944 Poor starting / misfire

[944Tom]

Hi

I was wondering if anybody could help: -

I own a 944 S2. It is not starting very well at the moment. When the key is turned, the starter motor spins around nicely – but it does not start very easily, it struggles to start. This gets even worse when the engine is hot. It occasionally misfires also.

I have changed the starter motor and the battery, no real change – it only spins faster. The next logical step to me is to change the fuel injectors. These seem to be about £3-400. I have just seen an Injector Cleaning Service here - www.porscheshop.co.uk/acatalog/944injector.html

I was wondering if anybody knows anything about this service or had it done? It seems a good idea?

I read in a past thread that people were talking about HT leads – could this be my problem?

Thanks in advance

Tom

[Thom]

Injectors on 944s are not parts that often go wrong, so cleaning those may prove enough. I'd have a look at igniton wires, too.

>> Edited by Thom on Tuesday 17th August 18:03

[944Tom]

Thom

Thanks for your thought - I think I will get the injectors cleaned

Thom said:

I'd have a look at igniton wires

Is that the same as HT leads, if not could you please expand on what you mean?

Thanks

[domster]

Yes, HT leads are ignition leads. But have you checked the plugs or changed them recently? They could be coked up or the gaps may be incorrect.

In all honesty, you are embarking on a dangerous exercise in replacing bits without knowing the cause - it gets expensive. There are probably at least a dozen or so items on your car that could interfere with cold or hot engine starts, from dodgy water temp sensors to plugs etc.

I'd try replacement plugs and leads as these are relatively cheap in the scheme of things, then if the problem persists, spend 40 GBP an hour on a decent independent.

[944Tom]

domster

Thanks for info

I had the car serviced about 2 months ago - which included plugs - (I saw him put them in!!!)

I am in full agreement with you when you say it could be various items interfering with the starting procedure and replacing these bits can be an expensive procedure.

I think I’ll buy some leads and then see what happens.

Also I have taken it to a Porsche Mechanic and he thinks the next step is to replace injectors! I was really asking for people views on the injector cleaning service!

Cheers

[axj]

Whilst I have no wish to add to your list of items- have you thought about simply replacing your DME relay ?

Mine went last weekend (original unit was Made in
W. Germany !). Common consensus is that some DME relays only last several years before giving starting problems.

Even from an O.P.C. a replacement relay is only
around £22.

No doubt a little less from a specialised parts supplier.

[944Tom]

axj

Cheers for that - I think i'll try that - worth a go for £22

Tom

[domster]

It is unlikely to be blocked injectors from my experience. Modern fuels have plenty of detergents in them (unless you are a supermarket fuel pikey) plus it is far more common for injectors to cause problems simply by wearing out. When they do, circa 100k miles, they cause idle problems normally - stalling at junctions etc.

Ultrasonically cleaning injectors is fair enough, a friend of mine used to do them on an exchange basis years ago, but my guess is it's a red herring. Either replace them, in case it's a wear issue, or look towards something else like the DME.

[poorcardealer]

Had similar problems with a 944 myself some years ago......was the "king lead" which goes from the ignition coil to the centre of the distributor.......get a friend to turn the engine over while you look under the bonnett, if you can hear or see sparking around the coil or dizzy cap this could be the cause. replace the lead.

Also check the top of the coil, for any burn marks where it has been arcing out, if you can see any replace the coil, dont think they are very expensive.

>> Edited by poorcardealer on Wednesday 18th August 17:25

[944Tom]

Cheers Guys - I better get under that bonnet!!!

[basil brush]

A leaking injector can cause starting problems as it lets the fuel pressure bleed off from the fuel rail. The engine will then take a while to start, and will run rough at first until the pressure builds up again. It's worse when restarting from warm after being stood for a little while as one cylinder will be full of fuel, as well as the lack of pressure and possible fuel vaporisation in the rail. The dodgy plug leads on mine caused problems under load rather than when starting and idling. I also had problems from the dme water temp sensor failing, and more so from the air temp sensor in the afm. Has your mech tried cleaning the flywheel sensor?

[BIF]

Got my DME Relay from Berlyn, mail order around £14 inc postage

[UK952]

Definately start with the dme relay. might be worth a look at the rotor arm as well.
Tony

[dern]

UK952 said:

Definately start with the dme relay. might be worth a look at the rotor arm as well. Tony

If you take the dizzy cap off you should be able to assess the state of it for free. The contacts in mine were all rough, broken and black and replacing the cap and rotor arm made my car run a lot smoother although that's a lux and not a 3.0.

Mark

[944tom]

Firstly Thanks guys

I have finally got around to fixing the car and now it is running sweetly.

So I changed the Dizzy + cap, rotor arm, DME relay and got 4 secong hand fuel injectors (one was leaking)

So thanks again for the advice!!!!

I'm off for a drive!!!!!

[944tom]

Just to let you lot know.........

The misfire problem returned in December and January but intermittently - AGGGGHHHHH

So I decided to let the pros look at it. So I took it down to JZ Machtech.

They found it was a broken valve spring - which has now been replaced and the problem has gone. It has two valve springs per valve one for low rpm and one for high rpm – the high RPM spring was broken into three pieces!!!!

I would highly recommend JZ Machtech - very knowledgeable and helpful people

I’m just glad its finally fixed

Tom

[domster]

Congrats Tom. Misfires can be a pain to nail, so I'm glad JZ found the problem and sorted it. Main dealers would just start replacing expensive parts with no guarantee of a cure...

[cuneus]

domster said:

Congrats Tom. Misfires can be a pain to nail, so I'm glad JZ found the problem and sorted it. Main dealers would just start replacing expensive parts with no guarantee of a cure...

and of course independents never ever do that, never

[domster]

Well, I never said that... but they can sometimes be more helpful when it comes to problem solving.

I once had an engine hot running problem on a VW Polo. Both main dealers I took it to could replicate the fault but not fix it. Their solution was to start replacing parts of the engine/fuel/ignition system until it went away. And once a part was fitted it wasn't unfitted and refunded if the fault remained. One ended up charging me 300 GBP for labour with the car remaining unfixed - I'd just paid for them to scratch their heads and be useless tosspots. Great.

The attitude of independents CAN be better. They don't have so many regulations re fitting new parts, and will often be prepared to 'borrow' parts from other cars or use second hand parts to see what difference things make. The more personal approach of a smaller operation often means you deal directly with the mechanic, who can see your frustration and may go the extra mile. There is no unsympathetic workshop manager to dish out unprofitable work to uninterested techs (worst case scenario).

[cuneus]

Fair enough Dom but it does go the other way. When I had the turbo and lived in NE Essex the independent changed a whole load of stuff to fix a running problem

Local OPC 20 minutes and a new coil lead

Probably helped that the mechanic owned a 944 turbo