Hey, I just droped in an ls vtec in my car a couple of days ago. I was driving around with just the header and downpipe and it ran great. The all of a sudden it started hesitating and backfiring when i rev it up. Do you think this is just because I dont have full piping or is it something else

 

Sounds like you have a ignition issue, pull the plugs.

The car will run fine with open downpipe, loud but fine

 

negatory, the air fuel mixture ration can change with lack of backpressure, that is your problem.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mavrick &raquo;</TD></TR><TR><TD CLASS="quote">negatory, the air fuel mixture ration can change with lack of back pressure, that is your problem.</TD></TR></TABLE>

Not the back pressure myth. The 02 sensor is before the open section, so how would the air/fuel mixture change ? People run 4 inch exhaust on some cars and never have issues, back pressure is not a myth but it does not effect things that drastically.

 

Have you replaced your spark plugs? check your Coil, it might be givin' up.

 

just do the basic tuneup 1st..plugs,cap,rotor,

and what ecu do you have? and are you sure its backfiring and not just making the pop noise cause of no exhaust ?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mr.speaker &raquo;</TD></TR><TR><TD CLASS="quote"> and are you sure its backfiring and not just making the pop noise cause of no exhaust ?</TD></TR></TABLE>

I was going to add that, good catch.

Backfiring is basically combustion in the exhaust system. Backfiring is usually really loud.

The popping noise after you let off the throttle is normal when you run no cat or exhaust. But if its a slight pop I would say its a misfiring in a cylinder.

 

well, it pops pretty loud and when it pops a spark comes out of the down pipe. I am running an ls ecu (my vtec is not hooked up yet) and i have drand new plugs, plug wires, cap, and rotor. I just dont know why it would run great and then start doing this

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GsrTurboCRX88 &raquo;</TD></TR><TR><TD CLASS="quote">well, it pops pretty loud and when it pops a spark comes out of the down pipe. I am running an ls ecu (my vtec is not hooked up yet) and i have drand new plugs, plug wires, cap, and rotor. I just dont know why it would run great and then start doing this</TD></TR></TABLE>

possibly timing? coil? is the check engine light on?

 

yea but the only code it is throwing is the speed senser. I broke the speedo cable during the swap

 

ok, so i messed with the distributor and moved it back a little bit and it ran alot better but after i drive it for a while, it starts to run like crap and cuts out until i get to about 2800-3000 rpm's and then runs better. It almost feels like it does when you are running out of gas and it cuts out. then once again after i mess with the distributor it runs fine. any more ideas?

 

the distributor is on tights so i know it is not moving by its self

 

BUMP

 

do a basic tune up and get a damn timing light.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 90_EF_Si &raquo;</TD></TR><TR><TD CLASS="quote">do a basic tune up and get a damn timing light. </TD></TR></TABLE>

yeah get a timing light..and moving the distributor back or forward does nothing at all without jumping the service connector...it will reset by itself