Misfire any thoughts

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Charles C. - 21 Jun 2007 19:46 GMT

Hi,

The car is 9000, 2.0 LPT, year 1997, 100K miles on the clock.

It showed some random misfire a week or so ago. Two days later took it
to the SAAB dealer who could not fix (not enough time), but replaced
some split rubber pipes relating to the turbo (?). They think the
misfire relates to the turbo, as it does not supply high enough boost.

At the time the misfire was only when the engine was under load and
gentle acceleration (town driving).

============

The car is booked to go back on Tuesday (by which time it may well need
a new catalyst... that will become an email of its own if it does).

The misfire now happens after about a mile from cold (or a bit sooner)
and it happens even when the engine is idling. I can't see what this
may have to do with the turbo.

Any ideas, what it may be or which is the best way to identify the problem?

BTW. Are the recommended sparking plugs for the car NGK or Champion?

TIA
Charles

PS. My experience unfortunately is from early non-turbo 900s with
conventional ignitions.

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johannes - 21 Jun 2007 21:06 GMT

> Hi,
>
[quoted text clipped - 7 lines]
> At the time the misfire was only when the engine was under load and
> gentle acceleration (town driving).

1. The dreaded Direct Ignition cassette (DI).

> The car is booked to go back on Tuesday (by which time it may well need
> a new catalyst... that will become an email of its own if it does).

2. That is also a possibility. Try to knock gently on the outside and
listen for loose material.

> The misfire now happens after about a mile from cold (or a bit sooner)
> and it happens even when the engine is idling. I can't see what this
> may have to do with the turbo.

This is probably the a rubber pipes that transfer a pressure signal to
a pressure sensor. You can diagnose that by listening for hissing air
noises in the engine compartment. Fixing is an easy DIY job. I
actually just cut off the split end and refitted.

> Any ideas, what it may be or which is the best way to identify the problem?
>
> BTW. Are the recommended sparking plugs for the car NGK or Champion?

NGK BCPR7ES-11, and do not even think of fitting any other plug type!
The ignition/anti-knock system is designed around this plug.

(Driving 1993 9000 CSE 2.0 LPT 135k and still in excellent cond.)

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Paul Halliday - 21 Jun 2007 21:20 GMT

> The car is 9000, 2.0 LPT, year 1997, 100K miles on the clock.

So ... Direct ignition? Red cassette?

> It showed some random misfire a week or so ago. Two days later took it
> to the SAAB dealer who could not fix (not enough time), but replaced
> some split rubber pipes relating to the turbo (?). They think the
> misfire relates to the turbo, as it does not supply high enough boost.

An air leak with increases with load or becomes apparent with a throttle
blip and engine movement is always a tough one to track down.

> At the time the misfire was only when the engine was under load and
> gentle acceleration (town driving).

Sounds like the DI cassette ... What do others think?

> The car is booked to go back on Tuesday (by which time it may well need
> a new catalyst... that will become an email of its own if it does).
>
> The misfire now happens after about a mile from cold (or a bit sooner)
> and it happens even when the engine is idling. I can't see what this
> may have to do with the turbo.

Sounds like the DI cassette :)

> Any ideas, what it may be or which is the best way to identify the problem?

Are you a late victim of the recent lambda poisoning issue with fuel in the
SE of England? It seemed that Morrisons and Tesco were the main culprits,
but other stations did give out fuel which caused lambda fogging ... This
was a good few months ago, but maybe you've not used your car much.

> BTW. Are the recommended sparking plugs for the car NGK or Champion?

NGK ... Without even thinking about it!

Does someone live near Charles who could lend him a spare DI cassette to
test out the theory? They're quite expensive and mentioning it to a garage
would simply result in a swap, a large bill and possibly not fix the
problem.

One trick is to pop down to Halfords, buy a can of carburettor cleaner, warm
up your engine and spray the fluid over vac pipes, where pipes are clipped
onto metal and any other union or orifice that looks dodgy. Spray into areas
that move when the throttle is blipped. If the engine increases in pitch
noticeably, you've likely found an air leak.

Happy hunting ... Come back with more questions if you have them,

Paul

1989 900 Turbo S
http://saab.go.dyndns.org/

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Charles C. - 22 Jun 2007 01:22 GMT

Thanks to both of you ...

>> The car is 9000, 2.0 LPT, year 1997, 100K miles on the clock.
>
> So ... Direct ignition? Red cassette?

Of course Red :-)

>
>> It showed some random misfire a week or so ago. Two days later took it
[quoted text clipped - 18 lines]
>
> Sounds like the DI cassette :)

This is my thought too ... I suspected it before I took the car to the
dealer but ... at the time it did not (or I could not feel) the misfire
when idling.

>
>> Any ideas, what it may be or which is the best way to identify the problem?
[quoted text clipped - 3 lines]
> but other stations did give out fuel which caused lambda fogging ... This
> was a good few months ago, but maybe you've not used your car much.

No. The fuel has been from Sainsbury's or Shell and in always super
unleaded.

>
>> BTW. Are the recommended sparking plugs for the car NGK or Champion?
>
> NGK ... Without even thinking about it!

I do not know what is there ... but SAAB had said they were fitting some
3 point Champion plugs (I remember them around £25 at Halfrauds) which
were good for 3 years or 36K miles (if memory serves me right).

> Does someone live near Charles who could lend him a spare DI cassette to
> test out the theory? They're quite expensive and mentioning it to a garage
[quoted text clipped - 8 lines]
>
> Happy hunting ... Come back with more questions if you have them,

I will ... I am in new territory.

> Paul
>
> 1989 900 Turbo S
> http://saab.go.dyndns.org/

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still me - 22 Jun 2007 03:20 GMT

>This is my thought too ... I suspected it before I took the car to the
>dealer but ... at the time it did not (or I could not feel) the misfire
>when idling.

A bad DI will throw a code in the computer. If you have misfires in
there (not just rough running) I'd suspect the DI.

>I do not know what is there ... but SAAB had said they were fitting some
>3 point Champion plugs (I remember them around £25 at Halfrauds) which
>were good for 3 years or 36K miles (if memory serves me right).

Replace the plugs with NGK's in the factory model. A Saab dealer
should be shipped for putting anything else in. They should know
better.

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Charles C. - 28 Jun 2007 22:11 GMT

> Hi,
>
[quoted text clipped - 16 lines]
> and it happens even when the engine is idling. I can't see what this
> may have to do with the turbo.

If it helps anyone out in the future.

On 2nd take all problems pointed to fuel starvation which could be
caused by a vacuum leak (hence the engine would cut off fuel). The car
became difficult to accelerate but reasonably happy to run with a few
misfires at a steady load.

However, it was the Direct Ignition cassette that was faulty. On 2nd
visit to the dealer they chanced that this was the problem. I had done
380 miles with the misfire. The catalyst apparently survived. I am
happy to settle for half the SAAB Experience.

Regards
Charles

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johannes - 29 Jun 2007 00:29 GMT

> > Hi,
> >
[quoted text clipped - 28 lines]
> 380 miles with the misfire. The catalyst apparently survived. I am
> happy to settle for half the SAAB Experience.

1. Direct Ignition systems are also used by other manufacturers.

2. They last over 60k miles and replacement is a simple DIY job, in
fact simpler than changing the air filter (which is tricky on a 9000).

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Charles C. - 29 Jun 2007 02:38 GMT

>>> Hi,
>>>
[quoted text clipped - 29 lines]
>
> 1. Direct Ignition systems are also used by other manufacturers.

Yes.

> 2. They last over 60k miles and replacement is a simple DIY job, in
> fact simpler than changing the air filter (which is tricky on a 9000).

Yes.

Not sure what you are trying to say. Are you trying to defend SAAB? I
have not complained. Sorry if I read your message the wrong way.

I am talking about symptoms and how to possibly diagnose the fault if
someone has the same symptoms sometime in the future. Whether the fault
is a good or a bad thing or if we should replace the cassette at 60K
miles as a service item is not something I am passing comment on.

:-)

Charles

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johannes - 29 Jun 2007 08:35 GMT

> >>> Hi,
> >>>
[quoted text clipped - 45 lines]
> :-)
> Charles

I wouldn't go so far as changing the DI as a service item, but keeping
a spare is a good idea. You can easily get them for 150 UK Pounds.
I was once stranded on a motorway incline and had to be recovered on
a lorry. That was very embarrassing, never happened to my FIAT.

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