Backfire

Tiny
LANGING
  • MEMBER
  • 2000 TOYOTA TACOMA
  • 2.4L
  • 4 CYL
  • RWD
  • MANUAL
  • 134,000 MILES
Single backfire, occasionally, on start-up.

As engine is trying to start, starter motor engaged and turning the crank, sometimes there will be a 'muffled' explosion thump-like noise emitted from the engine bay.

Have not isolated exactly where the sound comes from, but have long thought it was inside the air intake tube, prior to the throttle body.

Problem has long standing, because I never figured it needed attention, being that it happens so infrequently.

When I began a search for information on engine backfires, I happened onto your website, which explained that backfires can cause damage. That is why I signed up.
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Thursday, July 20th, 2017 AT 3:09 PM

5 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
See our handy link on backfires and what to do about them. it may be just in need of spark plugs etc.
https://www.2carpros.com/articles/engine-backfires-while-running
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Thursday, July 20th, 2017 AT 3:41 PM
Tiny
LANGING
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This is not a case of backfires while running. Only happens when attempting to start, prior to running.
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Friday, July 21st, 2017 AT 3:49 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,554 POSTS
Yes this could be the ignition system cross firing into a cylinder with the intake valve open causing the backfire. Do plugs and wires here is a video to help you get the problem fixed.

https://youtu.be/rU6uxV5dLoA

and

https://www.2carpros.com/articles/how-to-change-spark-plugs

and it might be if you have a large leak in the air intake boot. Here is a video so you can check that.

https://youtu.be/h8jOlZubz0c

Please let us know what happens.

Cheers, Ken
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Friday, July 21st, 2017 AT 2:22 PM
Tiny
LANGING
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  • 3 POSTS
Thanks, Ken. Haven't had time YET to change out the spark plugs, but will do that.

What is 'cross-firing' and why does it happen?

Have a question about the air intake boot. Before I toss money at a new boot, how do I determine that there is actually a hole in it? Or, what did you do to diagnose it as a problem?

Sometime back, I had to replace the VSV for the EGR, and cleaned out the throttle body along with the EGR system. At that time I had to remove the air boot and it did not seem to be in bad condition, visually.
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Friday, July 21st, 2017 AT 3:52 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Just look for a hole in duct work normally between maf and engine that is where it will cause it to idle /run funny
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Friday, July 21st, 2017 AT 5:01 PM

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