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The following was taken "Idling Trouble" section in the Official VW D-Jetronic troubleshooting guide 1. 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 D. 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 (Variatin less than 100 rpm) If idle is still varying by more than 100 rpm, go to D. 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, look for fault in "CO value too high" section if guide D. 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 2. Hunting at idle at all temperatures NOTE: This point concerns only vehicles with deceleration fuel cutoff - Type 3: up to Chassis No. 311 2 500 000 - Type 4: up to Chassis No. 411 2 100 000 Test condition: - Engine warm (50C-70C/122F-158F) - Engine running at idle A. Leakage in intake manifold Pull auxiliary air regulator hose off at intake elbow and close it with the thumb If idle is steady, go to B. Auxiliary air regulator not closing. If engine continues to hunt: Pull intake elbow oye®tle valve support Close off by-pass drilling with thumb and listen for sucking noises (picture) Possible causes for leaks: - Hoses between intake manifolds and intake air distributor - Intake manifold gaskets - Rubber mountings for injectors - Vacuum hoses Eliminate all leaks found B. Auxiliary air regulator not closing Type 3 (automatic) and Type 4: Run engine and check if there is voltage at the connection on auxiliary air regulator If voltage present, replace regulator If no voltage, check wire to terminal 87 on pump relay and repair. Type 3 (manual) Replace mechanical regulator 3. Hot engine stalls at idle Test condition: - Engine cold A. Valve clearance incorrect Check clearance and, if necessary, set exactly (very important) Warm up engine and check if it will idle properly If engine stalls, go to B. Trouble in electrical part of injection system. B. Trouble in electrical part of injection system Connect tester 1218 and run through the guide Possible trouble: - Throttle vavle switch incorrectly adjusted - Control unit defective - Pressure sensor defective (too lean) 4. Uneven idle in driving range (Automatic Type 4) Test conditions: - No variation in idle with lever at "N" - Idle speed with engine warm 850-900rpm A. Idling speed regulator incorrectly adjusted Check adjustment and correct if necessary (picture) Note: - Engine oil temperature must be 50C-70C (122-158F) - Regulator must be adjusted with engine running. Adjustment: 1 - Set idle to 850-900rpm. 2 - Apply parking brakd and select driving range. In this condition, idle should be approximately 600-700rpm Play at "a" should be 0.5-1.0mm (0.02-0.04in) (picture) 3 - Adjust play as required on M5 screw (arrow) (picture) (Idling speed regulator - only Type 4/Automatic Transmission) If idle is still uneven, install regulator with softer spring (Production: From Engine No. W 0 105 249) 5. Idle irregular (like misfiring) Test conditions: - Engine warm (50C-70C/122-„"7 Engine running at idling speed A. Inductance from ignition system Check if the injection system wiring is coming into contact with the high tension ignition cables Note: The area near the plug connector for No. 3 cylinder on the Type 4/Wagon is particularly critical. Repair instructions: (picture) 1 - Pull wires off pressure sensor, temperature sensor II (cylinder head) and injectors for cylinders 3 and 4 2 - Route wiring behind fuel line on pressure regulator (see illustration). 3 - Connect wires again. Route wiring so that it is as far as possible from ignition cables If idle is still irregular, go to B. Trouble occurs only when heater is switched on. B. Trouble occurs only when heater is switched on Switch heater off and watch idle If idle is still irregular, go to C. Inductance from some other source. If idle OK when heater is switched off, go to D. Trouble in heater electrical sytem. C. Inductance from some other source Possible trouble: - Powerful radio station in immediate vicinity - Two-way radio on vehicle near engine D. Trouble in heater electrical sytem Possible trouble: - Defective condenser in combustion air blower Replace combustion air blower. 6. Idle too high Test conditions: - Engine warm (50C-70C/122F-158F) - Engine running at idle A. Throttle valve not closing Press throttle valve with thumb to see if it is fully closed and watch idle If idle does not drop, go to B. Adjusting screw out of adjustment. If idle drops, go to C. Throttle valve sticking. B. Adjusting screw out of adjustment Adjust idle by turning screw If idle cannot be properly set, go to D. Auxiliary air regulator not closing. C. Throttle valve sticking Possible trouble: - Throttle controls stiff (accelerator cable or pedal) - Throttle shaft stiff in operation - Throttle valve switch incorrectly adjusted - Throttle valve switch base plate bent D. Auxiliary air regulator not closing Pull regulator hose off at intake elbow and seal with thumb. If idle does not drop: T:Lwake elbow off throttle valve support Close off by-pass drilling with thumb and listen for sucking noises (picture) Possible causes for leaks: - Hoses between intake manifolds and intake air distributor - Intake manifold gaskets - Rubber mountings for injectors - Vacuum hoses Eliminate all leaks found If idle drops, go to E. Auxiliary air regulator defective. E. Auxiliary air regulator defective Type 3/Automatic, Type 4/Manual and Automatic: Run engine and check if there is voltage at connector on auxiliary air regulator If voltage is present, replace auxiliary air regulator If no voltage, check wire to terminal 87 on fuel pump relay and repair Type 3/Manual: Replace mechanical regulator Hope this helps. I am in the process of converting the manual to a web page (unless someone else here already has one ;-) Jay Decker > ---------- > From: Jim Adney[SMTP:jadney@vwtype3.org] > Sent: Monday, April 05, 1999 8:16 PM > To: type3@vwtype3.org > Subject: Re: [T3] FI Idle speed.... > > On 5 Apr 99, at 15:24, Latherow, Robert wrote: > > > Oh my 412...I mean Fastback, the D JETRONIC (Same as the Type 4, > > curiosly enough) isn't idling down on command. > > On the D-Jetronic FI the speed is controlled by the amount of air let > into the intake manifold. The brain then just provides the > appropriate amount of gas to go with it. If your idle is too high > that only means one thing: there is too much air getting in. You need > to find out where the excess is getting in. > > The only leaks that count are those after the throttle valve. Look > > for hoses pulled off, or cracked or throttle valve not closing all > the way. It is common to find many worm gear hose clamps on the large > hoses t> hat connect the intake air distributor to the air runners, but > this is usually a misdiagnosis. Look for something that has really > come loose. > > Jim. > - > ******************************* > Jim Adney, jadney@vwtype3.org > Madison, Wisconsin, USA > **************************iˆiÙ > ------------------------------------------------------------------- > Unsubscribe? mailto:type3-request@vwtype3.org, Subject: unsubscribe >