I know this has probably been beat to death, but what does an opti act like when it's going bad? I have had my car for about one year and the prevous owner did kind of a wierd thing in that the engine still uses the opti to product the spark signal, but it then goes from the opti to an MSD 6A, and then of course to a coil. The coil wire (plug wire) then goes into a regular distributor (with a flat cap, the LT1 manifold has been adapted for a distributor) for spark distribution. Otherwise stated, the guts of the dist are not used, just the cap and rotar for spark distribution. I asked the previous owner why he did this and he said because the button in the opti can explode at high RPMs. Anyway, I've noticed that the last two times I've taken it through the automatic car wash (one that shoots water from the bottom and all other angles) that the car dies while it's idling and is VERY difficult to start.... luckily I was able both times to get it started before the end of the car wash. Anyway, yesterday it started in the morning and I drove to work, it ran fine. Got in it to come home and it suddenly started missing REAL bad. Now today the car started popping REAL bad, so bad in fact you could hear it through the throttle body.

I instantly thought I had blown a head gasket, I did a compression check and all of the cylinders were between 190-210psi. All of the valve springs looked fine and there is no sign of a milkshake. There was some oil on the plug going into the opti, but I wouldn't think that would be enough to start a misfire situation.

Since I bought this car it has always seemed to "pop" at idle, but smooths out at about 2,500-3,000rpm. It has never sounded right to me.... What do you guys think? Oh, are optis hard to install.. what's involved?

Thanks Guys!!!!!!!!!!!!

 

I've seen automatic car washes wipe out several otpi's before, even the improved vented style. I would say there's a good chance your otpi is the problem.

 

 

Does anyone know if I can simply make a harness for the guts of my HEI distributor and still use the factory ECU? I'm not sure it can put out the low and high ref signals needed for the HEI.

 

The LT1 ECM "requires" the low-resolution and high-resolution signals from the Opti-Spark for spark timing (EST) and fuel-injection timing.

So, if you are going to do away with the Opti-Spark, you will have to use a different ECM or somehow duplicate the low and high res signals.

Keep in mind, the LT1 does not have a timing mark for a timing light, and the hub has no key.

Tom Piper

 

Wouldn't the HEI dist also be able to deliver the signals to the ECU....

Also, I noticed last night that the fuel regulator on the fuel rail does not have a vacuum line running to it... which makes sense because my car always smells extremely rich while at idle. My wife stated that she doesn't ever like to follow me because it makes her eyes water... I think I need a vacuum line there... right? Thanks!

 

Not to the LT1 ECM it won't.

The LT1/LT4 ECM is looking for only low-res and high-res pulses.
The HEI does not produce low and high res pulses.


Tom Piper

 

Wow, that is a very interesting setup. The previous owner was right: the rotor in the optispark distributor can explode, particularly at high rpms (happened to me).

 

Well, I replaced the opti and it made no difference whatsoever.

As I sit here and think, right before all of this started the "Low Coolant" light came on. This immediately made me think that I had a blown head gasket from the coolant leaking into the offending cylinder. Nope, removed the valve covers, no sign of a milkshake. Oil level is fine. Compression check shows all cylinder between 187-210 psi.

The car is getting good spark, although I have not yet checked the fuel pressure. This car violently pops and backfires upon any attempt to start it. The car has never had cats and has been tuned via LT1 edit (or whatever it is called) and drove perfectly right before this happened.

I unplugged the MAF and it made no difference whatsoever.....

Any ideas?

 

when my opti got wet & went bad....

I was able to still start it after letting it sit for awhile. But, when it ran...it was missing real bad. So bad it scared the crap out of me. I ordered a new opti & in the process....a few weeks went by before I was able to replace it. FYI....it didn't dry up...& does not get any better.

 

I've now checked the fuel pressure and it has about 35 psi by simply turning the ignition key to the "on" position, but it instantly goes to zero after a second. I also removed the ignition module and cleaned the back plate that bolts to the head just in case the ground was bad... Once again, the car backfired violently when trying to start it... it won't start.

It's definiately getting spark, definately has compression, and I "think" it's getting fuel.... It sounds like the motor is out of "time", but the timing chain is a double roller that is pretty tight, too tight to slip. What am I missing? Thanks.

 

I've now ohmed the injectors and plug wires

Injectors:
Cyl. 1- 14.5 ohms
2- 14.9
3- 14.5
4- 14.7
5- 14.7
6- 14.4
7- 14.8
8- 14.4

Plug wires:
Cyl. 1- 1158 ohms
2- 1134
3- 1011
4- 1001
5- 917
6- 849
7- 803
8- 786

 

I do not know about LT1s and optis but, the fuel pressure should not drop to 0. It should take several minutes at least to drop that much.

 

my LT1 will hold pressure overnight, a leaking injector could be flooding the engine and keeping it from starting

 

But wouldn't that have to be one heck of a leak to instantly go to Zero... I mean, I turn the key on, the gauge immediately jumps to 37 psi, the pump runs for maybe one second, then goes off and the guage goes IMMEDIATELY to zero. I did hook a vacuum line up to my fuel regulator as the car ran extremely rich at idle...but I actually did that AFTER the car wouldn't start...as there was no vacuum line on it all for perhaps years....

 

actually just one leaking injector could do it. or possibly the check valve in the pump letting it leak back into the tank

 

also the fuel pressure regulator can leak into the vacuum line and flood the intake..

 

The car does have a Walbro pump.... so maybe that's why it won't hold pressure. I have another car that has an Aeromotive pump, and the second it shuts off the regualtor or pump allow the pressure to return to zero very quickly. Someone somewhere else mentioned a check valve... but I can't imagine that's what it is... The car acts as if it's having a difficult time cranking.... even with the battery completely charged. If an injector was leaking wouldn't the car start, but just run pig rich? This thing is backfiring violently....

 

I've been reading elsewhere that certain opti sparks are no good. I bought a supposedly brand new "overstock" AC Delco off of E-bay from a discount Ignition House for $149.00. I do have spark at the plugs, but I'm starting to think I got taken for a ride, although I do have spark at the plugs. I bought a $200 scanner today and it shows no codes. I am so stumped...

 

Bump... anyone else?