Ok, this may sound dumb, but I have a really bad Back Fire in all gears wether it's cold or up to temp. I have checked the Wires, they are with in the Resistence it needs, Coil, its where it needs to be, Cap and Rotor nothing odd there. checked the timing, ok. So, Im down to spark plugs, Could the Gap already need to be checked?? I know your supposed to Gap check them before you put them in, But I was in a hurry when I did the ReBuild and just put them in. Now my Chiltons or Haynes isnt specifying a Proper Gap. BTW: 89' 2.6L 4ZE1. and its really loud when it does it only while shifting gears. If anyone has pointers and gap Spec that would be Great. Thanks.

Sure it's not an exhaust leak?

Im sure it's the Plugs, but I cannot find the Gap at all to eliminate the plugs from this, We checked for an exhaust leak, but that wasnt very though since its comming through the muffler.

1MM PLUG GAP .040 IN THOUSANDS JERRY

I'd recheck the timing and check the valve clearance again. Passing exhaust valves are a classic for backfire. Cat converters don't last long with detonation and passing valves burn up so don't delay. And don't be in a hurry or you'll be doing your re-build again...soon... It took me two head rebuilds to figure out that ...

There is no Cat... We put a Piece of test pipe in to see what Difference it would make with those Brick Style cats mine had. So far its Great, High Flow Cat is up next. As far as Valve Lash Goes, We set them at every 5000 miles to keep on top of it ( its been done 3 times with in 3000 Miles from noise in the Valve train). I dont wanna buy another head for this thing for a long time. Ill check the timing again to make sure. Thanks Jerry Ill try that and see what that does. Im using Octane Booster on Mid grade for fuel mileage reasons, Its done it before this but its getting a little worse this time around.

Im using Octane Booster on Mid grade for fuel mileage reasons

Octane does not equal mileage. You are wasting your money.

Michael

You Sure? Im getting 21 to 24 MPG Average. On Reg. Im getting 16 to 19 Average. Im pretty sure its helping. But you may also be right, maybe the Mid Grade itself it just doing it just fine, and Im wasting money. Ill run a couple of tanks to see. Im letting the Trooper sit for a bit so I can gap the plugs and see if it helps any. Its running awsome though.( these little 2.6's run really really well- before it was running on 3 due to a burnt exhaust Valve on #3 Cyl.) Had to pull a car out this morning due to them sliding into a ditch after screwing around. Low Range Baby!

If mine hadn't dropped a valve guide, I would have never guessed I was running on 3 cylinders. The #2 exhaust valve was burnt with about a 1/4" side cut out. And yes it backfired in every gear..

Well Due to mis Gapped plugs, and and a vacuum hose that had split that was what was causing it to back fire.. got it fixed after I had seen the hose and it runs great. again. <img src="/forums/images/graemlins/scared.gif" alt="" />