LT4 Cold Engine Problems
Thread Starter
Advanced
Joined: Jun 2001
Posts: 90
Likes: 6
From: Allen, TX
LT4 Cold Engine Problems
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!
Burning Brakes
Joined: Dec 2001
Posts: 777
Likes: 1
From: Fort Worth Texas
Re: LT4 Cold Engine Problems (1Sully)
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
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
Thread Starter
Advanced
Joined: Jun 2001
Posts: 90
Likes: 6
From: Allen, TX
Re: LT4 Cold Engine Problems (Louis Bartay)
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?
Did this correct your problem? I am thinking that maybe wires and plugs would help - they are original. What do you think?
Burning Brakes
Joined: Dec 2001
Posts: 777
Likes: 1
From: Fort Worth Texas
Re: LT4 Cold Engine Problems (1Sully)
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 :)
Thread Starter
Advanced
Joined: Jun 2001
Posts: 90
Likes: 6
From: Allen, TX
Re: LT4 Cold Engine Problems (Louis Bartay)
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:
$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:
Melting Slicks
Joined: Jan 2000
Posts: 3,418
Likes: 1
From: NW Chicago Suburbs
Re: LT4 Cold Engine Problems (1Sully)
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
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
Eric
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
2027 Corvette vs The World: Every Model vs Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
10 Things C8 Corvette Owners Hate (But Won't Tell You)
Joe Kucinski
10 Best Corvettes Coming to Barrett-Jackson Palm Beach 2026!
Brett Foote
Every Corvette Grand Sport Explained! (C2, C4, C6, C7, & C8)
Joe Kucinski
Grand Sport & Grand Sport X Launch Alongside All-New 535hp LS6 V8!
Michael S. Palmer
