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Location: Manassas, VA
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Angry emissions got worse after fixing vac leaks?

HI:

I am having trouble with 83 944 fluctuating idle and failed emissions.

little history...car failed NOX 2 years ago with new plugs, wires, cap,rotor, injectors, filters. replaced O2 sensor and cat. Passed easily. (Idle was unstable after car was up to operating temp.)

here in VA need emissions every 2 years and last month i failed NOX again.

I found one disconnected vac line, questionable air boot so I decided to check and clean throttle body, air flow meter and check other sensors, etc (according to HAYNES manual values). I found everything ok except idle stabilizer valve (there is no voltage at the connector).

when i fixed one obvious vac leak and put everything back together I heard a sucking sound near the intake manifold at cylinder 1. Looked like gasket wasnt quite flat. I decided to replace the idle stabilizer valve while replacing the gaskets for intake manifold and relaced air boot and one questionable vac line.

Got it all buttoned up and seems to run well except that the idle is still unstable 900-1200-900 etc but now at any temperature. Also after emissions check this AM i didnt improve nox

AND NOW HC's AND CO HAS FAILED AS WELL! DAMN CAR,
i love this car..i hate this car..

BTW...I also found the O2 sensor connector frayed near the ceramic connector and I spliced the wire by removing the ceramic connector (i soldered it...did I screw up?)

I am convinced I have at least 2 problems and I am not sure how to trouble shoot. If I read the forums here and other sites correctly I need a DME to fix my Idle stabilizer problem. Should I do that before anything else?

any ideas of what to do next and in what order should i perform testing/replacement would be greatly appreciated

thanks
john
Old 06-05-2004, 03:46 AM
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Biker, where in VA are you?
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Old 06-05-2004, 06:57 AM
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My understanding of these cars is 99% of the emissions-related problems go back to the O2 sensor. I'd check your readings on it to make sure your soldering didn't mess it up.
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Old 06-05-2004, 10:23 AM
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The early 944 idle valve is a bi-metalic spring and heater setup. It gets it's voltage from the fuel pump circuit. The engine has to be running to check for voltage at it. The bi-metalic spring closes a blade valve to lower the engines idle.

The later (post 85.1) 944's have an active idle valve that the DME does control. But not your 83.

The wire from the DME to the O2 connector has a floating shield. When you replace the plug your have to strip back this shield and use the center wire. If you ground the center wire to the floating shield you can cause problems. The wire from the connector to the O2 sensor does not have this shield.

Take a look at www.clarks-garage.com and www.frwilk.com. You may need to adjust the throttle switch. You may also have the vacuum hooked up wrong. There have been several postings here with the correct vacuum diagram for the early 944's. Do a search.

High NOx is lean. High HC's is rich. When all are a bit high it's the CAT.
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When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
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Old 06-05-2004, 10:45 AM
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thanks

siberian; i live in manassas

so cal driver: i did check voltage to idle stab valve with motor running.

thanks for tip with wire, i do recall seeing the two conductor cable
and being confused by it since i couldn't see any insulator between them.
Old 06-05-2004, 05:17 PM
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I think solder is a no no, I recall Auntie Wilk saying something about the O2 sensor needing a fresh air supply to have a basis of comparison, and it draws this air from the wire. he said butt connector. 'course, he is a butt man, so whatya expect?
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Old 06-05-2004, 05:59 PM
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If you have an idle that is hunting...

Troubleshoot the TPS as well...........
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Old 06-05-2004, 07:09 PM
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Quote:
Originally posted by biker43
...
so cal driver: i did check voltage to idle stab valve with motor running.

thanks for tip with wire, i do recall seeing the two conductor cable
and being confused by it since i couldn't see any insulator between them.
Not a two conductor cable. Shielded cable. Like cable TV wire. The outer shield is grounded to the DME case.

If you didn't get any voltage at the idle valve with the engine running then you have a break in the wire somewhere. Otherwise the fuel pump wouldn't be running either.
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Hugh - So Cal 83 944 Driver Person
NOT a 'real' Porsche -- Its Better!!!!
When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
New Users please add your car's year and model to your signature line!
Never break more than you fix!
Old 06-05-2004, 09:52 PM
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I had a variable idle for a while on my 84, it turned out that the screw that the throttle cam rests on had fallen out, leaving a small 1/4 inch gap which allowed enough expansion in the throttle cable to cause idle problems, not to mention driveability problems.

I replaced screw, which i found in the grime on the top of the engine, and the problem went away.

Also you might want to think about upgrading to a 3-wire heated 02 sensor, it was pretty simple on my 84. Although i had to have the local garage extract my old 02 sensor which seemed to be welded in.

Those 02 sockets are crap, get your self a decent correctly sized wrench, can't remember what size.

Mine failed emissions a few times for high NOx, i replaced the AFM as the old one was wornout, and it still failed but only just on NOx by a few points. The guy came out asked what i'd had done, so i went through a long list of things, he then disappeared again and came out 10 minutes later with a pass, not sure how...
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Old 06-06-2004, 03:11 AM
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thanks everyone i have some things to check today.

i still dont know how that supplementry air valve works on the 83 944. it gets powered from the fuel pump circuit then does it operate by the heat generated "radiating" from the motor to the valve? otherwise i dont see how it operates.

where are breaks in the wiring most likely to occur? the wires coming from this valve are part of the harness that contains other engine wiring and they are all wrapped to pass through the paasenger compartment. guess i just answered my qustion...
Old 06-06-2004, 03:12 AM
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There is a heating element in the valve. This is what the power is for. The heating element causes the bi-metalic spring to change length and close the blade valve shutting off the air that is bypassing the throttle body.

The valve gets crudded up inside from the crank case fumes and vapor being sucked into the intake from the oil filler.

The breaks usually are at the wire side of the pins on the connector.

Pelican has the electrical diagrams for the early 944's.

http://www.pelicanparts.com/944/electrical/944_electrical_diagrams.htm

This is the page you need to study.



Lines 28 and 29.
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Hugh - So Cal 83 944 Driver Person
NOT a 'real' Porsche -- Its Better!!!!
When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
New Users please add your car's year and model to your signature line!
Never break more than you fix!
Old 06-06-2004, 09:43 AM
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Biker, we're putting a timing belt party together for the Saturday before the 4th of July. It's probably going to be in Gainsville. Would you want to join? It's becoming more of a No. VA 944 meet and greet, beers, snaks, etc. Should be fun. e-mail me at IKARCHOV AT HOTMAIL DOT COM.
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Old 06-06-2004, 10:17 AM
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When I had to smog my '86 951, I waited untill the gas tank was almost empty and added a bottle of rubbing alcohol in the gas tank. Passed with flying colors. Credit this also to auntie wilk.
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Old 06-06-2004, 12:11 PM
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Bosch needs air? Funny. When I put in a Bosch gerneric last year the part came with a crimp connector and shrink tubing. Hard to get outside air through the wires that way.
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Hugh - So Cal 83 944 Driver Person
NOT a 'real' Porsche -- Its Better!!!!
When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
New Users please add your car's year and model to your signature line!
Never break more than you fix!
Old 06-06-2004, 12:20 PM
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I think I got it.

I found that I had voltage to the bl/g wire at the harness then I rechecked the idle stabilizing valve again and sure enough I had 11.5 volts!! I think the harness connector was not making a good conection. Idle was fine (better actually... see below) .

I also fixed O2 splice which i had forgotten that i soldered the ground to the center lead (not sure how i convinced myself to to that).

Ok ..while car was at idle i was doudle checking vac lines. when i pulled the small vac line from the throttle body the unstable idle was developed. (maybe a tip for some others....check that vac line)

went for a drive and for 5 or so red lights and stops I had perfect idle (that is ...lift off pedal revs go to 900 then up to 1150).

two times during the drive i did experience unstable idle but it resolved itself by the next stop. I think i will clean up that connector again.

one more question...I couldnt find the br/y ground from the stab valve.

thnaks folks
Old 06-06-2004, 01:52 PM
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Quote:
Originally posted by FR Wilk
Funny. Air tight heat shrink?
The O2 sensor does not breath through the wires. The outside of the housing is where the ventilation takes place. The sensor has to have one end in the exhuast the other in "regular" air.
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Hugh - So Cal 83 944 Driver Person
NOT a 'real' Porsche -- Its Better!!!!
When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
New Users please add your car's year and model to your signature line!
Never break more than you fix!
Old 06-06-2004, 06:06 PM
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Your idle is too high. Check your TBS setting.
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Hugh - So Cal 83 944 Driver Person
NOT a 'real' Porsche -- Its Better!!!!
When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
New Users please add your car's year and model to your signature line!
Never break more than you fix!
Old 06-06-2004, 06:08 PM
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Quote:
Originally posted by FR Wilk
In the 70's and 80's. Technology moved on without you Hugh.
Sorry Wilk's. I have great respect for you, BUT this is not what Bosch says.
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Hugh - So Cal 83 944 Driver Person
NOT a 'real' Porsche -- Its Better!!!!
When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
New Users please add your car's year and model to your signature line!
Never break more than you fix!
Old 06-08-2004, 11:25 AM
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