HI all
I have a pretty broad question. Firstly I have a 76 EFI kombi. Recently the idle has been very erratic - after the cold start finishes the bus has a problem keeping idle and stalls.

When driving at normal speeds the bus is great and feels strong

After driving for a while the revs at idle are very high on occasion and can then switch to a low idle and stall.

So naturally I have tried to source any potential air leaks and replace as many hoses as I can.
I have clamped and tied down any offending potential air leaks I can find and even used "Start You Ba#%tard" spray to see if the revs increase around any of the manifold etc and there is noting I can hear (does not increase idle after spraying)

So my question is - should I still be looking at air leaks or is there any other advise from anyone that has had the joy of working with EFI

thanks

Matt

Definitely sounds like an air leak

Main culprits are the brake booster vacuum hose on the manifold

OK - thanks guys

Firstly - to Bizarre - thanks mate _ will look into that area (um where is the break booster vacuum hose on the manifold )

Matberry - your response I guess is the one I don't want to believe.
So does this mean pulling the engine and doing a "top end" rebuild or is it more simple than that.

thanks

Does it die when you put your foot on brakes at idle??

I'm meaning it's possible to be state of engine and not efi or intake system problem, need to get things checked out if your not sure. Start with the simple cranking check or even a compression test.

Where are you to recommend somewhere to go ask?

Hey Bizarre - yep it does (but not always)
After I have traveled for a while - say 20 mins the revs can stay pretty high.
However up until then it does die - I have to put my left foot on the clutch to hold it in, then the brake with my right toes and the accelerator with the right right heal - getting pretty good at this.

Matberry - hey mate - I'm on the sunshine Coast - and I saw a great guy the other day around my way, but he was talking a full engine build, so I was just looking into solving this darn idle problem while I figure out how the hell I am going to get the $$$ together to do a bigger job

thanks Guys

Have you got yourself a manual???

Well I got Muirs VW book and I did just download a l-jetronic manual from ratwells site - so I can start to educate myself on the EFI issues - but I tell you it is a lot different from your standard carbie model

If you could eliminate the cracked hoses it would be a start

that fact it changes with brake pressure it is at least worth a look

Would be a lot easier if you had a manula so you could find the hoses

ok thanks Bizarre

got this link to go off for now - http://www.ratwell.com/technical/VacuumHoses.html 

getting off this computer so I can start the fault finding again - also should I be able to hear the leaks or is testing with Start ya b#@tard the way to go?

Hi

Every now and then VW failed in some areas, the vacuum booster hook to the motor up is one of them.

Have you given the throttle body a clean? Also make sure that the throttle stop is stopping the butterfly from jamming.

Steve

Thanks Steve

I haven't given the throttle body a clean - not sure where to start there

For the throttle stop - is this easily accessible?

I have this image here to go by

There's lots to look at for your symptoms.

Throttle body worn or sticking
idle speed controller not working or has intermittant electrical connection
air leaks.
Need to start with basics too, when were the valves last adjusted, plugs changed and timing set?

Hi

I'm not sure where the stop is located, but it will be there.

If you have leaky tappet covers or a torn dipstick boot these will cause an erratic idle.

Steve

Throttle stop is just the beginning of the throttle body problems. The problem is the return spring loads the butterfly laterally and wears the bore and the throttle plate badly, thus allowing more air therefore increasing the idle speed. You need to remove the throttle body for inspection/repair, but this won't necessarily cause idle to be erratic.

just pop under the back and kake sure the leads to the starter are tight i once had a similar problem with a carbyed van
dont ask me how but the heavy lead to the battery was loose tightened and no more shit

Thanks All

It never rains .. it pours. Looks like I need new heads, so I'm going to source those and then look at doing the job myself. I'll update this with what I find and hopefully be able to solve a few issues when the motor is out

cheers

Matt

Matt.............what happened??

How did you get to that stage??

Quote:

Originally posted by matberry Quote: Originally posted by Bizarre Definitely sounds like an air leak I had one with similar issues come in last week. It has head gaskets leaking and so as far as the efi is concerned, is like a manilold leak. To check, there should be no compression leaking noises during cranking, before it fires up (or take a coil lead off). You'll need to have someone else operate the key while you stick your head at the engine .

Yep like MattBerry said earlier - there is no doubt there is a leaking noise when cranking - I ahve been flat out with work so haven't been able to do the formal compression test. In saying that - the recommendation are all good from Matt regarding throttle body sticking. I know the heads are on their way as well due to the number 3 inlet valve closing after about 2000km

So I figure - lets just get the engine out and explore all of the option put here

I'm planning for about a week from now to start so will let you know.
Also for reference Mics Motors have confirmed the AMC complete heads are fine and it was a bad run back a few years ago that got them a bad rap - apparently they have amended and all cut with the 30 -45 -30 ratio

OK still going.

So did the whole new heads routine in the backyard job. Never do that again. Taking the engine out with a jack and blocks of wood was bad - getting it back in the same way was a nightmare - but good news is new heads on, check all rings and and pistons, cleaned and replaced all fuel lines and any houses that were suss. Basically updated anything I could at the time.

The bus now runs so well - loads of compression and just fly's along BUT ...
still have a fast idle.

I took note of what Matt mentioned in the early part of this post about the throttle body and thought it looked ok but then again I don't really know what the hell is ok or even what I am looking at half the time.

There didn't seem to be any sticking of the butterfly type mechanism in the throttle body but is possible as stated I don't know jack. I could push it freely and it retuns ok.

So now the idle screw is all the way in and it is still high.

I remember that my old 1800 carb buss had a similar issue with irratic idle and it turned out to be a distributor issue with the vacuum. Is this a possibility?

I guess all that is left are the AFM if all of these are exhusted

any advice as always greatly appreciated

cheers
Matt

Well done on the repairs.

As for fast idle, it'll be the buterfly/throttle plate in the throttle body.

Remove the tb, while looking inside at the brass throttle plate, crack ofen the throttle and then move the shaft up and down. You'll see the brass plate has a lot of the side worn away from the return spring loading the shaft upwards and wearing the plate on the side of the tb. This needs to be replaced! I usually modify one from a 40mm Weber to suit the efi tb.

Problem is due to too much air bypassing the plate when fully closed.