82 Vanagon Westy Missing then Backfire Intermittently

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Manaman
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82 Vanagon Westy Missing then Backfire Intermittently

Post by Manaman » Wed Jun 28, 2017 11:56 am

82 Vanagon Westy Manual Fed Rebulit motor 3K -4k on it

I'm driving down the road at 50mph and then a sudden jolt ..miss ...quick loss of power, I back off then drive some more and then it really misses and then back fires, I make it home , but I have no idea what could cause it.....any suggestions please

after I got it home i checked for lose wires and grounds the next day I drove in my neighborhood and it didn't happen, then I drove it out to place where i work on it and the problem didn't happen, drove it couple more days nothing and then today driving 45mph steady and it missed for a second like a quick jolt , kept driving didn't happen and no backfire
1982 Vanagon Westfalia Federal Manual FI
1985 Vanagon L WBX
1972 Super Beetle

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SlowLane
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Re: 82 Vanagon Westy Missing then Backfire Intermittently

Post by SlowLane » Wed Jun 28, 2017 3:59 pm

These were the same symptoms I had the first time I discovered a failed AAR elbow on my van, and it's the main reason I continue to bleat about the ruddy AAR elbow about every fifth post I make.
'81 Canadian Westfalia (2.0L, manual), now Californiated

"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
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Amskeptic
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Re: 82 Vanagon Westy Missing then Backfire Intermittently

Post by Amskeptic » Wed Jun 28, 2017 8:12 pm

Per SlowLane, and check grounds and TS II for secure connection.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Randy in Maine
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Re: 82 Vanagon Westy Missing then Backfire Intermittently

Post by Randy in Maine » Thu Jun 29, 2017 4:14 am

If you are running points, make sure the condenser is secure.
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Manaman
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Re: 82 Vanagon Westy Missing then Backfire Intermittently

Post by Manaman » Fri Jun 30, 2017 11:18 am

I'm going to check the grounds and Temp2 for connection, drove it today and it started doing it again,when it does it feels like the fuel stops and its trying to find it and then it comes back if it has problems getting it back then it backfires. It did it in first, second and third gears.
1982 Vanagon Westfalia Federal Manual FI
1985 Vanagon L WBX
1972 Super Beetle

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Manaman
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Re: 82 Vanagon Westy Missing then Backfire Intermittently

Post by Manaman » Fri Jun 30, 2017 11:19 am

Randy in Maine wrote:
Thu Jun 29, 2017 4:14 am
If you are running points, make sure the condenser is secure.
I have electronic ignition ..no points
1982 Vanagon Westfalia Federal Manual FI
1985 Vanagon L WBX
1972 Super Beetle

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Manaman
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Re: 82 Vanagon Westy Missing then Backfire Intermittently

Post by Manaman » Fri Jun 30, 2017 1:54 pm

Cleaned and checked ground and temp2 is not loose, I also replaced the fuel filter thats post of the pump, when I blew through the end of the old one a lot of black dirt came out about half tsp. I ordered a new AAR elbow just in case, so when it comes I will check it out
1982 Vanagon Westfalia Federal Manual FI
1985 Vanagon L WBX
1972 Super Beetle

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Amskeptic
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Re: 82 Vanagon Westy Missing then Backfire Intermittently

Post by Amskeptic » Fri Jun 30, 2017 4:14 pm

Manaman wrote:
Fri Jun 30, 2017 1:54 pm
Cleaned and checked ground and temp2 is not loose, I also replaced the fuel filter thats post of the pump, when I blew through the end of the old one a lot of black dirt came out about half tsp. I ordered a new AAR elbow just in case, so when it comes I will check it out



Also, clean the wiper and track inside the AFM with a kleenex, you will need to gently lift the wiper contacts from the board.

This is a weird one. Do the basics, like clean and gap spark plugs, check for carbon inside the distributor cap between the terminals, make sure oil filler/dipstick is not leaking air, as this changes the mixture.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Manaman
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Re: 82 Vanagon Westy Missing then Backfire Intermittently

Post by Manaman » Fri Jun 30, 2017 8:57 pm

Amskeptic wrote:
Fri Jun 30, 2017 4:14 pm
Manaman wrote:
Fri Jun 30, 2017 1:54 pm
Cleaned and checked ground and temp2 is not loose, I also replaced the fuel filter thats post of the pump, when I blew through the end of the old one a lot of black dirt came out about half tsp. I ordered a new AAR elbow just in case, so when it comes I will check it out



Also, clean the wiper and track inside the AFM with a kleenex, you will need to gently lift the wiper contacts from the board.

This is a weird one. Do the basics, like clean and gap spark plugs, check for carbon inside the distributor cap between the terminals, make sure oil filler/dipstick is not leaking air, as this changes the mixture.
Colin
Thanks Colin I will try all those, I took it for a drive after doing the grounds, temp2, and new fuel filter and it didnt do it again, I going on a drive tomorrow up to Ft Myers which is about 45 min away so I will see if it happens again....fingers crossed
1982 Vanagon Westfalia Federal Manual FI
1985 Vanagon L WBX
1972 Super Beetle

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Manaman
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Re: 82 Vanagon Westy Missing then Backfire Intermittently

Post by Manaman » Sat Jul 01, 2017 9:25 am

Well made it half to Ft Myers and it started doing it again , I limped home, I had cleaned track on AFM and checked the oil dip stick, I will do the dist cap and spark plugs see what happens next
1982 Vanagon Westfalia Federal Manual FI
1985 Vanagon L WBX
1972 Super Beetle

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SlowLane
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Re: 82 Vanagon Westy Missing then Backfire Intermittently

Post by SlowLane » Sun Jul 02, 2017 12:20 am

<bleat>So your AAR elbow checked out okay then, did it?</bleat>
'81 Canadian Westfalia (2.0L, manual), now Californiated

"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
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Manaman
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Re: 82 Vanagon Westy Missing then Backfire Intermittently

Post by Manaman » Sun Jul 02, 2017 1:23 pm

SlowLane wrote:
Sun Jul 02, 2017 12:20 am
<bleat>So your AAR elbow checked out okay then, did it?</bleat>
I checked it but you can never tell, so I ordered a new one just waiting for it now
1982 Vanagon Westfalia Federal Manual FI
1985 Vanagon L WBX
1972 Super Beetle

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Manaman
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Re: 82 Vanagon Westy Missing then Backfire Intermittently

Post by Manaman » Mon Jul 03, 2017 12:48 pm

Ok some more info, I drove it out to where I work on it with my guy VW Fred, it didn't do it when driving out there from cold start he is about 20 mins from my house, it started when i left his place about 15 mins down the road so I went back and had him drive it, he's the one who rebuilt my engine. It started doing it for him missing then come back ,it backfire one time as well , he put the van in neutral and give it a little gas and it started doing without any load. Got back to his place started checking

van would idle fine in neutral .....give a little bit a gas and hold it there.... it either would shut off or start idling up and then down...... idle up then down rapidly
Took the cover off the AFM....started it...... idles fine,..... give it throttle slowly as soon as its at a certain place on AFM it cuts off and dies

Idle again this time give a lot of throttle past the certain spot on AFM, its revives up and down but not as much or not as rapidly and doesn't die off

Fred seems to think its electrical and heat.........I'm wondering should I get a rebuilt AFM or go through all the adjustments that Colin has on the site here with my old AFM.....I'm at a loss here .......any help or suggestions
1982 Vanagon Westfalia Federal Manual FI
1985 Vanagon L WBX
1972 Super Beetle

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sgkent
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Re: 82 Vanagon Westy Missing then Backfire Intermittently

Post by sgkent » Mon Jul 03, 2017 10:21 pm

have you done a smoke test of the intake system to look for vacuum leaks?
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SlowLane
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Re: 82 Vanagon Westy Missing then Backfire Intermittently

Post by SlowLane » Tue Jul 04, 2017 9:07 am

So what Steve (and I) are obliquely trying to get across is this: before you start mucking about with the AFM, make sure the fundamentals are in order.

To wit:
  • Make sure that there are no vacuum leaks. The list of potential leak sources is extensive and has been covered in past topics. The smoke test that Steve recommends is a great way to "smoke them out"
  • Make sure that all electrical connections are sound. Grounds as well.
  • Make sure that your ignition is performing correctly. Not just a nice strong spark, but that the distributor is advancing smoothly as RPM increases and un-advancing just as smoothly as RPM decreases.
  • Make sure that your fuel pump is providing sufficient pressure and volume for all operating conditions.
Too often a person will dive into the AFM trying to compensate for an undiagnosed vacuum leak because tweaking the AFM is more "wizardly" than chasing down mundane cracks in the rubber bits. Really, the factory setting of an AFM should be correct for pretty much the normal life of an engine.
'81 Canadian Westfalia (2.0L, manual), now Californiated

"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
- Terry Pratchett

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