93 VR6 intermittently cutting out and intermittently not starting

[GreenRado 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.

 

Thanks for the tip, I haven't found anything obvious on that front yet, but I'll have a proper look today.

 

I measured the values while running with vagcom today and managed to video it as she stalled out (and wouldn't start again - crank, no fire).

The video is only short, as she stalled out quite quickly. As you can see in the video, I give her a little bit of throttle and as I release she just dies:

https://www.youtube.com/watch?v=tOitC3eWSeU&feature=youtu.be

 

I'm seeing that she died reading 12.65V. Surely this isn't the settled voltage of the battery AFTER she's died? Is it possible that the voltage regulator on the alternator is causing the varied voltage readings while running and it's actually just dying for lack of sufficient voltage from the battery?

[GreenRado 10]

All wiring looking good. Tested twice after cleaning up all connections and still no change.

 

Still stalling out after a random amount of time with no hesitation or hunting etc beforehand, then not firing up again for a good while.

[robrado974 1]

I know you said that you have checked and cleaned the electrics . It sounds to me like a sketchy connection somewhere . Have you tried fitting a different ISV ? , just another thought .

[GreenRado 10]

I know you said that you have checked and cleaned the electrics . It sounds to me like a sketchy connection somewhere . Have you tried fitting a different ISV ? , just another thought .

 

Yeah my friend has also told me to keep checking electrics. I'll start from scratch again and try to be more thorough. I gave my ISV a really thorough clean out with intake cleaner. I know someone nearby doing up an obd1 2.8 VR6. Would the ISV be the same/compatible off that?

[easypops 8]

Bit of a long shot but it happened to me, on my old 16v. I found 2 split wires and the plastic sheathing was still intact, the wires in question were under tension where they plugged in and gave up eventually. I found them while rummaging around while the car was running.......I was chasing a very bad idle at the time, fixed the wires and all was well.

[robrado974 1]

I would have thought it was the same ISV . Someone will correct me if I'm wrong .

[GreenRado 10]

I would have thought it was the same ISV . Someone will correct me if I'm wrong .

 

Well this morning I started her (always first time when last run was hours ago or more) waited until she cut out and wouldn't start (always not starting after cut out) and checked the ISV without unplugging its connector, and its valve was still open.

Surely it would be closed if it was the problem?

 

On a different note, she only seems to be stalling out once she's warmed up. Last 4 tests have all lasted around 10 minutes, all starting first time from cold and then not starting after a warm stall.

 

Had another close look at the wiring and all really does look good on that front. She has only covered 1500 miles in the last 9 years, so that would surely lean more away from wiring issues wouldn't it?

 

Reseated all fuses and relays again this morning with no change.

[Jim 2]

I was going to say something about the lambda probe. I remember a friend having a faulty one of these on his Corrado (though it was a G60) - would be fine during the warm up process as the lambda is generally ignored until the car is up to a certain temperature, and then after about 10 minutes it would be like someone flicked a switch with lumpy / rough running and bordering on stalling.

 

It may manifest itself in a different way in the VR6 so would certainly be worth looking into. At least check the wiring to the lambda probe as it's not uncommon for it to be come damaged or break due to brittleness with age.

 

I was also curious to know if whether, when you're driving even with the car running at like a fixed RPM at speed on a road, does it simply just cut out? Or will it be fine until the engine switches to idle (like you put your foot on the clutch) and then cuts out and won't restart?

[VAG-hag 0]

Yeah Lamda would be worth a shot. Let me know if you need one

[GreenRado 10]

This is the connector for the lambda probe isn't it (I took the pic)?

 

I'm guessing that weird silicon all over one side of it isn't promising.

[fla 9]

Yes thats the one in the bay. Best remove and check it.

in fact whilst you're checking connectors have a look at the crank sensor wiring at the front. The connectors often come out of the retaining bracket and this may damage the wiring as they shake around.

[Jim 2]

Well that looks like we may have a candidate for causing the issues judging by the state of that connector!

[deano46 10]

Seems like a similar problem to mine. I will check the lambda wiring myself once I put all the other bits (thermostat housing and senders etc.) all back together.

[VAG-hag 0]

yes thats the one :)

[kaptinkangaru 10]

have you by any chance tested a known working ecu? i had a very similar issue, car would start, die 30 seconds to several minutes later. sometimes at a stop, other times on the highway, but never due to weather/road conditions. after shutdown, the car refused to start again right away. wasted months trying to diagnose, replaced relays, sensors, etc.. finally grabbed an ecu off ebay, plugged it in, haven't had an issue since. they can be had for around 100 USD.

[GreenRado 10]

have you by any chance tested a known working ecu? i had a very similar issue, car would start, die 30 seconds to several minutes later. sometimes at a stop, other times on the highway, but never due to weather/road conditions. after shutdown, the car refused to start again right away. wasted months trying to diagnose, replaced relays, sensors, etc.. finally grabbed an ecu off ebay, plugged it in, haven't had an issue since. they can be had for around 100 USD.

 

Hmmm, well I investigated mine and it looks like it's original? 06/93 being the date of manufacture?

[GreenRado 10]

So the lambda sensor plug was actually fine under the silicon.

 

Also she isn't firing from cold at all this afternoon, just endless crank. Fuel is at the rail, under pressure. Spark is present on all leads.

 

So either MAF/ECU left to swap out? Anything else worth trying?

[GreenRado 10]

Finally found a fault!

She hasn't been starting at all now and decided to check for fuel again while cranking. Fuel was present, but hardly under pressure at the rail.

Gonna check out the pressure properly with a gauge and see if I can narrow it down to the FPR or the Pump.

The fuel filter is new, but I put that new one in when I switched tanks (old one had a leak from a weird repair), so it may have gotten plugged a bit?

Fingers crossed I can find the culprit!

[robrado974 1]

Good news that you have narrowed it down . Very wise to check the pressure first , to find the fault . The pump is not cheap and nor is the regulator for what it is . What year did you say the car was ?

[GreenRado 10]

Pressure is non-existent and now so is fuel. (Definitely just been getting worse and worse until now something has just died).

 

Replaced relay 109 with a brand new one and still nothing.

 

Popped off the feed hose to the fuel filter and a decent amount of fuel was in the hose.

Continued to try starting with that hose off and not a drop came out.

 

Would it be correct to assume the pump has had it? Anyone know if there's any tests you can do on it from the electrical terminals or even once removed?

[fendervg 33]

Check out my thread for fuel pump fun. You can try testing the voltage at the pump electrical connector.

[fendervg 33]

Also check your fuel filter and relay 67 for the pump

[GreenRado 10]

Also check your fuel filter and relay 67 for the pump

 

I thought the pump shared relay 109 with the ECU?

[GreenRado 10]

Connector is getting just under 10V with ignition on and I've thoroughly cleaned both sides of the terminal with no change.

Dead pump then surely?

[seanl82 23]

No fuel pump has a separate relay. 67 or 167 depending on date manufactured mate. Pop the fuse cover off, and put a finger on the relay whilst you turn the ignition to position 2. You'll feel it energising by a little ping if the relay is working mate.