throttle body back fire
Thread Starter
Cruising
Joined: Feb 2017
Posts: 14
Likes: 0
From: argillite kentucky
throttle body back fire
hard to make idle and below 1600 rpm it surges and pops in throttle body above 1600 rpm it smooths out and runs normal i have replaced the tps and set it a 54 volts, replaced the spark control module
Thread Starter
Cruising
Joined: Feb 2017
Posts: 14
Likes: 0
From: argillite kentucky
1985 tune port hard to make idle and below 1600 rpm it surges and pops in throttle body above 1600 rpm it smooths out and runs normal i have replaced the tps and set it a 54 volts, replaced the spark control module
Last edited by humming bird; Feb 13, 2017 at 01:42 PM.
Oil Producer
Joined: Apr 2014
Posts: 9,365
Likes: 2,734
year?
i assume its an l98?
stock form? history? did you recently have any work done to the car?
are you sure the pop is coming out the intake or could it be out the tailpipe mostly? (small explosions in the cat)
if its coming out the intake then yeah its gotta be timing related, or, intake valve seats.
is your dizzy positioned correctly? or are you one tooth off and the dizzy was rotated to try and compensate?
did you check your tdc timing mark on the balancer to see if its moved, using a piston stop in cyl #1? google how to make your own piston stop tool or buy one. very easy, instructions on youtube. this shoudl be your first thing to do...verify that the mark you setting your timing from is correctly positioned.
i assume its an l98?
stock form? history? did you recently have any work done to the car?
are you sure the pop is coming out the intake or could it be out the tailpipe mostly? (small explosions in the cat)
if its coming out the intake then yeah its gotta be timing related, or, intake valve seats.
is your dizzy positioned correctly? or are you one tooth off and the dizzy was rotated to try and compensate?
did you check your tdc timing mark on the balancer to see if its moved, using a piston stop in cyl #1? google how to make your own piston stop tool or buy one. very easy, instructions on youtube. this shoudl be your first thing to do...verify that the mark you setting your timing from is correctly positioned.
Instructor
Joined: Feb 2004
Posts: 160
Likes: 3
From: Gilbert AZ
Check you plugs to see if there is a crack in the porcelain, I chased a similar issue before and turned out to be a barely visible crack on one plug. Good luck.
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Thread Starter
Cruising
Joined: Feb 2017
Posts: 14
Likes: 0
From: argillite kentucky
thank you all for comments i think i have a timing problem the number one piston when a top dead center and the rotor button pointed at number one plug wire on the cap my timing indacator is at about 2 oclock on my timing cover and my timing mark on the ballancer is at about 8 oclock
Racer
Joined: Jul 2016
Posts: 320
Likes: 23
I know you said no work was done but a wire could be grounding itself out or jumping to another plug.
I did plugs/wires on a buddies lt4 for him and he insisted on using Carbon conductive grease, well some got on the outside of the boot and it was backfiring threw the intake. Shut garage lights off and started the car and sure enough the spark was jumping between wires and even jumping from one plug to another, 5 hours layer of cleaning the wires and plugs with iso alcohol and it ran great again.
Either at night or In a dark garage LIGHTLY mist some water over the engine compartment and start the car and look for fireworks... a simple/cheap and effective test.
