Sputtering, backfiring?

[joelouisb]

My 85 van runs good.. Most of the time. Some times after running for a little while it will start sputtering or backfiring a little bit. It only happens at certain speeds around 20,35,50 mph. Almost like the vanagon hiccup that the 2.1l waterboxer can get. But I haven't read anything on a pre 86 vanagon. An help is greatly appreciated. It's still drives fine when not doing it. But I'd like to take care of it

[geo_tonz]

My '85 used to runn pretty good but backfire on deceleration, especially bad when engine-braking downhill. Determined it was my Swiss-cheese exhaust system sucking in air and detonating un-burnt fuel. Probably the O2 sensor doing screwy things too with all that extra external air getting sucked in and messing up the exhaust mixture; maybe causing it to run richer and exacerbate the problem. New exhaust and quiet as a mouse (except my damn squealy brakes!). I've heard the backfiring can be hard on the exhaust valves but things seem ok so far.
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"Ron Burgundy": 1991 Vanagon Multivan (Weekender) 2.1L Auto - Driver/Camper

[Danwvw]

I would think any FI engine would not do that if all is well with everything! Not sure how your distributor works but if your engine gets it's spark pick up off of a distributor it could just be the distributor is worn out! On the Type 1 engines they can fire the plugs at 5' advance etc on #2 and #4 when they get worn. If the ignition circuit had a bad connection to the sensor I suppose that could be the problem.
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1960 Beetle And 1679cc DP W-100 & Dual Zeniths!

[Ahwahnee]

[joelouisb]

Thanks for the help! I know my exhaust definitely needs to be replaced there's a leak at the manifold and its in pretty rough shape anyways. So that is probably the problem, and upon going to change my oil now, I noticed one of the fuel lines has a decent leak in it so I'm thinking that may be a problem also. I'll try all of these suggestions though. Super appreciative of the suggestions and so glad there's a community of vanagon enthusiasts put their to share information. Owning a van just keeps getting better, even when things need work aha

[Vinzanto]

Incorrect ignition timing can cause sputtering and backfiring symptoms.

[morymob]

I had #4 ex gasket ,at head, blow out. Never thought it would cause so much backfiring, each shift,letting off gas and eng holding back. Changed and back to all quiet.

[joelouisb]

Yea, timing was one of my first guesses, I was going to try an electronic ignition so I wouldn't have to deal with setting points anymore, and I know my exhaust needs some sealing up. Hopefully it is timing so I can fix it before I can afford to order a new exhaust.

[DFD]

I had problems with stalling, sputtering and the occasional backfire too. Checked everything. It was so frustrating. I ended up finding water in the gas. Fuel filters would clog shut. Two different mechanics at the time couldn't pinpoint how the water was entering the fuel system or where ( a brand-new tank).

The cause turned out to be cracked fuel expansion tanks. I noticed the cracks while cleaning the tanks when I resealed my gas tank (mechanic also didn't seal the fuel sender gauge properly when he installed the gas tank the first time - gas tank eventually started leaking on fill ups within a year). Needless to say, I don't use the same mechanic anymore.

Water was getting in the fuel system from wheel spray (and leaky fuel sender gauge grommet??) and wreaking havoc with how the van would run. There was a lot of sediment in the exp tanks before I cleaned them.

Is your fuel pump screaming too? If so, then it is likely water in your fuel system. Check your fuel expansion tanks and grommets (including fuel tank itself).

I repaired my fuel expansion tanks by plastic welding them (I found a good tutorial on YouTube). Sorry for no 'after' pics. To date, I haven't had any of the same problems. Good luck.

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1990 VW Vanagon GL Westy
2.1L Auto

[vanaglobal]

Hey guys,

Was reading your posts. I have a similar situation. Vanagon was backfiring and losing power especially in 4th gear. Seemed like one of the plugs wasn’t firing.
White smoke when I start the car from engine compartment even though it goes away after a bit. Smell gas but I feel like I always smell gas lol. I was seeing some gas seep through what I believe is the head gasket... (see photo) I assume it’s the unburnt gas from the misfiring plug.

I started by changing the spark plugs and ignition cables. Looks like the white smoke is gone as well as the leaking from head gasket. Does this mean I need to replace head gasket seals?

I’m going to get new distributor cap and rotor. Hoping this remedies the problem, but seeing that gas through the head is worrisome.

Here are some other problems that I need to fix that might be related or not:
My gas tank is leaky and I need to replace the seals. Same with some fuel lines around the injectors, but ok for now after a bit of tightening.

Also found one screw missing where exhaust and manifold connect.

I’d appreciate any thoughts. As of now my car will not start. Turns over but will not fire up. Uploaded pics of spark plug in question as well as distributor parts and the area where I saw the leak.

[Steve M.]

Backfiring on deceleration or when you take your foot off the gas is sure sign of a vacuum leak.
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[vanaglobal]

[jlrftype7]

Distributor cap and rotor look like they need replacing, or at least a gentle cleaning with rubbing alcohol as a test to help prevent arcing inside that cap.
Those ground connection eyelets all need attention at the cyl. head. Since insulation has cracked off with age, you are going to see a faster spread of corrosion up the bare copper wire once it takes hold.
Cyl. Head bolt threads need to be wire brushed while you’re cleaning the eyelets of the ground wires, then spray everything with Electrical Contact Cleaner, available from hardware stores and auto parts stores. It leaves a bit of protection on the connections too after removing crud and corrosion.

As noted, vacuum leaks need to be corrected too.

Your white smoke could be coolant dripping from the engine cyl seal/gasket onto the exhaust, then it seals up with some engine heat from running.
Does your coolant tank level drop down with continued driving of the engine?
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'68 Westy- my first VW and vehicle/Bus- long gone.- sold it to a traveling Swiss couple....
'67 Type 3 Fastback, my 2nd car- gone
'69 Semi-Auto Stick Shift Beetle-gone
2017 MINI Coopers, our current DDs
‘84 Tin Top - Hilga....Auto

[Steve M.]