Suddenly Got Worst!! WTF!!

[Donne Trav]

Some of you have read my THREADS about HARD STARTING, etc. Well,
things suddenly got worst this evening. First, the hard starting weeks
ago — possible leaking injectors; second, strange noise/clicking sound
coming from the rear — possible fuel pump going bad; both things
suggested by a few forum members. BUT NOW! The strange
noise/clicking sound previously heard when key turned to the ON
POSITION has stopped, hence, the ROUGHEST ride I have ever had.
No power in 5th & 6th gear! Somebody please tell me that the
first & second problems have resulted in A BAD FUEL PUMP and NOT
THE OPTI. I'll even settle for the already mentioned BAD injectors. But, not the OPTI! Please! I mean, at 65, I getting to old for this crap. I only
have 68,000 miles on the '94. What's next?

[KANE]

Some of you have read my THREADS about HARD STARTING, etc. Well,
things suddenly got worst this evening. First, the hard starting weeks
ago — possible leaking injectors; second, strange noise/clicking sound
coming from the rear — possible fuel pump going bad; both things
suggested by a few forum members. BUT NOW! The strange
noise/clicking sound previously heard when key turned to the ON
POSITION has stopped, hence, the ROUGHEST ride I have ever had.
No power in 5th & 6th gear! Somebody please tell me that the
first & second problems have resulted in A BAD FUEL PUMP and NOT
THE OPTI. I'll even settle for the already mentioned BAD injectors. But, not the OPTI! Please! I mean, at 65, I getting to old for this crap. I only
have 68,000 miles on the '94. What's next?

Its not that bad... well, taking it in all at once is!

Let's start looking at what is wrong by moving system by system.

First, have you replaced the thermostat ever? If so, you could have had coolant leak over the Opti-spark and that could create a moisture problem in the Opti-spark.

Next let's look at fuel pressure. Do you have a gauge? Do you have a shop manual for your car? Check your fuel pressure on the fuel line. Make sure it is creating enough pressure and not bleeding off to quickly after power is shut off either. Check your pressure on the rail. Ensure the vacuum line is connected to the pressure regulator and the intake. Leaky injectors will show up with tell tale signs on your plugs.

FYI- even a bad fuel pump can sound like it is working. When you rotate the key forward, you should hear the pump engage. It should sound like a monotonous buzz for about 3-5 seconds. If it doesn't sound like an even buzz, the you might have a problem.

Check your plugs. Make sure your plugs have an even amount of wear. If one is suspect, check your wires and replace the plug (and perhaps a wire). If a new plug and wires don't fix it and its not the opti or the fuel pump... then it could be the opti.

If the fuel pressure, spark plugs, and a compression test indicate everything is okay... very well might be the Opti-spark. You'll need to connect a scan tool and watch the 02 sensor reading from bank to bank. When the 02 sensors fluctuate wildly, the ECM will try to compensate by adjusting the advance etc. However, all of the ECMs actions won't be enough when moisture scatters the light beam in the Opti-spark. It won't trip the check egine light either. You may see a noticeable drop in the current on the car as it essentially crossfires. It will be also be intermittent and seem to strike when least expected.

Although I don't have an LT1, I did have a 94 Firebird Formula with the LT1 and the same problem. I replaced a fuel pump and wasted all kinds of time trying to figure that one out myself.

The Optispark is easy to replace. You'll have to drain the coolant, remove the accessory drive belt, intake ducting, and numerous small parts- but I'd rather do that than replace a fuel pump.

If it is the Opt-spark, Jeg's carries a couple of kits to replace the OEM parts. MSD makes a replacement unit as well. They aren't too costly either.

[gmjunkie]

I'm with DarkShark!! LT1 cars are ex-specially sensitive of fuel pressure,41-47 lb is perfect!! I like 44+,but they will run with 39-40 but not good at high RPM!! I suspect that Fuel Pump,or plugged Fuel Filter is your problem,but you won't know till some simple tests are done with a fuel pressure gage!! The test port on a 94 is at the back of the intake close by the Pressure Regulator!!

PS See photos below,The test port is directly above the FP regulator in the stainless line with a black plastic cap!!

Fuel Filter is located on the inside of the right frame rail below the A/C,you will have to access it from under the car!!

The fuel pump on a C4 isn't a big job,about an 1-1 1/2 hours!! Can be easily accessed through the rear panel with the gas filler door removed!!

[killain]

FWIW, I know and have read so often about the coolant leak and the Opti-spark unit. I read a few of the corvette magazines. One, 'Corvette Fever' has a Master mechanic who writes for them every month, Chris Petris. A few years ago he describes how he fixes the opti-spark unit gone bad on a LT1, and i found it interesting. After he stripes down the engine, he installs the opti-spark, but before he leaves it, he modifies the unit slightly. He routes a very fine vacume line from the intake manifold hoses connections and inserts it into a very small hole drilled into the lower side of the opti-spark unit, seals it and then finishes the repair with the water pump and ECT. What he has found is that the tiny vacume line is small enough to not affect the engine running, but it constantly keeps sucking out the Opti-spark unit in case it get water in it from a motor wash or going through a big puddle of water. Just my $0.02

[gmjunkie]

FWIW, I know and have read so often about the coolant leak and the Opti-spark unit. I read a few of the corvette magazines. One, 'Corvette Fever' has a Master mechanic who writes for them every month, Chris Petris. A few years ago he describes how he fixes the opti-spark unit gone bad on a LT1, and i found it interesting. After he stripes down the engine, he installs the opti-spark, but before he leaves it, he modifies the unit slightly. He routes a very fine vacume line from the intake manifold hoses connections and inserts it into a very small hole drilled into the lower side of the opti-spark unit and then finishes the repair with the water pump and ECT. What he has found is that the tiny vacume line is small enough to not affect the engine running, but it constantly keeps sucking out the Opti-spark unit in case it get water in it from a motor wash or going through a big puddle of water. Just my $0.02

No need for modifying the opti,the vent holes are already there,all they have to have done is plumb it in!! GM started pluming them in 95 I believe!! But lets make sure it's not a Fuel problem or a Coil,Plug Wire,Plug,Ignition Module or Injectors first,instead of throwing Expensive parts at it and still not fixing it!!!
I'd be willing to bet there have been more Good Opti's Blamed and Changed than Bad ones!!With out Trouble Shooting and Testing your just piss'n in the wind!!!

PS I've changed 3 Opti's in my lifetime,with 100's of customer vehicles and 100,000's of miles!!
1. 92 LT1 Automatic (Broken by Collision) Years ago!!
2. 93 LT1 6 sp (Could have been cleaned and repaired, but wouldn't have been cost effective) JimmiJam's last summer!!
3. 94 LT1 6sp (I started to repair it and a tiny hard steel screw broke off in it that holds the rotor button, I drilled and started to tap it and the tap broke off in it!!) I got bent and slung it up into the woods!! Mine!!

I've always found mostly Bad coils,Bad Ignition Modules,Bad or Corroded Connections!!

[Robertwav1]

Hey, don't forget the FP regulator...notorious for hard starting.