Help! Opti Testing??

[Donne Trav]

Is there a way test the Opti still in the engine on a 1994 Corvette?
My car cranks normal — at the turn of key — but after a few miles,
it appears to idle a "little rough" especially at low speeds in 4th,
5th and 6th gears. This just suddenly started to happen. Opti was
replaced a little over 2 yrs. ago. Thanks

 

[68 4 spd]

Is there a way test the Opti still in the engine on a 1994 Corvette?
My car cranks normal — at the turn of key — but after a few miles,
it appears to idle a "little rough" especially at low speeds in 4th,
5th and 6th gears. This just suddenly started to happen. Opti was
replaced a little over 2 yrs. ago. Thanks

Need to scope the ignition under load to see if that is your issue. A/C on and a snap of the throttle will reveal weak ignition, a simple way to check for bad wires is to mist water from windex bottle onto plug wires in the garage. If they are bad in the low lightyou will see the spark grounding out along them.(door open) Hope that starts to help you.

 

[compyelc4]

Need to scope the ignition under load to see if that is your issue. A/C on and a snap of the throttle will reveal weak ignition, a simple way to check for bad wires is to mist water from windex bottle onto plug wires in the garage. If they are bad in the low lightyou will see the spark grounding out along them.(door open) Hope that starts to help you.

1. Check for hard codes and let us know what is reported. On my '95 I can pull those codes right on the dash without using any fancy reader tools. If you do not have that capability, go to Autozone and ask them to check for you.

2. Check your water pump weep hole to see if there are signs of a leaking pump. If leaky you are not far from a failed opti.

3. You can pull the Opti to ECM signal harness. Check the opti-side terminal to see if it is sufated. Another sign of a.) leaky water pump, b.) a failing opti due to water intrusion from the pump leak.

Good luck.

 

[Donne Trav]

"Service Engine Soon" Indicator

Will the "Service Engine Soon" light appear if the Opti is bad? When I
had an obvious bad Opti, I never noticed that warning before. And a
BIG THANKS for the replies.

 

[compyelc4]

Will the "Service Engine Soon" light appear if the Opti is bad? When I
had an obvious bad Opti, I never noticed that warning before. And a
BIG THANKS for the replies.

I've had two bad opti-sparks (distributor) in 52,000 miles. Each time I got a Check Engine light. Code set too but I can't remember what it was. Maybe someone chime in with the probable code. First time leaky water pump took out opti at 15,000 miles! GM replaced opti but forgot to change the pump (little known to me). The new opti failed in about a month at 15,250 miles.
Symptoms: Intermittent hard starting, no starting, running rough, if I could start it at all. The last straw was when the car started acting up while on an errand. The ECM commanded "limp home mode" (ECM fuel/air program defaults to "who cares about polution.. just get it back to the driveway") and it DID let me get back to the house....slowly.

 

[Schrade]

Is there a way test the Opti still in the engine on a 1994 Corvette?
My car cranks normal — at the turn of key — but after a few miles,
it appears to idle a "little rough" especially at low speeds in 4th,
5th and 6th gears. This just suddenly started to happen. Opti was
replaced a little over 2 yrs. ago. Thanks

That's when it goes to Closed Loop / warmed up.

You can bring up History H and Current C codes on '94 with key punch sequence. It's in the manual.

If no codes history or current, and data scan will show opti readings out of normal operating parameters.

Any shop can plug in and printout logged data.

Get the USB connector on eBay ($30), for your laptop, and download free software. Watching the PCM readout is fun.

;;;;;;;;;;;
ed:
See if you can get mods to merge your threads - makes following procedures easier for readers here...

Sprayed water on wires — no "4th of July" — wires GOOD!
6th gear under load — assuming Opti GOOD!

But, I can smell fumes reeking from somewhere — strange?
Purchased MAP Sensor. Looking to purchase MAF & possibly
an IAT sensors too, if necessary. One of the 2 appears to be
very expensive.
Still concerned about the smelling of the fumes — anyone have
a clue?

Thanks again all.

Smell the oil stick for gas.

Pull the vacuum hose from the FPR, and see if it has gas inside it. Do you MAX gas in the tank at fill-up? Not good if so. Gas fills the EVAP purge line to cannister, and EVAP purge command pulls liquid, not vapor.

How's fuel pressure bleed-down time?

Why the new MAF and IAT sensors???

Do you have FSM? It really helps everyone if you can get and follow sequences for diagnostics. It ain't hard, and it's easy detective work. Do you have multi-meter?

 

[Donne Trav]

That's when it goes to Closed Loop / warmed up.

You can bring up History H and Current C codes on '94 with key punch sequence. It's in the manual.
If no codes history or current, and data scan will show opti readings out of normal operating parameters.
Any shop can plug in and printout logged data.
Get the USB connector on eBay ($30), for your laptop, and download free software. Watching the PCM readout is fun.

;;;;;;;;;;;
ed:
See if you can get mods to merge your threads - makes following procedures easier for readers here...




Smell the oil stick for gas.

Pull the vacuum hose from the FPR, and see if it has gas inside it. Do you MAX gas in the tank at fill-up? Not good if so. Gas fills the EVAP purge line to cannister, and EVAP purge command pulls liquid, not vapor.
How's fuel pressure bleed-down time?
Why the new MAF and IAT sensors???
Do you have FSM? It really helps everyone if you can get and follow sequences for diagnostics. It ain't hard, and it's easy detective work. Do you have multi-meter?

Yes, I have FSM. I don't own a Multi-Meter of any instrument for pulling codes.
I have been MAXing at fill-up — won't do that anymore.
Thanks Again! Very interesting about the fill-up MAXing.