The Crocodile Hunter

I have an annoying problem with my saph and I need some help.

It has an annoying misfire on boost problem. So far I have tried 3 sets of plugs (both 071's and 57c's), new leads, cap and arm, checked the gap on the crank and phase sensor which both seem ok, but it's still doing it?

Yesterday I noticed that if you feed the boost in more gradually it's ok, however if you just bang full throttle open as soon as it hits full boost (about 25psi) it will misfire once and then pull cleanly up to the top end?

I'm now thinking it's not an ignition fault but something else?

Anyone had something similar before?

Cheers

SBT83

I'm gonna throw sticky injector out there, but not too sure myself. At least there are lots with knowledge on here, you'll get a answer soon enough mate

KSA-Cossie

iTrader: (4)

Were the tops of the spark plugs tight ? Had this on mine once and the part the HT lead goes onto needed tightening up.

The Crocodile Hunter

Injectors are 803's only done about 15k?

Thing is that driving normally it is fine, at part throttle on boost it's fine too?

SBT83

My inferior logic was down to the initial fuelling at open throttle on boost. It's worth checking the lead connection like the other post said. If he's had the prob before it's worth a shot.

The Crocodile Hunter

Yeah I also thought of this and checked them. On the champion plugs you can't unscrew the plug tops so eliminated that.

Another point, when I first fitted the 57's it seemed ok for a while but the misfire soon returned?

The Crocodile Hunter

One thing I've noticed is that the fuel pump is quite noisy on it.

It's the original pump that has been rewired but when it was last on the dyno the fuel was set as high as possible to keep the AFR ok at the top end

If the pump has got worse still could that be causing the problem with there not being enough fuel there at peak boost? Just a thought, but if this was the case you'd thing it would be at high revs more than anything else?

It's running a t34.48 and greens.

gingerturbo

iTrader: (2)

Shit/dirt in the throttle body/plenum?

Jay,

iTrader: (4)

Checked the voltage at the pump and fuel pressure oh fuel filter ?

SBT83

I would have thought it would suffer at the top end if it was the prob. Could it be down to fuel pressure if the pump is set high?

The Crocodile Hunter

That's exactly what it feels like!

Could a dodgy TPS cause it I wonder?

gingerturbo

iTrader: (2)

If it was setup at peak pressure and the pumps starts to fail at peak pressure then yes that could be a possibility, hench why its fine with progressive throttle as its not putting as much strain on the pump as full boost?

gingerturbo

iTrader: (2)

You can test it to eliminate it as its just a potentiometer

SBT83

TPS could cause the prob. I would have thought you would feel it randomly throughout the revs?? Not just that specific moment every time

The Crocodile Hunter

The volt meter in the car reads ok, the pump has both pos and earth straight from the battery. I will check the voltage though.

Fuel filter is quite new.

Talking about voltage, yesterday the battery died and won't hold a charge at all now, although you still get about 14v on the gauge once it's running by jumping it?

If it does turn out to be the battery I'll be happy but I can't see it?

Jay,

iTrader: (4)

If the voltage isnt high enough at the pump then it will run lean , if the fuel pressure has dropped through a knackered regulator then it goes lean , if the fuel filter is blocked itll go lean ! All the above will cause the symptoms of missfire on boost plus a bad earth to the coil amp !

Does the rev counter jump when it misses i.e jumps to 7k when your at 5k

is it 2wd or 4x4 ?

SBT83

Like gingerturbo said, clean the throttle to eliminate that, I'm more thinking along the lines of the fueling tbh.

gingerturbo

iTrader: (2)

Your be surprised as the battery plays a big part in the management

SBT83

Go for a new battery!

Jay,

iTrader: (4)

Iirc anything below 11.8 volts at the ecu will give a lot of symptoms

gingerturbo

iTrader: (2)

Yep^^^ most components need a constant 12v and under load even with the alternator generating 14v a dead battery can't cope with feeding a 12v feed to all components

SBT83

Was just gonna say that lol

jontysafe

Mine has a misfire at 2700-3000rpm just when turbo should be spooling up. Means I'm hitting full boost 300rpm later than I should be. I was thinking TPS (are these easy to change?) on the other hand my battery is knackered so will try that first.

Jay,

iTrader: (4)

then he might as well buy a new pump and reg new car loom phase sensor ect and along the way it might get fixed surely testing first then spend money ?

SBT83

If it's fooked then he wants a new one!

gingerturbo

iTrader: (2)

Yeh testing is free

gingerturbo

iTrader: (2)

There only Ł30 for a battery in all fairness

SBT83

Obviously test everything before you go throwing money at it! Hence go buy a new battery????

At least he can rule the battery out that way too

mattman1234

try closing the plug gaps

Paul_RS

iTrader: (4)

Friend had similar, it was a dodgy actuator.

I had something along those lines too, it was a faulty fuel reg. However with that the car wouldn't rev at all on boost.

The Crocodile Hunter

Ok, I need a new battery, that's a given so will sort this first.

I also have a group A fuel pump (courtesy of the kitchen devil) so will get this fitted.

Mattman1234 - I have closed the plug gaps to about 0.45mm and it helped but has not cured it?

Personally I'm sure it's a fuel problem rather than ignition but it us baffling me a bit.

Gingertutbo - where can you get a square terminal battery for Ł30? Cheapest I can find is Ł52 on eBay but I've no idea if it's a half decent battery?

gingerturbo

iTrader: (2)

Trade I get them at cost through my work

opposite lock

iTrader: (3)

Check the map sensor piping.

The Crocodile Hunter

Good idea, I'll check it out.

Picked up a new battery today, will have time to have a play with it over the weekend, see if I can get it sorted.

Michael Dunne

i have the same problem and today my battery went flat. did you ever get it fixed ?
im buying a battery tomorrow.

pastymuncher1

I too had this issue..boosting would bring battery light on, secs monitor alarm would go off, car would misfire badly and run like a tractor which was embarrassing when overtaking I fitted a new battery as car needed it anyway, but this didn't solve my problem. However I solved this issue completely by replacing cable from alternator to battery..voltage at battery rose but more importantly was consistent. With car running and boosting voltage is steady (albeit still only a little over 12v at ecu) car drives great and can boost all day with no splutters or cutting out and importantly no warnings or alarms.. Ł24 for new cable from auto dynamix in Paignton. Sorted


Hope this helps

martysmartie

iTrader: (1)

The battery does not supply any power when running, the alternator does.

As to the issue, its sounds like a spark 'blow out issue', due to the cylinder pressure, the spark is not powerful enough to occur (on the standard ignition system) hence resulting in a misfire, hence why you have to run smaller plug gaps, which isn't ideal.

This is the reason why some fit WS.

I would't just go and buy a new battery, he will struggle with as square terminal's are no longer available from the majority of motor factors.

Martin

pastymuncher1

Eurocar parts stock them.....I got mine from there 2 weeks ago and even had a 20% discount email the day before which made it even cheaper.

pastymuncher1

Got my battery from euro car parts. Same day and have them in stock

Guinnless

I'd put a pound on that you are simply be hitting the 'boost cut' on a stage 3 greens chip.

This would explain why you can "nurse" the boost in as it won't spike doing it that way.

Check the actuator pre-load. 3-4mm of preload IIRC. If it's ok then you'll need to jet the amal valve to reduce the boost.

Also make sure there are no leaks and all hose clips are tight.