2.0l 16v problems when hot

[Dandan62 10]

I'm having one last go at solving this on my son's car. Hoping someone has solved a similar issue.

Car starts and runs perfectly when cold. When the water temp reaches 80 degs small idle surges start happening. This becomes rough running. Once up to full temp he says its almost undrivable. The engine will run ok at high revs but is too erratic to drive normally. When sitting at idle at full temp it runs rough but with occasional moments of smooth running for a few seconds. Have wiggled everything to check for obvious poor connections etc.

Replaced Lambda, isv, coil, all leads. Checked plugs. Checked and repaired all air leaks. There were some solits in the air intake. Checked maf. Checked mixture, timing.

Next thing to try i think is the wiring for the lambda. Do the wires go straight to the ecu? If so what pins on the plug so i can check continuity.

Any ideas other than that?

Cheers

[easypops 8]

ISV Idle Stabilisation Valve plus the Throttle Potentiometer.

The ISV gets clogged up and can possibly be revived with a bit of cleaning/lubrication. Many years ago i had a similar issue eventually tracked(by luck) to the wiring plug for the throttle potentiometer.

Plenty written on this issue previously but the lack of pictures might make some of the old threads a bit useless

[easypops 8]

http://www.the-corrado.net/showthread.php?35823-16v-Kangaroo-fixed-Worth-a-KB-piece&highlight=kangaroo

 

http://www.the-corrado.net/showthread.php?37235-Another-2l-16V-idle-problem&highlight=16v+idle+problem

[Dandan62 10]

Thanks very much. Isv is new and have checked for broken wires on the tps as that is a common problem. I think the sensor must be ok as all is good up to 80 degs . All good suggestions though . Thanks.

[Keyo 47]

At this point I would call Vince at Stealth racing and have a chat.

[Dox 22]

When running rough you could pull each lead off in turn to see if it’s cylinder related?

 

A good cylinder would see the idle worsen

Edited October 29, 2019 by Dox

[Simeon 0]

Got to be temperature related right, so old wiring breaking down when it gets hot, or a temp sensor. Can't remember what the temp sensors are on the KR, but think there's three on the side of the head that often cause probs? Google it and see.

 

Might be worth un-wrapping the engine loom and cleaning it up looking for breaks/damage etc.

 

You say you've checked the timing, but do you mean static or dynamic? Have you put a light on it to see what the timing is doing when it is idling rough? When was the cam chain last changed? Could have stretched causing issues if it's a high miler.

 

No guarantee on 'new' ISVs in my experience either, best thing you can do is test it on another vehicle if there's another 16v owner in your area

[vw rule 19]

To be honest this could be anything from electrical including distributor or fuel system.

 

Have you checked the thermal transmitter also known as the coolant temperature switch, as they can break up/burn out and cause the engine to flood from cold, or can cause problems once engine is up to running temperature.

I think the Lambda sensor is partly on the same circuit as the fuel governor/pressure regulator, and coolant temperature switch.

 

A faulty hall sensor in distributor can cause running issues, which also can be heat related i.e up to running temperature, plus the ECU needs to see correct signal from hall sensor, as it confirms the engine is rotating, and I think sends pulse signals to coil.

Have you checked condition of distributor cap and rotor arm ?

 

The ECU has a connector plug with 35 terminal pins, terminal 12 is to fuel relay, terminal 7 is to Lambda sensor I think, which is also linked in circuit to the fuel governor/pressure regulator.

 

 

Si

[Dandan62 10]

Thanks. Lots of useful info. Going to go down the temp sensor road. Only 2 by dizzy. Think one is fan sensor. One to guage? Also one bolted to top left of engine. Also will check wiring from new lambda now i have some pin numbers. I have stopped him just buying stuff hoping it will fix it. Trying to be more methodical. New dizzy cap, rotor, coil and leads. Pulling each plug lead makes no odds so pretty sure its fueling so ecu getting wrong into from somewhere. He's now bought a cheap car to keep him going and takes time pressure off sorting it.

[vw rule 19]

Thanks. Lots of useful info. Going to go down the temp sensor road. Only 2 by dizzy. Think one is fan sensor. One to guage? Also one bolted to top left of engine. Also will check wiring from new lambda now i have some pin numbers. I have stopped him just buying stuff hoping it will fix it. Trying to be more methodical. New dizzy cap, rotor, coil and leads. Pulling each plug lead makes no odds so pretty sure its fueling so ecu getting wrong into from somewhere. He's now bought a cheap car to keep him going and takes time pressure off sorting it.

 

Right ok I think sensors in back of head under the distributor, the 2 pin connector one is coolant temperature switch, the small temp sender with the 1 wire is for your temperature gauge.

 

Small temp sender in side of head on exhaust side at the top right around the back, (on right side if looking at engine head on) is for oil temperature, again only has the one wire.

 

The temperature sensor attached to front of valve cover near cam belt/ air filter area, is the fan over run sensor normally has a yellow stripe around centre of sensor, it monitor's heat still trapped in engine bay once parked up, tells radiator fan to come on every minute or 2 untill heat reduced in engine bay.

 

Si

[Dandan62 10]

Excellent info. Will start with coolant sensor. I know that just unplugging it makes no difference.

[Dandan62 10]

Confused by these sensors. I'm reading that the 2 pin one is the radiator fan switch. The fan comes on correctly when hot so I'm assuming its giving the correct reading. Is it also communicating with the ecu?

[vw rule 19]

Confused by these sensors. I'm reading that the 2 pin one is the radiator fan switch. The fan comes on correctly when hot so I'm assuming its giving the correct reading. Is it also communicating with the ecu?

 

There's a 4 pin fan sensor in bottom left of radiator that's the main fan sensor, then the over run temp fan sensor with one wire, is attached to front left of valve cover.

 

The coolant temperature switch is the one with the 2 pins, this is the one that should communicate with the ECU.

I'm not aware of the coolant temp switch being partly connected to the radiator fan, they're usually independent I suppose it's possible it could send a trigger signal.

I'll have to check the wiring diagrams this evening after work.

 

Q: What are you reading from another manual ?

 

Si

[Dandan62 10]

That makes sense. I've read so many threads elsewhere on this. Your reply answers this perfectly. Many thanks. First thing I'll check next weekend. Cheap part at least! Will check resistance first.

[vw rule 19]

That makes sense. I've read so many threads elsewhere on this. Your reply answers this perfectly. Many thanks. First thing I'll check next weekend. Cheap part at least! Will check resistance first.

 

The resistance reading should be high when temperature is cold, then drop down as temperature increases.

 

All the Bentley manual says is at 50°c should read approx between 700 & 900 ohms,

then at 90°C should read approx 200 to 300 ohms.

If the coolant temp switch is cold or temperature is 0°C then ohms reading will be a lot higher.

 

The Bentley manual says if readings are different i.e not in above range at 50°C and 87-90°C then coolant temp switch is faulty.

 

Si

Edited October 31, 2019 by vw rule

[Dandan62 10]

Thanks. I've only ever tested single pin ones before. Body of sensor to either pin to get resistance? Sorry. Probably a basic question!

[vw rule 19]

Thanks. I've only ever tested single pin ones before. Body of sensor to either pin to get resistance? Sorry. Probably a basic question!

 

Normally check across/between the 2 pins.

 

Si

[vw rule 19]

Q: is there plenty of water in the coolant expansion bottle, is your oil level ok ?

Only asking as the head gasket can sometimes fail across two cylinders, but you won't have any problems untill it's up to running temperature.

 

You can check/test compressions with compression tester, first when engine is cold, then when it's hot.

I've had this before on a VW Passat years ago.

 

Have you checked the valve timing ?

As that can cause weird running issues.

 

Are the exhaust fumes popping/banging when exiting exhaust tail pipe, is it smoking at all ?

 

Is there a strong rich smell of fuel ?

 

Si

[Dandan62 10]

Hi. Head gasket good. Was my first thought. Timing all good too. Runs beautifully cold. No fumes when rough.

[vw rule 19]

Hi. Head gasket good. Was my first thought. Timing all good too. Runs beautifully cold. No fumes when rough.

 

Ok so possibly could be electrical,

you could like I say try a replacement coolant temperature switch, or have you tested it ?

 

Test values should be I think:

 

Cold = 0°C to 3°C

9000ohms to 8000ohms but should start dropping down once temperature increases.

 

Hot = 80°C to 87°C

250ohms to 175ohms

 

Si

[vw rule 19]

Some more info here if needed from the Bentley manual for the 9A eng code.

 

 

Spark plugs (normally tripple electrode)

can cause none start or rough running.

 

HT leads (cause misfire under load)

 

*********

Distributor (none start & misfire)

Also you could check your hall sensor.

The hall sensor has a 3 terminal/pin plug on side of distributor.

 

1 is earth (-)

2 is possibly the trigger/signal

3 is live (+)

 

Using your multimeter again set at 20v DC check across/between terminals 1 & 3 ideally you should have 9v to 12v here with ignition on.

If no voltage is found then do continuity test below.

 

Looks like terminal 3 of hall sensor is partially linked to terminal 30 of ECU,

as it says check for continuity with ignition off between these two terminal/pins.

 

Terminal 1 of hall sensor is earth connection goes back in ECU main wiring loom

 

Terminal 2 of hall sensor is trigger/signal is linked to terminal 30 of ECU

 

Terminal 3 of hall sensor is linked to terminal 21 of ECU

i.e as live feed to hall sensor.

***********

 

Distributor cap (none start & rough running)

 

Rotor arm (none start & rough running)

 

Pickup sensor (normally on HT lead n.o 4)

 

Ignition timing = affects idle & rough running if set wrong.

Should be set at 6° +or- 1°

idle speed 800rpm to 1000rpm

1990 onwards

 

Knock sensors = engine can be down slightly on power or slight misfire.

Terminal 27 and 29 when using multimeter should see 1.5 ohms according to Bentley manual, I think with knock sensor connector plugs still plugged in.

If no readings or don't match 1.5 ohms possible there's a break in wiring from ECU or sensor/s are dead.

 

Ignition coil/coil pack.

so on the coil at the live end you should see where the HT King lead is attached.

Each side of this there should be two terminal contacts.

1 = - (minus)

15 = + (positive)

With a multimeter set to 20v DC put the meter across/between these two, you should see 2v for a few seconds with ignition on.

 

Ignition module control unit.

I think this has a 7 terminal/pin connector plug.

This unit is normally close to coil but on the back of bulkhead same side as wipers, possibly under plastic tray.

Or it could be right beside coil on a alloy heat plate.

 

Terminal 2 (-) earth

and

terminal 4 (+) I think goes to terminal 15 on coil.

check with multimeter pins 2 & 4 you should have 12v DC with ignition on.

 

If showing no power to coil or ignition module then could be a broken wire / wiring fault somewhere.

 

Si

Edited October 30, 2019 by vw rule

[vw rule 19]

Fuel system according to the Bentley manual

 

Coolant temperature switch = can cause none start & rough running when cold or hot.

Check terminals 3 and 35 on ECU for coolant temp switch with plug attached to sensor,

cold 8000ohms + or -

hot 200ohms + or -

According to Bentley manual

 

*********

Air flow meter/sensor = cause none start & rough running.

Check terminals 26 & 23 on ECU = air flow sensor plate at rest position = should see 5000ohms + or -

If no readings then possible break in wiring to air flow sensor.

 

Also check terminals 26 & 35 on ECU = air flow sensor plate at rest position = should see 4000ohms + or -

If no readings then possible break in wiring to air flow sensor pin 3 or break in earth wire from ECU i.e terminal 35

 

Air flow meter sensor.

This sensor has a 3 terminal/pin connector plug.

 

1 = live (+)

2 = possibly the trigger/signal

3 = earth (-)

 

Again check you have power to this sensor.

 

Terminal 1 of air flow sensor is linked to

terminal 26 of ECU.

 

Looks like terminal 2 of air flow sensor is linked to terminal 23 of ECU.

 

Terminal 3 of above sensor says is earth connection goes back in ECU main wiring loom.

 

Also in the Bentley manual it says it's possible to check condition of the air flow sensor, with a multimeter set at 20 Volts DC

 

Switch ignition on and check voltage between terminals 1 (+) and terminal 3 (-)

reading should be 4.35v to 5.35v for input voltage if the voltage is not in above range or no readings then possible wiring fault.

 

NEXT switch ignition off and connect the multimeter between terminal 2 (signal pin) and terminal 3 (-) now start engine and allow to idle for at least 2 to 3 minutes, the output voltage should drop to 0.7v to 0.9v if not in range this can cause running issues.

 

The Bentley manual states the output range can be adjusted, BUT ONLY IF OUT OF RANGE as the air flow sensor/metering head is set up at the factory when car was new.

 

*************

 

differential fuel pressure governor/regulator.

This item is on the fuel metering head, attached to the front side facing the alternator pulley of air filter box,

it's normally got a thick plastic cover protecting it.

It says the pressure regulator is held in place by two ANTI MAGNETIC BOLTS, so I presume not to cause any interference,

as this sensor receives variations in resistance flow, from ECU via throttle response and air flow meter sensor plate,

plus signal from coolant temp switch.

 

Again you need to check this pressure regulator is working,

looks like you do this by checking the resistance flow via the 2 terminal/pin connector plug.

 

Or by terminal/pin 4 and terminal/pin 5 of the main 35 pin ECU harness lead.

 

Resistance readings should be 15 to 20 ohms

 

Also it says the pressure regulator/governor if found to be faulty CAN NOT BE REPAIRED as it's a sealed unit.

 

Si

Edited October 31, 2019 by vw rule

[vw rule 19]

9A ECU has 35 terminal pins on ECU and wiring harness plug.

 

(Main power to ECU is terminal/pin 19) 1.5mm red wire,

you should have 12v DC here when ignition is switched on,

and still when key is turned to crank engine.

If no power then check fuses, just in case.

 

(Earth points for ECU is

terminal/pin 35)

1mm brown wire,

looks like this is the main earth for unit. This earth goes through ECU wiring harness/loom possibly to fuse box.

This wire changes colour in harness/loom or from fuse box, (changes to 1mm brown/white wire) and goes to valve cover at the back on the right in engine bay,

close to where the distributor is. Should be a small rectangle bracket with 1 or 2 threaded stud/s, there are several earth wire's bolted to it to ground.

 

Si

[Dandan62 10]

Lots of great info from everyone. Looks like its a weekend with a multimeter. Will report back. Many thanks everyone.

[Dandan62 10]

Did a check on the coolant temp sensor ( 2 pin connector to left of dizzy. 2300 ohms at room temp. 400 ohms sitting in freshly boiled water. So its working but a bit out of range maybe?