Mechanics

POOR PERFORMANCE AND STALLING

1983 Volkswagen Rabbit

Engine Performance problem
1983 Volkswagen Rabbit 4 cyl Front Wheel Drive Manual 120000 miles

New fuel pump, fuel pump relay and injectors. Previously the engine would start and run good for about 15 minutes and then stall but always restarted. Now engine does not stall but performance is sluggish.
Car had sat for a few years and am trying to put back in service.
AD
Avatar
Cowpoke
April 22, 2010.



You fail to say you replace the fuel filter, have you checked the condition inside the fuel tank? It may be contaminated by sitting for so long that is why you had to replace the fuel.
AD

Dr Loot
Jun 16, 2010.
Tank is clean and new fuel. Filters and tank fuel pump have been replaced.

Engine starts and runs good for about 15 minutes and then will just die. Starts right back up but then it may die again quickly or run for a short while and then repeat.

Tiny
Cowpoke
Jun 16, 2010.
Here are a few diagnostic procedures that you can do for your performance problem.

TESTING NOTE: Testing procedures described below will apply to all models using the CIS Lambda system unless otherwise noted. Not all models will use all components. PREPARATION FOR TESTING All CIS systems are very sensitive to air leaks. Check condition of rubber boots, hoses, and gaskets. Other areas of leakage are injectors, cold start valve, and PCV system (filler cap and dipstick).
Install a pressure gauge to perform fuel pressure tests. On all models, pressure gauge is installed between the control pressure regulator and the center fitting on fuel distributor. See Fig. 5 .


http://www.2carpros.com/forum/automotive_pictures/307270_Vw_Rabbit_fig_5_1.jpg



To operate fuel pump with engine not running, disconnect fuel pump relay from relay panel. Insert a jumper wire into sockets that correspond to terminals 30 and 87 on relay. See Fig. 6 .


http://www.2carpros.com/forum/automotive_pictures/307270_fig_6_1.jpg



To operate fuel pump turn ignition on. Place pressure gauge as low as possible in engine compartment, then open and close valve 5 times to bleed gauge. Place valve in open position and hang in convenient location. Turn pump off.

AIR/FUEL MIXTURE CONTROL OR AIR-FLOW SENSOR Remove rubber bellows to expose air-flow sensor plate. Disconnect electrical connectors on auxiliary air valve and control pressure regulator, then operate fuel pump for ten seconds to build up control pressure.
Using extreme care not to damage sensor plate, lift sensor plate slowly with magnet or pliers. Constant resistance due to control plunger pressure should be felt throughout range of lift. Release plate slowly, lever and control piston should follow. See Fig. 7 .


http://www.2carpros.com/forum/automotive_pictures/307270_fig_7_1.jpg


Lift plate, then return it rapidly to lower position. The piston moves more slowly and should be heard hitting the lever. If not, control piston is sticking. Remove 3 screws from fuel distributor and lift off of air flow sensor housing. Be careful not to drop control plunger. See Fig. 8 .


http://www.2carpros.com/forum/automotive_pictures/307270_fig_8_1.jpg


Clean plunger in solvent. Remove any deposits with finger nail; DO NOT use tools. Slide plunger in and out while turning it. If any sticking or binding is felt, replace fuel distributor. Reinstall fuel distributor. Check air flow sensor plate alignment. Plate should be even with bottom rim or 0.02" (0.5 mm) lower. If not, bend spring clip to correct, or reposition stop pin (tap lightly with punch). See Fig. 7 . Plate should be centered in housing. If not, loosen center screw and align plate with 0.004" (.1 mm) feeler gauge at four points around rim. Apply Loctite to screw and install and tighten. COLD ENGINE CONTROL PRESSURE TEST Testing must be done on cold engine. Unplug connectors at auxiliary air valve and control pressure regulator. Place valve on pressure gauge in open position and operate fuel pump. Check pressure quickly. Reading should fall in shaded area of graph. Be sure to check air temperature and read correct area of graph. See Fig. 9 . If control pressure is not correct, retest with new control pressure regulator. No servicing is possible.


http://www.2carpros.com/forum/automotive_pictures/307270_fig_9_1.jpg


NOTE:Some models have a control pressure regulator with atmospheric pressure compensation. Pressures may vary slightly on these models. Fig. 9: Cold Engine Control Pressure Test Graphs WARM ENGINE CONTROL PRESSURE TEST Connect plug to control pressure regulator. Leave auxiliary air valve and air flow sensor (if equipped) plugs disconnected. Place valve for pressure gauge in open position and operate fuel pump. After about 5 minutes, pressure should rise to indicated level. See Fuel Injection Pressure Testing table. On models with vacuum hose connected to control pressure regulator, leave hose connected to read pressure. Start engine and allow to idle. Pressure should remain the same or rise slightly. On models with control pressure regulator vacuum line, remove and plug hose. Pressure should drop. If pressure does not reach level specified, disconnect plug at control pressure regulator. Check for voltage across terminals with test lamp or voltmeter. At least 11.5 volts should be present. If not, check wiring. If voltage is present and pressure not correct, replace control pressure regulator.

FUEL INJECTION PRESSURE TESTING Application Specifications: psi (kg/cm2 )
Line Pressure68-78 (4.7-5.34
Warm Control Pressure49-55 (3.4-3.9)
Rest Pressure36 (2.4)
Nozzle Opening Pressure51-59 (3.6-4.1)

SYSTEM (LINE) CONTROL PRESSURE TEST
Close valve on pressure gauge. With engine off, operate fuel pump. Pressure should rise to level specified. See Fuel Injection Pressure Testing table.
If pressure is too low, check fuel pump output. Disconnect fuel return line from fuel distributor and run a hose from fuel distributor to container.
Operate fuel pump and measure output after 30 seconds. See Fuel Pump Output Specifications table. If not as specified, check fuel lines, filter, fuel accumulator, and fuel pump.

FUEL PUMP OUTPUT SPECIFICATIONS
Application30 Sec. Flow Rate: Oz. (cc)
Quantum23 (700)
Except Quantum32 (1000)
If pressure is too high, check for kinked or blocked fuel return line. If lines are clear, system pressure regulator must be adjusted. Turn pump off, loosen return line fitting, and relieve pressure.
Loosen line pressure regulator nut. Remove shims, spring(s) and plunger. Raise system pressure by adding shims; lower pressure by removing shims. Be sure "O" rings are in good condition. If piston is scored or damaged, fuel distributor must be replaced. See Fig. 10 .


http://www.2carpros.com/forum/automotive_pictures/307270_fig_10_1.jpg


COLD START VALVE, THERMO-TIME SWITCH & HOT START PULSE RELAY
If engine coolant is below 85 °F (30 °C), disconnect plug on cold start valve and connect test lamp across terminals. Remove coil high tension wire to prevent starting. Operate starter.
On models without hot start pulse relay, test lamp will light for several seconds, then go out. On models with relay, lamp will continue to flash off and on.
If lamp does not light, test thermo-time switch for continuity below opening temperature. If good, check wiring to starter terminal.
Remove cold start valve from manifold but leave fuel line connected. Place valve in a container. See Fig. 11 . Connect a jumper wire from one terminal to ground, and from other terminal of cold start valve to a switch. The other side of switch should be connected to a source of battery voltage.
CAUTION: Do not connect wire directly to battery. Extreme fire danger is probable due to atomized fuel. Sparks may result if wire is touched to battery.
Operate fuel pump. Turn switch to "ON" position. Cold start injector should spray. Turn switch "OFF", but leave fuel pump running. Injector should not spray. Wipe off nozzle and check for leakage. With pump running, no drops should form within one minute.


http://www.2carpros.com/forum/automotive_pictures/307270_fig_11_1.jpg


Replace cold start valve if faulty. Install original valve if good, making sure that "O" ring is properly positioned.
FUEL INJECTORS
Remove injectors but leave hoses connected. Place injectors in individual measuring containers. With sensor plate in idle position, connect jumper wire in place of fuel pump relay.
Disconnect fuel pump when measuring container with highest level of fuel reaches specified capacity. See VW & Audi Fuel Injector Specificationstable.
Compare amounts of fuel in measuring containers. Fuel should not vary by more than specified amount. Repeat test with sensor plate in full throttle position.
VW FUEL INJECTOR SPECIFICATIONS
Application Fuel Capacity: Oz. (cc)
Idle.58-.78 (17-23)
Full Throttle2.43-2.98 (72-88)
AUXILIARY AIR VALVE
Disconnect hoses from auxiliary air valve. Use a mirror and small flashlight to inspect valve. See Fig. 13 . At room temperature, valve should be slightly open. If equipped, disconnect wires from air flow sensor. With ignition switch "ON" valve should cover opening within 5 minutes.


http://www.2carpros.com/forum/automotive_pictures/307270_fig_13_1.jpg



http://www.2carpros.com/forum/automotive_pictures/307270_fig_12_1.jpg


If valve does not operate properly, check for power at connector with engine running. Connect a test lamp across connector terminals. If lamp does not light, check fuse and wiring.
If lamp lights, check resistance of auxiliary air valve. If no resistance is measured, valve is defective. Ensure electrical connections are tight and terminals are clean, prior to measuring resistance.
LAMBDA CONTROL SYSTEM CHECKS
PREPARATION FOR CHECKS
NOTE: The frequency valve is operated by pulsating voltage from the electronic control unit. By measuring this signal, certain functions of the system can be tested. A special tester (Bosch KDJE 7453) is recommended, but a high-quality dwell meter may be used instead.
Connect dwell meter to testing connector. Connector is located on behind throttle valve housing (Black/White wire).
Set meter on 4-cyl. scale. Connect positive lead of voltmeter to battery and negative lead to pin 3 of diagnostic plug.
Start engine and run until warm. Disconnect oxygen sensor and observe meter needle (should not fluctuate). Place a piece of tape on meter face to indicate 50% position.
OPERATION CHECK
Remove fuel pump relay and connect jumper wire across sockets corresponding to terminals 30 and 87. If equipped, remove plug at air flow sensor. Turn ignition "ON".
Frequency valve should operate, making a buzzing noise. Dwell meter should indicate 45-65 °. Disconnect wire from oxygen sensor and touch wire end to ground. Readings on dwell meter should rise. Ground one end of a 1.5 volt flashlight battery, and touch positive end to sensor wire. Readings should drop to less than 15 °.
On models with throttle enrichment switch, operate throttle. Readings should be higher at idle or wide open throttle. See Fig. 13 .
If valve does not operate properly, check for power at connector with engine running. Connect a test lamp across connector terminals. If lamp does not light, check fuse and wiring.
If lamp lights, check resistance of auxiliary air valve. If no resistance is measured, valve is defective. Ensure electrical connections are tight and terminals are clean, prior to measuring resistance.
LAMBDA CONTROL SYSTEM CHECKS
PREPARATION FOR CHECKS
NOTE: The frequency valve is operated by pulsating voltage from the electronic control unit. By measuring this signal, certain functions of the system can be tested. A special tester (Bosch KDJE 7453) is recommended, but a high-quality dwell meter may be used instead.
Connect dwell meter to testing connector. Connector is located on behind throttle valve housing (Black/White wire).
Set meter on 4-cyl. scale. Connect positive lead of voltmeter to battery and negative lead to pin 3 of diagnostic plug.
Start engine and run until warm. Disconnect oxygen sensor and observe meter needle (should not fluctuate). Place a piece of tape on meter face to indicate 50% position.
OPERATION CHECK
Remove fuel pump relay and connect jumper wire across sockets corresponding to terminals 30 and 87. If equipped, remove plug at air flow sensor. Turn ignition "ON".
Frequency valve should operate, making a buzzing noise. Dwell meter should indicate 45-65 °. Disconnect wire from oxygen sensor and touch wire end to ground. Readings on dwell meter should rise. Ground one end of a 1.5 volt flashlight battery, and touch positive end to sensor wire. Readings should drop to less than 15 °.
On models with throttle enrichment switch, operate throttle. Readings should be higher at idle or wide open throttle. See Fig. 13 .
If valve does not operate properly, check for power at connector with engine running. Connect a test lamp across connector terminals. If lamp does not light, check fuse and wiring.
If lamp lights, check resistance of auxiliary air valve. If no resistance is measured, valve is defective. Ensure electrical connections are tight and terminals are clean, prior to measuring resistance.
LAMBDA CONTROL SYSTEM CHECKS
PREPARATION FOR CHECKS
NOTE: The frequency valve is operated by pulsating voltage from the electronic control unit. By measuring this signal, certain functions of the system can be tested. A special tester (Bosch KDJE 7453) is recommended, but a high-quality dwell meter may be used instead.
Connect dwell meter to testing connector. Connector is located on behind throttle valve housing (Black/White wire).
Set meter on 4-cyl. scale. Connect positive lead of voltmeter to battery and negative lead to pin 3 of diagnostic plug.
Start engine and run until warm. Disconnect oxygen sensor and observe meter needle (should not fluctuate). Place a piece of tape on meter face to indicate 50% position.
OPERATION CHECK
Remove fuel pump relay and connect jumper wire across sockets corresponding to terminals 30 and 87. If equipped, remove plug at air flow sensor. Turn ignition "ON".
Frequency valve should operate, making a buzzing noise. Dwell meter should indicate 45-65 °. Disconnect wire from oxygen sensor and touch wire end to ground. Readings on dwell meter should rise. Ground one end of a 1.5 volt flashlight battery, and touch positive end to sensor wire. Readings should drop to less than 15 °.
On models with throttle enrichment switch, operate throttle. Readings should be higher at idle or wide open throttle. See Fig. 13 .

Dr Loot
Jun 16, 2010.
If engine is cold, enrichment switches will be closed. Disconnect lead at temperature sender. Readings should drop slightly. If engine is hot, connect temperature sender lead to ground. Reading should rise. ,
If starter enrichment relay is used, disconnect high tension lead at coil and crank engine. Readings should rise above normal level. If vacuum switches are used, apply vacuum to switch and note readings. Level should be higher with switch closed, and lower with switch open. ,
Connect oxygen sensor and start engine. With cold engine, dwell reading should be stable. When engine warms up, meter needle should fluctuate 10-20 °. It may be necessary to run engine faster than idle to heat oxygen sensor and cause needle fluctuation. ,
Fig. 13: Bosch CIS Lambda Electronic Control Unit Wiring Diagram,
Connect a CO meter to exhaust test point. With oxygen sensor disconnected, reading should be stable on dwell meter. Note CO% reading. With sensor lead grounded, reading should rise and CO% increase. With lead connected to flashlight battery, reading and CO% should decrease. ,
If dwell reading does not rise with sensor grounded, check sensor wiring (see "Electrical Testing"). If wiring is good, replace control unit. If dwell rises, but CO% does not, check frequency valve and wiring see Electrical Testing. Replace if necessary. ,
If dwell does not decrease with battery connected to sensor lead, check sensor wiring and replace control unit if wires are good. If dwell decreases but CO% does not, check frequency valve wiring and replace valve if wiring is good. ,
Adjust CO% to rich level (3%) with oxygen sensor still disconnected. Reconnect sensor. Reading should drop at least 1%. If not, replace oxygen sensor.
ELECTRICAL TESTING
NOTE:Electronic control unit is located near glove box.
Locate electronic control unit and press locking tabs back to disconnect connector. All connectors are wired with pin numbers in the same location. Obtain a high-quality volt-ohmmeter for testing.
Refer to wiring diagram for pin locations. With ignition "ON" and fuel pump jumper wire in place, check for battery voltage at terminals 8 and 15. Connect ground lead of voltmeter to terminals 5 and 16 while checking for battery voltage to ensure these wires make a good ground connection.
If battery voltage is not available at terminal 8, check Lambda and fuel pump relays. If no voltage at 15, check frequency valve connector. One wire should have battery voltage; the other wire should have continuity to terminal 15. Frequency valve should have 2-3 ohms resistance. Repair or replace as necessary.
Fig. 14: Throttle Enrichment Switches
Disconnect oxygen sensor and check for continuity between sensor lead and terminal 2 (4 on Mercedes-Benz). No continuity should exist between ground and lead wire.
All models use enrichment switches. See Fig. 14 . All switches provide continuity to ground when switch is closed. Actuate throttle to test throttle switches.
Thermal switches can be checked by removing switch and heating in water. Repair wiring or replace switches as necessary.
After testing is completed, connect electronic control unit, oxygen sensor, and all switches. Remove fuel pump relay jumper wire and testing equipment.


http://www.2carpros.com/forum/automotive_pictures/307270_fig_14_1.jpg


MIXTURE CONTROL UNIT
CAUTION: On all models, disconnect battery and relieve fuel pressure before removing component parts.
On most models, top of mixture control unit must be removed to extract mixture screw plug or steel ball which blocks access opening. Tap plug or ball out with a pin punch.
Clean around all fuel line connections. Remove fuel lines and wipe up any spilled fuel. Disconnect electrical wiring and remove rubber boot to manifold. Remove Allen screws and lift off mixture control unit.
To install, reverse removal procedure. Replace gaskets and seals and check for leaks after installation.
FUEL DISTRIBUTOR
Remove mixture control unit. Remove 3 screws from top of fuel distributor. Lift off carefully, ensuring that plunger does not fall out of distributor.
Only pressure regulator shims may be replaced. If plunger or piston is scored, replace fuel distributor. Be sure "O" ring is in place and in good condition when replacing unit.
CONTROL PRESSURE REGULATOR
Disconnect electrical plug and vacuum lines (if equipped). Remove fuel lines and wipe up any spilled fuel. Remove bolts and regulator. To install, reverse removal procedure.
AUXILIARY AIR VALVE
Remove and plug hoses. Disconnect electrical plug. Remove mounting bolts and air valve. Reverse removal procedure to install.
COLD START VALVE
Remove electrical connector and fuel line. Loosen mounting bolts and remove cold start valve. Check "O" ring and replace if necessary. Install valve.
FUEL INJECTORS
Clean area around valves. Hold valve secure and remove fuel line fitting. Do not allow valve to turn.
Remove retaining plate if present, and pull valves out carefully. Do not remove insulator sleeve, if possible.
To install, reverse removal procedure. Replace "O" rings and lubricate with a drop of oil. Place injectors in sleeve and press until seated. Tighten fuel lines and check for leaks.
THERMAL SWITCH
Drain coolant below level of switch. Be careful not to damage connectors on switch while removing. Coat threads of sensor with sealant and reinstall.
FREQUENCY VALVE
Disconnect electrical connector. Hold small nut at hose and loosen larger valve nut. Do not spill gasoline on rubber mounting insulator as it will cause the rubber to swell.
Remove return lines at fuel distributor and/or control pressure regulator. To install, reverse removal procedure, using new gaskets. Check for leaks after installation.
ELECTRONIC CONTROL UNIT
Disconnect plug from control unit beneath glove box. Remove mounting bolts and control unit. To install, reverse removal procedure.
NOTE: Removal and installation procedures were not available for other models.
OXYGEN SENSOR
Disconnect wiring from sensor. On Porsche 911SC, remove left rear wheel and protector plate. Remove shield from sensor if equipped. Remove sensor.
Coat threads of new sensor with anti-seize compound. Take care not to get compound into slots on end of sensor. Install sensor and tighten to 25-30 ft. lbs. (35-41 N.m). Refit shield and connect sensor wire.
That should keep you busy for a while make sure you check all systems that they are working properly.

Dr Loot
Jun 16, 2010.
All Bosch CIS injected VWs that sit for too long wind up with this symptom. The culprit is almost always a bad ground connection or a bad Oxygen sensor relay that affects the power supply to the Lambda valve, or frequency valve, -or in later models the differential pressure actuator valve. All these valves are located on the side, or near the side of the fuel distributor. You can identify the type you have by shape. The Lambda or frequency valve is round with fuel lines coming from each end. It looks a lot like a small electric-pulsed type fuel injector. The differential pressure actuator valve is square shaped and is attached to the side of the fuel distributor.

The frequency valve makes a loud, distinct buzzing noise when operating correctly. If you are not certain it's running, place a long handled screwdriver against it and listen by placing the handle to your ear. You should hear a clear BUZZZZZ! If yours is quiet, that's your problem. This presents as a symptomatic rough idle with stalling on rev-up of the engine or acceleration of the car. Basically you can't load the engine at all. The car will start and barely run but it's not drivable. This problem is typically due to a bad relay or electrical connection. First check for a faulty oxygen sensor relay, then check for bad ground connection where the ground wires attach to the intake manifold near the "cold-start" fuel injector valve. There are usually two sets of brown wires that attach here. Pull each and clean. Test for continuity. Most of the problems I fix are right there. Finally, pull the electric connection at the frequency valve and use a multimeter to check for voltage on one of the two connectors in the harness. That connector is VERY HARD to remove, as the wire retaining clip is difficult to release. Be careful and don't break it. So. If you have voltage in one of the harness connectors, next check the frequency valve windings for resistance. Correct resistance is 2 to 3 ohms. Any other reading means bad frequency valve.

Troubleshoot of the differential pressure actuator valve is similar, please refer to Bently manual.

Tiny
Bruce Vandiver
Mar 29, 2011.

AD