cold misfire *updated* HELP

Okay

My car has a cold start miss fire sometimes thats getting on my nerves now and im just wondering if worm valve stem seals could actually cause a miss fire ?

my problem

leave the car for a week

start the car fine leave idleing until warm with out moving its fine ( no miss )

drive the car with not letting it get warm and pull off up the road light load starts to miss badly sometimes black smoke back fires and all sorts sometimes,

but after the car is warm (not full temp) 2-3 minutes its fine

if i go into boost with the miss fire it goes away and then comes back when not in boost again until warm

i have changed

plugs

coil clips

coil packs (twice)

ecu water temp sensor

injectors

bypassed fuel pump ecu

could oil coming down the valve drip on the piston that it could cause this ?

just wonder if anyone has any ideas what to check next really,

You've changed the obvious. But to answer your question,VSOS can cause a misfire, If the spark plug(s) is/are encrusted with oil ash, oil might be leaking through worn valve stem seals or potentially piston rings. But this would be noticeable on your plugs and a worse case scenario. Could it be an intermittent injector fault? Is the misfire cylinder specific or a few when it starts?

it does seem to be more then one cylinder missing sometimes, i may get the injectors out and have them flow tested im starting to think one or more is sticking open,

i may as well do the vsos as well at some point, it does seem to worse the longer i leave the car so could point to them

I would think the vss's would have to be leaking very badly to cause a missfire, mine were totally

scrap but it didn't missfire

How long does your car blow out blue/grey smoke for when first started ?

Mine used to be less than 5 secs at its worst

it does seem to be more then one cylinder missing sometimes, i may get the injectors out and have them flow tested im starting to think one or more is sticking open,

 

i may as well do the vsos as well at some point, it does seem to worse the longer i leave the car so could point to them

Does your car smoke on start up? Or whilst driving? Mine ended up more a smoke machine than car

I would think the vss's would have to be leaking very badly to cause a missfire,

Defo worse case scenario to get it. My cure was a rebuild. To be fair it was head damaged by an hks iridium tip that failed and fell into cylinder 5

Sounds like an over fueling problem to me, stuck injector etc.

Sounds like an over fueling problem to me, stuck injector etc.

Gets my vote and possibly even the cold temp sensor perhaps ?

Leaking valve stem oil burns off pretty quickly and doesn't re occur until the engine isn't run

for sometime

I would think the vss's would have to be leaking very badly to cause a missfire, mine were totally

scrap but it didn't missfire

 

How long does your car blow out blue/grey smoke for when first started ?

 

Mine used to be less than 5 secs at its worst

blue smoke very little maybe 2 secs if that, from a week standing,

but black on the other hand lots for about 1 minute afr is between 12 - 13 on first cold start up, but even then once black smooke has gone its still got a miss for a little while,

when i start the car and if i rev it there is a spray on the floor from the exhuast as well as black smoke i will check to see if thats fuel i just asumed it was condensation

I'd go for injectors next - Take them out and get them flow tested. If that doesnt work take the car to SRD or whifbitz for a checkover

What duty cycle are you injectors running at?

Gets my vote and possibly even the cold temp sensor perhaps ?

 

Leaking valve stem oil burns off pretty quickly and doesn't re occur until the engine isn't run

for sometime

what cold temp sensors are there to check ? i was starting to think there could be a sensor issue

bigger injectors next time if it comes to it then turn my boost up lol 1.3 on a t67dbb is so last year

what cold temp sensors are there to check ? i was starting to think there could be a sensor issue

ECU coolant temp sensor (the one with two wires) although if this is faulty you would be seeing constant rich AFRs and fuel consumption would be high, this sound more like a single injector problem, this can be offset by the other cylinders when monitoring AFRs.

ECU coolant temp sensor (the one with two wires) although if this is faulty you would be seeing constant rich AFRs and fuel consumption would be high, this sound more like a single injector problem, this can be offset by the other cylinders when monitoring AFRs.

cheers rick, i did notice the other day that the afr did stay at around 13, but hasent done it since , i may just get a new one and see anyway, failing that is there any wasy of checking the injectors ,

i do have a fic that can monitor the injector duty but im unsure if a sticking injector would show up.

if it was a injector faulty would a flow test even pick it up ? as they work as normal when warm?

No a flow test will find it no problem whether its stuck or just malfunctioning, how do you know if its working normal when warm?

well i guess i dont but the car runs smooth and has no misfire when at normal temprature.

so the flow test will pick up a leaking injector too? sorry for the newb questions i dont know anything about the flow tests or how they are done

well i guess i dont but the car runs smooth and has no misfire when at normal temprature.

 

so the flow test will pick up a leaking injector too? sorry for the newb questions i dont know anything about the flow tests or how they are done

As far as im aware, They bench test the injectors pumping fuel and pressure through each injector

As far as im aware, They bench test the injectors pumping fuel and pressure through each injector

yes that what i thought

but do they

1 build pressure to see if it leaks

2 do a low duty test to see if they are slow acting

3 test repeatedly for consistancy

or is it just plug them in all full chat and see if they deliver 650cc ?

well i changed the ecu water temp sensor last night its not that , but did see my afr lean out 17 -18 afr way to lean (sticking injector highly likely ?)

i will change back to my original coil packs tonight to see if that improves

i just cant get round why it only does it when cold and when driving , but idles and revs fine stationary

Riped the injectors out today, going to get them sent off too chris wilson to have a look at and see if they are the cause, I will also refurb the plugs for the injectors as they look to be not the best

Okay had injectors tested come back as bad but after a clean was okay but chris still surgested replacement would be best, so fitted a new set and well its not a injector problem

So that was an expensive waste of time

I have now replace the fuel pump relay.

If not that I may well completly bypass the fuel pump ecu and go from there,

its not the fuel pump ecu totally bypassed that and yet it still happens,

i even changed coil packs again still happens

im starting to run out of ideas any help would be great.

im thinking of changing the plugs again as im at a lose now

What ECU are you running? Sounds like you've eliminated everything apart from that. Have you checked all the engine bay earthing points etc?

im running the AEM fic8, i did some time back i may well give them a good clean and check the ecu earths as well,

As Chris said in the other post, Id be looking at the ECU. FICs dont have the best reliabillity record.

^I went at it going over all ecu connection and started to check injector feeds, pulled number one injector while I had misfire and no change , so checked wires from injector to ecu and they was ok , so went to check the condition of the plugs, and coil packs unplugged and plugged in the coil clip , and was not missing again , so proceeded to check the clip conections inside and took it apart bent the legs up, put back together and still the miss^^so moved the wires and stopped missing, so thought the wires where broken to the coil pack, so stripped the wire back as far as I could to replace and look what I found inside the heat sheald,Well the good news is that its not missing anymore but we will see as it was getting hot while I was testing it running but in sure it might be done, im shocked how far back the wires where damaged