weber carb conversion and backfiring?

[hugginsvilleH&A]

I got a couple questions, I did the weber samari conversion on a rocketman adapter on a 88' carbed LX , but i am having issues , a little history , this car has been sitting for about 4 yrs, was parked do to carb issues and frustration, so i thought i would do the weber and ditch all the emission crap, and thats what i did, took all emissions stuff off, including egr, charcoal can.

here is the issue : coming off idle ,it backfires, i tried moving the timing(distributer) to all positions , stills backfires off idle and if you try and drive it, forget it its backfiring all over the place

my setup i had all vacuum ports plugged including the ones underneath the manifold, i had the both vacuum advances teed together and then tried one plugged the other hooked up , both setups are connected to the port under the choke on the carb, carb choke is wired to the original choke wiring.

i DID NOT disconnect the ecu/eca YET (dont know if that would cause the problems?) all the distributer wiring is hooked up as original EXCEPT one blk wire that is hooked to what looks like a 1" square 1/4" thick sensor on the exterior of the distributor fwd side( Where does this wire connect to?)

the thing idles really nice but when you come off idle it backfires , you can throttle on thru it and it runs smooth, but when back to idle and then try to come off idle again it will do the same, when the cooling fan comes on it idles down like it suppose to and no issues, but when trying to drive it , it can not take the load and starts to backfires to the point that it is undriveable

any help and suggestions would be greatly appreciated , Thanks Rick

[Spike]

Are you using the jets that came with the carb? They're like .140, which is about 40% too rich in my case.

I had backfiring a lot when I first installed a Weber; could turn the A/F screw all the way in and it would still run. I've leaned it out loads and still get an occasional backfire.. I kinda gave up trying to find the issue.

-Joe

[bravekozak]

Fuel/air mix issue or bad exhaust.

From what I have determined only the barometric pressure wire runs from the ECU to the distributor. I left mine disconnected. Go ahead and disconnect your ECU. You will find it makes no difference.

Are you certain you don't have a blockage in your exhaust? Like in your catalytic convertor? Too bad you don't have a test pipe to put in it's place to see if that was causing the problem. If it was the problem, you could leave it in until you could afford to (never) replace the catalytic convertor.

[Rocketman]

If the camshaft timing was off a tooth or two, would that cause an issue like this?

[bravekozak]

Yes. A backfire is the explosion that should be inside the cylinder with both valves closed. The explosion is occuring with one of your valves still open. Also try a higher octane gas that doesn't detonate early. Super duper.

[Flyin4stroke]

It could be also too much fuel sitting in the carb. I could see it being caused by not enough air movement from clogged exhaust. Does it smoke at all idling? Like, unburnt fuel is black.

[hugginsvilleH&A]

no i had read your guys post on webers and changed the main jets to .100 before i put it on.

there is exhaust coming out of the tail pipe , it has always smoked a little and still does,,,, but funny you should mentioned exhaust blockage, i live in BFE no joke and this thing has been setting for some time, when i first started it my kids were saying "dad there was lint coming out the tail pipe" lint??? so when i walked to the back , sure enough look like a small pillow was blown all over the place , apparently some mice had taken up residence in the muffler/pipe.

like i said earlier there is exhaust blowing out the tail pipe, and i can rev/stumble thru the backfire and it will then rev to the moon all smooth like, its just coming out of idle and also with a load as in driving that it really backfires at its worse. / maybe there is still a partial blockage causing too much back pressure????

i dont really see how the cam could be off a tooth or 2, never went into the belt for anything and when it was parked it was having idling issues, no backfiring ever before.

another question also was there are 2 each 3/4" hard lines that went to the old breather assy, 1 came off the fwd side, looks to have been connected to part of the exhaust and the second was connected in the rear lwr part of motor, again to part of the exhaust, maybe some sort of preheater for the air breather assy, either way if left unplugged it was blowing exhaust out of those 2 hard pipes, so i just put a piece of the original rubber hose from the breather and just routed from 1 hard line u-turned to the other, what did you guys do with yours, if you had it ,, could that some how cause my problem?

thanks for the quick replies

[Spike]

^Those 2 hard pipes, you did exactly what you're supposed to do. Loop 'em.

[bravekozak]

You still have mouse bedding blocking your exhaust. Time to ream it out with compressed air at a muffler shop. Ream out the inside of the cat with a big long drill bit while you are at it. Make sure there is no mouse furniture in there too!

[zoe60]

Wonder if it could be running way too lean? I know they are too big, but what if you put the 140 mains back in for the fun of it? It does sound like a clogged exhaust could be the problem too, but maybe the backfiring is a result of a severe lean stumble. What size are the idle jets? How many turns out is the idle mixture screw?

[hugginsvilleH&A]

the idle jets are the ones that came with the carb, dont know the size off the top of my head right now(.055 maybe?), and i did the adjustment per the instructions, bottomed out back out 2 turns and start from there and it seems to be within the half turn from that position so all that looks good unless i missed something, think i will start with a rotor rooter of the exhuast and see if get anything else out of it

did you guys reset your timing? and if so what is your timing set at?

[bravekozak]

I don't know what my timing is set at. I can't even see the marks with all the junk in the way (power steering and A/C). I just set it based on sound and power. I almost can't believe I was almost right on the money after rebuilding my B6, installing the kit & kaboodle, and rewiring the whole car. I only had to retard it just slightly to fire up for the first time. It ran solid, smooth and strong. I had no jet adjustments for my carbs. After you mentioned the story about the mice, I am willing to bet your exhaust isn't completely clear yet. Get some new bolts, remove the cat and begin your inspection. Popcorn anybody?

Now what?
Quickoats.

1. Dryer sheets
“Try Bounce fabric softener dryer sheets. Mice don’t like the smell, but you’ll like it better than moth balls. Use them in several places in the car.”
“One of the best things to deter rodents is to put multiple sheets of a fabric softener inside the car (“Bounce” is excellent!). There is a very low odor associated with the smell after taking the car out of storage, yet rodents hate this item!!!

4. Mothballs
“The ultimate prevention to mice invasion, or any other rodent invasion, is the good, old-fashioned mothball. By the first of summer the mothballs are gone. By opening up the car and taking a few rides, the smell is gone as well.”
“This is the second winter I've tried Bounce, in the car and under the hood. It worked OK last year, so hopefully it will continue to. But of course, there's that half box of mothballs spread around and under the car and in the far corners of the [old] garage, so it may be this combo that works. It sure keeps the chipmunks – destructive monsters compared to mice – out of the garage and from under the porch. “

6. Steel wool
“In addition to the soap and mothballs, I put wads of steel wool inside the pipes on my modifed '48 Willys Jeepster.”

Or tape.

[hugginsvilleH&A]

well I pulled the cat yesterday and i beleive that was the biggest culprit(seeing how the car is 25 yrs old and looks to be the original cat), as clogged as it looked i dont see how it ran at all, i modified the cat with a 12" drill bit,12" pry bar and hammer, she should flow nice and easy now , i blew out the rest of the exhaust with compressed air, put it all back together,,,, then i had to go be Santa, then back to work tonight, so i hope to try it out again in a couple days ,fingers crossed, figured since i had the car up on ramps i would go ahead a change the oil filter, oil. when the stores open back up

i have tried mothballing my truck , but really those suckers stay in it anyway, the only deterant i found is to crank things up weekly/ever 2 weeks and strategically placed D-CON within the vehicle, we have had the little bastiges get into wiring harnesses on my wifes car and really mess things up , when i lived in the city the only vermin i ever delt with had 2 legs, still would rather live in the country and deal with the 4 legged variety,

[hugginsvilleH&A]

ok i am LOST, after punching out the cat, blowing out the exhuast, i went thru the weber carb setup paperwork and the paperwork on carburetion.com/weber setup, I went thru this setup 3 times to make sure i was doing this right,

what i ended up at was idle stumbled at 1.5 turns out ,on the mixture screw, so i tried 1.75-2.0, that seemed the best. on the idle speed it was set at 1.75 turns from contact with the set screw,,,, the results were the same backfiring coming off idle , really bad when in gear,, WTH????? my car smoked before, but the thing smells like its running rich,, but according to the paperwork 2.0 + on the idle speed is a lean condition,,,getting really confused on this, you guys running webers what idle jets do you use? any on the east coast running webers?

I sprayed everything down with carb cleaner to see if there were any vacuum leaks, all checked ok, adjusted the timing by ear to where it ran the smoothest.

could a fowled plug do this or maybe the sparkplug wires in the wrong order ? disty cap? i am grasping at straws now ???

Any suggestions on what to try?? man i want this thing to work out and get it back on the road!

[Spike]

Do you have a vacuum gauge? I had pretty much all these problems until tuned WITH a vacuum gauge, not by ear.

http://www.centuryperformance.com/forum/showthread.php/42-Engine-Tuning-Using-a-Vacuum-Gauge

I can't tell jack by ear. It required more leaning out than those guides tell you. Those guides are NOT for Festivas, as they don't realize we even put these Webers on Festivas.


Also, I'm running stock idle jets (.60), and .100/.105 main jets.