TheSamba.com :: View topic

Sun Mar 21, 2010 9:42 am

Thought I'd run this past the learned group here before diving into the investigation.

I've read that this is either valve adjustment related or a small air leak on the intake manifold. Minor tightening of the manifold should fix it.

But, I did a valve adjustment about 300 miles ago. So I'm thinking I may have been a little hasty in my work. It did not backfire before this.

Any other suggestions?

Sun Mar 21, 2010 9:51 am

type 1 or type 4 with carbs - air leak into exhaust and typically you are running too rich

type 4 if FI most likely your deceleration valve is either bad or not hooked up.

Sun Mar 21, 2010 9:54 am

I think we need a little more information. what kind of vw are we talking about. Engine, carb ,fuel inj..

Sun Mar 21, 2010 10:03 am

Blind stab-Air leaking into exhaust somewhere.

Sun Mar 21, 2010 10:05 am

Sorry, it's a 1600 DP engine.

Sun Mar 21, 2010 10:18 am

I would definitely check the valves... You said it yourself - did not do it before, does it now..

I am not saying thats the problem, but I would hate for you to burn a valve...

Sun Mar 21, 2010 10:27 am

I'm pretty sure I set them at .006 clearance. But I left a couple alone eventhough they were a tad tight as .004 is considered ok as well. Mistake??
I'll recheck. Took the plugs out yesterday and they looked perfect.

Sun Mar 21, 2010 10:41 am

Just doing what Spock would do, looking for logic...

Anyway more often then not that is the sign of an exhaust leak...

Sun Mar 21, 2010 10:44 am

i would double and triple check my exhaust donut gaskets...

ive repaired the same problem youre describing several times by fixing a leaky exhaust

Sun Mar 21, 2010 10:50 am

JT's Westy wrote: .004 is considered ok as well. Mistake??.

Mistake, .004 is too tight for a 1600, better to be on the big side of .006, but I'm going with the exhaust leak as the main cause.

Sun Mar 21, 2010 11:14 am

Thanks. As usual, the crew here has it wired.

Sun Mar 21, 2010 12:06 pm

it's been my experience that I get exhaust popping or slight backfire going downhill and/or shifting slowly when the timing is too retarded
also happens at altitude if I'm lazy I don't do a bit of advance, but it clears up at sea level
Aloha
tp

Sun Mar 21, 2010 12:28 pm

Tell us how you have it timed and what distributor you are running.

From the factory this would have come with a DVDA distributor timed to the notch on the pulley which was 5º ATDC and time at correct idle speed.

Sun Mar 21, 2010 3:29 pm

009 at 7 degrees tdc. pertronix pointless set-up

Sun Mar 21, 2010 3:55 pm

JT's Westy wrote: 009 at 7 degrees tdc. pertronix pointless set-up

Is that BTDC or ATDC?

Sun Mar 21, 2010 3:59 pm

You have to time it with a light 28-30 with the advance all in.

Sun Mar 21, 2010 4:10 pm

That is sort of common on a 009. They are not a great fit for what you have (a 34PICT 3 carb) + the only way to get the dead spot out of them is to run the carb pretty rich.

Time it this way to 28º BTDC please....as was mentioned above.

www.type2.com/library/electrip/bosch009.htm

Sun Mar 21, 2010 6:24 pm

I set the total advance at about 30 degrees with my timing light. It idles at about 7 degrees. Maybe I should lower it to 5 degrees?

The plugs look perfect tan color, about about 700 miles, so far. Although I checked this afternoon and #3 was missing it's compression ring. Probably my bad.

I'll also check the exhaust manifold to see if it has loosened for some reason.

Sun Mar 21, 2010 6:43 pm

Actually you want to reduce it to 28º BTDC when it is all in. We don't care where it ends up at idle.

Sun Mar 21, 2010 8:41 pm

Quote: but it clears up at sea level

A/F mixture changes between sea level and altitude. The mixture leans out the closer to sea level you go.