VZ Misfiring?

[exanVZ]

Hey guys,

I've gotten some great advice here before, so thought i'd try my luck again.

Firstly I have an 04 VZ exec auto 3.6L which I've had about two years. It has 240,000km on it, I've done about 40,000 of those in the last 2 years. The problem has only emerged in the last 6 months or so...

I've been having some problems with my car misfiring (I think) when accelerating. Doesn't happen all the time, but it happens almost every time I want to speed up from around 80km/h to 100km/h such as when driving on the freeway. As I put my foot down, nothing happens, then I get a bit of shaking/shuddering from the engine then it will slowly creep up in speed, or sometimes surge forward. It doesn't happen so much under 60km/h but it has happened, again, usually when I go from a cruising speed like 60 up to a higher speed like 70 or 80.

I've had a mechanic look at it and had it for two days. He did a major service the first day and said he didn't notice the problem, so I said check again and then he said he could definitely notice it and kept it a second day. He has checked the plugs, the coils and the fuel filter and says they are all fine. He was a bit stumped and says he will need it for anothe full day at least to take it to another workshop and do more advanced testing, which won't be cheap.

I have run since some injector cleaner through it and I've also given the MAF a good clean with the right stuff. Slight improvement so far.

When it is idling, I can hear a slight clicking sound from the engine, its not really audible with the bonnet closed but it is if you listen closely. Not sure if this is significant, can't recall if it has always been that way.

Anyone have any idea what to try or how to diagnose this, without spending too much money? I am looking at making other improvements to this car eventually, but am reluctant to do anything if it won't even drive well.

Fuel pump on its way out was suggested, is there anything else it could possibly be?

Any advice welcome, thanks guys.

Patrick

 

[richardpalinkas]

Fuel pump usually will be evident at high rpm. When we're plugs last changed? Could also be a bad coil pack, they do fail and there's not really a way to determine the prob if it's intermittant, unless it's doing it at idle as such. Clicking in the engine bay is prob the evap solenoid, that's normal. My guess would be trial and error with the coil packs, just change one, if it continues, swap it over with the next and so on.

 

[exanVZ]

Thanks mate, seems to only happen when I put my foot down a bit so it may be the fuel pump. Apparently the mechanic has pulled out the coils to inspect, but not sure he did more than that.
Plugs aren't too old, think they have done about 20,000km if that. They were changed about 225,000km I think.

It does seem significantly better after a good thrashing tonight, after cleaning the MAF, I might get a quote on a fuel pump replacement and just do it if its affordable.
I've no idea how to swap a coil pack myself, is there a link or video I could look at, or would it be covered in a service book somewhere?

 

[richardpalinkas]

Coil pack is on the rocker cover. just the electrical connection and one 10mm bolt that holds it in. Each spark plug has a coil pack directly on it.

 

[exanVZ]

Thanks again mate, looks like a manifold off job, something I've not done before. Doesn't seem particularly difficult, but I'd be worried about stuffing something up.
I've also no idea about how to tighten bolts properly.. to the correct tension etc. Wish I had a good mechanic mate

 

[mattsv6]

Thanks again mate, looks like a manifold off job, something I've not done before. Doesn't seem particularly difficult, but I'd be worried about stuffing something up.
I've also no idea about how to tighten bolts properly.. to the correct tension etc. Wish I had a good mechanic mate

It's not that difficult to fit the new coils yourself... I gave it a go with basically no mechanical know how and it was quite easy.

You will need to undo the manifold and you can then chock it up with a bit of wood or something to give yourself access to the coils...

Attached is a guide that will give you step by step instructions on how to remove the manifold...

http://www.maceengineering.com.au/W.../C0A8/D240/2EA6/ALLOYTEC_MI_INSTALLATION_.pdf

Note that in step 14 - there will be no bolt in the bottom right location, instead the last bolt can be found at the back left of the manifold... As I mentioned above instead of removing the whole manifold just loosen it and chock up with something. This will be it a lot easier to refit.

As mentioned above you then simply undo each coil and replace them. I picked up a set on ebay and it solved a misfire problem that I was experiencing under 70%+ throttle.

Hope this helps.

 

[exanVZ]

Thanks for that guide mattsv6, doesn't look too hard step by step.

I took it for another drive later tonight and it seems better yet again, might have just needed the MAF cleaned after all.
If it is still giving me the shits over the rest of the week, might give this a go on the weekend.

Would it be worth just doing all 6 if I can get them cheap enough, given the high KMs on my VZ?

 

[GoodTimes]

Apparently all 6 is cheaper to get compared to going one then one. And keeps them all fresh and at the same point. I don't know how to do it but if you click on my name and find the post I did. It was the similar thing.

 

[exanVZ]

Thanks GoodTimes, one last question then, is there a difference between Bosch coil packs and Genuine coil packs, or are the Bosch ones the same as genuine?
Cheers

Edit: The good news is the car has been remarkably better since cleaning the MAF so I am wondering if that was the issue all along. I am talking about 90+% improvement in driveability. Even after a seriously fun thrashing last night and a cold start + commute today, didn't notice any problems!

This is the guide I used to clean the MAF which only took 5 mins.

I'm going to keep putting it through its paces this week, and am prepared to change fuel filter and replace my coil packs if it keeps up, but I am keeping my fingers crossed it's going to be easy and cheap for me (for once, last issue was thermostat which was bout $500 to fix).

Appreciate your input everyone.

 

[Benboy]

Hey guys,

He was a bit stumped and says he will need it for anothe full day at least to take it to another workshop and do more advanced testing, which won't be cheap.

Best advice I can give you is to ask the nechanic to define (explain in detail) what is meant by......more advanced testing - considering he's already had it for 2 days !!!!!!!