idle surge 81 corvette
Thread Starter
Heel & Toe
Joined: Dec 2020
Posts: 22
Likes: 11
idle surge 81 corvette
Bought a drivable but needs a ton of TLC 81 corvette in December. Car was turtle slow and ran rough. Wouldn't stall, but came super close.
So in order to make the car run a bit better, I have:
replaced cap and rotor
replaced plugs and wires
found and replaced some bad vacuum lines
new air filter
everything is better, car is still slow but maybe angry turtle slow now. However, I can't get rid of this idle 'surge' thing. Here's a video - I did not blip the throttle, car did that on it's own. I was in drive with the brakes on. What's left that this could be? Fuel filter? Carburetor? It does have the stock L81 engine and computer setup including the carb. Brief video attached to show what I'm talking about.
So in order to make the car run a bit better, I have:
replaced cap and rotor
replaced plugs and wires
found and replaced some bad vacuum lines
new air filter
everything is better, car is still slow but maybe angry turtle slow now. However, I can't get rid of this idle 'surge' thing. Here's a video - I did not blip the throttle, car did that on it's own. I was in drive with the brakes on. What's left that this could be? Fuel filter? Carburetor? It does have the stock L81 engine and computer setup including the carb. Brief video attached to show what I'm talking about.
Drifting
Joined: Aug 2019
Posts: 1,339
Likes: 225
You really need to hook a scan tool to see if there are any codes, and to look at sensor values to see if anything is out of spec, and to see if it can go into closed loop.. My 81 runs fine with everything hooked up.The sensors I would look at is the coolant sensor. map, tps and O2 for starters. Have you replaced the thermostat with anything other than a 195?
Thread Starter
Heel & Toe
Joined: Dec 2020
Posts: 22
Likes: 11
Yep, it's a Quardajet with all the computer controlled crap on it.
Never even thought of a plugged catalytic converter. Thanks! It's likely original from how everything looks under there.
Not sure if the thermostat is a 195 or not, I've never changed it but only owned the car a few months. Some of the stuff I've found / fixed has amazed me so far. Last owner wasn't much of a DIY guy, or at least he wasn't good at it.
Thanks guys! Good info.
Never even thought of a plugged catalytic converter. Thanks! It's likely original from how everything looks under there.
Not sure if the thermostat is a 195 or not, I've never changed it but only owned the car a few months. Some of the stuff I've found / fixed has amazed me so far. Last owner wasn't much of a DIY guy, or at least he wasn't good at it.
Thanks guys! Good info.
Drifting
Joined: Aug 2019
Posts: 1,339
Likes: 225
A quick check if you think it's the converter. Rev the engine to 3000 and hold it, if the converter is bad you will see the rpm's drop from the converter choking the engine. If that happens, take out the O2 sensor, then run the same test. If the rpm's hold, then it's the converter.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
If the car is sluggish......first thing to do is set the base timing. Find an 81' repair manual for the procedure as it requires you disconnect a wire to set it.
Set timing first.
Post a pic of the engine with the air cleaner removed.
Jebby
Set timing first.
Post a pic of the engine with the air cleaner removed.
Jebby
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1st Gear
Joined: Feb 2007
Posts: 1
Likes: 0
From: Rio Rancho New Mexico
Bought a drivable but needs a ton of TLC 81 corvette in December. Car was turtle slow and ran rough. Wouldn't stall, but came super close.
So in order to make the car run a bit better, I have:
replaced cap and rotor
replaced plugs and wires
found and replaced some bad vacuum lines
new air filter
everything is better, car is still slow but maybe angry turtle slow now. However, I can't get rid of this idle 'surge' thing. Here's a video - I did not blip the throttle, car did that on it's own. I was in drive with the brakes on. What's left that this could be? Fuel filter? Carburetor? It does have the stock L81 engine and computer setup including the carb. Brief video attached to show what I'm talking about.
So in order to make the car run a bit better, I have:
replaced cap and rotor
replaced plugs and wires
found and replaced some bad vacuum lines
new air filter
everything is better, car is still slow but maybe angry turtle slow now. However, I can't get rid of this idle 'surge' thing. Here's a video - I did not blip the throttle, car did that on it's own. I was in drive with the brakes on. What's left that this could be? Fuel filter? Carburetor? It does have the stock L81 engine and computer setup including the carb. Brief video attached to show what I'm talking about.
GerryLP 😎
