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Topic: 86 3.8 back firing (Read 1013 times) previous topic - next topic

86 3.8 back firing

OK so i have a 3.8 and is backfiring when every i rev it at first i thought it was my ler because it was all banged up but after i replaced that it still backfires. took it to a mechanic n said all my wires and timing is in order and said it could be my carb or whatever i have under the hood not sure what it actually is because i have a cfi motor anyone can help much appreciated

thanks  Brian

86 3.8 back firing

Reply #1 –
Generally it is a plug firing while a valve is open or excess fuel flooding into a hot exhaust system.
Does it backfire while revving or after you get off the gas?
Is it backfiring through the exhaust or the CFI?
A little background on the car would be helpful.
Is this an "on the road" car, or one that has been sitting a long time?
How does it run otherwise?
Did it just start happening out of the blue or after some work was done?
Is everything stock as far as you know?

86 3.8 back firing

Reply #2 –
ok so it back fires after letting off the gas
the back fire sounds like its coming from just behind the motor

background: 86 thunderbird base automatic 3.8 cfi ummm as far as i kno all stock 156+ thousand miles been having this back fire since i got the car and thought it was going to be something with the ler but replaced that already soo not sure what it can be

on the road car my daily driver and other than the backfiring runs pretty good just shakes a little in idle but hardly anything

pretty much what i kno of it

86 3.8 back firing

Reply #3 –
You should cheak your EGR vavle opertion and make sure its not leaking. That could cause a backfire by the rear of the motor and cause a rough idle.

86 3.8 back firing

Reply #4 –
ok honestly i dont kno what that is haha if you can tell me where its located and how to check it i would really appreciate it thanks

86 3.8 back firing

Reply #5 –
Quote from: Base92;385235
ok so it back fires after letting off the gas
the back fire sounds like its coming from just behind the motor

This is when a carbed engine would typically backfire through the exhaust.
Are you sure it is a CFI? Some 86 3.8L built for export to Canada and Mexico were carbed.
Have you taken the air cleaner off and seen the two injectors?
I am surprised your mechanic doesn't know the difference between carb and CFI.

If it is CFI you need to run the computer self-tests and get the error codes.
The self-test connectors in the diagram are under the hood near the left shock tower.

Lets just start with the KOEO (Key On Engine Off) tests.

86 3.8 back firing

Reply #6 –
yea is a cfi has those 2 injectors on the top of the air filter
i think my mechanic just didn't wanna mess with it because he just told me to take it to a shop to run the machine on it to pull the codes
what do i need to do the self testes is there a certain tool?

86 3.8 back firing

Reply #7 –
Quote
what do i need to do the self testes is there a certain tool?

My previous post shows how to run the tests using a test light or an buttstuffog volt meter.
These tools can also be used for trouble shooting electrical problems.

You can buy a code reader at a car parts store.
 

86 3.8 back firing

Reply #8 –
how do you check the egr valve? can you tell just by looking at it?