Ye Olde HPi Misfire

[Black Pearl]

The PDF on the HPI, ive come across this before, i couldnt figure it all out so i gave a printout to my old boss who knows his way around engines so much hes hand built a rover V8 with hand lathed throttle bodies and injectors, so as he desyphers it to me i understand it as : ( ill try and remember what he said now, it was over a pint or two early last year ) as i remember....

The reason for the High Pressure Injection ( HPI ) has been made is to try to have complete combustion and lower emissions, Where the High pressure comes in is the pump puts the petrol under such a high pressure it breaks it down into a fine mist, so less is needed and injects it directly into the specially shaped cylinders, causing the air and fuel to swurl and mix in the top of the piston, rather than in a seperate chamber then sent into the engine, but this way the air and fuel is stratisferically ( posh word for layered ) mixed and at such a high pressure it atomises the mix upon detonation, which burns everything thats put in the cylinders, this is why we got so many sensors on the damn thing, monitoring how much of fuel, air and exhaust gas return ( EGR - another apparent way to cut emission is to reburn whats not fully burnt monitored by that oxygen sensor in the pre-cat chamber on the exhaust which tells the EGR to open or close depending on running stresses and mixture levels ). The clever bit is the atomisation of the mix, Becuase of the high pressure the engine sounds like a diesel as they also run under high pressure and nowt more to ignite the diesel. With the atomisation stuff goin on and being under a high pressure the engines do run hotter than a normal injected engine. The deal with the weird spark plugs he tells me is that the coilpack gives out a great deal of current to create a good big spark to create good solid detonation, probably plays a part for a bloody big gapping setting to literally make a good BIG spark. Also with the sparkplugs i know that you cant cross reference them to a citroen C5 HPI the bore size for the sparkplug is a lot larger, praps there top end is a bit different to ours or they made it so that its just one of them " dealer only " swizzes. Which makes me think that in the instance of a misfire after a while of re-gapping they creep with the high temperature theyre subjected to.

if ya after some more information and such have a look see on here ---> http://www.psa-peugeot-citroen.com/modu ... e_hpi.html

[Longintooth]

Hi
hummmm - Long before ecu's and technology this would have been easy to locate now we have to fix the things that fix the thingy if you get what I mean.
You can go on forever feeling your way in the dark but in the real world you have to go with the flow and this is use as much test gear you can get your hands on and one little bastion of salvation for now is the OBD2 scanner that can be used together with a laptop. PCMscan produced by Palmer Performance is what I use to diagnose running live diagnostics data on the cheap - more so on petrol engines. At least you can use it on any OBD2 complient motor. It still needs a good knowledge of diagnostics to spot the faults but you have a chance. Petrol IC's use more electronics to control the beast. On my scanner you can sit in the passenger seat and just monitor each component on the graph - MAFF, Lambda, MAP, fuel pressure,timing, misfires, etc and play it back as many times as you like.

I just read a statement by the Motor Industry pros who admit the aftermarket is facing a losing battle - my interpreted words. One little glimmer of hope is the Pass through system which may extend the dignostics for affordable aftermarket diagnostics a bit longer. Unfortunately the manufacturers are finding ever new and diverse ways of capturing the repair business, if you can get your hands on an Oscilliscope these are still very good at fault diagnosing with a scanner but soon, even if you know what's gone, you will need an interrogator to replace it since they are fitting everything with small chips that need to be assigned to the ECU before it will work. Stealer Job. Guess we will have to hang up our spanners soon.

[Welly]

they are fitting everything with small chips that need to be assigned to the ECU before it will work. Stealer Job. Guess we will have to hang up our spanners soon.

Yes I experienced this briefly with her indoors BMW I was faced with a "dealer only" repair and was told by my usual mechanic (who rents the most upto date diagnostic machine you can) that certain replacement parts are "coded" to the ECU

Given the huge number of sensors fitted to new cars for emissions, braking, steering etc etc then it looks like the dealers own garage centre will be doing very nicely thank you and at the expense of Johnny Motorist

[DaiRees]

Hi
hummmm - Long before ecu's and technology this would have been easy to locate now we have to fix the things that fix the thingy if you get what I mean.
You can go on forever feeling your way in the dark but in the real world you have to go with the flow and this is use as much test gear you can get your hands on and one little bastion of salvation for now is the OBD2 scanner that can be used together with a laptop. PCMscan produced by Palmer Performance is what I use to diagnose running live diagnostics data on the cheap - more so on petrol engines. At least you can use it on any OBD2 complient motor. It still needs a good knowledge of diagnostics to spot the faults but you have a chance. Petrol IC's use more electronics to control the beast. On my scanner you can sit in the passenger seat and just monitor each component on the graph - MAFF, Lambda, MAP, fuel pressure,timing, misfires, etc and play it back as many times as you like.

I just read a statement by the Motor Industry pros who admit the aftermarket is facing a losing battle - my interpreted words. One little glimmer of hope is the Pass through system which may extend the dignostics for affordable aftermarket diagnostics a bit longer. Unfortunately the manufacturers are finding ever new and diverse ways of capturing the repair business, if you can get your hands on an Oscilliscope these are still very good at fault diagnosing with a scanner but soon, even if you know what's gone, you will need an interrogator to replace it since they are fitting everything with small chips that need to be assigned to the ECU before it will work. Stealer Job. Guess we will have to hang up our spanners soon.

Hiya mate, the problem is that the garages depend too much on the diagnostic kit and have no idea how to fault find anymore. I have my own scanner for the laptop, which to be honest isn't much use other than reading and resetting fault codes, but my misfire problem has also been to Peugeot and to an independant Peugeot / Citroen Specialist. Both of them just stuck it on the computer, and when it said "no fault found" they just said "sorry, nothing wrong with it!" despite driving it and feeling the fault for themselves. The independant guy even said that if the computer doesn't indicate where the problem lies his only course of action could be to randomly start changing bits until it was fixed.

Anyway, touch wood, it's like a completely different car so far this week.

[Black Pearl]

As dairees said mechanics aint mechanics no more, they dont know what a spanner is other than an annoying ( an more often than not an expensive ) icon that flashes on the dashboard to tell em to stick the laptop on when theres a problem, tell em to fetch you a 3/8" spanner they'll look at you gone out, and they do as i am an engineer and i had to show an " apparent qualified mech university-dude" round the factory not long ago, there i was in a boiler suit dirty as hell ( it is a furnace and chemical stripping plant, hardly the cleanest place you can think of ) he turns up in a god damn suit !! i asked him to re-seal a water joint with PTFE tape and didnt know what it was ! no doubt on paper and theory of such things he'd walk all over me but a bic pen aint gonna fix a 30 horse power, 3 phase motor is it anyways my point is people aint trained properly how to diagnose the basic of faults. The kind of faults that need no fault code or fancy computer as its blatantly obvious to a PROPER mechanic what it actually is, like a misfire, a misfire is a misfire, even the fanciest of engines with all electronic control gear and sensors get em, but some simple steps to follow as a basic mech knows, is there a spark ? does it spark at the right time ? obviously theres more steps but fundamentally the clue is in the name. Ok there maybe contributing factors a laptop may pickup on but as we know it wont solve the problem of having a plug down or a blocked injector. Can ya tell it makes me mad what these colleges and universities are teaching people ya might as well train to be an I.T technician than a mechanic.

Another perfect example written off my mates old renault espace, he took it in for a misfire funnily enough, V6 petrol engine, simple, basically it cost him 300 quid cus the diagnosis machine wasnt old enough to communicate with his car and they had to ship it over from bloody france, they stripped the top end ( really dont know why ). When he did get it back, the only reason he did get it back was because the garage had written it off as more expense than the cars worth, just out of interest i checked it for him, it turn out to be a couple of points on the distributor had burnt away with damp leaking through a cracked dizzy cap...... he aint no mechanic so i wouldnt expect him to understand it without sounding offensive. But as im sure people here will know how easy a fault that is, and they written the car off for the sake of a £7 quid dizzy cap.

I'll stop ranting now, and urge people not to hang their spanners up, just encourage folk not to be frightened of all this fancy wiring and engines that look like dyson hoovers, strip all that crap away and your left with ( more often than not, though i do wish it was a V8 ) a straight 4 engine that sucks squeezes bangs and blows, something that this sorta concept has been doin for a long long time, they still get the basics of fault like fan belt squeal and misfiring but it does put you off with all these flashing lights and strange unknown parts that you think " how the hell can a cam diffuser make my car misfire " when it aint got nowt to do with that part of the system anyway. Trick is to Troubleshoot it as basic as possible, if it was a mini say, it'd be - its misifiring ive got a plug down or a HT lead shagged or me points are out. Same deal just a lot more plasitc, more wires, and thankfully less rust

[Longintooth]

Hi
I do like your approach and long may you reign. Sadly I was around when dynamos were the in thing and when the worst fault on an engine was a dwell angle too short on a set of points. But now the devices that control the spark, timing fuel injection and climate controls can only be determined by the use of computer aided live data. EG try to detect the pre,mid and post injection phases without an oscilloscope is ni on impossible. But that's ok for now since that's what we are doing. But shortly it will be proved that when you find the faulty injector with your scope you will need another computer program to pair the new part with the ECU. I have been holding back as long as possible from getting a program since the cheapest I can find is an after market scanner by Maverick Technology but it is £3350 plus VAT. I think like many it may be time to give up. I have an expensive scanner and oscilloscope and it won't be enough soon. Oh and your right they don't teach the basic technology anymore and they don't like being called Mechanics - They are Automotive Technicians no less. I'd like to see one of them tackle an Automatic transmission with clutches and bands that need replacing.

[steve_earwig]

Oh come on you guys, we bitched for years about rust so now they don't do that, but they still have to f#"k them up somehow, or they'd never sell new ones!

...they written the car off for the sake of a £7 quid dizzy cap.

Bunch of retards. Engineering's all about changing cards these days, no-one goes down to component level anymore 'cos it's quicker to just change the whole board and you can get a retarded monkey (or Renault-trained tech) on minimum wage to do that!

[Black Pearl]

I do agree on both counts, in a way im sitting on the fence of progression, i do like nowdays with throw away parts and modulated equipment, if its knackerd unbolt it and fit a new one that idea aint bad.

on the other hand i do like old fashioned ways in terms of D.I.Y mechanics and the fact that as i said earlier on a 4 stroke engine is a 4 stroke engine, we was doin alright bout 20 years ago id rather change a wing and spray it than fork out 100's of pounds to fix a jobby with pipes and all manner on we was alright with simple engines that ran and ran well and if you conked out on the motorway ya could make do with a laggy band and a bog roll if you had to. nowdays ya gotta get ya tired eyed AA mechanic with his yellow laptop out to plug it in an tell him whats wrong. Then after all that ya still gotta get on the back of a lowloader to take you home cus even he aint got a clue. In my opinion there is way too much fancy electronic controlled crap put on engines, i know they do it on purpose to make the engines more " intelligent " but if the chimps at the peugeot stealer themselves dont know how to fix it when it WILL go wrong then they shouldnt make it complicated in the first place. Who else ya gonna turn to if ya local stealer dont even know !! or if it is a component thats chuck away it wouldnt hurt if they actually knew which component they need to throw away, isnt that the whole point of the laptop telling you where, what and who is broke ? if the manufacturers dont want us to mess with our OWN cars and want to make a bit of money when you got no choice to take it to the stealer, fair enough. But not by the means of fancy gadgetry that gets their own garage chimps stuffed, wastes a lot of time and gets expensive. If it came to them and them alone working on our cars, or the bits they dont want us to mess with they should just machine the parts in such a way that it requires a dealer only tool rather than a fancy piece of crap that costs you the earth. Spose an example of this already exists as me and dairees know, the bi-hex sparkplug 3/8" socket. Unfortunately that was put on a bit of equipment ya do pretty much want to see for youself, peugeot eh ? the lights are on but...only cus they used a cheap ass switch that broke now ya cant switch em off

[steve_earwig]

[DaiRees]

Shwmae bachgen

Righteo, it was perfectly well behaved for a good while after the last plug gapping / change, including my half-term 1000 mile trip to Scotland , but the misfire's been creeping back in over recent weeks so today I gapped up another set of plugs off my shelf and stuck them in, again cleaning the coil pack extensions out, pulling the springs through past the lip and adding a little lube to help them slide over the plugs as they go back on. Appears to be job done again

BUT, she's only done about 3K since last time and the gaps on the plugs I took out today don't appear to have opened up alarmingly, they're still less that 1mm (gapped them to 0.9mm to put them in) so to my mind they should still be working fine, they're certainly no-where near the 1.2mm I was seeing before .

So I'm now wondering whether the cause might be more to do with the coil pack extensions & springs than the plugs themselves IIRC I lubed last time with a little ordinary high temp grease, but when I took the coil pack off today it was dry in there, with a horrible sticky residue. D'ya reckon that during the heating / cooling cycle (and these plugs get bloody hot!! There are scorch marks at the bottom of the ceramic body) the rubber extensions could be creeping up the plugs to the point where they eventually hold the spring just off the top of the plug?

If so what lube would you recommend? I used a smear of copper grease today but the first time I ever took the coil pack off there was a white paste in there, so I was thinking of trying to get hold of some thermal compond "silver grease" like you'd use between a chip and heatsink, thinking it needs to withstand pretty high temperatures, and it's conductive . Or is there a more suitable product out there?

....or am I clutching at straws?

What do you reckon dudes?

[teamster1975]

Very strange Dai!
You could be right with the thermal compound, I wonder what Pearl used on his & whether it's still working?

[steve_earwig]

Shwmae bachgen

Bless you!

Not sure if "pretty high" is high enough, a chip doesn't get all that hot and from what you said about scorch marks I'm thinking hundreds of degrees.

A quick Gurgle seems to say 200 degrees or so

[Black Pearl]

hmm, tis a good un this is aint with the misfire,

righty then, just tryin to remember as much as i can when i was faultfinding to make it stop for definite, lets see, when it started to appear again ( took about a month to come back throughout this time i was still faultfinding--long sodding time too lol ) i took the coilpack off, and myself i did notice the conductive grease had dried to a waxy kind of vaseline sort of texture, a quick spray of WD40 soon watered it back down to a grease again and a quick wipe of some more over the top satisfied my mind in thats been worked on and not gonna cause a problem, my next idea was to coat the insides of the sleeves with WD40, that i mind i sprayed down the sleeves and re fitted them ( noting the spring dont catch on the ledge inside ) next thing i did was further stretch the spring, this time i stretched it so that was a couple of spirals proud of the sleeves collar, the spark plugs i gapped & cleaned to a tight 1mm, probably more likley to be a good 0.9 and chucked them back in the block ( with great care o course ) then when i refitted the coilpack i did notice that there was some resistance pushing the coilpack away from the plugs, as ya can guess its the springs pushing on the top of the sparkplugs, with that in mind i tried to make the coilpack push equally along the top of the plugs, just to be certain contact is made, then whilst holding it down bolt it up. Till i did this a good 4-5 months ago the misfire has gone. Another factor i thought of at the time BP ultimate was so damn expensive i stopped using it and filling up with sainsburys unleaded instead, just a thought really that some of ya may agree or disagree with is higher octane fuel burns hotter, simple enough theory, does anyone share the thought of that extra temperature in combustion and with the sparkplug ground electrode being over length compared to a normal sparkplug that it warps in its position with expansion when under load and contraction on cooling ? i werent too sure if it would make a difference but just to test it, i stopped using. touch wood an all that the misfire has kept away- hope some of this random rambling helps

[Longintooth]

Hi D
I 've been watching your post with some interest - to state the obvious intermittent faults are the most difficult to pin point even with the best diagnostic tools.
But I always revert back to basics amongst the plethora of technical gizmo's fitted. With High pressure fuel systems now the mantra it has introduced a possible fault that is very similar to an electrical fault in that the injector spits in the exact amount of fuel to each cylinder so if that misses a beat you will get the same effect as spark plug missing a beat. Now since you say it occurs on throttle response I would be inclined to focus on the injectors, if you have thoroughly checked the ignition system and not found anything it could be on the fuelling, starting with the TPS, MAFF, which as you know can be read on your scanner. The problem with OBD2 scanners is they are not quick enough to spot the blip and unless it is missing a lot, no code will throw up . The only way I have solved these problems is by hooking up to an oscilloscope that is fast enough to show that blip. That is what your stealer will do and charge you a bucket of devalued pounds. However, this does not stop you checking the injector plugs and wires closely for water ingress etc. Always bear in mind an electrical miss can occur when the cylinder pressure increases on demand, suppressing the spark so be sure about those spark plugs and leads.
Hope this helps
John

[DaiRees]

Hmmm, thanks guys, food for thought....

I'm pretty sure it's ignition rather than the injectors Longy, 'cos fiddling with the plugs and coil pack made it go away for a couple of thousand miles last time, and appears to have cured it again (lovely today again, a pleasure to drive!). I haven't touched the injectors at all, ever .

Any ideas on where I could source some suitable grease type stuff?