Backfiring though the intake... WHY? - Hyundai Performance Forums

Jed118 · 04-28-2006, 01:43 AM

So I recently tuned my motor, and I have noticed that it backfires through the intake. Many say it's due to the distributor... I have no idea!

THe distributor is CRANKED all the way and all I can get is +5 deg TDC. I've messed with the distributor vacuum bulb and that yeilds me another 5-6 deg +TDC. The distributor is recurved (IE it gives more timing faster, and more of it due to bored out cam plate) and the springs have been readjusted to open quicker (thus providing more centrifugal advance - sooner) but my base timing is still only 5-10 ATDC. What gives?

The car wants to rev after about 2.5-3k RPM (it boots after that) but before that it's SUPER slow and sometimes backfires through the carb (sometimes it stalls due to this) I've recently done my plug wires, coil, and set the dwell angle (the amount of power going to the spark plugs, at the cost of point life) and the damn thing still acts retarded. If I move teh distributor back like 10 degrees, the car simply stalls. And if it doesn't, then it runs like absolute garbage, taking YEARS to spin up (on a lightened flywheel, should take no time at all) but once it hits 2.5-3K RPM, it soars, like VTEC kicked in or something.

I just don't get it! What is causing the backfirnig? Could it be that the timing is advancign too quickly and causing the spark curve to creep up on the intake stroke? It's not the carb or any of the vacuum lines... the vacuum bulb works fine, the timing is stock spec (i'd like 7 deg more on the base timing but I can't pass +10 deg ATDC) and the car idles fine at 800 RPM (mind you the AF metering screw has snapped, so Im assuming a relatively stoichometric ratio based on previous readings)

I'm gonna put the stock distributor (no recurve, stock cam specs and advance springs) and see what happens...

Any ideas?

pucci · 04-28-2006, 04:02 AM

just a guess but could you have installed the distributor a tooth off? hence only being able to get +5* with it maxed out...

Jed118 · 04-28-2006, 11:23 AM

There is a distributor "tooth" at the base of the gear, which will only allow me to put it in 2 ways. If I put it 180 deg out of phase, I get HEAVY exhaust backfire and the car does NOT start at all.

187sks · 05-03-2006, 04:36 PM

Did you get it figured out?

If not maybe you can do what I have to do on the Bronco. Adjust it entirely by ear. If I adjust timing by the book it runs LIKE CRAP. A little experimentation and listening to the engine as I adjust it is the only way to get it to run right.

TataBobu · 05-04-2006, 07:51 AM

I dunno how is the distributor angrenated in your car, but if it is like in my Dacia 1300 (by the oil pump, via a gear) check those, too. And set your advance by ear, not by the book because the book is good only for perfect engines.
The vacuumatic advance functions right? (does you car have one? :embarrassed

Backfire thru intake = ignition before intake valve closes (detonation or one intake valve doesn't close properly). Are your valve springs in order? Might want to check the valves, too.

[Edited by TataBobu on May 4, 2006 7:50 AM]

wilburisthecoolest · 05-04-2006, 03:26 PM

Are all your spark plug wires in the right spot?

Whats the dwell? Cause you run that off and no matter what you time it it will run like shiznit.

Jed118 · 05-08-2006, 03:59 AM

well the engine WAS involved in a front end collision with a minivan at a combined rate of 150 KMh... maybe something got knocked around.

Dwell is at 65 deg, specs say 55 but I wanted a good kick out of the spark. Even at spec it does nothing different. Vacuum advance is fine, the bulb works well.

I will try some more things, see what I come up with.