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Valve adjustment and timing mystery
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World'sWorstVegan
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PostPosted: Thu Aug 31, 2017 8:11 pm    Post subject: Valve adjustment and timing mystery Reply with quote

I rebuild my 1.9 engine back in May and have great oil pressure, decent gas milage (17,18, or 19 mpg) and finally no more exhaust leaks. Just 2 mysterious problems that I can't seem to figure out.

Timing

When I adjust my timing according to consensus on this site (35 degrees BTDC), it has very little power and acceleration and when I decelerate or shift, I can hear pops from what I think must be unburnt fuel running through the exhaust (pop, pop, pop!). As I increase the advance timing to 50 degrees it has much more power and ability to accelerate and the pops are less (only pop, pop! instead of 5 or 6). When I increase the timing this much the van runs great but then at idle the engine surges which tells me, this probably isn't the right timing even though it drives much better.

I took it to a mechanic shop and they called me back saying they didn't hear the problem and for me to come there and show them what I was hearing. When I showed up it made the popping noise exactly the way it had been before and they said, "I don't know..." Luckily they also said they wouldn't charge me since they didn't know what to do. There are no good VW mechanics in my area...

The Valves

When I set the valves to 3/4 turn, the engine idles like total garbage. When I set the valves to zero lash it runs fine. I've read a lot of people saying that it may not be a good idea so I turn in the screw 1/8 of a turn and that seems to be all I can get away with. I've tried every combination of valve adjustment and zero lash seems to be ideal. Its almost as if I'm running solid lifters (I'm not, I put in new lifters from Go Westy during the rebuild) and when I turn past zero lash the valves are closing all the way, I dunno.

These 2 things have to be related. They are the 2 things that when I set them to spec they make the van run like crap, they have to be related. I understand the basic idea of how the rocker arm components open the valves and I have a basic understanding about how the advance timing works.

When I did the engine rebuild I had a machine shop measure the cam and they said it was within the spec of wear so I don't think its the cam.

Are the valves staying open too long? Unburned fuel getting into exhaust because exhaust is staying open too long?

Are valves not opening enough? Making fuel to air ratio incorrect and unburned fuel goes into exhaust?

Any help would be greatly appreciated!!!
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Wildthings
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PostPosted: Thu Aug 31, 2017 11:24 pm    Post subject: Re: Valve adjustment and timing mystery Reply with quote

It sounds like you may be missing the point of zero lash. It can be very subtle and easy to miss. Use only your bare fingers to turn the screws in and feel for the slightest change in the amount of pressure needed to turn the screw. If you miss the point of contact and turn you screws in too much, the lifters will hold the valves open.

If your lifters are all the way pumped up it may be necessary to adjust the valves on one head at a time. Find the point of zero lash for each valve and then turn the screws in another 1 1/2 to 2 turns. Now run the engine for several minutes until the valves self adjust. Now set the valves on the other head.

Your timing should be 42 BTDC at 3500+ rpms with the hoses on

or 28 BTDC at 3500+ rpms with the hoses off and plugged.

Sounds like your TPS is not working
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PostPosted: Fri Sep 01, 2017 4:11 am    Post subject: Re: Valve adjustment and timing mystery Reply with quote

It begs to be asked, when you reassembled the Camshaft and crank, were you very aware of the timing marks on the gears and are you 100% positive that they are properly installed?
One tooth off will create a lifetime of running woes.

Dave
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World'sWorstVegan
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PostPosted: Fri Sep 01, 2017 6:08 am    Post subject: Re: Valve adjustment and timing mystery Reply with quote

Fortunately I know how to find zero lash. I have done it many many times and if I do the 1 and 1/2 turns my van will not run well. The lifters are fully pumped so I guess I could try 1 at a time but I don't think that will solve this problem.

I have adjusted the TPS and checked it with a ohmmeter, it is working great! I thought this was the problem at first and spent A LOT of time playing with it until I realized it was not the problem.

I am 100% positive I have the timing gears lined up too. I was having this issue before completing the rebuild.

Any other suggestions?
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Wildthings
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PostPosted: Fri Sep 01, 2017 6:30 am    Post subject: Re: Valve adjustment and timing mystery Reply with quote

Make a piston stop and verify that your TDC mark is accurate.
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World'sWorstVegan
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PostPosted: Fri Sep 01, 2017 8:52 am    Post subject: Re: Valve adjustment and timing mystery Reply with quote

Good call, how do you recommend doing that?
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PostPosted: Fri Sep 01, 2017 2:14 pm    Post subject: Re: Valve adjustment and timing mystery Reply with quote

World'sWorstVegan wrote:
Good call, how do you recommend doing that?


Pencil in the spark plug hole as you slowly rotate the engine by hand.

Dave
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World'sWorstVegan
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PostPosted: Fri Sep 01, 2017 2:41 pm    Post subject: Re: Valve adjustment and timing mystery Reply with quote

Right, I've done that in the past to find TDC just didn't realize that's what it was called. So you don't think it's running rich from the pops in the exhaust? Don't mess with AFM?
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Wildthings
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PostPosted: Fri Sep 01, 2017 3:15 pm    Post subject: Re: Valve adjustment and timing mystery Reply with quote

Very lean would also require a lot of extra timing and could cause the exhaust to pop. What do you plugs look like after a 10 mile highway run?
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World'sWorstVegan
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PostPosted: Fri Sep 01, 2017 4:08 pm    Post subject: Re: Valve adjustment and timing mystery Reply with quote

Should I clean them first, take a ride the take a look?
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PostPosted: Fri Sep 01, 2017 4:10 pm    Post subject: Re: Valve adjustment and timing mystery Reply with quote

World'sWorstVegan wrote:
Should I clean them first, take a ride the take a look?


You could pull one first to see what they look like now, but unless they were covered with thick deposits I wouldn't bother with cleaning them.
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PostPosted: Fri Sep 01, 2017 5:14 pm    Post subject: Re: Valve adjustment and timing mystery Reply with quote

How are you checking your timing?

There is a lot of confusion on how to.

Dave
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PostPosted: Fri Sep 01, 2017 7:36 pm    Post subject: Re: Valve adjustment and timing mystery Reply with quote

If your engine at any time in the recent past was run on old gasoline with varnish, this could have caused varnish deposits on the intake valve stems. That varnish is incredibly sticky and can keep the valves from closing fully at lower engine speeds like idle. At higher engine speeds, valve train inertia overpowers the stickiness.

The Digijet system maintains idle speed by varying the ignition timing at idle, advancing ignition or retarding it to keep the idle at 940 rpm. So, yes, the ignition timing and idle speed are related. Be sure that the pulley mark you are using for timing basic setting is the correct mark.

Regarding popping, that is usually a sign that the TPS is not properly adjusted or is not functioning electrically. The Digijet system cuts fuel to the injectors when the throttle is closed and the TPS is correctly adjusted and functioning electrically. The popping is usually caused by the fuel cut not occurring. This feature is supposed to cut fuel when the throttle is closed and RPM's are over 1,500.
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PostPosted: Fri Sep 01, 2017 10:29 pm    Post subject: Re: Valve adjustment and timing mystery Reply with quote

EDITED BY MODERATOR: ........ you may have a vacuum leak, which would throw things off.
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PostPosted: Sat Sep 02, 2017 5:03 am    Post subject: Re: Valve adjustment and timing mystery Reply with quote

atomatom wrote:
EDITED BY MODERATOR: ........ you may have a vacuum leak, which would throw things off.


I agree ^^ check all of your intake connections, hoses and components carefully for small cracks, loose connections.
Did you use new gaskets on your rebuild? Particularity the intake to throttle housing rubber seal?

Dave
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PostPosted: Sat Sep 02, 2017 7:39 am    Post subject: Re: Valve adjustment and timing mystery Reply with quote

THere are two vacuum hose setups on early 1.9l with dual port vacuum distributors. Early, and late. The repair manual clearly shows how to route the lines for each. When troubleshooting timing, always start with basics, and work your way to the more complex possiblity. Cam/crank correlation-check, distributor clocked and installed properly-check, valves adjusted-check, vacuum supply lines plumbed and working-check. Then, I would set basic timing, get engine idling, warm, and set it to the stock marks. 5 deg ATDC if its early style with two switches, etc. Make sure to differentiate the two marks on the crank. The early pulley-first mark is V for 5 atdc, the round second mark is TDC. Use your timing light, turn distributor so its flashing on the first mark. Then, to verify, set your timing light to the total advance spec, rev engine to 3krpm and it should be flashing correctly at TDC mark. It will pop like that if its too retarded and you rap the throttle. Disconnect DIS unit (plug in connectors together) during adjustment of timing. Its job is to change the timing to adjust the idle, so it will mess you up.
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PostPosted: Sat Sep 02, 2017 3:25 pm    Post subject: Re: Valve adjustment and timing mystery Reply with quote

I have the TPS switch adjusted properly. I spent a lot of time tackling this when I first noticed this problem.

I'm positive there isn't an intake leak or vacuum leak because I replaced the boots and all hoses and gaskets during the rebuild. Also, I sprayed some brake parts cleaner around typical leak locations and heard nothing.

The heads are brand new so I don't think it's sticky valve stems.

Also, I had some exhaust issues after the rebuild (collector pipe broke right next to O2 sensor) and I hunted down all exhaust leaks so I'm positive that's not a factor.

I put in a GoWesty rebuilt AFM and when I installed it the screw to adjust rich/lean mix was very much on the rich side. I've been hesitant to take off the cover and mess with it because GW says I'll lose my warranty...so I've just tinkered with the screw.

I'm going to take a look at the plugs today and see if it's been running rich during the 6k miles since the rebuild.

Thanks a lot for all of your insight and keep it coming, I really need it!
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PostPosted: Sun Sep 03, 2017 5:18 am    Post subject: Re: Valve adjustment and timing mystery Reply with quote

Still curious, when you check and adjust ignition timing, what is your procedure?

Dave
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PostPosted: Fri Nov 17, 2017 7:54 pm    Post subject: Re: Valve adjustment and timing mystery Reply with quote

The mystery is solved!!! I got a new muffler and it runs like a dream! I took the van to get inspected and it didn't pass because it needed a new muffler. It had a made in US muffler with a connecting pipe that was nowhere near stock so I got one from van cafe that is like the original muffler with the tail pipe and gaskets, put them in and no more popping between shifting. The mechanic said that would probably solve the problem because there wasn't enough back pressure. As far as the timing and valve adjustment go, the timing is still above spec its running at zero lash. However, the inspector works on vanagons and said there is nothing wrong with running it at zero lash. Additionally I talked to a guy at Go Westy who says his van also runs best with more advanced timing. Its running good, I'm happy!

The muffler from van cafe was is really bad shape, which they said in the description, was because of the ways the supplier ships them from Europe, but the holes in the muffler didn't line up with the holes in the gasket at all. If anyone is looking to get a new muffler, get a stainless one instead! Its not that much more!
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