Fast idle on '77 bus
-
Elrick
Fast idle on \'77 bus
Put your thinking caps on....I have a yellow '77 Westy. Bus continues to refuse to idle correctly once warmed up. After the beast is warmed up the idle stays at 2000 rpm even after restarting. No vacuum leaks, good timing and tune up parameters are good. I followed the Bentley's troubleshooting steps but can't pin the problem down. I suspect the decelleration valve and it seems to act as it should but it's difficult to tell. Does anyone know where to purchase a replacement deceleration valve or have any thoughts on this maddening problem. Volt-ohm checks on the temp sensors seemed OK but Bentley seems to be a little general when describing correct resistance. Oh, obviously the idle adjusting screw is turned all the way in. Thanks for your ideas.
-
Elrick
Fast idle on \'77 bus
I did check the auxiliary air valve per Bentley and it was right on. Aslo, timing, dwell and valve gap are correct. The only thing I have changed recently is I installed a bug pack muffler to replace the old rusty stock assembly. I think tomorrow I'll bite the bullet and take it in to the only guy in town who works on aircooled FI. I hope I don't know more than him.
-
ray greenwood
- Posts: 1941
- Joined: Thu Jul 19, 2001 12:01 am
Fast idle on \'77 bus
One more check....check the gasket on the oil breather tower and also check that the throttle cable is not sticking, crimped or that the cable where it slips into the ferrule in the back of the sheet metal bulkhead has not slipped out and is riding on the edge shortening the cable. Also check that the positive return spring wrapped aroung the TB shaft is not broken or malfunctioning. Lastly....do you have an auto transmission? If so, check the vacume line to the modulator valve. Also check the one way valve to the power brake booster by crimping the hose. Ray
-
ray greenwood
- Posts: 1941
- Joined: Thu Jul 19, 2001 12:01 am
Fast idle on \'77 bus
Two things to check. It actually sounds like your auxiliary air regulator is messed up, or disconnected. Its that little witches hat looking thing next to the center manifold with two wires coming out. After 5-10 minutes of running, it should close and pass no air to the manifold. The deceleration valve should be checked two ways. Pull off the small vacume line running to it. If it is set too low and is staying open...that will close it. Then crimp the incoming air line to th valve with pliers to see if cutting off the air supply stops it. It is rare for a decel valve to fail. If you have an electronic one....pull off one wire. That should stop it if it is stuck open. Check for power at the terminals. Is power...then check by crimping the hose as before. You chould not actually have a PCV valve on this year...but you might have one monted in the breather tower if that part has been swapped. Check to see if its failed. Check the gasket behind the TB...check your timing...just in case. My money is on the aux. air regulator. Check for power at the terminal before replacing. Ray
-
germansupplyscott
- Posts: 887
- Joined: Fri Jul 20, 2001 12:01 am
Fast idle on \'77 bus
elrick,
i know you said you checked the aux air valve, but just to make sure, why not try one last test - the valve can "check out" in the bentley (esp the electrical tests) and still not close all the way, which is really what your problem sounds like. it doesn't take much of a leak in the valve to bump the idle way up. i just fixed this exact condition on my '79 westy. what i did is clamp off the hose from in aux air valve to the intake elbow. i used a fuel hose clamper not to damage the hose. if your idle drops, you know what is wrong. you have to do the test with the van running in its 'hot high idle" condition. when i clamped the hose completely, the idle settled down nicely. i was even able to use this as a temporary "manual aux air valve" until i got a good new one.
scott lyons
[This message has been edited by punkinfair (edited 02-01-2002).]
i know you said you checked the aux air valve, but just to make sure, why not try one last test - the valve can "check out" in the bentley (esp the electrical tests) and still not close all the way, which is really what your problem sounds like. it doesn't take much of a leak in the valve to bump the idle way up. i just fixed this exact condition on my '79 westy. what i did is clamp off the hose from in aux air valve to the intake elbow. i used a fuel hose clamper not to damage the hose. if your idle drops, you know what is wrong. you have to do the test with the van running in its 'hot high idle" condition. when i clamped the hose completely, the idle settled down nicely. i was even able to use this as a temporary "manual aux air valve" until i got a good new one.
scott lyons
[This message has been edited by punkinfair (edited 02-01-2002).]
-
rich2481
- Posts: 1539
- Joined: Tue Dec 18, 2001 12:01 am
Fast idle on \'77 bus
Ray and Scott, are you saying the aux air regulator should shut completely off ( ie. not allow air through) when the van is warmed up?? and are they adjustable do you know.
Richard
Richard
-
germansupplyscott
- Posts: 887
- Joined: Fri Jul 20, 2001 12:01 am
Fast idle on \'77 bus
rich,
yes, the aux air regulator should allow almost no air to pass through it once the engine is warmed up. the plug attached to it just supplies battery voltage to energize a heat operated spring, closing it over time as the engine warms up. the air passing through it is unmetered air, which means it is not accounted for by the air flow meter. the system "needs" to know how much air is passing through in order set the mixture, so little or no air should enter the combustion chamber that does not pass through the air flow meter.
second, they are adjusted at the factory. if yours it not working you could try re-adjusting it by loosening the small nut on it and setting the base position of the spring loaded aperture. but this will be a hit-or-miss proposition at best and i would only do it if i had a spare unit to play with.
i recently replaced my old one (probably the original from '79) and it made a big improvement on warm-up and idle and especially hot starting.
scott lyons
yes, the aux air regulator should allow almost no air to pass through it once the engine is warmed up. the plug attached to it just supplies battery voltage to energize a heat operated spring, closing it over time as the engine warms up. the air passing through it is unmetered air, which means it is not accounted for by the air flow meter. the system "needs" to know how much air is passing through in order set the mixture, so little or no air should enter the combustion chamber that does not pass through the air flow meter.
second, they are adjusted at the factory. if yours it not working you could try re-adjusting it by loosening the small nut on it and setting the base position of the spring loaded aperture. but this will be a hit-or-miss proposition at best and i would only do it if i had a spare unit to play with.
i recently replaced my old one (probably the original from '79) and it made a big improvement on warm-up and idle and especially hot starting.
scott lyons