Crossfire knocking when accelerating
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
A little more information. The CEL works fine. A complete tune up was done recently. I only use Shell 91. I had to replace the faulty O2 sensor which was causing the engine to dump extra fuel and blackened the plugs severely. A ton of black carbon was burned off and plugs replaced . No smoking at all now. Car runs well otherwise except when stopped and in gear it runs rough like it has an upgraded cam, which it doesn't. Intake gasket replaced a year ago.
90% of these are petrified after 40 years and suck air….
Jebby
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Who did the "tuning" and are they experienced with tuning a CrossFire engine system?
I suspect that either ignition timing was set improperly and/or there was a vacuum hose left disconnected or a brittle sensor fitting cracked or broke off leaving a vacuum line sucking air. Just do a careful and thorough visual of EVERY component on the engine to be certain that no such fault remains. The CrossFire engine is a very 'busy' system and it is EASY to miss something simple.
I suspect that either ignition timing was set improperly and/or there was a vacuum hose left disconnected or a brittle sensor fitting cracked or broke off leaving a vacuum line sucking air. Just do a careful and thorough visual of EVERY component on the engine to be certain that no such fault remains. The CrossFire engine is a very 'busy' system and it is EASY to miss something simple.
Melting Slicks
Joined: Feb 2017
Posts: 3,232
Likes: 1,232
From: PHX AZ
If you locate the manifold vacuum tap in the top of the intake manifold and remove the main hose and plug the tap, this may help you determine hose vacuum leaks vs manifold leaks.
The basic premise is that 'excess air; entering the manifold from a leak, LEANS OUT the intake charge and causes lean detonation.
This is the simplest phase one of the investigation.
Unkahal
The basic premise is that 'excess air; entering the manifold from a leak, LEANS OUT the intake charge and causes lean detonation.
This is the simplest phase one of the investigation.
Unkahal
Safety Car
Joined: May 2001
Posts: 4,757
Likes: 1,647
From: Fairfax Virginia
Your OBD1 Oxygen sensor was designed to be used for 24 months or 50k miles. IF the sensor is over 24 months old be sure to replace it. They can do strange things to your engine when they fail.
In the old days of VW air cooled engines we used to pour cold water down the throat of the carburetor and watch the carbon come flying out the muffler. Today I would pour a bottle of BG 44K Fuel System Cleaner as it helps get rid of carbon just as well but less obviously.
Knock sensors can fail as well. Never assume any NEW part is automatically "good" until you have tested it (if you can). A knock sensor will produce a small voltage when it hears a knock sound and normally I test them by tapping on the engine block with a wrench, if working properly the engine's Idle should change a bit.
I have little knowledge of the Crossfire engine but on the L98's if/when the EGR fails the combustion chamber temperatures Rise and the engine can start pinging. If you do have an EGR on that engine be sure it is working properly.
Good Luck on your Winter Project!
In the old days of VW air cooled engines we used to pour cold water down the throat of the carburetor and watch the carbon come flying out the muffler. Today I would pour a bottle of BG 44K Fuel System Cleaner as it helps get rid of carbon just as well but less obviously.
Knock sensors can fail as well. Never assume any NEW part is automatically "good" until you have tested it (if you can). A knock sensor will produce a small voltage when it hears a knock sound and normally I test them by tapping on the engine block with a wrench, if working properly the engine's Idle should change a bit.
I have little knowledge of the Crossfire engine but on the L98's if/when the EGR fails the combustion chamber temperatures Rise and the engine can start pinging. If you do have an EGR on that engine be sure it is working properly.
Good Luck on your Winter Project!
