small back fire at start up!

I have noticed that some times when I start up my truck in the morning, specially if it is a little colder, that I hear what sounds like a mild back fire, or a sudden "puff" sound from the exhaust. I don't know why. I took it to the dearlership and left the truck there overnight so they could start it up first thing in the morning to hear it for themselves. They heard for themselves what I was talking about but they told me that there is nothing wrong with my truck, that they hooked up the diagnostics and everything checks good that it was "normal" and that it is doing that to warm up engine faster and bring it up to operating tempratures quicker!!!

Have any of you experienced anything like this?

 

I've heard what I think you're describing in mine too... and it's only a couple of weeks old. I think it's normal. It's nothing like a *POW* backfire. Not really a "pop" at all... more like "pfft"... sometimes a couple fairly close together. Only right after starting the engine when it's completely cold - like after it's sat overnight. Right? It's probably just the unburnt rich-mixture exhaust from the cold start lighting off in the cat or muffler. I think the purpose of the air pump in the emission system is to enable exactly that. Nothing to be concerned about. Now, if yours is worse than that - and it's something new that it's just recently started doing, then you mave have some kind of problem.

 

that is a good discription of what I am experiencing. more of a "puff" sound than a loud "pow". I am glad to hear that is not any thing to worry about. I figured it would have something to do with maybe too rich a mixture at start up, probably commanded by the computer and temperture sensors to crank the truck faster on cold mornings (some thing to that effect).

 

Mine does this as well from time to time when I start it up in the morning. Started a thread on it a while back and a couple people said theirs did it too. http://www.tacomaworld.com/forum/4-cylinder/25229-exhaust-pop-stock-09-a.html

Don't think it's anything to worry about.

 

Mines a 95 and it does that too.

 

My 09 backfires on startup. Sometimes small, other times it's a pretty loud pop / puff....

 

The Batmobile used to do the same thing.

 

Mine did that for a wile. I started to let it sit till it idled all the way down( about 20-30 seconds) before I shut it off and havent had that poof or back fire since then.

 

My 09 does the same thing...

 

This is a release of cold pressure from compression. What you are hearing is the first strokes of the motor before shes making power. it should sound like air is blown out all at once in between the strokes. listen close, my 2007 does it every time I start it in the morning. nothing to worry about.

 

I will admit that I like it when I start up in the morning and hear this with the flowmaster but that's just me as long as it runs strong and there is no check engine light lol