TheSamba.com :: View topic - 1984 Westfalia Backfiring on Deceleration

Mon Aug 18, 2008 5:19 am

I recently began bringing a 1984 Westy back from the brink of extinction. When I got it, someone had cut off the catalytic convertor, leaving me to replace the connector pipe, cat, muffler, and tailpipe.

I got all of that done to the best of my ability, and now when I run the car, I get a pretty significant backfire on deceleration. This vehicle had some pretty old gas in it which I'm sure has gummed up the works somewhat.

I know the condition is caused by a lean condition causing fuel to combust in the exhaust. Could my installation of the new exhaust components be to blame for this? Would a new distributor cap, rotor, timing adjustment, and fuel filter help?

Any ideas would help!!

Thanks,

Joe

Mon Aug 18, 2008 6:03 pm

You sure you just don't have a bad exhaust leak? In my experience, backfiring when decelerating is typically from a bad exhaust leak. Of course, I have only had this happen on my aircools not my waterleakers.

Tue Aug 19, 2008 3:46 am

Like I said,

I had to put a new Catalytic converter, connector pipe, and muffler on. Would the leak be at the heads, or in this system?

Tue Aug 19, 2008 6:45 am

When you say "backfire" do you mean flames shooting out the tailpipe or popping noises?

In order to get flames you have to have an excess of unburned gas dumped into the exhaust. I'd check the idle throttle switch adjustment on the throttle body first. It could also be a rich running engine or leaking injectors.

As for the popping noises, an exhaust leak contributes to them.

Wed Aug 20, 2008 3:56 am

Backfire can be unburned gases in the exhaust that ignite from a hot exhaust. Was the catalitic you installed new or used?

If you had exhaust leaks at the point where the header tubes mount to the heads, run the engine with the rear engine cover off, and listen for an annoying "ticking" sound.

Wed Aug 20, 2008 5:00 am

I definitely get some annoying ticking, but it's not all that loud.

I can state for a fact that I'm no expert on installing Vanagon exhausts....but I bolted that stuff on as hard as I could. The headers are rusty, so I'm wondering if they just have some holes in them.

I'll have them off when I do the inevitable head gaskets, so all will probably work out in the long run.

Wed Aug 20, 2008 9:32 am

just out of curiousity, did you instal new exhaust gaskets when you did these repairs??

Wed Aug 20, 2008 11:56 am

Run the old gas out and give it a proper tune-up. Have you replaced the fuel/injector lines? How many fuel filters does your 1.9 have, what do they look like (SEARCH)? I'd run a can of BG 44K or Tecron fuel system cleaner with a fresh tank of gas (some recommend using premium with it). What weight oil are you using? The ticking is normal but can be reduced/eliminated with a good oil and filter. I'd leave the idle/CO screw for last, and only adjust it 1/2 turn at a time when you do. Welcome to wasserboxer klub.

Thu Aug 28, 2008 4:17 am

So far as I can tell, it's got only one filter...the square job under the passenger side. I'm running fresh Castrol 20w50 and a Bosch filter. The gas in there right now, is a funny hodge-podge of the old gas, premium gas, and sea-foam. As soon as I get that through, I'm going to run a bottle of BG44k through...that stuff is good.

I'm getting much more intimately involved with this engine, which is in many ways really similar to my 1966 1300....I rebuilt that thing myself.

I had the engine running yesterday and I can tell for a fact that there is exhaust (at idle) coming at a decent clip from the place where the exhaust bolts onto the heads on the passenger side (rear of vehicle) and the drivers side (front of vehicle)....I can feel it pulse. Doesn't look to be holes in the manifold, just some worn out gaskets. I'm going to have to pop the head off of the drivers side at least, as there's a seep there of coolant. So, I figure I'll have that opportunity to reseal the manifolds to the heads.

I have no fear of doing head gaskets (water jacket seals) on this motor, but I DREAD trying to get the exhaust unbolted from the heads with all that rust....I may have to end up taking it to a shop for that reason only.

Thu Aug 28, 2008 9:40 am

10c recently published an article on oil filters in case you missed it. Heres some info on the fuel filters for ya.
http://www.thesamba.com/vw/forum/viewtopic.php?t=263991&highlight=fuel+injectors