I've searched high and low on the ls1 fourm, and I found 1 other case of this, and it was unanswered. I recently pulled my 5.3 back out of my blazer, and did a refresher to try and stop the rear main leak.... Unsuccessfully. And now after I let the car sit for a bit and I turn the key to ON it will backfire / spit so violent that it blows hoses out of my intake. I noticed that my fuel pressure is leaking down all the way to 0, and I put a new pressure regulator in it and it still does it. MY theory is that all the pressure building up in the gas tank is evapaping into the intake and igniting when the coil turns on. Please help, I don't want to bend a rod in my new engine because of a bad sending unit. Please if anyone has any ideas please help.

 

If that were the case, I would expect it to happen when you turn the key to off. The coil actually fires when the primary magnetic field (12V coil circuit) collapses.

 

Do you think that it could be a bad coil, or possibly there is just that much pressure building in my tank that when it purges it sounds like an explosion?

 

It shouldn't be either of those things, but I'm not really sure what it is, either.

 

"I let the car sit for a bit and I turn the key to ON it will backfire" Are you cranking the engine to start, or just turning the ign on?
If you think tank is building pressure take fuel cap off and let it sit and see if it does the same thing. Will be interested to hear what you find.
Here is some information that I found, know it not the same engine but?
https://blazerforum.com/forum/engine...r-issue-46969/

#9
07-22-2010, 06:56 PM
TipOTexas

New Member


Join Date: Sep 2009
Posts: 6



check maf again
I had very similar situation with my blazer only thing it is a 2000. changed all kinds of sensors no dice. The only one I had not changed was the MAF. No trouble codes this went on for almost a year farting through the intake, not wanting to rev when gas was pressed hard same thing you are describing. One day cruising ebay found a MAF for 30 bucks said what the hell nothing to lose. Well what do you know that was the problem all along!!! just a suggestion, maybe borrow another MAF from a buddy or something and try it out if it is your problem you will see an immediate change. Good luck!!




#10
07-29-2010, 01:00 PM
Shalom

New Member


Join Date: Feb 2010
Posts: 60




Same here, on a 99. If I gave gas and then closed the throttle abruptly, blam. Took it to the dealer (still had the service contract on it then) and they said it was the MAF sensor. I still can't see what the heck the MAF sensor has to do with backfiring, but I told them to go ahead and change it anyway, and it fixed the problem.