82 Vanagon Westy Missing then Backfire Intermittently

Find/Fix/Report Back

Moderators: Sluggo, Amskeptic

User avatar
Manaman
I'm New!
Location: Honolulu HI
Contact:
Status: Offline

Re: 82 Vanagon Westy Missing then Backfire Intermittently

Post by Manaman » Tue Jul 04, 2017 9:42 am

SlowLane wrote:
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.
Thanks Slowlane and Sgkent we will go through all those checks before messing with the AFM, we have all new vacuum tubes but will check again I'm still waiting on new AAR elbow, will recheck all grounds, I have an electronic ignition Crane Cams XR-700 with Fireball Coil PS20 and will check that too, as well as the fuel pressure and the fuel pump,

It doesn't do it when engine is cold is when it gets up to operating temp, cross my fingers we will find whats wrong I will report back
thanks again
1982 Vanagon Westfalia Federal Manual FI
1985 Vanagon L WBX
1972 Super Beetle

User avatar
sgkent
Addicted!
Location: Citrus Heights CA (near Sacramento)
Status: Offline

Re: 82 Vanagon Westy Missing then Backfire Intermittently

Post by sgkent » Tue Jul 04, 2017 6:56 pm

there is also the TS2 to check. Be aware that the fuel injection gets its base line pulse from the ignition. Anything that goes on there can affect how the ECU interprets things. I'd look at the TS2 first and for a leaky CSV next. Stay out of the AFM until everything else is known to be 100% running perfect.
TBone208 wrote: "You ppl are such windbags. Go use your crystal ball to get rich & predict something meaningful. Nobody knows what's going to happen. How are we supposed to take ppl who don't know the definition of a recession & "woman" seriously?"

Merlin The Wrench

User avatar
SlowLane
IAC Addict!
Location: Livermore, CA
Status: Offline

Re: 82 Vanagon Westy Missing then Backfire Intermittently

Post by SlowLane » Wed Jul 05, 2017 1:04 pm

Manaman wrote:
Tue Jul 04, 2017 9:42 am
we will go through all those checks before messing with the AFM, we have all new vacuum tubes but will check again I'm still waiting on new AAR elbow, will recheck all grounds, I have an electronic ignition Crane Cams XR-700 with Fireball Coil PS20 and will check that too, as well as the fuel pressure and the fuel pump,
Great that you're tackling it methodically. FWIW I ran a XR-700 ignition for decades (starting with the original Allison XR-700 before Crane bought them up), and was very happy with it. Much preferred it over the more common Pertronix. But spark aside, you would be amazed at how much better your engine runs if you do a partial disassembly of your distributor and lube up all the moving bits so they move freeely. 35+ years can really cause the original grease to cake up into wax.

A warning about the AAR elbow: back when I was figuring this out about 15 years ago, I discovered that the aftermarket elbows available then were of dreadfully poor quality. I had the first one fail within a month of installing it, and of course while troubleshooting that I mentally ruled out the AAR elbow, because, well, I had just replaced it a month before.

Unless things have changed for the better (which I doubt), I would advise you to only use a genuine OEM VW elbow (for which you will pay dearly). The difference between the OEM part and the aftermarket part is quite evident when you have them both in hand. The genuine part is supple and rubbery, whereas the aftermarket part feels hard and plasticky.

Now Airhead Parts has been making improved replacement rubber bits out of Viton for our vehicles for a few years now. I don't know if their current AAR elbow offering is made of Viton. Their website doesn't specify, so I would make the assumption that it isn't.

I acquired quite a collection of failed AAR elbows until I got fed up with the whole thing and put in a 1/2" ID silicone elbow instead. At $35, a bit on the pricey side, but I've never had to worry about the stupid AAR elbow since.
'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

User avatar
Manaman
I'm New!
Location: Honolulu HI
Contact:
Status: Offline

Re: 82 Vanagon Westy Missing then Backfire Intermittently

Post by Manaman » Fri Jul 14, 2017 10:46 am

OK update...we switched out the XR700 electric ignition and put the old one back in points and kept the PS20 coil, drove the hell out of for the last couple days with no problems, then of course I go drive to my VW guys place just to talk told him it's been running well, it's super hot here in FL and it sat at his place for about 45min so I drove home and on the way it sputtered not like before, then it did it again and double backfired . So I got it home and I switched out the PS20 coil and put my old original Bosch coil on and drove it and it did it as well. The problem is related to heat and when the motor is at full operating temp. I drove all day yesterday and it didn't happen, we also checked the tempII sensor but on the multimeter, I have a new one so maybe I will change it out. So it continues....I will update more later
1982 Vanagon Westfalia Federal Manual FI
1985 Vanagon L WBX
1972 Super Beetle

User avatar
sgkent
Addicted!
Location: Citrus Heights CA (near Sacramento)
Status: Offline

Re: 82 Vanagon Westy Missing then Backfire Intermittently

Post by sgkent » Fri Jul 14, 2017 1:17 pm

is the backfire out the exhaust or into the intake plenum?
TBone208 wrote: "You ppl are such windbags. Go use your crystal ball to get rich & predict something meaningful. Nobody knows what's going to happen. How are we supposed to take ppl who don't know the definition of a recession & "woman" seriously?"

Merlin The Wrench

User avatar
Manaman
I'm New!
Location: Honolulu HI
Contact:
Status: Offline

Re: 82 Vanagon Westy Missing then Backfire Intermittently

Post by Manaman » Fri Jul 14, 2017 6:58 pm

sgkent wrote:
Fri Jul 14, 2017 1:17 pm
is the backfire out the exhaust or into the intake plenum?
Exhaust...
1982 Vanagon Westfalia Federal Manual FI
1985 Vanagon L WBX
1972 Super Beetle

User avatar
Manaman
I'm New!
Location: Honolulu HI
Contact:
Status: Offline

Re: 82 Vanagon Westy Missing then Backfire Intermittently

Post by Manaman » Sat Jul 15, 2017 10:53 am

Well it has nothing to do with heat because I let it sit all night and then drove it today from a cold start and it started doing it immediately, it's hunting up and down and had another backfire or it just dies out, I'm not a mechanic so I need Help, please....
1982 Vanagon Westfalia Federal Manual FI
1985 Vanagon L WBX
1972 Super Beetle

User avatar
Amskeptic
IAC "Help Desk"
IAC "Help Desk"
Status: Offline

Re: 82 Vanagon Westy Missing then Backfire Intermittently

Post by Amskeptic » Sat Jul 22, 2017 9:16 am

Manaman wrote:
Sat Jul 15, 2017 10:53 am
Well it has nothing to do with heat because I let it sit all night and then drove it today from a cold start and it started doing it immediately, it's hunting up and down and had another backfire or it just dies out, I'm not a mechanic so I need Help, please....
Hunting too? Backfires? If I am in Naples region and this car is misbehaving, we shall conduct a symposeum devoted solely to your troubleshooting skill set.

Meanwhile, you must knock down all basics, carefully.
Valve adjustment
Vacuum leak check (this includes removing the brake booster/decel valve hose and blocking the intake nipple and the decel valve hose)
Timing (dwell)
Sensor resistance check and wiring integrity check (with ohmmeter on the TS2, for example, you would wiggle the wire where it joins the sensor to see if you get any short/open jerks on the ohmmeter

So, no concordance of symptoms to a hot ignition coil or anything?
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

Post Reply