Engine stalls

[matthewb]

Hi all

Here's a peculiar one for you experts.

• Fully charged battery. Fully filled tank. New HT leads a year or so ago. I drive her hard, frequently up to the rev limiter.
• She starts on first turn of key.
• Then sometimes, directly after starting (30-60 seconds), she has an idle problem and stalls. Then sometimes she stalls while driving (disconcerting) shortly after starting.
• Fix by pressing the accelerator hard whilst turning key. Then she seems to run without any problem.

Assuming it's not the battery, I'm guessing it's possibly something to do with fuel supply or ignition - pump, distributor, injectors?

Any ideas?

Thanks.

 

[wilsonny]

when was the isv last cleaned?

 

[BarryN]

That’s the ISV.
A good clean with brake cleaner or isopropanol.
It should be free enough to rattle when you rock it back and forth.
Then disconnect the battery for a few minutes so it resets everything.

 

[matthewb]

Many thanks. Seems a likely candidate (having read-up on ISVs - never heard of them before - I had to do quite a bit of work to find out that ISV stands for idle stabilisation valve [])

I'll ask the chaps to have a look at it.

Thanks again.

 

[matthewb]

I did once consider a low-mass flywheel in a mad moment - soon dismissed as impractical[8|].

Thanks

 

[matthewb]

Hi folks

Thanks for all your replies.

I took it to my indie who removed the ISV and cleaned it. Everything was as you described - difficult to remove as screws at an awkward angle - felt gloopy when shaken. He flushed it through with brake cleaner. Wiped it clean with some paper towel. No longer felt gloopy when shaken.

The battery was disconnected for about 15 minutes to reset the ECU.

BUT - although a little better, it's still not right by a long way. It starts from cold no problem. Idles at 1100 for a short while. Drops to 800 for a short while. Then revs drop very low and only just recovers, after which the revs sort of stabilise at 1000. If I just touch the accelerator at this point, the revs go up to about 2500 and back to 1000, then back up to 2500 and back to 1000, each cycle taking 4 or 5 seconds. I turn it off at this point. It can be very difficult to restart when warm.

A friend knowledgeable with Volvos laughed and he said he'd had the same occur to him. He laughed again at my plans for having another go at 'fixing'. Cut your losses and buy a new ISV, he said.

Any further thoughts?

 

[matthewb]

Thanks Maurice

I've fitted a new ISV (not cheap - £625 incl labour and VAT).

A lot better but still not perfect. I'll give the ECU a little time to settle-in. If not, then an OBD error code check and a vacuum check seem to be the way to go.

Best
Matthew

 

[matthewb]

Yes - I had it fitted about a decade ago. I don't have the original. I don't know where JZM source their chips.

I have had no issue like this before - 2 decades of pretty much trouble-free motoring (and starting).

I shall contact Wayne.

Thanks

 

[matthewb]

Thanks Maurice

I'll certainly set up a session with Wayne.

But first --- I've got to sort out the problem I've now got with starting the engine.

Just a brief recap ...

1. Problem first surfaced when engine cold - just after setting-off the power suddenly dropped, engine stalled, and I couldn't restart. Waited for 15 mins or so. Tried again and it started with difficulty by pressing accelerator hard. Lumpy but it settled down.
2. Cleaned ISV - slightly better - no more power drop or stalling when driving but crazy rev behaviour, after which starting again very difficult.
3. Replaced ISV - quite a lot better but still sometimes unwilling to start and stay running- have to watch rev counter and give it some help if revs dropped too low. I thought things were on the mend. The ECU seemed to be learning.

But yesterday, after a visit to a pub for lunch with a friend, I tried to start the car to go home. Not even a hint of the engine catching. Petrol smell very strong, so fuel pump working. Waited for 15 minutes and tried again - same thing. My friend suggested putting the car in 1st and trying again. He admitted it sounded crazy but it had worked for him once. The car moved forward under the starter motor and finally the car spluttered into life. Some serious revving later (to clear out the flooding) and the car settled down to 800 revs and behaved perfectly.

In summary - now the car seems to run perfectly once started - but getting it started can be a real problem. I can't guarantee I'll get home, so scared to go anywhere.

Any thoughts? I'm planning on getting MAF, O2 and Engine Head Temp sensors checked-out on an OBDII.

 

[matthewb]

Hi Maurice

Well - things are looking good. It's taken a bit of patience and persistence but she now seems to start on demand regardless of warm or cold start etc. and behaves well at idle. Thank goodness the ECU seems to be learning at last. Nothing worse than not knowing if you'll be able to start the car after filling up.

I am aware that liquids are not compressible but I hadn't thought about the consequences in this instance, I must admit. Judging by the smell of petrol, most of it seemed to have been ejected into the atmosphere.

I did read somewhere that non-US 993s are only OBD-I compatible. I have found this - https://www.bergvillfx.com/index.php/products/obd-diagnostics/t-obd-diagnostics-for-porsche-968-964-and-993.html - but don't think I need it just yet.

I gave her a 400 mile trip over the weekend - visit in-laws and back. Didn't miss a beat. 28 mpg at 70 mph avg. door to door.

Off topic - the only thing that spoilt this trip was the ac not working. I've had it re-gassed on a few occasions but it only lasts a short time. I've tried all the usual 'experts' and all say there's no problem - no sign of leaks etc. But it's obviously not OK. Do you know anywhere near Reading / Newbury, not necessarily Porsche-related, who knows how to fix ac properly and not just re-gas it (again)?

Thanks for your advice.

 

[tomwinton]

Maybe a bit too far west for you, but I used George at gocool services in Bristol on both of my 993s with good success rates

http://www.gocool.co.uk/

TOm

 

[Stephenjk]

On the aircon the 993 is like the 964 and i had a similar issue to you with multiple regasses. Turned out to be the evaporator behind the fuel tank/behind the dashboard. When the leak is there it is quite hard to spot as the leak is not easily visible. In my case they werent sure till they had removed the evaporator, it had a leak in the middle and you could see the oil on it once it is out. If it is the evaporator it is fairly expensive to fix as it is around 10 hours of labour to replace, mine was around £2k to fix all in.

 

[matthewb]

Phew. My aircon guy has decided to go with a new condenser (it is visibly damaged) and a re-gas with something fluorescent to see where any leaks might be - and we'll take it from there.

 

[matthewb]

The aircon has been fixed thanks to the new condenser.

Finally.

 

[matthewb]

Hi Maurice et al

All fixed.

My indie tested the sensors for MAF, O2 and Cylinder Head Temp. The CHTS was malfunctioning and telling the ECU the engine was cold (on a summer's day) and was therefore putting in too much petrol.
Fitting a new CHTS and ISV has transformed the engine. It's starting easily and idling beautifully - she sounds fantastic.

 

[matthewb]

It's the journey as much as the destination itself. I love the way human beings, when faced with a plea for help, often respond wonderfully. I almost make problems just so people can help me [8|].

Thanks again to you and everyone else who has contributed.