93 VR6 intermittently cutting out and intermittently not starting

[GreenRado 10]

This problem has been getting becoming slowly more apparent.

She sometimes will crank endlessly with no actual start, happens cold or warm, although happens less when cold. Other times she starts up right away. Idle is fine at all times and engine pulls well through rev range.

She is also intermittently cutting out, sometimes at a stop, sometimes at speed. Sometimes within a few seconds, sometimes a few minutes, sometimes a good drive. It takes a few seconds to actually cut out and when this happens she will still crank fine, but won't start for a good 5-10 mins.

 

Vagcom shows no faults at all and all readings I can get off the engine when she does run look on point. Very new spark plugs, ht leads and battery.

Battery light has been on for a while, but confirmed alternator putting out ~14v when engine running and battery reading 12.8v when engine off. I'm inclined to believe the battery light is on from the alternator's voltage regulator, which I haven't replaced yet (alternator is 120amp).

 

Could these things be related?

 

What should I check?

[robrado974 1]

I would start with the fuel . Change the filter and make sure you have no problems there . Leave it running or drive locally . Take a tool kit with you . When it cuts out , remove the fuel lines to check fuel is present . Be careful ,if there is fuel it will be under pressure , so protect your eyes . If all is ok , you may need to check the spray pattern in the injectors . This is obviously a bit more complicated . Next . Everything electrical from the ECU , down the the fueling and ignition system needs to be checked . I would unplug one at a time , spray them with electrical contact cleaner and plug back in , checking for corrosion and any faulty wires . I would also have a look at your ignition switch , alarm / immobiliser . Also when it cuts out , remove a lead and connect a spark plug and lay it on the block , you will then see if you have a spark on cut out . All you need for a car to run is a spark and fuel . So if both are present, it may point to a faulty immobiliser .

All the best , hope this helps .

Rob

Edited July 19, 2015 by robrado974

[GreenRado 10]

I would start with the fuel . Change the filter and make sure you have no problems there . Leave it running or drive locally . Take a tool kit with you . When it cuts out , remove the fuel lines to check fuel is present . Be careful ,if there is fuel it will be under pressure , so protect your eyes . If all is ok , you may need to check the spray pattern in the injectors . This is obviously a bit more complicated . Next . Everything electrical from the ECU , down the the fueling and ignition system needs to be checked . I would unplug one at a time , spray them with electrical contact cleaner and plug back in , checking for corrosion and any faulty wires . I would also have a look at your ignition switch , alarm / immobiliser . Also when it cuts out , remove a lead and connect a spark plug and lay it on the block , you will then see if you have a spark on cut out . All you need for a car to run is a spark and fuel . So if both are present, it may point to a faulty immobiliser .

All the best , hope this helps .

Rob

 

Forgot to mention filter is also fairly new (fitted before these problems started though). Should I just check for fuel at the bleeder valve on the fuel rail? I'll have to have a look into how involved the injectors are, never done anything with them before. Ignition switch was replaced less than 1k ago and recently had a look at it to make sure connection is tight. Will have a look at the electricals where you said. Is there a specific colour spark I need to look for when checking spark?

 

Thanks for the detailed suggestions :)

[fla 9]

Change ecu relay 109, check and clean the MAF. Also clean and lube the isv.

If you can, borrow a working crank sensor. These are around £100 new so you don't want to change it in a rush!

[robrado974 1]

As Fla said. Regarding the fuel , remove the fuel line from the rail . As for the colour of a spark I'm not sure , as long as it's healthy and nice and bright it should be ok .

[Jim Bowen 1]

Worth checking the wiring behind/under the battery. Is an earth point there and the wiring can also corrode there.

[GreenRado 10]

Getting fuel at the rail and all ht leads giving spark.

 

Change ecu relay 109, check and clean the MAF. Also clean and lube the isv.

If you can, borrow a working crank sensor. These are around £100 new so you don't want to change it in a rush!

 

I took the casing off relay 109 and it looks like new with solid connections etc. Should I still replace it?

MAF and ISV already cleaned up last month (this won't have changed as I only drive her once a week at most.)

 

I originally thought about the crank sensor, but resistance is within 500-700 and I gave it a clean anyway. Wouldn't a faulty one always give a code?

 

Worth checking the wiring behind/under the battery. Is an earth point there and the wiring can also corrode there.

 

I'll check those points in the morning :)

[GreenRado 10]

Weirdly haven't had a single cut out while performing tests (plenty of revving, although she hasn't been driven anywhere).

 

Earth behind battery is good.

 

Does anyone know what resistance the coil pack should have if I test it?

Or is the coilpack fine as long as I'm getting spark on all leads?

 

Besides the injectors is there anything else I should check?

Wouldn't the MAF be throwing codes if it has problems?

[fla 9]

The crank sensor wont show an error on VAGCOM.

Also, pulse the relay with a 12v source and then hold the power on it to see if there is any 'chatter'. That will tell you whether is duff or not.

 

As its a cheap item i would replace it for peace of mind. For such a small device it is incredibly influential on smooth running!

[lee55233 0]

The crank sensor wont show an error on VAGCOM.

Also, pulse the relay with a 12v source and then hold the power on it to see if there is any 'chatter'. That will tell you whether is duff or not.

 

As its a cheap item i would replace it for peace of mind. For such a small device it is incredibly influential on smooth running!

 

Check relays are seated well in the fuse tray by bending the blade contacts out a little, worked for mine

[robrado974 1]

Bear in mind if you do vagcom the car , the crank sensor will show as a fault if the car is not running .

[GreenRado 10]

Bear in mind if you do vagcom the car , the crank sensor will show as a fault if the car is not running .

 

Yeah I was aware of that already, luckily!

 

New relay 109 has made no difference :(

 

Can't get hold of a crank sensor to test with unfortunately either.

Might have another go testing its resistance, but I've heard even when they are duff they can show good numbers...

[robrado974 1]

Personally , I think the crank sensor gets a lot of blame when a Corrado fails to start or whatever the circumstances . They rarely fail in my opinion. Yes they are in a vulnerable position , where they are situated and are prone to getting a lot of crap on the plug . But a good clean of the plug and they should be fine .

[GreenRado 10]

Well through doing all these tests etc she hasn't stalled out once, with plenty of revving (but no actual driving for fear she will leave me stranded).

 

So I'm not sure if the problem has been rectified or not.

 

Personally , I think the crank sensor gets a lot of blame when a Corrado fails to start or whatever the circumstances . They rarely fail in my opinion. Yes they are in a vulnerable position , where they are situated and are prone to getting a lot of crap on the plug . But a good clean of the plug and they should be fine .

 

I gave the sensor a thorough clean and by the looks of it the sensor isn't original, so I'd lean away from that being a problem more so.

 

Not sure where to go from here, besides just braving a trip out to see what happens...

[fla 9]

Make sure where the sensor bolts to the block is nice and clean and free from any corrosion

[GreenRado 10]

Grabbed a decent multimeter today as my cheapo one seemed to be giving weird readings/no readings etc.

 

Tested the resistance of the crank sensor and it's actually in the 100-200 range, sometimes below 100.

So I take it that its knackered? From what I understand its meant to read between 500-700.

[robrado974 1]

I have a crank sensor , that I believe to be in working order . Your welcome to borrow it .I can send it to you , to see if it makes a difference . I can't remember the cost of the new one I bought ,I do have the receipt for it in my folder . At least it should rule out weather your one is shot or not . Let me know if you need it .

Rob

Edited July 25, 2015 by robrado974

[GreenRado 10]

I have a crank sensor , that I believe to be in working order . Your welcome to borrow it .I can send it to you , to see if it makes a difference . I can't remember the cost of the new one I bought ,I do have the receipt for it in my folder . At least it should rule out weather your one is shot or not . Let me know if you need it .

Rob

 

That is a really kind offer!

 

I've spoken to enough people about the resistance reading now to confirm its definitely knackered, so I've ordered a new one.

 

Thanks again!

[robrado974 1]

Hope it sorts the problem bud .

[GreenRado 10]

New Crank sensor arrived and fitted.

 

No change in behavior, although she does seem to idle even better and settles quickly from cold which is something I suppose.

 

So still no good. Started her up on drive and after 15 minutes (revved her a couple times during this) she just stalled out and wouldn't start again.

Meant to be taking her to Volksfest Wales on Sunday which can't happen if she's still doing this :(

 

 

To re-cap:

New battery, new starter, all earths and connections checked and looking good. Alternator also putting out 13.5-14V when running.

ISV cleaned and also damper box deleted (problem occurred before I did this though.) MAF cleaned.

Fuel is at rail, changed relay 109 anyway, new fuel filter.

New HT leads (Magnecor) and NGK spark plugs with confirmed spark on all leads.

Coil pack looks OK although cracks have formed on the plastic casing which have I've sealed.

Ignition switch is new.

No codes on VAGCOM, but my battery light has been on for ages (charge level is good, think it's from Alternator Voltage regulator going?-not checked yet).

 

Only suggestion I haven't followed up is fuel injector spray pattern. Is this all I can have a look at?

[fendervg 29]

@GreenRado - Just out of interest do you have the part# for the crank sensor handy and how much did it cost you? Troubleshooting similar issues myself at the moment. Also, have you checked all your vacuum leads?

[robrado974 1]

These intermittent faults are a right mare to sort out . You mentioned cracks in the coil pack . I know you have sealed them , but try turning it over in the dark . If you have a small firework display , then there's a problem .

[GreenRado 10]

@GreenRado - Just out of interest do you have the part# for the crank sensor handy and how much did it cost you? Troubleshooting similar issues myself at the moment. Also, have you checked all your vacuum leads?

 

Just checked vac lines and intake and all seems fine, good call though. I got a FAE brand crank sensor from Euro Car parts. They sell 2 cheaper ones than the FAE one on there too.

[GreenRado 10]

Well she is starting up every time now weirdly, and I finally got an actual fault code when scanning after a stall!

 

00537 - Lambda (Oxygen Sensor) Regulation

11-10 - Control Limit Not Reached - Intermittent

 

Now the MAF talks to the Lambda probe doesn't it?

I've heard that its often just as likely to be the MAF to be at fault in this sort of thing?

Is the lambda probe only accessible from underneath the car (Is it plugged into the catalytic converter in the exhaust?

[Hassan. 10]

I had a similar issue with my 16v last year. It ended up being a loose wire that leads to the distributor. It looked fine with some insulation tape round it but when undone it was loose only figured this out when the car ran rough/cutting out /overfueling...ended up checking for sparks from the cool/leads/distributor whilst a friend was turning the key over luckily he was there. Could be as simple as this so I agree with Rob keep a tool kit handy and follow the electrics down. Hope this helps.