Duke failed emissions for high NOx. I replaced the EGR valve, and it passed. I also noticed that its slight tendency to ping went away, afterwards.

The only time the EGR really does anything is at a steady-state cruise. Moderate RPM (2-3K?) and moderate steady throttle.
The ECM has a bump in the ignition timing table that coincides with that set of conditions. I have to believe that's to accommodate the EGR.
My tuning software is on a different computer, or I'd post the graph. It's easier to see than it is to describe.

[Donster]

So I ordered the TB gasket on December 29th, 2018. Yesterday, January 7th, 2019, the German company tells me they are out of stock and refund my payment. Price was €20.00 plus shipping € 6.00 = appr. $30.00 US.
Turns out, RockAuto.com ships to Germany at reasonable prices for low cost items. (Gasket = $2,49 + $9,50 express shipping). Expected to arrive within 4-6 business days. We shall see.

I think I will plan a trip to the US, make a list of all the small hard to get parts, take an extra suitcase and combine it with a well deserved vacation. Heaven knows I don't get enough vacation working in Germany! :-)

\D

[GTRS Fiero]

You'll get busted trying to take contraband on the airplane...unless the TSA is still calling out "sick".

[TopNotch]

It should be OK if he checks his bag.

[GTRS Fiero]

Turns out, RockAuto.com ships to Germany at reasonable prices for low cost items. (Gasket = $2,49 + $9,50 express shipping). Expected to arrive within 4-6 business days. We shall see.

Gasket for $2.49 is good.  It's about $5, here.