Sully_Tex

I have an LT4 with 61,000 miles and about 6 months ago or so I started to notice that when the car was not warmed up, it really ran bad when I was trying to accelerate. It will run really rough with little power for a block or two and then it begins to run normally. If I let the car warm up in the garage, it runs fine. Any ideas? Thanks in advance!

Louis Bartay

Hello,
Have the opti-spark checked, mine did this too and I had the unit and plug wires changed. Are you getting a check engine light??
Louis :chevy

Sully_Tex

I just had the optispark replaced about 4K miles ago. It was doing this before I had the optispark replaced. I was getting a check engine light (different trip to the mechanic) when I would accelerate from about 50-60 (5th gear). The mecahnic told me that the knock sensor had been unplugged, there was a fuel leak at the filter and there was a vaccum leak. This was just last week. Due to the knock sensor, the timing was off. Had all of that fixed and it's running fine after the warm up period.

Did this correct your problem? I am thinking that maybe wires and plugs would help - they are original. What do you think?

Sully_Tex

Love those wheels on yours!

vader86

so you fixed the check engine Code? you have no codes right now?

Louis Bartay

If you have a volt/ohmn meter use the ohmn meter to check the plug wires. Mine had some small crackes and one wire that had a short in it. I would replace with G.M. parts to keep it orginal. Make sure the vacumm hose that goes to the opti-spark is connected and is not leaking as mosture is pulled out of the opti-spark with this vacumm line. The Fiske FM 10 wheels were on the Vette when I purchaed it from my best friend. Let us know how this problem is fixed as this is not the first time I have read that a LT1 or LT4 with the opti-spark does this. :chevy :)

Sully_Tex

Well, it was the mass air flow. My mechanic said that it threw a mass air flow code 686 miles ago and then another one on my way to the shop. It is great to have all 330 horses back on tap. It runs like a Corvette should now.

$500 ($407 parts - $80 Labor)

For future reference:

Symptoms:
Very rough acceleration when engine is cold - major power loss
No effect on gas mileage
Check engine light when accelerating from 50 - 75 (5th gear)
The check engine light will go off in about 50 - 75 miles
Feels kind of like a miss at high speeds when accelerating
:yesnod:

silver & red CE

Cold start roughness and high speed miss while accelerating is the classic optispark's failing symtom. If your dealer charges $500 for a new MAF, a new opti is going to run ~$1200.

Eric

92LT1Roadster

Good information to remember :yesnod: