81 Scirocco smog check fixes update

Is there a vacuum hose under the throttle body? Maybe it is off. Maybe a closer inspection of the throttle body! Gasket is ok? How did you check that both throttle plates were closed? Test the idle with the accelerator cable off of the throttle linkage. I remember seeing an intake manifold loose on a 1981 Cabriolet. That really messed up its idle! Does the engine die if you remove the main intake boot on top of the fuel distributor?

Running out of ideas here!

Reply to
dave AKA vwdoc1
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With a high idle you only have to check for leaks after the throttle body! All the stuf before the t.body has only effect on fuel, advance etc. So inspect the whole intake manifold and all it's attachments.

SFC

"nutso fasst" schreef in bericht news:ToBDk.1183$ snipped-for-privacy@flpi148.ffdc.sbc.com...

Reply to
SFC

Pull the plug out of the old hose and stick it in the new hose. It was just a metal plug inside the old hose so it should come out. Leaky valve cover? As the other person mentioned false air somewhere. Have you tried to squish the valve cover hose flat to see if the idle changes?

Did you plug the vacuum hose to the brake booster? I do not recall if that is hard plastic but you do not want to squeeze a hard plastic hose shut.

On my old cars I had to replace all the little plastic vacuum lines. They were all brittle. You can get that stuff at a good auto parts house. I used to grab those lines when I was in the junk yard.

If your hood is original and not butchered there should be a vacuum hose diagram listing every hose. It may not list every plug or cork that may be there to block of unused vacuum sources. Triple check that every line starts at the correct port and finishes at the correct place. Block off the line that goes to the golf ball vacuum reservoir on the hood which also goes to the inside the car vacuum system to control air flow. You do have the golf ball reservoir on the hood?

Have you made sure that the air flow sensor moves freely? There is a procedure in the Bentley for that. I had a fuel distributor plate mess up in my 84. I tried to fix it but a trip to the junkyard to get a distributor from an 85 with some other spare parts fixed the problem. I spent a few hours at one guy's house trying to figure out a starting problem that was fixed when the fuel distributor was changed. Please do not start messing with this stuff as you may introduce yet another problem. It is easy to goof up when you start messing with that distributor.

When you attach a timing light to the distributor and apply vacuum to the vacuum advance line does it advance? Does it go back when you remove the vacuum? When you attach vacuum to the vacuum retard does it retard? Does it go back when vacuum is released?

So you d>

Reply to
Jim Behning

I noticed that: (1) a small leak in the intake manifold (remove small hose) raises idle speed (2) a large leak (remove large hose) stalls the engine (3) a small leak before the throttle body slows the idle (4) a large leak (open a rubber boot) stalls the engine

#4 had to be the case. Without vacuum in the intake tube, how can the air sensor plate lift enough to supply fuel to the injectors?

I suspect the crack in the plastic intake tube occurred after the first smog check (failed for HC only). Vacuum dropped at the air sensor and caused a leaner fuel/air mixture which explains the big rise in NOx. By the time of the third test the crack had opened even more, giving the 'gross polluter' rating for NOx.

With the idle air screw fully closed, the AAV fully closed, and the throttle plates fully closed, there should be no vacuum at the air sensor plate and the engine shouldn't run even if there are leaks elsewhere in the manifold, correct? So the basic problem is either leakage through the throttle body from the intake tube or an AAV that leaks even when closed. The throttle plates seal tightly enough to dam up carb cleaner in the venturis and the air screw looks to be sealing OK. So maybe I should recheck the AAV.

I noticed the idle drop briefly when the cooling fan came on but turning on the lights has no effect.

If I up the CO enough to get a smooth hot idle (1050-1100 rpm) and then the engine is allowed to cool completely so the AAV is open, the cold engine idles at about 800 rpm initially, and then rises to 1050-1100 after 5 minutes or so as the AAV closes.

If I lower the CO to get the hot idle below 1K, and then shut off the engine and allow it to cool for a while but not so long that the AAV opens, and then start the engine, it hardly idles and needs to be run for a minute before it will idle OK.

The diagram inside the hood shows the plastic "on/off" valve to which the distributor advance vacuum hose attaches. The output hose from the valve goes to a "carbon cannister." Other small hoses are still a mystery.

The air flow sensor plate appears to be at the top of the 5mm tolerance (top of plate at narrowest opening). Maybe I should lower it slightly and see what happens. (I'm measuring it with key off. The Clymer manual gives a complicated procedure using a fuel pressure gauge and a special VW tool.)

Thanks much to all who have taken the time to offer insight into this problem. If I don't find a 'good' fix soon, I'm going to set the CO lean enough to idle

Reply to
nutso fasst

the aav is not airtight. There is nothing to really check. You visually look to see that it closes.

You do not adjust idle speed with CO adjustments.

Throttle plates are not supposed to be totally closed otherwise they wear out the housing. They are cracked open just a tiny bit.

Why don't you take a picture of the hose diagram on the hood and post it along with a picture of your engine compartment. Kodak has a free picture gallery that I use.

I saw no posting about trying to install your restrictor from the old crankcase vent hose into the new crankcase vent hose.

Reply to
Jim Behning

Which I did. And it does. If it is not airtight then I think I'm OK there. I had the hose off the closed AAV and blocked it to the manifold. This decreased idle speed slightly. But there was a bit of vacuum at the closed AAV. When I blocked the hole to the AAV the idle speed increased slightly. All in all, completely blocking the closed AAV produced almost no change in idle speed.

Taking CO lean brings idle speed down. Idle speed >1K is immediate smog test fail.

Many years ago I took this car to a BMW 'mechanic'. I don't remember what was wrong with the engine, but when I picked up the car the idle was bad. The 'mechanic' told me the engine was near death (115K mi). When I got home I discovered the idle stop screw had been screwed out and the throttle plate was sticking in the venturi. That made me aware of the purpose of the stop screw. Both throttle plates now close as much as possible without sticking.

I already posted a link to pictures of my engine compartment. They're at:

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Looking closely at the diagram I see the 'mystery hoses' are for the air conditioner. I turned the stop valve around so those lines are blocked. (I disconnected the air conditioner long ago.) Too dark to take pics of the diagram right now, my DV camera has no light.

Apparently you aren't seeing all of my posts. I did not buy the new hose. There is nothing wrong with the old one. The only difference is that the restrictor in my hose is more restrictive than the restrictor in the new one.

nf

Reply to
nutso fasst

It has been too long for me, since I have not seen one of these in 10-15 years. lol So I am not sure if the PCV is routed correctly. I guess it is, since you have owned the car since new or close to new.

Those little hoses in the upper picture should go to the vacuum reservoir and the heater controls inside the car.

If you have plugged ALL of the hoses at the same time and dialed the idle screw all the way in and you still have a high idle and no intake manifold leaks then............ throttle body.

If the intake manifold gasket is blown at the bottom will propane still be sucked in?

I should have some spare throttle bodys if you need one. I was about to recycle a lot of the stuff I have in my basement that I probably won't need ever again! Are you sure that your secondary throttle plate is free and fully closing? I have had to free up many of them that were sticking from corrosion.

I vote you take off that TB again and inspect it and test it!

JMHO

Reply to
dave AKA vwdoc1

That's normal..

To little air flow passing the meter, so not enough fuel...

Less airflow passing the meter, so leaner mixture

No air flow passing the meter, so no fuel...

I agree, altough it's hardly a vacuum, more to do with flow.

Yes, no air passing the air meter meanse no fuel injection..

Could be a vac. line going to the instr. panel. This is used for measuring fuel comsumption. Does it have MFA (small computer showing oil temp, speed etc)?

No, this is good. Tolerance is between the top of the cyl. part and 0,5mm below it.

SFC

Reply to
SFC

You block vacuum lines with a screw or a bolt. That little thing you turned around is a check valve. It will not function as a plug with any guaranteed performance. Just remove it and stick a screw in the hose. read further for my ideas on that line.

Your pictures are missing a lot of hoses. Well maybe not as I turn the page in my Bentley. There should be a T in the vacuum advance/Evaporative emission control valve/vacuum port after throttle plates, or is it before the throttle plates. Looks like after the plates but I can't tell without a throttle body in my hand.

I think you are working off the center diagram on my page 2 unless you have EGR.

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Your first picture shows what you believe to be hoses for the AC and vent control system. That hose heading to the left or to the front of the car should be attached to a vacuum reservoir. On my Rabbits that reservoir was attached to the hood with two rubber straps and looked like a bunch of golf balls. I do not recall looking under the hood of a Sirocco with AC to know what your reservoir is supposed to look like. Just put a screw in the vacuum hose just before the T to block that all off.

That set of black hoses with the T fitting where one to the right goes to the check valve and off to the ventilation controls. Might as well block it before that check valve. The left side of the T goes to the vacuum retard on the distributor. Make sure you have no leaks with your Mighty Vac.

I do not have any throttle bodies laying around anymore. There may be ports on the throttle body that are supposed to be capped off with rubber plugs if not used. Make sure they are capped. The vacuum advance in the picture shows it sourcing from as close to the intake manifold as possible but off the throttle body. Make sure it is on the correct port.

Are the hoses to the charcoal canister and the accumulator tank in perfect shape? Have you eliminated them during your troubleshooting with big plugs?

You may not be understanding what I said about CO adjustments. Yes playing with the CO will make differences in the idle speed. That is not how you adjust the CO. You get out your dwell meter and set it accordingly. Of course you cannot ever properly set the CO with false air leaks. I can adjust the idle speed of my car with the gear shifter and the clutch. I just put the car in gear. Let out the clutch a bit with the parking brake en gauged. The idle speed adjusts. :-)

Eng>

Reply to
Jim Behning

OK, I bypassed the A/C hose completely (vacuum reservoir is in the front of the right wheel well, BTW). The center diagram you posted is not quite right. See additional photos - including the diagram inside the hood - at

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The vacuum advance is the only hose connection on the throttle body. The tiny hole is just outside the throttle plate. There is no measureable vacuum until the throttle is opened.

Hoses to the charcoal canister look good. I don't think that line's at fault. Sucking on the vacuum hose that goes to the on/off valve for the charcoal canister causes idle speed to increase. I need to find some rubber plugs.

I understand what you meant regarding idle and CO. But I really want to get this car smogged so I can get current tags (registration paid, tags pending smog check). Ol' lady can't/won't drive my truck and I'm tired of being a chaffeur.

Question regarding the dwell meter CO adjust: 49-state spec is 1.5% CO. California spec is .3% CO. Shouldn't the dwell be different for Calif. cars?

nf

Reply to
nutso fasst

I bought the car in 1982 w/10K mi on the odometer.

What could go bad in the throttle body? If the manifold gasket were blown, wouldn't the vacuum measured on the timing retard line be low? It's currently 16".

Please hold them a little longer!

I'll have to order a new gasket again.

Reply to
nutso fasst

So what does bypass mean? It should be plugged. Insert screw in rubber hose. Now it is plugged. The check valve is not a plug.

You cannot work on "they look good theory." You need to eliminate problems. You do that by corking all potential problems up. You could have a split wide open or gapping hole you cannot see the canisters.

You can't pass a smog test by leaning the car out to get the idle down. The test should be looking at hc, co, nox, and idle speed. I would guess. Failing any one is a failure of the test. You play with one adjustment and the others are going to go about. You really need to find the false air leaks.

I live in Georgia. I don't know anything about California CO adjustments but I bet the dwell does need to be different.

If you have high nox this article suggest it is running lean/false air.

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Reply to
Jim Behning

I am so tempted to ask you where you live :)

I still have my valve clearance shim set and tools (which I never used, BTW) but got rid of all my VW spare parts when I sold my Scirocco, as I was living in a rented place and running out of room...

nate

Reply to
N8N

chicago I sold a few sets of those tools on ebay. I still have enough shims of different sizes and tools to keep my '83 GTI engine running well! ;-)

"N8N" wrote

I am so tempted to ask you where you live :)

I still have my valve clearance shim set and tools (which I never used, BTW) but got rid of all my VW spare parts when I sold my Scirocco, as I was living in a rented place and running out of room...

nate

Reply to
dave AKA vwdoc1

I am with Jim here! Plug up all vacuum connections to the intake manifold and throttle body! Use more hose and screws/bolts. BTW I don't think that vacuum hose is an a/c hose. It should be a vacuum hose for the "controls" for the heater and a/c system!

California usually sticks more emission controls on their vehicles. CO is measured & set through the test pipe before the cat and the cat usually cleans it up some more. Using the Dwell meter should be good enough since most people don't have a CO/HC tester. ;-)

Vacuum can still be "good" especially if the idle is too high! I would triple check the secondary throttle plate after plugging up everything.

Reply to
dave AKA vwdoc1

AC was on a T connector. T connector was removed (as shown in the photo). AC no longer connected to intake manifold vacuum. In what way would it be better to put a plug in the line?

True. But the on/off valve and cannister connect to the intake upstream from the throttle body. We agreed that a leak there *decreases* idle speed.

Idle speed must be below 1000. But emissions aren't tested at idle. Testing is at 15 mph and 25 mph (between 1900 and 2000 rpm). At what rpm is the idle mixture adjustment irrelevant to emissions?

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The failure was high HC *AND* high NOx (CO was 0.3%). The article suggests that's something of an oxymoron. ;-)

Anyway, I'll try plugging everything all at the same time and see what happens.

nf

Reply to
nutso fasst

Hmm. The diagram inside the hood

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has the line goingto the inside of the car as "AIR CONDITIONING ONLY". That line did seem to have a leak somewhere because the one-way valve was making a buzzy noise. But removing the line (by removing the T connector) did not noticeably affect idle speed.

Is the "reservoir" for holding vacuum so controls work with engine off?

I finally learned what the charcoal canister and plastic on/off valve are about and why the valve is opened with vacuum in the distributor advance line. Based on the suction test I did it seems to be working OK.

okey dokey!

Reply to
nutso fasst

Some controls or devices are there BECAUSE you have Air Conditioning, but they might not be "Air Conditioning" parts. Some of your engine pulleys will be there since you have a/c but they are not "a/c" pulleys! ;-)

And to stabilize the vacuum to that system when you might accelerate thereby dropping the vacuum to almost '0'.

Reply to
dave AKA vwdoc1

That is not an idle mixture screw. That is a mixture screw. It affects the mixture from idle to 6,000 rpm's. It works in conjunction with the oxygen sensor and a frequency valve to keep the mixture "ideal." When you attach the dwell meter you are reading the frequency valve cycling. A proper mechanic would be attaching his exhaust gas probe to the line on the right side of the intake. It is covered with a blue silicone plug. This is attached to a stainless steel line that attaches to the exhaust manifold. So that test probe is sniffing the mixture before the catalytic converter gets a chance to clean things up. When you are done adjusting the mixture you are suppose to install an aluminum plug or on the older cars the rubber plug in that hole so you do not get false air or such excessive dirt into the engine.

I do not recall seeing or reading how you plug the line that is supposed to go to the ventilation controls and the vacuum reservoir. The check valve is not a plug. You stuck a screw in the rubber hose as close to the vacuum source?

Best policy is to block off any and all possible vacuum leaks. Do not rely on theories that something is not relevant. I get a piece of hose and an old lug bolt and seal things off. There is false air somewhere or your throttle plates are not properly adjusted.

Also I start fuel injection work by getting out my fuel pressure gauge. I check my pressure according to the book and I make sure that the control pressure is correct. If it is not then the idle could be high. I also make sure that my flow rate is correct on all injectors and my spray pattern is correct. I use 4 glass jars to test that along with my fire extinguisher which is properly charged and recently shaken up so the yellow stuff inside is not all caked up. A fused jumper wire to bypass the fuel pump relay.

There are a lot of simple steps that have to be done. Troubleshooting is not binary. There can be many things wrong so you start by eliminating the most frequent and basic things. Pressure and flow is

201. Timing is 101. Air leaks should be 301. Of course if you do not have a pressure gauge you cannot cross your fingers and hope it is not an issue. I have had bad injector patterns, clogged control pressure regulators, junk in the fuel distributor, bad coil, bad coil wire, bar hall sensor connectors all cause drivablitiy issues. That is besides installing a timing belt one tooth off.

An emissi>

Reply to
Jim Behning

I found some silicone plugs at the local car parts store. With all hoses to external devices plugged (including the aux air reg), there is a slight drop in idle speed. However, the warm engine still runs when the idle screw is screwed all the way in.

Is it true that if the throttle plates are properly adjusted and the aux air reg is closed, then the engine should die if the idle air screw is turned all the way in? If that is the case, then you must be right: something's wrong in the throttle body.

nf

Reply to
nutso fasst

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