Viewing 37 posts - 1 through 37 (of 37 total)
  • Car Mechanics! What the duck is going on with my van?
  • walla24
    Free Member

    Following on from my ‘is there a duck in my engine’ thread….please help me figure out what is up with my poor little van.

    The van:
    2002 Renault Kangoo in the sporty 1.2l petrol engine, with a dual fuel LPG conversion. Manual.

    The problem:
    In low rev’s (1-2k) if you put your foot down reasonably hard the engine noticeably stutters and you can hear a ‘pop’ like a big packet of crisps being popped open. Usually it is just a single ‘pop/stutter’ as you accelerate but if you really load the engine say low revs in 5th gear there are a number in quick succession.

    After running the engine till warm the idle would be perfect then as though a cylinder had missed it would drop lower then pick up again, again just as though a single cylinder had missed.

    Today I pulled the leads off one by one to see which cylinder it might be but they all sparked normally (as far as i can see) and the engine didn’t cut out.

    I put in new spark plugs today and drove a few miles, I would say it was perfect initially and an improvement overall but if I put it in 5th and tried to accelerate the ‘pop’ came back.

    What do you reckon folks?

    I REALLY appreciate the help, I can’t really afford to go to a garage until the last resort.

    wobbliscott
    Free Member

    When you took your spark plugs out did they have a black sooty deposit on them or were they wet/oily? Or did they have a nice light brown coating?

    somafunk
    Full Member

    At a very outside guess it sounds like a vacuum pipe issue or perhaps an air leak in the inlet side from the airbox to inlet manifold – check all the vacuum pipes/lines are intact and fitting well, they’re may also be a few vacuum valves to examine, if these leak then they can occasionally “pop” under load.

    Obviously diagnosing such an issue on this side of the keyboard is nigh on impossible but ^ is a good place to start.

    walla24
    Free Member



    walla24
    Free Member

    Thanks guys, the plugs have only been in 6 months.
    I would say on the ignition ends they are a nice light brown dusting.

    The ‘upper/outer’ ends are a little greasy (especially in 1 and 2) with a thick dried on something.

    walla24
    Free Member

    And what is a vacuum pipe, are they small diameter rubberish type houses?

    wobbliscott
    Free Member

    Spark plugs look ok, I was trying to establish if combustion was good and if the popping sound was a backfire or not, but all looks like it’s probably ok. Probably as sumafunk has suggested and a vacuum leak/air.

    maxtorque
    Full Member

    I reckon the air to fuel ratio is going critically lean on tip ins!

    When the AFR increase a lean misfire occurs, which is the duck “quack” you can hear, combined with a stutter from the engine.

    At low rpm, the engine needs more fuel to be added when you open the throttle quickly (for various complicated reasons i won’t go into here) and too little extra fuel (called acceleration enrichment) results in a lean spike and in bad cases (AFR > ~ 16:1) misfires.

    However, you also suggest that the engine misfires continuously at wide open throttle at low rpm. I am going to assume that this is when it is operating on the LPG system (generally, speaking, most LPG systems are frankly s**t, in terms of systems engineering and specifically calibration)

    You need to get a scan took and take a look at the lambda sensor output (the sensor in the exhaust that reads AFR) during these events. You may find that disconnecting the battery for 15mins helps, as that will generally reset any learnt fuel adaptions.

    maxtorque
    Full Member

    PS> If it only happens at high throttle openings, it is not an air leak (although you might have one of those too) as the plenum pressure gets very close to atmospheric pressure at WOT

    walla24
    Free Member

    Hey thanks for the reply:

    The ‘quack’ is only on cold start, apparently a sticky starter motor…I am not too worried about it.

    Yes the LPG system is definitely shoddy and badly wired.

    The ‘pop’ is when in Petrol or LPG but never at high revs, only at low revs when accelerating.

    I will try disconnecting the battery and reset.

    At low rpm, the engine needs more fuel to be added when you open the throttle quickly (for various complicated reasons i won’t go into here) and too little extra fuel (called acceleration enrichment) results in a lean spike and in bad cases (AFR > ~ 16:1) misfires.

    How is this solved?

    maxtorque
    Full Member

    It could suggest your throttle position sensor is faulty.

    The EMS system looks for a rapid change in throttle position, and automatically triggers some extra fuelling to account for the fuel needed during transient acceleration.

    Generally speaking, you get a lot of faults on LPG that “disappear” when running on the original petrol system. That is usually because the LPG system calibration is awful! (the add-on LPG system suppliers do all sorts of bodges and tricks to get there systems to run, but they are no way near as accurate (in terms of fuel delivery and control) as the original petrol system.

    Well worth trying to get hold of a scan tool and see what sort of fuelling adaptions have been stored (the system attempts to learn how much fuel it should be adding, but often the addition of LPG system completely **** that learning up, and you can get systems that have “learnt” large negative fuel trims (taking out fuel) due to the LPG system

    trail_rat
    Free Member

    When was it last serviced.

    My lpg v8 backfires through the inlet when the air filters minket

    walla24
    Free Member

    It sounds like I need to see a specialist?

    Or can most garages handle this sort of problem?

    trail_rat
    Free Member

    An lpg specialist would be good. If they not used to lpg they will be guessing.

    walla24
    Free Member

    trail rat…good point:
    Last time it was in the garage for the MOT they refitted an engine mount but somehow it started only running on 3 cylinders while they were working on it. The mechanic told me that the wiring on the ECU was damaged and he resoldered part of the board which sorted the problem.

    Could this be related?

    Marko
    Full Member

    Maxtorque talks a lot of sense above.

    Always rule out a mechanical fault first. Next up on the check list would be a cylinder leakage test – NOT a compression test.

    And chuck the LPG conversion in the bin . . . 🙁

    Marko

    walla24
    Free Member

    So would you guys recommend going to my local garage or an LPG specialist first?

    suburbanreuben
    Free Member

    +1 !
    Does it do this on lpg only, petrol only, or both fuels?
    If it’s on both your local garage might be able to help. If it’s on gas only they probably won’t have a clue.
    The ignition system on LPG powered engines needs to be in tippy top condition and you will probably benefit from running different plugs. You don’t show the business end of the plugs above…
    Has the lpg system been serviced recently?
    How long has the lpg been fitted and what system is it?
    There are some good lpg specialists but they are few and far between.

    suburbanreuben
    Free Member
    bikerdan
    Free Member

    Not sure if the engines are the same but on our 03 1.2 Clio I had a similar sounding issue. Would have real issues when I accelerated and would then also sometimes get an engine fuel exhaust warning light flashing. I changed the coil pack and leads and now it is all sorted.

    walla24
    Free Member

    It has this problem on BOTH petrol and LPG

    I have no idea at all which LPG system is fitted other than it is impossible to find ECU replacements for. I no it is not a fancy multiport systems just a condenser/blows into the intake. It has been on the van for 5 years i think.

    It has probably never been serviced, and it looks like it has been wired by a half drunk monkey….having said that up until now it has been extremely reliable and the LPG switch over is always instant and responsive on the throttle.

    walla24
    Free Member

    bikerdan what is a coil pack?

    walla24
    Free Member

    just googled it…I can only hope it turns out to be something easy to sort like this!

    maxtorque
    Full Member

    A Flashing MIL indicates a misfire is occuring. If this happens enough, you will then get a “solid” MIL that will store the code of the misfiring cylinder.

    I don’t like the sound of “resoldered part of the board” tbh!

    If you have a basic voltmeter (multimeter) you can monitor what your lambda sensor is doing. Google “lambda sensor voltages” for more info.

    maxtorque
    Full Member

    PS, i don’t think it’s going to be an ignition related issue. Possible of course, but why would it only misfire at low speed or during tip-ins from low speed?

    walla24
    Free Member

    hmmm true it runs perfectly smooth above 2000rpm regardless of load etc

    thisisnotaspoon
    Free Member

    Left field suggestion……….

    Is the clutch slipping? Fit’s everything bar the pop sound, and I guess it could make some funny noises if one of the springs was broken?

    walla24
    Free Member

    Funny you would say that…

    The clutch(?) has recently started ‘clunking’ when I bring the clutch pedal back up while driving?

    thisisnotaspoon
    Free Member

    Spigot

    walla24
    Free Member

    Spigot

    are you insulting me or is this a technical term? 😀

    and define ate itself?

    I was going to just ignore it until it got worse due to money 🙁

    thisisnotaspoon
    Free Member

    i miss read that it’d been replaced recently for some reason, and did a (not so) ninja edit.

    It’s a bearing in the flywheel that allows the gearbox shaft (and hence clutch when not pressed into the flywheel) to spin at a different speed to the engine. On my midget it just disintegrated, but thats the crap British Leyland design which used a brass ‘hoola hoop’, modern cars usually have a needle roller bearing that will outlive the engine.

    It’s a 50p to £5 part, but you need to take the clutch out to get at it so may as well fit a new clutch while it’s apart.

    walla24
    Free Member

    nope hasn’t been replaced as far as I know, would that share some symptoms of my problem?

    molgrips
    Free Member

    PS, i don’t think it’s going to be an ignition related issue. Possible of course, but why would it only misfire at low speed or during tip-ins from low speed

    Timing adjustment? Will probably be electronic these days so.. Crankshaft position sensor?

    Not sure though, not had this particular part of any of my cars go wrong yet so no cause to learn about it 🙂

    walla24
    Free Member

    not had this particular part of any of my cars go wrong yet so no cause to learn about it

    So true, If anyone ever need help with CV joints i’m a pro, but otherwise….not a clue.

    Thanks for all you help guys, I will go and sweet talk an expert when I get chance.

    walla24
    Free Member

    Quick question:

    Does the voltage going to the fuel pump relate to the fuel flow and hence the air/fuel mix, eg. higher voltage-pump faster-richer mix?

    Or is the flow regulated else where?

    Reason I ask is I have had problem with a relay where there is an input from the Petrol ECU and the LPG ECU with one of the outputs definately going to the fuel pump.
    The output melted previously and was rewired…now could be me going crazy or I can here it click twice when pulling away/stopping

    walla24
    Free Member

    Update- swapped out the coil pack and leads…..she’s running sweet.

    Thanks guys, much appreciate the advice as always

    konabunny
    Free Member

    Nice!

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