Help diagnose a 94 LT1 problem

[Al 96 Ram Air T/A]

My buddy owns a shop in town...he's a ASE Master Mechanic, specifically with the last 10 years working on GM cars (mostly Pontiac).

Anyway, he gets a car in two weeks ago with a no start condition. It's a 94 Firebird with the LT1. He diagnoses the problem as an Opti taken out by a leaking waterpump. Against my advice, he replaces the Opti with a "no-name" unit, to save the customer money. Anyway, about a week later, the car is back in with a no-spark condition. He takes my advice this time and replaces the Opti with a GM unit. While it costs almost $400 bucks, I tell him it's the way to go.

Anyway, everything checks out fine, he test drives it...no problems. He scans it to clear the DTCs, and drives it for about 10 miles - no problems. The customer picks it up, and goes on her way.

Yesterday, she's back. The car stalls out, and won't restart. After checking the DTCs, it's the same probelm - no spark. Every code (I don't remember which, I think code 16) points to a bad Opti again.

What can be causing this? The Opti looks fine on the inside, no coolant or arcing visible. I told him to check the coil to see if there is spark from the primary. I also had him check the Opti harness but he found all to be normal. The fact that he's asking me shows he's stumped (LOL).

What could be causing this? Is it possible the cam pin is worn causing the Opti to jump out of time? I'm not as familiar with the Opti opn the 94s as my 96. Could the problem lie in the ignition?

Puzzling...

[Jeff_in_Atl]

Check the connector that plugs into the OPTI for corrosion. I know you hear check this and that all the time but I bet you it is corroded. Mine had to get replaced twice while I owned it due to corrosion. The last time I told them to put some silicone dielectric on the connector before they plugged it in and it never had another problem. That is a must.

Code 16 means loss of signal from OPTI. That means the computer is not getting the low res signal. That doesn't necessarily mean the OPTI is bad. A bad connection to the OPTI can cause a loss of signal too. There is also a connector where the OPTI harness plugs into the main harness. There could be a problem there too.

[Joe 1320]

The difference between the two Optis is that the 94 is a non vented design. Ozone from electrical dischage was building up within the cap and causing problems. The vented design circulates intake air through the cap to vent the gas buildup.

Has a copmplete diagnostic been performed? Codes don't tell much........Is there spark from the coil but not from the plugs? Is there no signal from the optical sensor?

here is a diagnostic for the ignition system if you haven't done it already.

http://www.f-body.com/forum/showpost...48&postcount=7


You just have to systematically eliminate all possible causes.

[Al 96 Ram Air T/A]

Cool...I'll pass the information along.