Cold start misfire

[Bushbasher]

OK, this has been bugging me for a few weeks now and I'm still not sure what the problem is but I'm guessing it HAS to be head gasket....... anyway.... on cold starts the motor is only running on 5 cylinders as #3 isn't firing. Problem is, I can't figure out the problem. It's not a dud plug as they've been changed twice, it's not the coil pack as it's getting good spark and it's not the injector as it's doing it on both gas and petrol alike. So that just leaves head gasket leaking coolant into the cylinder or maybe a sticky valve right? Thing is, it doesn't appear to be losing any noticable abount of coolant and the cooling system isn't being pressurised. Off idle at about 1500rpm it seems to come good but dropping back to idle #3 drops out again till it's warm. Working on the theory that it's coolant in the pot I revved it and held it at 2500rpm for 10-15 secs thinking that would blow the water out and it should run clean but it still dropped #3 again after I tried this. Also, if it's a sticky valve surely there'd be some noise to indicate something's not right but it runs quietly as normal so all in all it's got me stumped. Anyone got any thoughts on my little dilemma as to what to look at next or my next coarse of action? Also, if it IS a very small coolant leak is there anything I can safely put in the system that'll seal the leak up without causing any other detrimental side affects so I don't have to shell out for a head gasket replacement?

Cheers
Bushbasher

[5.0 ED]

What about plug leads, and what colour was the spark plug when you pulled it out, sometimes injectors go faulty and leak into the cylinders causing problems too, but if it did you should see it on the plug being black and with build up.

Could also be a recessing valve that isn't quite sealing properly. Best thing to do would be a compression test first and see, if it's low on that cylinder then your looking at valve/head gasket etc, if its not then it should be an external problem like plug leads or leaking injector.

Could also be that you have a intake manifold vacuum leak at no 3 causing it run lean at idle, easiest way to find this is when its cold and missing get a can of wd40 and spray it around the injector and intake port and if the miss goes there's ya prob.

With the injectors start the car on petrol, pull the fuel pump fuse out and let it stall, so that you have no petrol in injector and then start the car on gas if it's still missing then not a leaky injector.

Hope this helps.

[Stav]

Cold start misfire...rough idling until warmup.Heheh the classical symptoms of cold start enrichment.The computer richens up fuel like an electronic choke.This accounts for the poor cold start. I would be looking at..ignition system or idle speed controller on the throttle body.

[Mechan1k]

Any lifter sounds ... a dodgy lifter can cause you what seems like a misfire ... although it should be bloody loud with a decent clacking sound.

Some coilpacks can be dodgy though and not throw codes either ... I had one that actually cause misfire on idle ... but drove fine ... then the odd misfire on WOT (causing a hell of a bang on gas).

[Bushbasher]

Thanks for all the input guys, most appreciated. After much fiddling around and testing it's definitely leaking coolant into #3 pot overnight. I tested the leads and coil pack and they are fine, there is no lifter noise and no manifold leak. I did the petrol injector leak test by pulling the fuel pump fuse, letting it stall out then letting it sit overnight with no fuel pressure. No joy there so after starting it up yesterday morning for 30 seconds and finding no difference I pulled the plug and found it wet so there's the answer, coolant in the pot. So now I'm up for a strip down to do the gasket but I was advised that I might as well change the head as it'll probably wind up going again as the valves etc. are probably a bit second hand by now after 165k and it could well have a tiny crack in it somewhere that may not be see-able .Hmmm............. But seeing as the cost to replace the head could be upwards of $1500 with labour it'd be cheaper to just go find another low k motor and do a swap. Having said all that, I've just moved half way across the country and the wallet is a bit low at the moment so any major work is going to hurt ALOT right now so I'm thinking I'm going to have to try and make this thing last as long as possible. With that in mind, and considering it's not losing any noticeable amount of fluid which tells me it's got to be only the tiniest leak, and only when cold, what can I put into the cooling system to seal up the leak in the short to medium term that won't cause any unwanted side effects? Does anyone have any experience with any of the leak sealers in the i6? What do you guys recommend?

Thanks for all your help.
Cheers
Bushbasher

[howesy]

Originally Posted by Bushbasher

Does anyone have any experience with any of the leak sealers in the i6? What do you guys recommend?

Thanks for all your help.
Cheers
Bushbasher

A mate just used one in his with good success. If it is only very minor give it a try. . He went for the one with clear liquid and brown muck in bottom, called seal up. It should at least give you time to get the funds together to budget for the full monty.

[5.0 ED]

Most of these leak sealers do work but although they may claim to not effect your cooling system, to some degree they have to,

Take 1 solution made to block up holes, and place into cooling system with radiator and heater core with many holes.

On that note i have used bar's stop leak several times on an EA that i didn't care about and it did solve my problem with a blow head gasket temporarilly, i found that after adding it if i later removed the water and put in clean water it would start to leak again and that it would only work if i left the stop leak in. Afterwards when fixed i'd give it a flush with bar's matching radiator cleaning, and i never had a radiator block up problem, but by no means am i saying you wont and that it doesn't cause some sort of blockages however minor and unnoticable they may be.

[mik]

i`m a bit of a fan off wynns stop leak for general leaks, have used it many times,actually i used it in my mums old heap there was a small leak under the inlet manifold that i could never locate which it stopped, my little brother later crashed car front end pushed up against the engine .............still no leaks , the car was an old nissan bluebird we straightened the car out it ran for another 12 months before we finally sent the old car the scrap metal mostly because of the general shoddy appearance, i found another product a while ago by accident and saved it to favorites i dont know if this product can be bought here(its a US product), but for blown headgasgets it looks quite good heres the link ,http://www.steelseal.com/eng/home.html
any one seen or used this product?

[Bushbasher]

Well, I tried some stuff the local mechanic gave me after I told him my problem and it did bugger all but I think that is because all of these different sealants need to be flowing to the leak once the engine heats up so as to react with the heat and seal the hole. The problem is that once the engine warms up enough to open the thermostat and allow the water/sealant to flow, the leak has sealed itself up and nothing can get through to do any good. So now I'm thinking that the only chance I've got is to have something like the Steelseal that Mik has found that is a liquid that will stay suspended in the water till it gets hot and does it's job, as opposed to the particulate types that will just settle till there is water flow to carry them to the hole (which is too late). Does anyone know where I might find this stuff locally or know of a local product that will do the same job? It sounds alot like chemiweld but I've heard alot of conflicting reports about that stuff and am very wary of using it.
Does anyone have any experience with chemiweld in a similar situation and what was the outcome?

Bushbasher