Missing Under Load

[RoboticCherry-Coke]

Hey guys,

So my ecotec VS calais has just starting missing when I put my foot down. It has had all new plugs and leads about 10000kms ago. It also had the coil pack replaced a few years ago.

I pulled some of the plugs out the other day and one of them had a fair amount of white build up on it. So I cleaned it up put it back in and it was good as gold.

However, last night the issue re-emerged. So I pulled all the plugs out, none of them were that bad but I cleaned them up none the less. This hasn't solved the issue and I have just noticed that when I put my foot down and it misses I can hear a knock come from the engine every now and then. If I accelerate gently it all seems fine. It also smells a bit but I figure that could just be power steering fluid burning off as my pump leaks pretty badly.

Any help would be great.

Cheers

Oh and not sure if its helpful but its currently running 98% octane fuel. Normally runs on standard unleaded but I run it on 95% or 98% every now and then and its never normally an issue.

[Not_An_Abba_Fan]

When you pulled the plugs out, did they have a black ring around a couple of them about where the lead finishes? Could be that you have a dodgy lead.

And I wouldn't really bother running anything other than standard unleaded in the VS, it doesn't have enough compression or timing to run premium. It won't hurt it, but you arn't gaining much by using it.

Have you done a code check? That would be the first thing I would do to see if it has logged any codes.

[Brett_jjj]

My VSV6 definitely runs worse on 91 octane fuel,It doesnt matter which brand I use, they just all run crappy.So I always run 98 octane fuel.I think that if you cant notice any difference in an Ecotec V6 running on 98 octane fuel compared to 91 stuff, then theres probably some other unknown issue with the engine.The ECU constantly varies the ignition timing according to sensor input,load,temperature and fuel octane rating,to which it uses the knock detected by the knock sensors during combustion to retard the timing.The 98 octane fuel will allow the ECU to advance the timing further before knock occurs, which means a more efficient and more complete burn of the fuel and air mix.Which translates into better economy and more power.For the engine misfiring under load ,Id be checking all 3 ignition coils by swapping them ,one at a time, with a known good coil, and then drive it and see if theres any difference..Ive found its best to replace all 3 coils at once,and only use genuine holden coils or a well known brand like mallory etc.Also Ive seen these coils show up ok when tested with a multimeter, but still caused misfiring under load.

[RoboticCherry-Coke]

Can't say I noticed anything like that on the plugs and yeah I did a code check and it came back all good.

As for the issue of running premium I have been told by a few people that say its a waste of time in a vs but others that swear by it. It could all be in my head but I seem to think it makes a difference I am just to cheap to run premium all the time

Anyway, I just had the RAA come out and take a look but it didn't fault when he got here. He had a look over the car anyway and found some oil in the coolant so investigated further. It looks as if the valley cover is leaking and sucking some water in causing the problem. So its going in on Tuesday to get pressure tested.

[jhon]

had the same problem with my ute , ran ok without my tools in, but then missed under load, had the plugs and leads changed and valley cover removed cleaned and replaced with no difference...ended up being the coils and efi module and also o2 sensor, one dead and the other on its way out.. still have to change the sensors but did replace the 3 coils and module and its driving like a new car :c

[matty m]

check ur coils and dfi was doin that with my vr used a mates one run like a champion

[VR_Acclaim]

mine was ruuning fine till i wet on the high way tonight and now acclerating at any pace its playing up really bad any idea i need to fix it like now so i can get to my course

[RoboticCherry-Coke]

Yeah well I wont know for sure whats going on till it gets pressure tested tomorrow but if it is the valley cover gasket anyone know much it would cost to get it replaced or how hard a job it is? I imagine it wouldn't be that difficult so am thinking I might do it my self if it is needed.

[greenacc]

you said your coil was replaced but you have 3 coils, did you only replace 1 of them ? the others could be stuffed now.

[RoboticCherry-Coke]

Um well my dad had it done a couple of years back and I think all three were replaced however I would have to double check with him.

[RoboticCherry-Coke]

Just picked it up from the local Holden dealer. They looked into the issue a bit further and it defiantly needs a new gasket. They quoted me $450 - $500 to replace it however I got a mate who is an apprentice mechanic who has offered me a hand if I want to tackle it one weekend.

[admir87]

wowww! $450-$500

do it yourself, you'll save a heap of money, just need gaskets, gasket goo, coolant, and few other bits.. guessing in parts maybe $150 or less

its not hard to change them yourself, and you'll learn along the way...

[RoboticCherry-Coke]

Yeah I spoke to my mate last night. He gave me a list of stuff to grab and said when I have everything he will come round and give me a hand. Also plan on replacing the power steering pump while I am at it

[RoboticCherry-Coke]

Replaced the gasket on the weekend with my mate. Turns out it was a lot easier then I expected but in the process we found that one of my injectors has a crack just around the end so think I am going to have to replace them as well