Please forgive us, but we're a bit new to this LT1 stuff...

We have a stock 1996 Z28 with 59K miles. The optispark unit and water pump were recently replaced by a reputable shop, and since that repair the car has been running very poorly. The car idles very rough and the SES lite stays on (code P0300 - misfire). We replaced the ignition wires, EGR valve and EGR solenoid with no change.
The optispark we used was purchased from Pace Performance Parts, and is the 'vented' unit. As far as I know, no other parts (other than the water pump) were changed as part of this repair.
Is the vented opti a direct replacement for the original unit in a '96 Z28? Is the firing order the same for all opti units? What could be causing the rough idle?

We really need help with this problem. Thanks very much.


Rick & Kristi

 

But there is a chance that you got an out of the box opti that was bad. This is a pain in the ear man.
first off, have you double and triple checked that the wires are in the correct position on the opti??
Do it again for peace of mind. Then check the plugs for cracks in the housing. if to no avail after that, maybe the wires have meltedin a spot that you cant see. I am sure that it is something rather simple, if you have further ?s pm me or email me . My address is in my profile.

 

yes, check the wires........then after that.....check them again. I don't even want to talk about the crap I went through last week and it ended up being the damn wires. Crap!!!

 

It is most definetely your wires.....reputable shop or not, a Z with stock manifolds is pain to work on. No matter how good a mechanic a person can be, the lack of space in the engine bay can easily frustrate anyone. I for one broke my wire looms when my car was stock.

Most suspect areas:
1. Check your wires around opti/distributer area on the passenger side. A wire loom should be present and is absolutely necessary to keep the wires from rubbing against the serpentine belt.

2. Check your wires at engine boots. In a stock car, GM used heat shields to protect the boots from the heat emitted from the manifold primaries. Not all wires have these boot shield, but if I remember correctly it should the ones closer to the cowl (rear or the engine).

Good Luck.

 

The rough idle began when the opti & water pump were installed. We replaced the wires and noticed no improvement.

 

opti was probably installed wrong if you are sure the plugs and wires were put on properly.

does it do this when the car is cold? or only when it warms up after a few minutes?

 

The rough idle is most apparent when the car is warm.

How can the opti be installed incorrectly? Is there phasing or timing involved, like a distributor? Can we be using the wrong opti?
We installed the vented unit - should we have installed the non-vented opti? Could this explain the poor running?