1975 bus 1800 fi

[Tim in alaska]

some more help please folks... Just put new tune up on vehicle with all new parts and timed per the 28 degree method. run s fine when on road but I cannot get idle above about 600 even when warm and after starting must wait for it to warm up to idle at all... I have adjusted out the air screw per the vw repair guide but does not make any difference. could you folks please advise what I should look at. Thanks tim

[busdaddy]

Which screw are you adjusting and where is it located?
_________________
Rust NEVER sleeps and stock never goes out of style.

Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!

Слава Україні!

[templeofspeed]

Check for vacuum leaks, particularly the 3mm vacuum hose to the fuel pressure regulator. This will cause over-richness, allowing to barely run, but the actually fairly minor vacuum leak prevents the by-pass idle screw from functioning properly. The over rich condition is usually misdiagnosed as a bad TSII...or AFM...or injector resistor block...or...

You get the idea.

Failing that, revisit your tune-up procedure.

Good luck!
_________________
Is your suspension broken?

[Tim in alaska]

thanks for these replies... regarding the screw it is I believe called the bypass screw large one that manual says to turn out to increase rpm... in to reduce.

sure appreciate your help.

[Tim in alaska]

by the way it has an after market electric fuel pump. Tim

[busdaddy]

[Tim in alaska]

I am not home at this time but it is on the throttle body and thought it was called air bypass.... timing was to 28 degrees with both hoses off one facing distributor plug. had my good wife do the pedal work and set it till it got to but did not bypass the 28 degrees. the manual which i have that is suppose to be the official one from vw showed photo and said it was the only way to adjust idle on the fi...out to increase in to decrease but did nothing so and going to look at vacuum hoses again unless you have other suggestions. I have only owned bus for two weeks and did this before and after tune up... has not used any oil in about 500 miles on trips. best to you tim

[sjbartnik]

The idle speed adjustment screw is located in the intake air distributor near the throttle plate. It's NOT the screw on top of the air flow meter (AFM).

So when the throttle plate is closed (idle), there is a drilling that allows air to bypass the throttle plate so the engine gets enough air to idle. The idle speed adjusting screw simply screws into and out of this bypass drilling to allow more or less air through, thus adjusting the idle speed.

If the idle speed adjusting screw seems to have no effect on idle speed, then a big suspect would be vacuum leaks, although those usually tend to make for a high idle rather than a low idle.

ALSO check out your auxiliary air regulator. This is one of the warm-up devices fitted to your engine. There's a relatively thick hose that comes off the S-boot and goes to the AAR, then continues from the AAR to the intake air distributor.

Inside the AAR is a rotary valve that opens or closes based on engine temperature. When the engine is cold, the valve opens to allow extra air in to give a higher idle speed so that the engine can overcome the extra resistance/friction of the cold oil. Kind of like a larger version of the idle speed bypass. As the engine warms up, the valve closes and the idle speed returns to normal. If your valve is stuck closed it could cause low or no idle when cold.
_________________
1965 Volkswagen 1500 Variant S
2000 Kawasaki W650

[Tcash]

Did it idle before you tuned it up?
Tcash

[Tim in alaska]

thank you all for your help... sure appreciate it. Nope same problem before tune up..... will get to the suggestions asap tim

[Tcash]