Misfire
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2nd Gear
Joined: Apr 2020
Posts: 2
Likes: 0
Misfire
I have a 1992 with the LT1 motor with no mods.I am having a bad Miss in the 2 to 3000 RPM range. If you floor it it's fine and it'll spin the tires no problem.if you're trying to just Cruise along and you barely touched the gas or barely let off the gas it will miss. Even if you kind of crawl along just speeding up slowly it will start misfiring before you even get to 10 miles an hour. Things I have replaced, fuel filter, optispark, plug wires, spark plugs, ignition control module, coil, map sensor, idle air control solenoid, throttle position sensor,I even got another set of fuel injectors and that did not make a difference. And I cleaned the EGR valve and it seems to be fine.The weird thing is well it's idling around 1200 RPMs and I cannot find any vacuum leaks.Someone had mentioned a ground problem to the motor so I ran a separate ground from the block to the battery as well. And I have no check engine light coming on. I did the old trick where you jump to 2 wires on the diagnostic plug and count the flashes and there's no codes in the computer.
Safety Car
Joined: May 2001
Posts: 4,741
Likes: 1,639
From: Fairfax Virginia
I would suggest a can of B&G 44K Fuel Injection system cleaner in a tank of gasoline and see if it clears up.
Having just dealt with an issue just like what you are describing and the fuel injector cleaner stopped the misses within 25 miles of driving. It is not the least expensive fuel cleaner but it really does work wonder on a neglected fuel system. It would also help if your gasoline is just plain old as the stuff with 10% ethanol only has a shelf life of 30 days.
Take a peek at your MAP sensor as these can cause a miss while under load like going up a long hill or something. I use a scanner to read what is happening in real time which really helps find pesky problems. It is likely your IAC or TPS causing the idle issue or it could really be a vacuum leak.
Be Well and Stay Well!
Having just dealt with an issue just like what you are describing and the fuel injector cleaner stopped the misses within 25 miles of driving. It is not the least expensive fuel cleaner but it really does work wonder on a neglected fuel system. It would also help if your gasoline is just plain old as the stuff with 10% ethanol only has a shelf life of 30 days.
Take a peek at your MAP sensor as these can cause a miss while under load like going up a long hill or something. I use a scanner to read what is happening in real time which really helps find pesky problems. It is likely your IAC or TPS causing the idle issue or it could really be a vacuum leak.
Be Well and Stay Well!
Advanced
Joined: Feb 2016
Posts: 68
Likes: 14
From: MotorCity
Yes it was most likely the problem, when it malfunctions or cannot seal you basically have a intake vacuum leak that causes a number of problems and because the OBDl is not as advanced as the OBDll it will not always set a DTC code. Also if you try and retrieve the codes with a paper clip it will not always reveille all the DTS codes unless you use a code reader even a cheap one.
Safety Car
Joined: May 2001
Posts: 4,741
Likes: 1,639
From: Fairfax Virginia
I would still run a can of B&G 44K through your system. Whenever I use it I am always surprised at the difference it makes in the engine's performance. It can't hurt and it will likely help so give it a shot when you have a chance. The EGR is another important part that can significantly affect your Corvette. Good work!
