low idle, 2.0 FI

vw76westy · Posted: Mon Mar 05, 2012 1:13 am Post subject: low idle, 2.0 FI

long story... short
i have a 2.0 fi type-4 engine that has just been rebuilt
i have been struggling with low idle from
the break-in to a couple 100 miles of driving

dwel is set
timing is correct

after turning the idle adjusting screw about 5-6turns out
the idle is barly high enough to keep the bus on
with no change if i continue to turn the screw out

if i barly tap the throttle, the rpms go from 500 to 550
then drop back down to 500(held consistantly)
a little more gas (held consistantly)the rpm's jump to 1300-1400

i made it a point to try to give it just enough gas (gas pedal) to
keep rpm's at 1000 but finding that sweet spot is near impossible
with rpm's staying abnormally low then suddenlly moving to high

1 valve adjustment has been made already (hydrollic lifters)
fuel pressure is 35 psi with no change at low rpm or high rpm
i have looked & looked for vacumm leaks but cant find any
fuel pump seems to be working properly
i have a clean,rust free gas tank
fuel filter & fuel lines are new

other than the low idle the engine & fi "seem" to be running fine
i have good power at high rpm
a little sluggish on take off (low rpm)but still in the ballpark of normal
im stumped............
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The Type 4 engine is considered by many to be VW's finest air-cooled motor,

Westfabulous · Posted: Mon Mar 05, 2012 8:29 am Post subject:

It sounds a lot like a vacuum leak to me. Checked your intake gaskets, CSV gasket, and injector O rings as well? The intake gaskets are easy to get hung up on the engine tin....I made this mistake myself.
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SGKent · Posted: Mon Mar 05, 2012 9:05 am Post subject:

did you make any changes to the FI system or are the parts the same as what were on the other engine?
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

pb24ss · Posted: Mon Mar 05, 2012 9:36 am Post subject:

double relay / AAR bad?

vw76westy · Posted: Mon Mar 05, 2012 11:31 am Post subject:

all the gaskets & o-rings are new
except for the plenum to intake boots & gassket for csv (did not remove)
i reused all the fi parts that were on before
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quote from bay window bus buyers guide........
The Type 4 engine is considered by many to be VW's finest air-cooled motor,

SGKent · Posted: Mon Mar 05, 2012 11:38 am Post subject:

just to be sure, the screw you are adjusting is the big one on the throttle body?
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

vw76westy · Posted: Mon Mar 05, 2012 1:33 pm Post subject:

SGKent · Posted: Mon Mar 05, 2012 1:48 pm Post subject:

make sure the plug on the back of the AFM is plugged in.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

Amskeptic · Posted: Mon Mar 05, 2012 5:18 pm Post subject:

SGKent · Posted: Mon Mar 05, 2012 10:15 pm Post subject:

two engines can have slightly different air to fuel mixtures if the cam, valve sizes etc are slightly different.

Raul - I want you to screw the speed screw in and tell me if screwing it in will drop the idle speed. Once it starts to drop, turn the bus off and count the turns in until it stops. Let me know how many.

Next, back it out to where it was just before the idle speed dropped. Then go to the mixture screw on the AFM and turn it exactly 1 turn in. That will richen it. If the RPM speeds up go to two turns. If there is no change at 1 turn, back it out 1 turn to where it was. Now go one turn out (lean) and see if the RPM speeds up or slows down. If it speeds up go to 2 turns. When you are done put it back to where it was when you started and post here.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

Westfabulous · Posted: Mon Mar 05, 2012 10:50 pm Post subject:

Since this is a fresh rebuild, I am trying to consider any possibility. Have you checked the harness connectors to see if they are right? Could the AAR connector be on the CSV, or something like that, causing the CSV to pee endlessly?

How's the exhaust? Stinky rich?
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"I will gladly pay you Tuesday for a hamburger today."

SGKent · Posted: Mon Mar 05, 2012 11:01 pm Post subject:

vw76westy · Posted: Tue Mar 06, 2012 12:44 am Post subject:

ill do these test tomorrow
didnt have time today

while i was trouble shooting i did count the turns

if i turn the idle screw all the way in
in takes 5 1/2 turns out for it idle hi enough to stay on
after 6 turns i dont notice any change in the idle

if it was a vacumm leak
would that mean that the leak is so small it only affects
vac at low rpm's
making it twice as hard to find ??
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SGKent · Posted: Tue Mar 06, 2012 9:58 am Post subject:

that screw on the throttle body is a bypass of the throttle plate. It does the same thing as stepping on the gas a little.

If the air to fuel ratio is too rich or too lean that could cause it to struggle to run right. So could low compression or the auto trans putting too much a load on the engine or the timing being off. The question is which of those is the culprit and what is causing that?

You might also so a cylinder balance test where the plug wire on each cylinder is pulled from the cap one at a time to make sure all are running with the same strength.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

vw76westy · Posted: Tue Mar 06, 2012 9:17 pm Post subject:

SGKent · Posted: Tue Mar 06, 2012 10:02 pm Post subject:

you made some headway. Turning the throttle body screw in causes it to die so we know that the throttle body is working and that it needs the air from the throttle plate to run.

We also know that opening the screw on the AFM allows more air to bypass the vane which makes the mixture leaner as the vane opens less. Since closing it does little but opening it kills it, we know that the engine is running lean.

You have a vacuum leak. Get the vacuum tester - aka Mighty Vac out and test each of the diaphragms - can on distributor, FPR, Decel, and canister purge on the air filter. If your engine has a vacuum line to the trans check that too. Some Plenums have two nipples instead of one so make sure you don't have a plenum with two hose nipples and one is open. If those pass, block the brake booster and see if that changes anything. If the EGR is hooked up, make sure the valve is closing at idle.

If that fails, remove the PCV valve and vent it to the air, cover the hose inlet with something that won't get sucked into the S-boot. If you have an air leak into the case and the PCV valve is bad it can let unmetered air into the S-Boot.

Simply put, something is causing the engine to be lean.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

vw76westy · Posted: Tue Mar 06, 2012 10:41 pm Post subject:

SGKent · Posted: Tue Mar 06, 2012 10:44 pm Post subject:

http://www.harborfreight.com/brake-bleeder-and-vacuum-pump-kit-92474.html

http://www.thesamba.com/vw/forum/viewtopic.php?t=494579&highlight=pcv+valve

Lithuania is where Bobby found my nos one.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

vw76westy · Posted: Sat Mar 10, 2012 8:52 pm Post subject:

alright here is where im at......

I had the chance to get a snorkel hooked up
and so I was able to get the afm dialed in.....
according to the machine it was running a little rich

also got the timing checked to be dead on 7.5 - 28

the timing was a little advanced before
but now that the timing & air mix is good
I just cant keep the bus “on” at idle

one by one
I disconnected the y-connector & capped off plenum -no change
I tried a different AAR with the old vacuum line & a new elbow no change
replaced the S-boot- no change
replaced the throttle body, new gasket -no change
disconnected the vacuum line(goes to fuel reg) from plenum & capped it -no change
I capped off the hose from the breather (pcv valve) -no change
I tried capping the hose to decel valve (from s-boot)–no change
I removed the clamps from the plenum to intake boots (very large 2inch hose)
& spun the hoses hoping for any change (I had to practically take them off to here them leak)
Then wrapped them with a heavy duty vinyl tape (maybe a crack or hole in the middle of hose)
Before re-clamping them –no change

What now……….
Im starting to fall apart here (no really depression is starting to set in)
Im ready to file down the flap inside the throttle body & pretend the problem went away

Could something be going on with the motor

It seems like the engine is starving for more air
If I had a vacuum leak & unmetered air was getting in
wouldn’t I have a “lean” mixture

for the record the egr is capped off at the plenum

if i place an object over the gas pedal
to bring the idle hi enough to keep it on,(this technic keeps throttle stable)
then disconnect the spark plugs, i do notice a equal change on all 4 plugs
although the "change" is very small
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order your BAY WINDOW T-SHIRT here http://www.thesamba.com/vw/classifieds/detail.php?id=1526918

quote from bay window bus buyers guide........
The Type 4 engine is considered by many to be VW's finest air-cooled motor,

vw76westy · Posted: Sat Mar 10, 2012 8:59 pm Post subject:

one more thing in the beginning i could not
get it to idle at 900-1000

now i cant get it to stay on at idle
but i can get to idle at 950-1000 if i give it a some gas

the problem has not changed though
just a drop more gas & the idle will jump
_________________
order your BAY WINDOW T-SHIRT here http://www.thesamba.com/vw/classifieds/detail.php?id=1526918

quote from bay window bus buyers guide........
The Type 4 engine is considered by many to be VW's finest air-cooled motor,


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