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2.5 engine misfiring/not all cylinders running
https://forums.tipec.net/viewtopic.php?f=25&t=22888		 Page 1 of 1
Author:  996driver [ Sat Aug 26, 2017 8:31 pm ]
Post subject:  2.5 engine misfiring/not all cylinders running
I got my 944 running again today after a long rebuild, but it's not firing right. Car starts but sounds very rough like it's not running on all 4.

It's been off the road for 10 months and had all fuel pipes replaced along with all fuel hoses/pump etc as well as sills welded and resprayed.
It looks like cylinders 1 & 2 are not firing properly, when the leads to both are removed it doesn't make a lot of difference to running. There is a spark on both at distributor and it looks like fuel is getting through as the spark plugs are wet. Other than fuel lines/fuel/pump/filter there isn't anything in the engine bay that has been changed since it was taken off the road last October.

Any suggestions of anywhere else is worth looking to fix it before I start changing out the leads and spark plugs?
Author:  Brett928S2 [ Sat Aug 26, 2017 10:12 pm ]
Post subject:  Re: 2.5 engine misfiring/not all cylinders running
Hi :)

Personally. I would CHANGE not check the plugs , and dizzy cap and rotor arm...then see how it runs...

All the best Brett :)
Author:  996driver [ Thu Aug 31, 2017 5:55 pm ]
Post subject:  Re: 2.5 engine misfiring/not all cylinders running
Thanks, plugs and leads changed and still no difference. Looks like a very good spark being given out.

Next step I think will be vacuum hoses and checking injectors but will also order new dizzy cap and rotor arm
Author:  Largie [ Fri Sep 01, 2017 7:48 am ]
Post subject:  Re: 2.5 engine misfiring/not all cylinders running
I don't suppose that there is any possibility that you have plug leads 1 & 2 swapped over, is there?

Largie
Author:  996driver [ Sun Sep 03, 2017 7:21 pm ]
Post subject:  Re: 2.5 engine misfiring/not all cylinders running
Largie wrote:
I don't suppose that there is any possibility that you have plug leads 1 & 2 swapped over, is there?

Largie

We did think that but on checking it looks like the leads will only fit one way. We also then checked the order and it did seem to match what was expected.

The car is running much better now but still doesnt seem like it's firing on all cylinders, possibly 3 of the 4 now so thinking it might be a sticky injector that's causing the problem. Next job to remove them and have a look
Author:  Sy924 [ Mon Sep 04, 2017 12:34 pm ]
Post subject:  Re: 2.5 engine misfiring/not all cylinders running
Maybe 4 containers under the injectors with fuel rail removed and see if you're getting same amount of fuel in each?
Author:  Waylander [ Mon Sep 04, 2017 2:26 pm ]
Post subject:  Re: 2.5 engine misfiring/not all cylinders running
the pintle caps can be very brittle on the injectors and can fall off and vanish in the cylinder I would take the inlet manifold off with the fuel rail and injectors still bolted in place

took me nearly a week to get the bits out of my no3 cylinder when the end of the injector fell off
Author:  996driver [ Mon Sep 04, 2017 10:36 pm ]
Post subject:  Re: 2.5 engine misfiring/not all cylinders running
Sy924 wrote:
Maybe 4 containers under the injectors with fuel rail removed and see if you're getting same amount of fuel in each?

Yes that definitely sounds like a good plan to test them, at least I'll know which if any, are faulty
Author:  Prophead [ Tue Sep 05, 2017 6:47 pm ]
Post subject:  Re: 2.5 engine misfiring/not all cylinders running
what state are the plugs in on those cylinders? i.e. what colour, are they wet, do they have oil on them ect the condition of the plugs can tell you a lot.

How old are the HT leads? they may well spark the plugs but if they are breaking down inside then the spark strength will be reduced and the engine will run badly the higher up the rpm range you go.
Author:  996driver [ Fri Sep 08, 2017 11:07 am ]
Post subject:  Re: 2.5 engine misfiring/not all cylinders running
Plugs are new, swapped out for new HT leads and made no difference.

Update today though, took it out for MOT and had to fill up as it had very little fuel in. Filled with VPower and it seems to have solved the problem. I think it might have been more to do with having such low amount of fuel in the tank previously but still good to have it running properly again.
Author:  sam [ Fri Sep 08, 2017 3:59 pm ]
Post subject:  Re: 2.5 engine misfiring/not all cylinders running
Sounds like a classic case of coil packs?
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