Wanderer85

Hi fellas,

Hope everyone is well. I have had this car for six months now and have been very happy with it's performance. The car is tuned in the open loop and no oxygen sensors are connected. That was done by the previous owner to avoiding lean condition under Nitrous. I have had no problems with it the way it was tuned.

Two days ago, I noted after hitting a dip, or atleast that's what I recall, the car started back firing a lot as soon as I will lift my foot from the pedal. At the same time I noted that the car felt really powerless and would not respond under load. I got worried and thought that I had hurt the motor. I drove back home and parked it. The only thing that I had noted was burning smell and headers on both sides glowing intensively.

Tonight I gathered up courage and started the car up again and noted that the car was running very normal. I took it for a spin and it looked normal even reaching operating temperature of about 170. After I want to say driving for 15-20 minutes the same symptoms came back i.e. back firing, loss of power, glowing headers and the increase in operating temp to about 190 even at 45 degrees outside.

I am happy that it does not seem to be a problem invloving a cylinder failure or something similar as the car was running great when I started up in the beginning 20 minutes.

Any clues as to where to look for the problem will be greatly appreciated. Thanks for staying with me for this long.

bogus

Glowing headers leads me to believe it's running super rich. I cannot comment on the tune, cause I don't know enough.

However, it sounds like a dying optispark to me.

If not the opti itself, the coil or coil wire.

If you have a bad ignition, the unburnt fuel will collect in the exhaust, especially if the engine was tuned in open loop, with no 02 sensors, it won't have any ability to change the flow of fuel.

I assume this engine has no cat?

Wanderer85

Thanks Bogus for your helpful hint. How can I check to see if the Optispark is the culprit here? Any other ideas will be greatly appreciated. Thanks all.

Z06_BluByU

I had this exact saem problem.. it was my optispark..these are pretty classic symptoms.. I would recommend replacing the waterpump as well while your in there.. it is the #1 cause for opti-failure..

bogus

What 383 said!

The engine will throw codes, I just don't know what they are for a 1994.

You really need a scan tool and Helms manual.

Check the coil wire, first.

I would recommend you consider some options here. With as much power as your motor is pushing, the Opti is at its limit, I feel.

There are four options:

1) Maintain factory

2) Dyna-Spark from DynaTech Engineering - this is an all new opti, essentially.

3) LTCC - This replaces the opti's high voltage side with 8 LS1 coil packs. I have this, kicks ***. www.bailey-eng.com

4) DelTeq - Replaces the opti's high voltage side with a Cadillac Northstar coil pack (lost spark).

The problem is that if your engine spins beyond about 6500 RPM too many times, the rotor WILL blow up.

REDC4CORVETTE

If you are going to throw parts at it ,try the moduel behind the coil.
Cheaper than an opti and if you have a 383 you must not have been into the engine that long ago.
Start cheap then when you feel rich go for the opti.

Z06_BluByU

As usual bogus is pretty much on the money in relation to the options he presented.. I would recommend option #1 or option #3/#4

I think the LTCC is a terrific setup (but costly)..with the DelTeq in a close second.. However, if your going to shell out the $$ to go this route the multi-coil pack best address coil dwell time.. wereas the delteq setup I believ only uses two coil packs..

If money is really tight I would just go replace the factory piece.. They seem to go 60k with alot of consistancey and some see over 100k.. my unit saw 144k miles with only one cap and rotor change before i needed to replace the whole unit..


I would like to point one thing out.. a bad opti will not always throw a code.. and I've found often does not (at least in the two failures I've had). Things like the coil and coil module usualy work or they don't.. its extreamly rare.. If you want to run diagnostics this is what I would do..


1st.. if you dont have a good Helms factory service manual invest in one.. it is the best thing i ever got for understanding my beast and I use it often..

then as outlined in the manual check..

1. Fuel pressure at the rail at idle
2. Fuel pressure at the RPM where the problem happens
3. ohm out the injectors
4. pull the plugs and wire.. check the gap and the resistance on all the wires.. gap should be .050 and resistance should be less than 30,000 ohms also check for cracks in the wires or spark arching by misting water on the wires and looking for a blue spark..
5. use a spark tester to test for spark at the coil (as outlined in the manual)
6. Verify EGR operation


I would think if all of that checks out its most likely your opti.. and if its not then id be suspect of mechanical failure.. i.e. brokern valve spring, worn cam lobe, collapsed lifter..etc..etc..

hope this was helpful..

FD2BLK

You do need to pull code but if it is the Opti good luck because it only trows a code 1/2 the time at best. If you do get a code it will probably be 16 (Opti Low res) On the 94 just jumper pins 12 and 4 on the DLC (ALDL) and it will display any codes.

Wanderer85

Thanks everybody for your valuable input. I was away from the internet and was not able to look at the great advice that I had gotten. I would definitely go and check my coils and wires before I embark on the Opti path.

One thing that makes me feel comfortable that it is not a broken valve spring, collapsed lifter or worn cam lobe is after noticing the problem for the first time, I had driven the car after few days and it drove with full power without a problem for the first 20 minutes before it started showing the same symptoms again. I am assuming with a faulty Opti it may be possible to have the problem at a certain temperature, whereas with a mechanical failure the car should always run like crap.

Any other comments would be greatly appreciated. Thanks!