81 Scirocco smog check fixes update

Probably excess air is getting into the intake manifold. Check for problems like a leaking brake booster, vacuum leaks around the throttle body, throttle plates not fully seating, ign timing way too advanced, leak in Aux Air Valve, or something else allowing this air in! You must solve any leaks and high idling before adjusting that CO!

Thanks, I'll keep looking. Very frustrating. Maybe all the crud should've been left in place.

Dave has the excess air leaks covered. I question electrical tape around vacuum leaks.

Replace tim>Probably excess air is getting into the intake manifold.

What happens if you disconnect and plug the auxiliary air valve? 1K is too high you should be able to get it down around 800 or so. In fact you should be able to stall the engine by turning the idle screw in, assuming it's the same as my old '84 GTI.

(diversion)

once upon a time, I did a "tuneup" myself on said GTI. Ran fine, except a short while after said tuneup I found that the car would tend to stall if I was in traffic and quickly shut the throttle and depressed the clutch at the same time. I put up with this for maybe a month or so until I got annoyed one day as I was stuck on I-66 and got sick of needing three feet (and having the car stall a couple times.) I pulled over, popped the hood, and backed the idle screw out a little. Idle went up to about 1000 RPM. Same thing happened. I pulled over again, bumped the idle up a little more, same thing. I pulled over, backed the screw out some more, idle got up to about 1300 RPM, I heard a "click" from the AAV and suddenly the idle was back down around 7-800. D'oh! I had screwed the idle screw in way too far and the AAV was wide open at idle keeping the engine from stalling. Once I readjusted the idle to spec with the AAV *closed* I never had another problem with it (well, until the alternator died, I found the allen head screw under the timing cover stripped, and I sold it to a guy in Rockville after buying a nicer Scirocco for about the cost of having the alternator replaced.)

Sounds to me like you still have air bypassing the throttle body, if you can't adjust the idle down far enough.

Definitely check it out. An 8V shouldn't bend valves if it breaks, but Murphy says if you end up walking it's going to be at the most inconvenient time.

Or, I'll be happy to take this POS off your hands :) (hey, the girlie needs a new car, and I've always had a thing for first-series roccets.)

nate

Thanks for reply.

I discovered the boot over the air flow sensor is leaky. Hope that's the culprit.

Aux air valve is only a few K miles old. I tried squeezing the hose and got no change in RPM.

Interesting experience with the idle screw and AAV. I'll try backing the screw way out if high idle persists after the boot is replaced.

Dwell meter was reading 43 in the 8 cyl range. I'm supposed to double that for 4 cyl. The lowest reading I could get was 26 (x 2 = 52).

Using your non-plastic-dissolving propane gas method, I found vacuum leaks around the rubber boot atop the air flow sensor. The boot looks OK but won't seal. I found a new one and will pick up and install tomorrow. Thanks for that tip!

For the sake of Googling Posterity I'll expound on cleaning injectors...

I did not use a puller. I clamped injectors with vise grips and levered them out with a very large screwdriver using rag-covered valve cover as pivot point. Injectors #1-#3 popped out cleanly, but #4 came out with bucket attached. I levered the bucket off using a box-end wrench and screwdriver. The old o-rings had turned into hard plastic, but snipping them with miniature wire cutters easily cracked them open. I cleaned the outside of the injectors with spray carb cleaner and rags, using Q-tips on the ends. Plastic buckets were not broken but threads were deteriorated so all were replaced. I cleaned the injector holes with Q-tips soaked in carb cleaner and blew them out with compressed air. I lightly applied Hylomar HPF to the new bucket threads. A 12mm hex socket was used to remove/install buckets. Injector o-rings were soaked in kerosene prior to sliding them on. Injectors popped in pretty easily. Subsequent vacuum test with propane gave no indication of any leakage.

ARG! I fixed the only leak I found - around the intake boot. Bypassed brake booster and windshield washer with vacuum line to distributor. Set timing to

Leaky injector seals and a cracked intake tube are now fixed, and yet the engine now idles worse than before. Idle screw all the way in and CO way lean to get down to 1K. Driving around the neighborhood car seems to run great. Lugging it doesn't produce any ping. But with stop and go driving it's running on the hot side of normal, and when I checked a couple of plugs they were squeeky clean with white insulators.

I checked the throttle plates when I had the throttle body off and they looked fully closed (of course, there was a bit more clearance all the way around them after cleaning). I don't understand how there could be significant leakage into the intake manifold. At idle, there is 16" HG in the hose that goes from the manifold to the distributor vacuum retard. There is 0" in the hose that goes from the back of the throttle body to the distributor vacuum advance.

OK just say the idle is higher. When I hear worse I think of a rough & shaking engine that is about to stall/die.

What did you do to the windshield washer again?

Are you sure the vacuum unit is not leaking and is working? I have had to free up the innards of a lot of distributors since most don't get oiled in their centers. Also the plates moved by the advance unit sometimes moves stiffly.

Oh I call this progress since all that you are doing/repairing creates changes! ;-) Now make sure that the throttle plates are fully closing. The stop screw stops the primary plate from jambing in the throttle bore. See if you can allow the throttle to close more.

Is there an EGR system?

So long as I'm willing to put up with high idle it runs fine.

I misinterpreted the line that runs into the firewall and under the windshield washer bottle. I don't know what it's for or where it goes, only that disconnecting it has no effect. There's another line that runs from a valve near the brake booster (which connects to the hose that runs to the aux air valve and also connects to the vacuum advance). My Clymer manual has nothing regarding those lines or the valve. Photos of them are here:

Sucking on the hoses causes visible movement of the Hall sensor. The mechanical advance moves freely.

First thing this morning I checked this and was able to back off the screw maybe a few degrees. Engine started right up and idled at about 800rpm (rough due to overlean CO). I upped the CO 1/8 turn to smooth the engine and idle was still below 1K. I thought maybe I was good to go, but as the engine warmed the idle went back above 1K.

Actually removed the hose and blocked the hole. No change. Engine has no EGR.

Much thanks for the suggestions.

sounds to me like the AAV isn't closing... have you tried unplugging it with the engine at warm idle? If that slows it down then maybe your thermo-time switch is bad?

nate

I tried pinching the AAV hose shut with smooth channellock pliers and idle did not change.

What role does the thermo time switch play? The test described in the Clymer manual makes no sense (connect a test light between the terminals...?!).

Thanks, nf

You have a vacuum leak or multiple leaks! Plug everything to the intake manifold but the throttle body. If it still idles high it would have to be the throttle body or intake manifold!

OK, I began checking again. There IS some air leaking into the manifold through the hose that connects to the valve cover. Completely sealing it lowers the idle ~100 rpm (still doesn't stop the engine even with idle air screw all the way in). I went to a parts store that still had the hose (049

Keep looking! :-)

Maybe a restrictor somewhere in that connection, like even on the intake manifold pipe. If that hose has never been changed then all should be good. Maybe I am remembering a water hose instead??????

Keep looking! :-)

Definitely what I was thinking since he can't get that idle down. Strange! thanks Jim I don't feel like I am totally losing my mind now! lol

I inspected the hose with a strong penlight. The plug with the hole is there. I felt a plug in the new hose as well, but the old is more restrictive. I can see light through the small hole but there's apparently crankcase vapor residue and simply shooting carb cleaner through doesn't remove it completely. Clearly though, this is 'measured air' that is going into the manifold, so perhaps the engine can't be shut down with the idle air screw alone.

Anyway, I'm now back to square 173 and will continue working at it today. One thought that comes in answer to "how could fixes and cleaning make things worse?" is the possibility someone screwed the idle screw in too hard at some point and damaged the seat such that it can't be closed. The crud I cleaned out was acting as a restriction. I wish I'd looked at that more carefully when I had the throttle body off.

nf

I checked the AAV (closed when hot). I blocked the intake hose from the AAV to ensure the AAV was sealing OK. I blocked the hose to the distributor timing retard and brake booster (thus increasing idle speed because timing advances quite a bit). I checked the idle air screw for seating using a pen light and dental mirror (don't see any damage). Throttle butterflies fully closed. I ran propane around everything again. Opened a vacuum line and sprayed propane around it just to confirm rpms went up.

From where comes air that burns the fuel to idle fast and blow my cool?

This engine is supposed to be timed with vacuum hoses attached to distributor. But changing CO changes manifold vacuum which changes timing which changes idle speed which changes...

(Oops. Slick little wet spot under the car. Never noticed that clutch-side crank seal leak before.)