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Volkswagen Rabbit, Jetta, Scirocco, Convertible: 1975-1984 (A1) 1984 Scirocco won't idle


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Last Post: Feb 6, 2012 9:07 PM Last Post By: FKH161
scirocco84

Posts: 67
Registered: 10/29/04
1984 Scirocco won't idle
Posted: Nov 21, 2008 11:46 AM
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Hey folks, My 84 Scirocco (ive had it for 5yrs) just stopped idling. if i let off the gas it stall immediately, no cough or sputter. just dead.

here's what happened

yesterday am (-10C or 14F)
the first crank backfired (it had never done that before)

second crank it started and idled as normal for 5 mins or so. you could hear the engine "firm up" as the injection system pressure increased.

I gave it a rev and the idle dropped and it stalled.

it now will not idle hot or cold, but it runs fine with the accelerator pressed. Ive driven to work with the throttle cable snugged up to hold the butterfly open abit so it won't stall in traffic.

did the backfire knock something loose and plug the idle circuit?
scirocco84

Posts: 67
Registered: 10/29/04
Re: 1984 Scirocco won't idle
Posted: Nov 21, 2008 4:05 PM   in response to: scirocco84 in response to: scirocco84
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I'm thinking that "firming up" of the idle is actually the OX sensor kicking in, rather than system pressuring up. I need to check the pressure still then, but its bloody cold to mess around out there.

Can I take out the idle adjust screw and blast the system with some TB cleaner spray or compressed air?

Message was edited by: scirocco84 because the man can't type

FKH161

Posts: 7,610
Registered: 12/29/05
Re: 1984 Scirocco won't idle
Posted: Nov 21, 2008 8:10 PM   in response to: scirocco84 in response to: scirocco84
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Yes, you can blow-out the idle speed screw hole... don't forget
to clean the carbon/dirt off of the speed screw tip before
you put it back in.
tcovenant2000

Posts: 1,761
Registered: 12/09/03
Re: 1984 Scirocco won't idle
Posted: Nov 21, 2008 9:23 PM   in response to: scirocco84 in response to: scirocco84
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I agree...it's more likely the O2 sensor than pressure. Pressure should be full within seconds of starting. Of course it could also be your CPR increasing the control pressure as it warms up. The O2 sensor usually kicks in within a minute or two, the CPR usually takes 5 mins.

I assume you understand that if you can move the idle screw by hand then the oring is bad and likely causing a vacuum leak?

There is one or two boost valves (two if you have AC) on the pass side strut. Sounds as though they aren't working. It's common for idle to be set incorrectly so the boost valve doesn't come on as it should.
When you get the problem fixed and you're ready to set idle, disconnect the boost valve(s) electrical connectors. Now set idle speed and then you can plug them back in. It's also possible the boost valve or relay isn't working. As RPM drops below 750 you should hear a loud click under the hood and the RPM should come up by 300 or so.

You should also check timing. Backfire could indicate hopped timing belt, which could be why it won't idle, but will run.

Thomas
tcovenant2000

Posts: 1,761
Registered: 12/09/03
Re: 1984 Scirocco won't idle
Posted: Nov 21, 2008 9:23 PM   in response to: scirocco84 in response to: scirocco84
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I agree...it's more likely the O2 sensor than pressure. Pressure should be full within seconds of starting. Of course it could also be your CPR increasing the control pressure as it warms up. The O2 sensor usually kicks in within a minute or two, the CPR usually takes 5 mins.

I assume you understand that if you can move the idle screw by hand then the oring is bad and likely causing a vacuum leak?

There is one or two boost valves (two if you have AC) on the pass side strut. Sounds as though they aren't working. It's common for idle to be set incorrectly so the boost valve doesn't come on as it should.
When you get the problem fixed and you're ready to set idle, disconnect the boost valve(s) electrical connectors. Now set idle speed and then you can plug them back in. It's also possible the boost valve or relay isn't working. As RPM drops below 750 you should hear a loud click under the hood and the RPM should come up by 300 or so.

You should also check timing. Backfire could indicate hopped timing belt, which could be why it won't idle, but will run.

Thomas
scirocco84

Posts: 67
Registered: 10/29/04
Re: 1984 Scirocco won't idle
Posted: Nov 22, 2008 5:06 PM   in response to: tcovenant2000 in response to: tcovenant2000
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I removed the idle screw and blasted a bunch of TB cleaner in there and cleaned off the screw itself.

it won't idle at any setting of the idle screw. but runs if you keep your foot in it.

its tough to check the timing, but I could get it to run at 2500 rpm and I can see the timing pointer (its a manual tranny).

I set it to TDC and checked the dizzy. the rotor points to 1.

I havent gone as far as pulling the cam drive belt cover off yet.

when its cold, if I turn the key (foot off the pedal), it fires and runs for 1 sec or so then stalls. so the cold start injector is getting fuel to the system.

could this be a fuel delivery thing? but its continuous injection so if it gets fuel at 120km\hr it should get fuel at idle, right?
FKH161

Posts: 7,610
Registered: 12/29/05
Re: 1984 Scirocco won't idle
Posted: Nov 22, 2008 6:16 PM   in response to: scirocco84 in response to: scirocco84
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Something's definitely weird here... when cold, the Aux Air Reg
should open-up, bypassing air around the throttle plate for a
higher cold idle.

If this alone does not keep the engine idling (at least until
the aux air reg closes)... there has to be something that is
preventing the Air Flow Plate from lifting enough to supply
fuel for idling.

Have you checked all the intake ducting for vacuum leaks?

How many boost solenoids do you have?

The engine isn't cis-e is it?

Does the throttle body have a "venturi insert"?

Have you removed the intake tube from the throttle body and
verified the idle passage being clear/open using a small wire?
scirocco84

Posts: 67
Registered: 10/29/04
Re: 1984 Scirocco won't idle
Posted: Nov 22, 2008 7:51 PM   in response to: scirocco84 in response to: scirocco84
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I've got only one boost solenoid.

OK, I took the idle screw out and ran a piece of copper wire into the idle bypass a couple of times. it came out kinda cruddy. so I blasted some TB cleaner up there and it sprayed out the hole for the adjuster screw.

It has started to Idle a bit, but not great -- it still wants to stall, but it does idle now. I think we've got it. that back fire must have packed some crap into idle bypass.

I don't think the aux air reg works that well; I never get much high idle, but the car always started so it wasn't at the top of my to-do list.

I'm gonna fuss around in the bypass a bit more tomorrow and pull the aux air reg too. too dark to work on it now.

thanks,

Ray
tcovenant2000

Posts: 1,761
Registered: 12/09/03
Re: 1984 Scirocco won't idle
Posted: Nov 23, 2008 9:37 AM   in response to: scirocco84 in response to: scirocco84
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I'd check the air flow plate rest position if you still have problems after cleaning out the idle bypass.
Also, if the CPR is staying shut you'll have too-high control pressure when she's cold.
You should also locate the lamda temp controller and pull the wires off and jumper them out and see if that helps. When the engine is cold the Lambda temp controller turns off the lambda system and tells the lambda controller to rich the mix until the engine warms up.

Thomas
scirocco84

Posts: 67
Registered: 10/29/04
Re: 1984 Scirocco won't idle
Posted: Nov 23, 2008 5:50 PM   in response to: scirocco84 in response to: scirocco84
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I've cleaned everything from the big air flow plate to the TB, but its not idling anymore. the idle bypass is good and clean.

I think Thomas is right about the cam drive belt slipping. the quality of the run is starting to deteriorate. its getting stuttery below 2500rpm now. I just realized ive put over 100k kms on it since the last belt change, and i run it pretty hard during the commute.

so I'm gonna give it a full tune up (belt, plugs, cap, rotor, air filter, fuel filter) and see.
scirocco84

Posts: 67
Registered: 10/29/04
Re: 1984 Scirocco won't idle
Posted: Dec 1, 2008 5:59 PM   in response to: scirocco84 in response to: scirocco84
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Nope. the timing is OK, and the belt is still in good shape.

I hooked a vacuum meter up and it looses vacuum pressure below about 2000rpm then stalls.

I've checked all of the hose connections with TB cleaner and they don't seem to be leaking. that would mean the intake manifold gasket must be blown, or is there another spot where I could be gettinga massive vacuum leak? what about the injectors? (btw the engine has 375k kms on it)

Is it true that I have to pull both the intake and exhaust mainfolds at the same time? if so is it easier to just pull the head with the manifolds attached and work on a bench?

Thanks all,

ray
tcovenant2000

Posts: 1,761
Registered: 12/09/03
Re: 1984 Scirocco won't idle
Posted: Dec 1, 2008 9:28 PM   in response to: scirocco84 in response to: scirocco84
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OK. Now we're talking. No vacuum at "idle" means no idle, as I'm sure you know.
To answer your questions:
1. It could be intake manifold gasket, yes.
2. It could be injector seats/orings, yes.
3. You do NOT have to pull both intake and exhaust manifolds together. I have pulled the intake on a couple of these cars. I seem to recall that there were some sort-of-hidden nuts that bolted the intake to the exhaust, but I know I was able to get the intake off by itself. Of course, I'm speaking of Calif cars with no EGR system. You likely have to remove the EGR valve if you have one. Bentley has warpage specs for the intake manifold. That's something that needs checking while it's off.
As for the vacuum leak, here's what I'd do:
1. Pull the following hoses (one at a time) from the intake side. Get some ziploc or other HEAVY plastic baggies. Put baggies on the nipples. Put the hoses back on over the baggies. No clamps needed:
Hose from aux air regulator to manifold.
Hose from brake booster to manifold.
Hose from idle boost valve to manifold.
Hose from air cleaner box to manifold.
WARNING: YOU WILL NOT HAVE POWER BOOST TO THE BRAKES! DO NOT ATTEMPT TO MOVE THE CAR WHILE THE BAGGIES ARE IN PLACE. Sorry...I don't think you're stupid...the lawyers make me say that!
Now see if she'll idle. If she does, put the hoses back on one at a time until she doesn't.
I've thought of something else. Clogged injectors will sometimes not flow well at idle, but will flow well at speed. Check your injector flows. While you have the injectors out, put new orings on them and have a close look at the injector seats for cracking. You can also use the spray on the injectors and all around the intake manifold gaskets to check for leaks. I've also heard of these manifolds cracking, so you may have to pull it to check for that.

Thomas
scirocco84

Posts: 67
Registered: 10/29/04
Re: 1984 Scirocco won't idle
Posted: Dec 3, 2008 3:40 PM   in response to: tcovenant2000 in response to: tcovenant2000
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LOL, no, not stupid, but absent minded and forgetful. thanks for the reminder.

I did the baggie trick (great test btw), but its still the same: no idle. it starts easy even though its -10C (18F) today.

just to confirm the hose to the air box is a small hose that comes out under he idle screw? i didn't see any other large nipples on the manifold.

the idle screw is easy to turn by finger, but I can't see that being the source of the vacuum leak; its too big.

I'm pretty sure there is a vacuum leak (rather than crappy injector spray) since the plugs are beginning to get white deposits on them.

so its gotta be either the injector seals or the manifold gasket.

too cold to mess with it any more today. I hope it warms up abit for the weekend so I can get this thing fixed.

/ray
tcovenant2000

Posts: 1,761
Registered: 12/09/03
Re: 1984 Scirocco won't idle
Posted: Dec 3, 2008 4:20 PM   in response to: scirocco84 in response to: scirocco84
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Well...typically you've got a bad idle screw oring if you can turn the screw by hand.
It does look like seals or manifold, though. Be sure to check for cracks and warpage when you pull it.
Let us know how it goes.
THomas
scirocco84

Posts: 67
Registered: 10/29/04
Re: 1984 Scirocco won't idle
Posted: Apr 7, 2009 10:19 PM   in response to: scirocco84 in response to: scirocco84
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So Its finally warmed up enough to work on the ol' 84. Its been bloody cold and snowy up here.

I've finally replaced all of the stuff I broke checking for vacuum leaks:
all the injector inserts broke pulling the injectors because the O-rings were so hard. the O-ring seals must have been original, they were so brittle, they shattered when I cut them off the injectors. no problem right? the inserts are a buck or so. nope the 84s have the "air-shrouded" injector inserts (part number 63133555A btw) they have 22mm OD at the treads whereas the normal inserts(part number 63133555) that comes up on the napaonline.com site for 84's are 24mm. the air-shrouded inserts not carried by anyone but the dealer up here in Canada. $12 each. greedy buggers. there is one place in the USA that does carry them-- just google the part number-- some rabbit parts place.

while fighting to pull the injectors I damaged the No1 injector fuel line. replaced it with one from a CIS-E system $5 at pick and pull.

I also busted a little plastic nipple on the back of the head just below the valve cover next to the No. 3 injector, that was free from Pick and Pull. do not wiggle those vacuum hoses to get them off in the cold!

it runs a bit better now, well it actually idled on its own today @ 1500 for a bit until it heated up, then back to the usual: runs OK above 2500rpm but dies at idle. I don't think they're any major vacuum leaks (at the intake for instance) since if I floor it just before it dies it will catch. if there was a massive vacuum leak that shouldn't happen cuz opening the throttle plate full-bore dumps vacuum back to the big airflow plate. if there was a really big leak, there wouldn't be any vacuum left to move the plate.

It was just over 10C today so I checked the control pressure cold was 10PSI warm 50PSI. the cold is too low, but the high is OK.

its acting like it gets no fuel unless its at half throttle, which make sense why it runs a bit with low cold control pressure but dies when the pressure comes up (it should be getting too much fuel when cold but the right amount of fuel after 3 or 4 mins of warm up according to the test). it also will false-fire if I crank it with my foot off the gas when its cold --> its getting enough fuel from the cold-start injector to catch.

does it sound like the fuel distributer is shot? I did not see any CIS at the pick and pull, lots of CIS-E though, can I use one of those?
LynaghCommunica...

Posts: 1
Registered: 11/28/10
Re: 1984 Scirocco won't idle
Posted: Nov 28, 2010 1:09 AM   in response to: scirocco84 in response to: scirocco84
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Did you ever find out the source of your 1984 idle problem? I have a 1984 Scirocco with an idle problem and I am trying to hunt down the culprit. I replaced the fuel injector seals and that helped a bit but it is still idling incorrectly. Let me know.
Schirotto

Posts: 1
Registered: 02/06/12
Re: 1984 Scirocco won't idle
Posted: Feb 6, 2012 7:32 PM   in response to: LynaghCommunica... in response to: LynaghCommunica...
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Hi
I own an 84 Scirocco 1.8cc Wolfsburg. As I recently went out of town the starter had been damaged, thus I had to use the kickstart method which of course is not good on these vintage cars. This jerking induced the engine to jerk hoses back and forth and several starts later the idling as you all report was off.

Vaccum hoses! Important. The jerking broke a ----4 way---- T hose connector below the large maniful intake tube which connects to idling sensors, vaccum reservoir and head return hose. Took me several days to get to the source of the leak. Now there are stalls and you can imagine. The vaccum hose system is designed so precise as to idle the engine when necessary. So Im searching the 4 WAY connector. Does anyone know the part#?

Engine is untouched and has no mechanical problems or has never had the wrong hands get into it. Ive diagnosed it and once the hoses get put back and the vaccum is tight idling begins to take place, OX sensor and so on. It has an oxygen idle stabilizer and the A/C stahilizer, so two in total. Dealerships in the US become lazy once the part is unavailable and they whine and tear up like babies when you ask for such a part.

Again its located right above the brake booster below the intake tube. Thanks.
FKH161

Posts: 7,610
Registered: 12/29/05
Re: 1984 Scirocco won't idle
Posted: Feb 6, 2012 8:25 PM   in response to: Schirotto in response to: Schirotto
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Don't suppose you can take a picture & post it?

I'll check an online catalog for part #, but I doubt it would still be available.

Most auto parts stores sell a variety of vacuum fittings adapters of various sizes... may not look stock, but might do the job.
FKH161

Posts: 7,610
Registered: 12/29/05
Re: 1984 Scirocco won't idle
Posted: Feb 6, 2012 9:02 PM   in response to: FKH161 in response to: FKH161
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Attachment 027300.png (15.4 KB)
Attached is a vac diagram... some items missing (cruise,egr).

PNG image file, my android tablet doesnt have an image converter installed.

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