Throttle lift up?

[f85gtron]

I'm experiencing a strange problem where when i accelerate, then hold the accelerator steady, the throttle then "lets off" a tad.  anybody know what is causing this?
Ron

[TopNotch]

Does it happen while under power, or under no-load condition? If under no-load, it could be normal. The throttle position does not directly control the engine speed -- the computer (ECM) does. But it shouldn't happen while the engine is delivering power to the wheels.

[Fierofool]

Have you checked engine and trans mounts and the dogbone bushings?  How are they?  The impression I'm getting is that the engine is moving.

Another thing to check is the cable sheath retainer on each end of the cable.  These are normally in a stationary holder at each end.  The ends may be loose.  You can see the cable and retainer at the engine in this pic.  The one at the front is a little more difficult to access. 

[f85gtron]

it is noticeable when under part throttle conditions. full throttle feels good, just happens at the beginning of cruising or light to moderate acceleration.  the motor moving around makes sense. 
I'll check for rotation.  how much is too much?
I'll check the throttle cable too. 
Ron

[Fierofool]

Normally with the cable sheath anchored at both ends, engine movement would not affect the throttle since sheath and cable would move together.  If one end is loose, it will allow the sheath to move with the engine, thus the true effect is that the cable is moving inside the sheath.  If it isn't anchored on both ends, any amount of movement of the engine would have some effect. 

[f85gtron]

i checked the cable and it checked out good. the dog bone is a little loose, but i rocked it in gear and the mounts are tight.  i checked out the egr to see if it's leaking because i only notice it at part throttle, and it checked out too.  i did find that it had 3 layers of gaskets on it, two of which where burnt and cracked....the third was good. so i reinstalled it with the good gasket.  no more bucking, but still have the condition.  i ran my inductive pickup from my timing light along a couple plug wires and found that #1 is bad. Sooooooo there you go. 
i haven't replaced it confirm yet. 
Ron

[f85gtron]

I figured out the problem and it ties into another thread. http://gafiero.org/bbs/index.php?topic=1718.0
Turns out it was a week spark condition.
Thanks for your suggestions. 
Ron

[f85gtron]

Oops, i spoke TOO soon! Problem still exists.  Maybe could be tps?

[f85gtron]

I need to tie a couple of these posts together, because a couple unrelated problems are becoming related.  I've sorted out an ignition mis, an egr leak, a tps and iac adjustment....all to find i still have a part throttle hesitation.  I'm coming back to the egr because it's either got to be that or dirty injectors. 
I remember that when i pulled the egr for inspection, it did NOT have a restrictor washer staked in place. 
Sooooooo my question is:
Will a lack of an egr washer restrictor create such a condition?  In my head, it makes sense because it is only actuated at part throttle, right?

Where would i get a hold of some washers?  I read that for the stock 85 2.8setup, it should measure around .34in.
Ron

[TopNotch]

If it's a stock EGR valve, it doesn't need washers. I happen to have a good (although a bit rusty) stock EGR for the 2.8.

[Fierofool]

Stock EGR systems have a washer, too.  It's located on the end where it bolts up under the intake manifold.  The opening should measure 11/32".  It should be on the intake end of the tube to prevent wide open throttle should the valve stick open or the tube gets a hole in it.  With air being pulled in through a crack or leak, the ECM will compensate for the lean burn by opening the injectors to maintain a correct air/fuel ratio, causing the engine to rev full throttle.  That washer acts as a restrictor. 

[TopNotch]

Are you talking about the little end of the EGR tube? It must not be necessary, because I've had two EGR tubes on my 86 that didn't have the restriction. The first was one of those tubes made out of a natural gas line (you may have seen them on Ebay. The second was the Fiero store braided EGR tube (which is still there).

[Fierofool]

Yeah, the end that bolts to the underside of the intake manifold.  As long as the EGR valve and tube are in good condition with no leaks, the restrictor washer isn't necessary.  It's there as a safety in event of a vacuum leak upstream.  That's why the factory didn't place them at the upstream end. 

The restrictor washer gasket can be obtained from Rodney Dickman.  I found them at the bottom of this page, along with an explanation of where they're placed and why.
http://rodneydickman.com/catalog/product_info.php?products_id=308

[f85gtron]

So, assuming i have the correct tube gaskets in place, there's no need for an egr restriction washer be staked in?
Ron

[Fierofool]

I remember seeing a thread about some of the replacement EGR valves and they had some kind of small washer that had to be inserted in the bottom of the valve.  I assume that they accept that the original tube and restrictor are in place.  If the EGR instructions say that one should be installed, then I would.  I looked at the BWD EGR valve from Advance and there's definitely a recess around the pintle port for a restrictor, but it doesn't show one in the package.  Neither could I find one at Rock Auto.  Compare your replacement EGR with the old EGR and see how the pintle area compares.  I have some leftover gaskets from my 3.4 swaps.  I'll check tomorrow to see if I have any of the restrictor rings.