RE: [T3] Fuel Injection/Tune up

["Decker, F J" <Decker.F@PSS.Boeing.com>]

Katie, 
Your FI system will be different than Matt's car as it has been pointed out.  Yours is a D-Jetronic system.
The following info is from the official VW D-Jetronic troubleshooting guide.

Rough idle during warm-up 
    Test conditions: 
     - Valve clearance and ignition timing correct (very important) 
     - Idling speed of warm engine within specified tolerances 
     - Let engine cool down to ambient temperature before starting test 

    A. Idle enrichment inadequate during the warm-up phase 
        Start engine 
        When auxiliary air regulator has closed (after 3-4 minutes) measure idle variation 
        If the variation is more tham 100rpm: 
            Type 3: go to C. Idle contact in throttle valve switch not in order. 
            Type 4: go to B. Idling CO potentiometer setting too lean. 
        Variations of less than 100rpm are acceptable 

    B. Idling CO potentiometer setting too lean 
            Turn potentiometer slowly clockwise until idle is normal (Variation less than 100 rpm) 
            If idle is still varying by more than 100 rpm, go to C. Idle contact in throttle valve switch not in order. 
            If idle is OK, check that CO is not too high when engine is warm (50C-70C/122F-158F) 
            If the CO is considerably above the permissible maximum, lookult in "CO value too high" section of guide 

    C. Idle contact in throttle valve switch not in order 
           Possible problems: 
                - Throttle valve switch incorrectly adjusted 
                - Wire 17 between throttle valve switch and control unit defective 
                - Throttle valve switch defective 

Hope this helps you.
Jay Decker

> ----------
> From: 	TOASTEDT3@aol.com[SMTP:TOASTEDT3@aol.com]
> Sent: 	Thursday, April 15, 1999 5:33 PM
> To: 	type3@vwtype3.org
> Subject: 	[T3] Fuel Injection/Tune up
> 
> I have a 1971 fuel injected notchback that I bought back in July.  It ran 
> great and all I've done to it is change the oil and put gas in.  Lately 
> however, it's started to do some things that make me wonder if there's a fuel 
> injection problem, or if it just needs a tune-up.  
> 
> First, if I don't sit for a good five minutes and let it warm up, it does 
> this awful jerking thing when I start to go.  It's only when I give it a good 
> amount of gas, not if I just idle it along in our alley.  Matt's car used to 
> do this too (it's a 92 GTi with Digifant fuel injection) and he had a thingy 
> that regulates fuel on deceleration replaced and now it's fine.  I have no 
> idea if fuel injection in a notch and a newer car can even be compared, but 
> it makes me think it might be a similar problem since it does the EXACT same 
> jerking thing.  The notch just recently started doing this...I've always let 
> it warm up, but now I have to sit for longer than I did before.
> 
> Second, yesterday I had to sit in traffic while waiting for a train.  I put 
> it in neutral and just let it idle for maybe 6-7 minutes.  The idle dropped 
> way down several times, but the car never died.  It's never done this 
> before...did it just get hot?  It was in the 60's with a nice breeze, so I 
> wouldn't think that sitting for 6 mins would do that
> 
> Any help is appreciated.
> 
> Katie
> 
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