Head gasket prob, maybe????

Just got back from Noble with a on boost misfire on full boost according to them its blowing the spark out, they didnt get chance to diagnose it fully due to a pin hole they found in the top water hose They did say a poss cause could be a head gasket which may be pressuring the system, hence the pin hole & Misfire oil and coolent seem clean
The misfire starts as soon as the boost hits 1 bar, ill try my old plugs back in over the weekend to make sure it isnt a duff plug.
Any ideas?

P.S If DG is looking; Do you have the top coolent hose in stock Dave (The one that T's off to the header tank(Blue)

Was hoping to get it on the drag strip at York race-way over the Easter W/E http://www.york-raceway.co.uk/

Just got back from Noble with a on boost misfire on full boost according to them its blowing the spark out, they didnt get chance to diagnose it fully due to a pin hole they found in the top water hose They did say a poss cause could be a head gasket which may be pressuring the system, hence the pin hole & Misfire oil and coolent seem clean
The misfire starts as soon as the boost hits 1 bar, ill try my old plugs back in over the weekend to make sure it isnt a duff plug.
Any ideas?

P.S If DG is looking; Do you have the top coolent hose in stock Dave (The one that T's off to the header tank(Blue)

Was hoping to get it on the drag strip at York race-way over the Easter W/E http://www.york-raceway.co.uk/

I have original top hoses, no Samcos.

On boost misfire could be loads of things (PG has had the same problems)

Plug gap, fuel pressure. PG has now fitted an adjustble regulator and increased the fuel pressure to eliminate the misfire on high boost through running lean..

Also the fuel pump, fuel pump wiring etc..Pete now has a highflow Walbro Pump which will cope with any flow requirements up to 500bhp.

If it was HG, it wouldnt just be at 1 bar, it would be at lower boost too..

Obviously the standard "leak-down" test will help identify HG problems, I think.....
How about removing the coolant cap and run a compression test?

How many times has it been to Noble now and they still haven't fitted the Zetec in it

I have original top hoses, no Samcos.

How much are the originals v the samcos, will there be a long wait for a samco hose PM if you prefer Dave

[stephendell]

will there be a long wait for a samco hose

Up to six weeks if not in stock

Can be even longer sometimes.

Just a thought with the high speed misfire (More like hitting a rev limiter) a mate had a similar prob and it was cured by changing the plugs from 7's to 8's just a thought with peters car having a similar misfire and running similar boost

Peter is running NGK's and had regapped them to a smaller gap. It did help, but running more fuel pressure has got rid of the problem.

My car is at a rolling road to sort it out this weekend. My misfire was merely a hesitation until I fitted the chargecooler....and is eliminated by higher fuel pressure. It shouldnt be like hitting a rev limiter unless something has gone wrong....I wouldnt think it is a head gasket but the thought did cross my mind too!!!

Just as a last attempt with any ideas re; the on boost misfire?
A bit lost with it really i didnt really want to take it on the dyno just as a fault finding mission but its maybe looking that way just to recap, it will run fine off boost (it was running fine when it came back from noble) as soon as it gets near full revs on boost its like a rev limiter Noble started to look but it had to be aborted due to a leaking hose, all they said it blowing out he spark and it could be ignition or poss a head gasket on its way? there no other sighns of this i.e. no over heating, no oil in the water or water in the oil, the leads are relatively new Magecor, distributor cap new, NGK's new,
Maybe it will have to be a dyno session
Just a thought could it be fuelling running 16psi, i was thinking of putting a fuel pump on same has Peter's and maybe this regulator Whould it be OK http://cgi.ebay.co.uk/JDM-NEW-UNIVERSAL ... dZViewItem

Yes, increasing the fuel pressure will solve it, as the way your system leans off the ecu to run 16psi means its running even less than standard, i bet you don't get the problem at 13psi.. (im not getting into this argument again! )

If you go for a Walbro pump (I have a new one spare if required) and an adjustable reg then you won't have a problem, though you will have to get your ecu remapped again across the rev range as it will be running rich due to the higher fuel pressure.

Problem with that reg on Ebay, is you can't see the adaptors for fitting the fuel lines. Is your car a single or dual reg model?

If you go for a Walbro pump (I have a new one spare if required) and an adjustable reg then you won't have a problem, though you will have to get your ecu remapped again across the rev range as it will be running rich due to the higher fuel pressure.

Problem with that reg on Ebay, is you can't see the adaptors for fitting the fuel lines. Is your car a single or dual reg model?

Single reg im sure Would you PM me re; the Walbro/reg Dave.

i bet you don't get the problem at 13psi.. (im not getting into this argument again! )

just turned the boost down to 0.5 bar and its still doing the same i am now thinking the head gasket has blown i will drive it for a while and keep an eye on coolant level

Have you double checked all the plugs and leads...one of my leads just wasnt connected properly under the charge cooler which enhanced the effect 3 fold!

i will have another look,cars doing my head in at the mo if it isnt one problem its another the joys of running an old car eh