Problem?????
Thread Starter
Pro
Joined: May 2007
Posts: 714
Likes: 0
From: Fort Worth Texas
Problem?????
My 85 has been really shaky lately. Its like you either have to floor it, or it doesnt move at all. Its weird. And when youre just barely holding the gas it just shakes like crazy. Has anyone experienced this problem, or does anyone know what it is? Thanks, Zak.
Race Director
Joined: Dec 2006
Posts: 10,383
Likes: 4
I've not had that problem on a Corvette but I did have it on a much older Grand Prix.
Visually check each spark plug wire. Make sure there is no crosstalk between them by using wire guides and seperators.
Has anyone else touched the car? What if any mods have you made? Can you verify that the injectors are receiving a pulse with a noid light? Can you verify they are opening with a stethoscope?
What is the fuel pressure at the rail?
Do you have spark at each wire? Are any of the plugs fouled?
Any diagnostic codes? Does the PCV valve rattle when you shake it off the vehicle? Any loose vacuum lines? (esp the big one going to the power booster)
Did you last buy gas at your normal station?
Visually check each spark plug wire. Make sure there is no crosstalk between them by using wire guides and seperators.
Has anyone else touched the car? What if any mods have you made? Can you verify that the injectors are receiving a pulse with a noid light? Can you verify they are opening with a stethoscope?
What is the fuel pressure at the rail?
Do you have spark at each wire? Are any of the plugs fouled?
Any diagnostic codes? Does the PCV valve rattle when you shake it off the vehicle? Any loose vacuum lines? (esp the big one going to the power booster)
Did you last buy gas at your normal station?
Thread Starter
Pro
Joined: May 2007
Posts: 714
Likes: 0
From: Fort Worth Texas
I've not had that problem on a Corvette but I did have it on a much older Grand Prix.
Visually check each spark plug wire. Make sure there is no crosstalk between them by using wire guides and seperators.
Has anyone else touched the car? What if any mods have you made? Can you verify that the injectors are receiving a pulse with a noid light? Can you verify they are opening with a stethoscope?
What is the fuel pressure at the rail?
Do you have spark at each wire? Are any of the plugs fouled?
Any diagnostic codes? Does the PCV valve rattle when you shake it off the vehicle? Any loose vacuum lines? (esp the big one going to the power booster)
Did you last buy gas at your normal station?
Visually check each spark plug wire. Make sure there is no crosstalk between them by using wire guides and seperators.
Has anyone else touched the car? What if any mods have you made? Can you verify that the injectors are receiving a pulse with a noid light? Can you verify they are opening with a stethoscope?
What is the fuel pressure at the rail?
Do you have spark at each wire? Are any of the plugs fouled?
Any diagnostic codes? Does the PCV valve rattle when you shake it off the vehicle? Any loose vacuum lines? (esp the big one going to the power booster)
Did you last buy gas at your normal station?
I can only answer two of your questions.
I have not done any mods, and yes. I buy gas at the same station every time. What was wrong with yours? It almost seems like the engine isnt getting the right air/fuel mixture. And sometimes it feels like one of the injectors are clogged????? I dont know. Any ideas?
Thread Starter
Pro
Joined: May 2007
Posts: 714
Likes: 0
From: Fort Worth Texas
Knowing my luck we need to start at the most expensive and drawn out problems first. Well find out whats wrong faster that way, but anyway. Last year we put new plugs in it, and it started doing this a couple of months ago. Also, the fuel filter and pump were replaced just before this started happening. My Dad is going to take it to the shop it has been taken to several times, and get them to check it out.
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Well there goes your $100 you saved up for mods.
(This coming from a guy who's put thousands into his car not including labor and it's still basically stock.)
(This coming from a guy who's put thousands into his car not including labor and it's still basically stock.)
Le Mans Master
Joined: May 2006
Posts: 9,226
Likes: 9
From: Irvine Ca
Mine did this as well and was running like crap. The Wire loom had broken off and allowed one or more plug wires to drop down and contact the exhaust manifold. The housing around the wire was almost completely burned through.
changed the wires and the plugs. Put on new looms and off we went. Smooth as ever.
I think you owe it to yourself to visually inspect the wires prior to taking it to a shop.
Pro
Joined: May 2007
Posts: 638
Likes: 1
From: Robesonia Pa
Or another trick is to pull the plug wires one at a time and replace it while the motor is running-if it runs rougher when off of plug then the cylinder is firing. no change when off the plug= that one is a problem
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
Thread Starter
Pro
Joined: May 2007
Posts: 714
Likes: 0
From: Fort Worth Texas
Le Mans Master
Joined: May 2006
Posts: 9,226
Likes: 9
From: Irvine Ca
Someone said the same thing about "just pull a wire off at the distributor". My question was while the motor was running?
Just being unsure of myself I didn't question further. But I'll say this......you only grab a wire, while the motor is running/starting, bare handed one time and one time only.
Race Director
Joined: Dec 2006
Posts: 10,383
Likes: 4
Burning Brakes
Joined: Oct 2005
Posts: 1,176
Likes: 0
From: Suffolk Va
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Any time the car isn't idling good, first check for vacuum leaks.
If that doesn't reveal anything, do the idle set procedure:
Put car in diagnostic mode for 30 seconds (jumper top right pins A & B on diagnostic connector under drivers side dash)
Unplug IAC
remove aldl jumper
Disconnect EST (recommended for automatics)
Start car and adjust idle screw to 450 rpm
Shut car off.
For early adjustable-TPS cars, adjust TPS to .56 volts
Reconnect IAC and EST
Disconnect battery to clear codes.
Reconnect and start car. Should idle at about 700 rpm (may take a little bump of the throttle for the first few seconds.)
If that doesn't reveal anything, do the idle set procedure:
Put car in diagnostic mode for 30 seconds (jumper top right pins A & B on diagnostic connector under drivers side dash)
Unplug IAC
remove aldl jumper
Disconnect EST (recommended for automatics)
Start car and adjust idle screw to 450 rpm
Shut car off.
For early adjustable-TPS cars, adjust TPS to .56 volts
Reconnect IAC and EST
Disconnect battery to clear codes.
Reconnect and start car. Should idle at about 700 rpm (may take a little bump of the throttle for the first few seconds.)
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
bad idle
you need to check the EGR valve, and determine that it's closing. Flooding the manifold with spent gasses while it is idling will not allow it to run good at all.