View Full Version : Back fire
HogWash
August 26th, 2006, 21:11
Some times my engine will back fire,not loud but you know it does it,but im not sure when(hot or cold). Any suggestions what it might be?
jeepdude10000
August 26th, 2006, 21:34
for one thing, we dont know what year, engine.
and another thing u are to tell us when so we can help u diagnose.
:confused1 :confused1 :confused1 :confused1 :confused1
HogWash
August 26th, 2006, 21:37
87 cherowagon,4.0 ax4 tran.i wanna say when its cold,but im not sure so i didnt want to post something i dont know,sorry
8Mud
August 26th, 2006, 21:42
Try to narrow it down some. Above 140 degrees and the sensor inputs change some. RPM is also a big indicator. Throttle position is also an indicator.
Totally random can be anything from plug cables, distributor cap, to the CPS.
Mid RPM range is sometimes the O2 sensor.
1/3 rd throttle is sometimes the TPS.
8Mud
August 26th, 2006, 21:51
If it happens cold and then gets better when hot. Take a look inside your distiributor cap. Spray a little brake cleaner in the cap and rag it out, to clean off the carbon and remove some moisture.
Moisture can condense on the inside of the cap, then evaporate or turn to vapor when hot. Only to condense on the inside of the cap again, when things cool down. This is more common on cold mornigs or in the colder months.
Plug cables are most always a possiblility. Either arching across the cables, which usually happens when one cable has a really high resisitance. Or various cables have cracks.
It can be moisture in the cable boots, at the cap or at the plug. High pressure engine washes will force some moisture behind the boots on occasion, causing all sorts of misses cross fires and grief.
Check the easy stuff first (basic ignition system stuff), then the sensors and connectors.
HogWash
August 27th, 2006, 06:34
I forgot to add in the mourning or the first time i start it up ,it does studder and you punch it and its fine.When I change the plugs and all ignition stuff and it did fine now im back to square 1.any insight,possibly carbon build up or something?
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