97 yukon backfireing thru intake.

[ezdaar]

Pull distributor as mentioned above, check the gear.
If its plastic immidiatly put a broze gear on it. regaurdless if its broke, worn , whatever.

Next pull water pump, harmonic balencer and timing cover.

take a look at the timing chain gears teeth. some will probly be chipped or broken completly.
more likely just extremly worn aka grooves in the face of the teeth.
along with ALOT of slack in the chain.

regardless of wear, replace it with this.
http://www.summitracing.com/parts/SUM-G6601/

------------------------------------------------

This lil item
http://www.autozone.com/autozone/pa...e-2WD/Ignition-Control-Module/_/N-j9305Z9n80t

Is notorious for going out at any time on older chevy / gmc's
If your not getting spark. my bet is its bad. you can replace it with distributor installed.
just pop cap and remove the 2 lil screws holding it down.
beshure to put the thermal greese on it.
I changed one in a parking lot at night with no light on a suburban one night. lol

I would change this last part first before anything else.
But once running, I would still replace the timing chain and gears. your vehical will run noticably smoother.

 

[99Yuk]

BTW, if you are going to check the distributor gear teeth, you should use a marker or something to mark where it was positioned before removing it. Just in case it is still good, you can align up the marks to get it back in the same tooth as before.

 

[ezdaar]

BTW, if you are going to check the distributor gear teeth, you should use a marker or something to mark where it was positioned before removing it. Just in case it is still good, you can align up the marks to get it back in the same tooth as before.

Ahh yea, LOL good call on that one.. completly forgot about marking the base to block.

 

[nokuy97]

The only problem I have is that it must have some spark to make it backfire .Can a coil get weak and still do it's job until it finnally craps out ?

 

[ezdaar]

yup.

Dude if it jumped time that would cause it to backfire Badly through the intake.
Check the timing chain.
I have had numerous chevy 305's and 350's jump time. See I used to have a habbit of blowing up motors due to over revving them and replacing them with high milage junkyard engines. Sooo.... I have had a few jump time.

 

[nokuy97]

Yea
the last time I had a timing chain jump was on my 1976 3/4 4x4 chevy and I changed the chain and gears then. I got to wait until it warms up here alittle because this is going to be a outside job.

 

[99Yuk]

Yea
the last time I had a timing chain jump was on my 1976 3/4 4x4 chevy and I changed the chain and gears then. I got to wait until it warms up here alittle because this is going to be a outside job.

HAHA... I just aquired a 1976 3/4ton 4x4 Chev last year. It's my snow plow truck after the guys here thought it would be a bad thing to install on my Yukon. http://www.tahoeyukonforum.com/forum/album.php?albumid=419
I love it! It's so much fun!

 

[nokuy97]

Great TRUCK !!! mine got to the point that when you started it after sitting for a week or two , it would use a half of a quart of oil. Great when you can clear out all the bugs for a half mile away in the woods , smoke like hell but ran like a bear.

 

[ravingmadman]

A weak coil won't cause a backfire like that, not to the extent you're suggesting. If the timimg is off, then the valves are open when the spark ignites the fuel/air mix, which is why you'll see flame pop out of the throttle body. That's really ******* your engine. If I checked anything first, it would be the distributor. But as mentioned, make sure you mark both the rotor to cap orientation, and the cap to base orientation, in the event you don't find anything. Happy hunting!! Oh, and your buddy absolutely owes you a case of beer.