Ye Olde HPi Misfire

[Black Pearl]

ive had a bit of a scout about on the net, hopefully this aint ya problem mate, it sounds expensive lol

http://www.honestjohn.co.uk/forum/post/ ... =i&t=26358

theyve sublinked off on here to a similar subject but on a citroen C5 were these engines are more frequently found, ive been scouting under the C5 alias and i did find a bit more info on our engine and more owners on forums like this talking about misfire problems A few of em have come back with stories of the coilpack being shot, the link above is a bit more serious and expensive hopefully it aint wrong with yours mate. I have heard meself that the expensive weak point on our engines is that bloody HP fuel pump, its even made by shoddy siemens, well mine is anyway i aint lookin forward to the day that packs in ( touch wood an all that ). Ill keep scouting to see what i can find, i wouldnt mind finding out meself in case mine gets the same fault

[jameslxdt]

dai that fault code reader would do just the job, though you can shop arround and get one cheaper than that

[DaiRees]

Right you are James, I'll keep a beady eye peeled....

[DaiRees]

Right I got me one of them thingies, specifically this one.

It comes with the software called scantool.net as you can see in the advert. The blurb says that it'll display maufacturer specific codes, it's still not reporting any fault codes at all though. I picked up Neil and we went for a spin, managed to provoke the misfire while Neil fiddled with the laptop but we didn't manage to spot any problems. Any clues what we should be looking for?

I'm thinking the software looks a bit basic and maybe I need to be aquiring something else. Any recommendations?

[jameslxdt]

ive got that software and the live data readout is quite good, you just need to look out for any spikes in the data readings when the misfire occurs, the main things too be looking at would be the fuel trims and the oxygen sensor data, does it display the fuel pressure?

[Black Pearl]

Ayup all

Mines been misfiring of late, ive posted a topic already, more info on there but basically mate mine was doing it because the EGR valve had seized and broke the actuator, its a valve that sends exhaust gas back into the engine to cut emissions, the location of it is where you have the ETM circled in the picture, its just north of that next to the intake manifold ( the top of the stepper motor is a grey colour with sagem written on it ), its got a white plug, similar to the grey one going into the ETM, the unit bolts into the block with a metal flexible pipe going into it visible from underneath the intake, 2 studs and nuts hold it into the block with a metal shim/ gasket between it and the block, its easier to remove the studs completley and take the unit out wholesale, for clearence of the intake manifold bracket ( ya will see better when/ if you take it off ) its worth a look if just to de-coke it ( easily done with some brake fluid or petrol ) as results are quite noticable, thats the fault with mine mate, but the symtpoms are very similar to what yours has been having too, the cost of one of these units is 140 quid, and yeah its main stealer only from many hours of trying to source one.

Hope this helps mate and cures the common fault with our cars, apparently

[DaiRees]

Nah mine's already had the EGR replaced last year, didn't affect the misfire at all. The diagnostics are coming up dry too, so all I'm left with is to change parts until I find the culprit, Since she's already had plugs then the next most likely cause would be the coil pack, but at £140 odd it's just not worth doing at the moment, the misfire is so intermittant and infrequent that I'm not going to mess with it until I know for sure what it is.

[jameslxdt]

Dai, could you read off the fuel pressure with the scanner?

[DaiRees]

I'll have a look on the weekend James..

[jameslxdt]

ok, thats the only thing i reckon could give you a misfire at the driving conditions you are describing

[DaiRees]

Righteo, the fuel pressure reads as follows...

around 205 kPa at tickover,
goes up to around 300 under acceleration.
steady 305 - 310 cruising at 70 mph.
Saw it drop as low as about 150 under braking.

Did manage to induce the misfire but failed to notice any change to the pressure on the computer (Neil was watching the screen), that means that either the scanner doesn't react quick enough to carch any temporary drop in pressure, or that isn't the problem.

What controls the throttle? I assume it's a "fly by wire" system so is there any potential for something in there to be dirty or worn? Seems to do it worse on the cruise control, driving at a steady 50 in a 50 zone, get to the derestriction and accelerate up to 70, slightly uphill, using the "+" button on the cruise and she'll sometimes miss quite badly. And this afternoon while driving 'round with Neil I was in 4th at 30mph on the cruise when we came to a short but steep hill, halfway up the hill we had one missed beat, obviously the cruise was increasing the power to stop the speed from dropping going up the hill. Otherwise I only notice it when feeding the power back in after braking or freewheeling for a bit. This it's what now makes me think it's something to do with the throttle. Any thoughts on this theory?

[jameslxdt]

does sound like the ETM is sticking, i would take the air filter trunking off and take a look at it, if its heavily carbonised i would recommend cleaning, this was a common problem with volvos and cleaning did used to fix it, after cleaning, it needs to be synchronised, turn the ignition on and listen to the ETM it will buzz for about 30 seconds and then click, turn the ignition off and then start

[DaiRees]

OK James, what's the best to clean it with? Any special procedures or just get stuck in there?

[jameslxdt]

carburettor cleaner, soak a rag with it and wipe it carefully, make sure its spotless, make sure you turn the throttle disc carefully

[DaiRees]

OK, it does look a bit manky in there, but I haven't got any carb cleaner here at the moment so that's a job for next weekend