HELP HELP 1.8 VALVER LUMP MISFIRE UNDER LIGHT LOAD

[joeshutt]

Hi people i hope you can help me !!!!

ive fitted a valver lump to my 340 it start fine and idles ok but with a very very slight miss, as you go to pull away so low revs and light throttle it misfires and hesitates , but as you rev it, it clears up and is perfect from about 2 or 3 k onwards

you can boot it once its past the cough and splutter and it pulls like a train and doesnt feel to miss at all.

just want to know if anyone has had simular issues and what it could be, it has new plugs , ht leads and dizzy + rotor. it also had a good working coil pack.

pleeeeeease help guys !!!!

[theo2468]

That looks Shit hot!!!!!

[jon-ovlov]

Was about to say check plugs, leads etc. Possible oil in the plug chamber? I had a problem with mine, were an O ring seal on the plastic bit that fits inside the tube ceased to exist, and began filling the part on top of the plug with oil, breaking the contact between HT lead and plug.

Replaced seal, cleaned oil, all was peachy.

What about the timing? did you replace the belt/check timing etc before the engine was put in?

[joeshutt]

cheers mate but i know thats ok as i checked that its just a miss on intial load. im going to try a new manifold air temp sensor and another idle control valve although i dont think its that , i am going to replace the cambelt in a week as my tensioner is noisey so ill check the timing then but i am sure thats ok . im wondering if it could be the little red sensor on the side of the throttle body ? the throttle position sensor i think ? do you know if when they come off idle a microswitch should click by the sensor ? just wondering as bmws do and the clio lump doesnt , although that may be normal .

[jon-ovlov]

If the tensioner pulley is noisy, it could well be the timing is off slightly. My TPS doesn't click as far as I'm aware, never heard it to that, but never really listened for it. Is it only one mis fire, not several? Could be that too. I'd try a few things, see what happens. Provided they aren't too expensive

[joeshutt]

urm to be honest i think it feels like 1 cylinder hard to tell tho it picks up thru it but if you blip the throttle it misses, so its could be a fault tps? are they pricey i may just get one so i know thats done . i only said about the click as i know some old beemers do but these may not anyways .wen i do the tensioner ill check its all in time , wheres the marks on these engines to check ? cheers mate

[jon-ovlov]

Dunno about the TPS pricing, but get on williamsclio.co.uk. Always things on there. Otherwise I would think renault do replacement ones. Timing is 2 marks on the belt, with 2 marks on the rocker cover directly above the 2 pulleys. theres also a mark on the bottom pulley where another single mark on the belt should line up with.

http://www.cliowilliams.co.uk/forum/vie ... a41afd7bb0

At the bottom of that thread in the link, there's a link to a clio williams manual, which has a load of info on replacing things like timing belts etc.

[CBA]

check them plug leads are making good connections.

Removing+refitting engine could have let some crud go down the fuel lines.

If the misfire is at low revs and maybe confined to one cylinder check for stiff or sticking valves.



Mine was doing exactly this - and was a loose lead.

[joeshutt]

ah sweet mate yeah i checked for them timing marks , i see should be nice n easy then ill do that tomoro and cheers ill check all connections tomoro too , think its going to be a process of illimination with this one . but please keep suggestions coming when its all sorted and ive actually cleaned it ill get some pics up

[CBA]

if you have changed anything, I was thinking wrong rotor arm.. if it isnt the right size and shape the spark will have to jump a long way.. also check for moisture in the cap, clean it as a matter or course.

[CBA]

Damp distributor cap!!, NEW means nothing - what you need is DRY
Stand a 300 in the rain for 48 hours, it will have a damp cap, never had one that didn't need a quick dizzy-cap clean after standing a few days.

[joeshutt]

lol ok matey ill wip it bk off and check it all thanks

[joeshutt]

i have done all of the suggested bits guys and still have a misfire on light throttle yet over about 3k its fine light throttle or heavy.

it has had new plugs leads dizzy and rotor,
i have tried another coil pack
cannot find any air leaks
has new idle control valve
new intake air temp sensor

tried unplugging the coolant temp sensor to ecu loom no change still there.

checked ecu has a good earth.

fuel pressure checked and all ok upgraded fuel lines too

all i havent changed is my tps but when adjusted it changes the way it runs , yet still misses
havent changed the map sensor but i couldnt see this causing a misfire ?
havent changed the fuel rail or injectors

the car smells fairly rich and i took the plugs back out to check and they were fairly black. could it be the screw for the c0 on the throttle body?

also guys im not running a oxygen sensor on this , but my mate never did on his and it ran fine & my other mate with the same lump has a simular fault and he fitted a sensor to his and it made no difference




hope some people can give me some more suggestions before i set fire to the bloody thing !!!!! lol

[Chris_C]

So are you running stock ECU for fuel and ignition? There are so many different ways people are running valvers you'll have to explain it completely.

If you are running the ECU will expect all sensors, without the lambda it'll keep trying to get richer and richer until the sensor output see's the correct value, which if it's disconnected will be never.

[joeshutt]

Yeah I'm running ecu and ignition , just seems wierd my mates ran fine with no lambda?