High Idle Mystery

[ossa7]

I'm new to vwcaddy. I have a humble 81 1.6 diesel caddy which has served me well. My question has to do with a high idle which can be brought down by shifting into a higher gear and using the clutch to pull down the rpm's or by a quick turning off of the key in the ignition and turning back on before the engine shuts off. I've read through the the posts and have checked the recommendations and haven't solved my problem. I've replaced the fuel filter, lubed the throttle assembly, run ATF through the injectors, checked IP bolts for tightness. No luck.

So here is where it gets interesting.

I assumed the problem was a sticking throttle sleeve and though the IP has no leaks and runs great except for the high idle problem, I thought I would get into the throttle sleeve and replace seals, etc. while in there. A friend with a Bosch shop had a used IP on his shelf and while borrowing his tools for pulley removal and IP timing I borrowed the pump as well. Just for fun, I put the complete pump on my caddy and had the EXACT same problem! High idle after warmed up, only to be brought down by methods already mentioned.

If I unscrew (counterclockwise) the air/fuel mixture screw on the IP the problem does go away but I am left with a powerless motor. I did not try screwing the screw in and lowering the low idle screw level because of the crimped on stop on the mixture screw.

Of course finding a random pump with the exact same problem leads me to believe that it's not the pump at all.

What else would cause a car that used to run great to have this high idle sydrome? Note: this is not a blowby problem.

Any help would be greatly appreciated!

[Fatmobile]

Bad injector spray pattern can cause left over unburnt fuel after the burn.
Enough left over that it burns on the next few revolutions.

Any white smoke?

[ossa7]

Fatmobile,
Thanks for the reply. No more smoke than before the high idle problem started. It puts out more smoke than our newer tdi beetle but that's to be expected. I mentioned that I did run some ATF through when replacing the fuel filter in hopes it would give the injectors a cleaning. The engine runs fine a freeway speeds and throughout the rpm range. Just the annoying high idle that acts like a "cruise control" when you don't want it!

[TonyB]

Did this problem appear suddenly, or gradually? Does the problem occur when cold or only when warmed up? When you reduce the idle speed by means of the clutch or turning the key on and off, does the idle remain where it should indefinitely? If it does, when you then step on the accelerator does the engine again idle fast?
TonyB
Jacksonville, FL
81 Dasher, 1.6na (work in progress)

[ossa7]

Tony B,

Thanks for your reply. The problem seemed to have come on gradually (over a couple of days). When it is cold, it does not do it. But within a 1/4 mile of driving it will start to do it. Yes, once I do drop the idle by means of braking or the quick key switch, it will idle all day and sound happy as a clam. Once at idle I can either twist the throttle assembly by hand or use the pedal and it will rev and drop back to the high idle. I visited two shops yesterday that both said the engine sounded fine and were stumped as to the root of the problem. One said that a worn head on the injection pump could do that but, again, two random pumps with exact level of a worn head (???). While idling high, one of the shops tapped the IP at various angles I'm assuming to see if something in the assembly was sticking and would drop the idle. No luck. I was asked if I left it in gear at the high idle (like a cruise control) how long it might stay like that. It's hard to say because I live in a hilly area so nothing is flat but as long as there is no uphill slope to drop rpms, it will just keep going.

[TonyB]

OK, let's assume for the moment that it's not the pump, although stranger things have happened than 2 pumps with the same problem. For the idle speed to increase then, it must be getting fuel from somewhere. If it's not the pump, the only other places I can think of to get fuel are, (1) as a previous poster suggested, from leftover fuel from a faulty injector, or (2) through the vent hose from the valve cover. Ruling out the hose is easy. I know you said it's not blowby, but if you haven't already tried it, I'd disconnect the hose & see if the problem disappears.
You might also do a search on the forum for "high idle". There are several threads that address this problem.

TonyB
Jacksonville, FL
81 Dasher 1.6na (work in progress)

[ossa7]

I've been living with this high idle problem for a year and decided it was time to change the engine mounts. The notorious pax side mount requires removing everything from the pully side of the engine so when I pulled the timing belt cover, I found the center cover bolt mounts were not even mounted to the engine. I also found that the two bolts that hold the IP mount to the engine block were missing! Duh! After replacing the pax side motor mount and bolting down everything that should have been bolted down all along, the engine vibration is minimal and the "high idle" problem is gone. Looking back, this would explain the reason that even though I put two different random IP's in during my trouble shooting, they both had the same problem... loose mounting. Thanks for all your help guys and happy motoring!!

[82vdub]

It's nice that you were able to solve the problem, and then posted on your original thread what you found. This could help someone else in the same situation.

[Fatmobile]

I've had those 2 bolts vanish before.
Lots of vibration on the accelerator peddle.

Now I always secure them with blue locktite.
Since those bolts are responsible for adjusting where the belt rides on the sprocket;
I tighten them, put the belt on, spin it a few times by hand and see where the belt is riding.
Then pull the pump and adjust, or loosen one and put blue locktite on it/install, then the other.

Just had the waterpump bolts wander loose on my daily driver,..
"damn no wonder the belt squeals the alternator is loose,
whaaat, the whole bracket is moving?"
Those will be getting blue lock tite from now on as well.

It's good to get in there and see what everything looks like,
especially when someone else has been working on it.
I refer you to one of my experiences:
viewtopic.php?t=6748

[avro]

I have the same thing happening to my 1.6 engine. I start it, it runs fine. As soon as I put it in second, it takes off ( high idle) could it be my IP bolts loose? Or something else?
Thank you.

[Fatmobile]

Feel any vibration on the accelerator peddle?

[82vdub]

Does it only happen in 2nd gear or when going to any gear and when does it go away (if it does)? Have you checked for loose bolts and did the problem come on suddenly?

[avro]

Yes I do get some vibration. ( but not all the time) My 1.6 diesel starts and idles fine. As soon as I go down the street and switch to second gear the engine takes off into high idle. No bolts loose anywhere. It did it all of a sudden last she's been running for the past 3 summers with no issues. I took the valve cover off and cleaned it well, replaced the gasket as well. I wonder if it's the hose going into the valve cover? It was really black, but I cleaned it out good. So, in a nut shell: it starts and idles perfectly. As soon as I put in second or rev the engine the rpm's runs right high.

[Fatmobile]

That includes the 2 bolts that hold the bracket to the block?
,.. and the other 2 bolts holding that bracket to the injection pump mounting bracket.
These bolts are behind the pump.

I also want you to put clear fuel lines between the injectors and watch for air being sent out from one of the injectors.
This can indicate a possible micro channel in the injector needle/seat causing an injector to spray funny and/or piss between firing.