About 2 weeks ago I posted in a different thread that, my car started to backfire at start up and when at WOT I was getting around 10 degrees of knock. At first I thought that maybe I had gotten some bad gas since I was getting no codes with the backfiring. So I bought a bottle of 104+ octane booster and started to run nothing but premium instead of midgrade. It seemed that doing this had taken care of the back firing.

Then a few days later, I floored it, ran it up to about 120mph and got an SES light along with a code 36, which is "Optispark High Resolution Signal Faulty". So I then started to think that it was my Opti on it's way out and ordered a new one. Since that time (about a week ago), the back firing on startup occasionally happens even though I've ran nothing but premium, but the code has cleared itself and I've seen no SES lights.

So I've started wondering if it could possibly be my coil on it's way out. And since it's not properly supplying spark to the opti that's why it's backfiring and threw the code? Since the code has cleared I've ran it up to about 100-110 mph with no SES light or code.

What do you guys think.......Opti or Coil?


Thanks!

 

TTT.

 

Hell. I'd swap out the coil first. It is a lot cheaper & easier. It is worth the extra $$ spent on a coil even if it ends up being an opti.. JMO.

 

I agree,get a coil first and if that does not cure it you will atleast have a spare coil.

 

That is true. I've already bought an opti. But I could always sell it. So what is a good brand of a coil for our cars? What do they generally run? Thanks for the info.

 

Well, I've replaced the coil with an MSD and the problem still persists....when it wants too. A symptom that I have noticed is that when it backfires at startup, I get around 2 degrees of knock at regular acceleration and 11 degrees at WOT.

I noticed too that the rubber boot on the end of the tube that goes from the EVAP Canister Purge Solenoid Valve to the Throttle Body is ripped and cracked on the Throttle Body end. Could this have anything to do with the backfiring?

Also, the intake elbow is also ripped where it connects to the TB. But it looks like the clamp is pulling it together enough so it isn't sucking any extra air.

Basically I am stumped. Because I am getting no codes on my Scanmaster. The backfiring only happens occasionally and only after start up when it's at idle. My ideas as of now are....... Spark Plug Wire, Opti, or maybe even the Air Pump? I say the Air Pump becuse I had the Air Pump code 29 all winter and blew around 15 fuses. Since it's gotten warmer the code has cleared, I haven't blown any fuses, but the backfiring has occured. I've been trying to track this down for the last 4 wks. or so and am getting VERY aggrevated with it. I am open to try or check anything at this point!

THANKS FOR ANY AND ALL HELP OR SUGGESTIONS.

 

Sounds like opti symptoms to me. The code refers to a fault in the optical section of the opti, not the high voltage side. The only other possible cause is a corroded electrical connector at the opti's wiring harness connection, and sometimes the wires leading to it have damaged insulation where they wrap down around the front of the engine by the alternator.

Quit procrastinating and start getting your hands dirty

Also, check the vent lines for obstruction.

 

I've already bought the opti, but wanted to check and replace all of the little and easy stuff first. I didn't want to overlook something easy and jump to the conclusion that it's the opti right away. I guess that's what's next though. Thanks.

BTW, exactly what vent lines are you exactly talking about?

Thanks!

 

I can understand that

Just didn't want people thinking that an opti resolution code indicated a problem with the coil. Once you start throwing those codes it's usually opti time

The vented opti has a line that runs from the intake bellows, to the opti, and then from the opti to the intake manifold. You want to make sure that the vent line is free flowing and that the check valve in it works.

 

I'm looking for anything guys. Just gimme your opinions.

 

the coil is extremely easy to swap and cheap to boot.

so change it and see what happens

 

Quote:

Well, I've replaced the coil with an MSD and the problem still persists....when it wants too. A symptom that I have noticed is that when it backfires at startup, I get around 2 degrees of knock at regular acceleration and 11 degrees at WOT.

 

I use to have a miss in my lt1 when I had it..try the knock sensor (not the module), but the sensor on the bottom side of the engine block. Got that replaced and it did wonders for the car.

-Corey