Misfiring badly

[granvit]

apologies for this being long question. we have got a Suzuki Grand Vitara 2002 2.0 16v petrol which has developed a misfire, we brought earlier this year (missus pride and joy) never missed a beat at all, but it had its first long run up to Cumbria...no problem, got back travelling down the M4 couple of days later, the wife said she noticed the power drop off going up the slip road, nursed it to a friends place, called AA next day..he started it up but it was misfiring took plugs out and said that's the problem no 3 plug had burnt it's electrode away, engines gone etc etc did we want to sell it (hmm!) I did notice he had tapped all the other plugs closed tight!, brought truck back home put a new set of plugs in started up first flick as normal running sweet as a nut, quiet as a mouse, went for a run got up the road..misfire (running on 3 cylinders) came back after about 1/2mile got back home, a friend brought his reader plugged it in, it said multiple misfire, fitted set of injectors )secondhand) ..started first time, running nice gave it a few light revs, misfire again...fitted 4 coil packs (secondhand) started up running on tickover for 1/2hr no probs...gave it increased light revs after a minute or so misfire again. went out there later started up perfect again ran for 3/4hr and would have continued on tickover I thought give it some revs after a minute or so..misfire came back, I thing I noticed is that something on top of the engine is clicking loudly when it misfires and the engine management light flickers it seems when you want more fuel or are asking it to do more you get the misfire, it's costing an arm and a leg at the minute albeit secondhand parts to no avail. If you need any further info, please ask. Can you wizards offer any help please.

[Darrell]

Welcome to the forum. Any more info on the code number. Is there any link between it misfiring and how hot it is. The camshaft sensor sometimes can suffer from heat soak and can cause a misfire once hot.

[ForrestHarris]

Hi,

Since you've had the vehicle plugged in I would guess you know which cylinder is missing
p0301 is cyl 1 p0302 is cyl 2 and so on p0300 is multiple cylinders

Start with the ignition system:
check plugs for cracks, carbon and oil/fuel fouling - also check the color of the plugs white electrodes normally mean engine is running too hot and plugs will fail quickly in these conditions
check coils for burns, oil and carbon tracks
check for a spark - either use a proper spark tester or pull plug and use a jump lead to earth it out (make sure to disconnect fuel pump)
Check your battery and alternator

Then fuel system
check injectors - a simple noid light test or resistance check
check fuel pump - check fuel pressure with a pressure gauge (a pump that puts out low pressure will cause the engine to run lean and will most likely misfire/rough idle once engine has warmed up) low pressure can also be a blocked filter start with filter if pressure is low as its cheaper than a pump
and a pressure regulator test - (check for fuel leaking from the vacuum hose inlet nipple common on older engines - ive seen that on some older vit's)

if none of the above has helped look at the engine
get a compression test done - will tell you whether you have burned or worn cylinder head valves or piston rings
check vacuum pipes for dry rot, tears and holes - simply spray a small amount of carb cleaner on pipes and around inlet manifold and listen for a change in engine noise this will pinpoint any leaking pipes/manifold gasket (do this only when engine is cold)
and check throttle body for carbon deposits if any are found simply clean them with an old toothbrush and some carb cleaner
Check valve timing - one tooth and engine will normally run fine but will hesitate and have a lack of power - two teeth and you will have a constant misfire

Hope that helps, if not get the trouble codes up like Darrell has said i'm sure someone will be able to help then

[granvit]

Hi Darrell & Forest Harris
Many thanks for getting back in touch so quick, I do think it is when she gets hotter...like I said running for 1/2hr or so on tick over, absolutely perfect you would never think that if I rev it a few times it would suddenly start misfiring and cut out as the revs were so low as it was misfiring you could hear this loud click from the top of the engine, could that be that camshaft sensor? when that AA guy also said multiple cylinder misfire. my heart sank but I have heard that if you close all the gaps up to nothing which is what he did it damages the ECU?? I wonder why the electrode hook burnt away on that number 3 anyway. put new plugs in it ran perfect until I road tested it and the misfire came back. Leave it to cool down for a while starts up perfect again on tick over. same with another set of injectors ran it on tickover then misfire when I revved it, same again with the coil packs. the guy who put his machine on said multi cylinder misfire. mentioned a sensor on the top of the engine, he said crank sensor and it was affecting timing could it be that camshaft one? I will have a good look around the engine bay and see if I can get that sensor you were on about. Is it easy to fit? what actually does it do? where is the fuel filter on the Vitara guys? i'll get back in touch with the lad with the reader and see what code it was.
thanks again
Bryn

[ForrestHarris]

Hi,

Camshaft position sensor determines which cylinder is firing to establish injector synchronisation and coil firing sequence in DIS systems
Crankshaft position sensor sets ignition timing, supply's rpm signal and determines engine speed

So what your saying is the vehicle misfires under load and when hot?
Personally I would work my way through the list mentioned above, at least then you will have covered all base's, without actually looking at it it's hard to pinpoint a fault on a description. But if I had to guess I would think that either you have fuel starvation leading to it running lean or your cam/crank sensor is failing through excessive heat transfer.

Closing the gaps on the plugs shouldn't damage any control module's, as you are basically shorting out the plug

[Darrell]

We seem to have a difference of opinion here , as far as I'm aware the camshaft sensor controls the ignition timing on the J20A engine. Either way this unit can suffer from heat-soak (fails when hot) and cause the symptoms you have. The only way to really test this unit is with an oscilloscope to check the wave pattern when the misfire happens. This is not very practical even if you have a scope. The crude method I have known used is when the misfire starts, stop the engine and cool the sensor with a wet rag for a few minutes and then start it back up and see if the misfire has gone (if only for a short while). If this cures it for short while it's most likely faulty. The black plastic part is actually the sensor. I like proper fault diagnostics but in this case it's not easy to do, chances are a multimeter test would say its OK. I guess it's your choice as a new sensor may not cure it and therefore be a waste of money. Best of luck .

[ForrestHarris]

Probably is Darrell, I'm not too clued up on Vit's. Being as I'm a hgv monkey
We used to check for excessive heat transfer in the same sort of way, although we used to use shock&unlock spray to rapidly cool the sensor. Probably not a good idea on a car though being as the part is plastic and quite small.
The signal probably switches to fast for a basic multimeter, although a good fluke meter might do the job.
Anyway hope you get to the bottom of it

[granvit]

Well Darrell and Forest Harris
Once again thanks for offering your help by virtue of your knowledge.
I wouldn't have said it was under load really as it is when I free rev it, yes it is hot when it is doing it, just cant believe it runs perfect on tickover. I will do exactly as you have suggested hopefully tomorrow and rapidly cool the sensor when it misfires. Did you think what sounds like something electrical clicking on top of the engine when its misfiring be anything to do with it? or is it something else. First I will try that cooling of the sensor and update you. Where is the fuel filter situated on it, any ideas.
Bryn

[zook123]

Could the clicking be a dodgy injector?