Is Miss-firing a Road worthy issue?

[shadowarrior]

Is miss-firing due to faulty coils and leads a road worthy issue if the car is running on 1 cylinder less?

[rock_it]

I would say it is ...

[Astron_Boy]

I would say it is ...

I'd agree.

For reasons beyond what you would normally comprehend it to mean a roadworthy failure... it still is.

[shadowarrior]

Thanks guys.

Are changing coils and leads a difficult job to do by myself?
Engine in question is a Mitsubishi 4G93 SOHC. Mechanic has run diagnostics and confirmed the miss-fire is affecting only one of the cylinders out of 4 and is not a mechanical fault. It needs couple of coils and coil leads replaced.

[rock_it]

Coil leads are easy .. Plug and play.

I haven't looked at the coils itself... My coils on my 4G63 are after market, and it is a separate unit housed on the firewall.. So easy to get to and replace, but just never done it myself.

If you were going stock for stock, I am sure it wouldn't be too hard.. Just got to make sure you replace in exact order...

[shadowarrior]

Thanks mate.
Let me go over the engine workshop manual.

[kiz]

Is miss-firing due to faulty coils and leads a road worthy issue if the car is running on 1 cylinder less?

Common issue over here in SA, if your car fails roadworthy there just put it up for sale over here

[Daniel2019]

Quick tip - replace the leads one by one so you keep the right order

[dstocks]

Kiz, just sent you a PM. DSpeed indicators arrived today. Sorry to hijack the thread

[kiz]

Kiz, just sent you a PM. DSpeed indicators arrived today. Sorry to hijack the thread

PM received

[Bennoz]

I would say it is ...

I'd agree.

For reasons beyond what you would normally comprehend it to mean a roadworthy failure... it still is.

It is because running rough (ie on 3) changes the emissions of the car... and as we know, anything that can change the emissions (fuel pressure reg, Piggyback ECU, boost controller, even a dropped cylinder etc!) is a big no-no.

As mentioned on FB Sidds, if she's running rough, just start pulling the electrical plugs outta the coils one at a time. The one that makes no difference to the running of the engine will be the culprit. If its an intermittent stutter, then you're best to grab an ohm meter to test for continuity. Good guide here: http://www.ehow.com/how_4912368_check-c ... meter.html

[shadowarrior]

Thanks Ben.
Giving it a go now. I can feel the misfire on idle as well, but more prominent under load (with AC on). According to the mechanic the car is running on 3 cyl instead of 4. But if a coil is dead, then theoretically it should run on 2 instead of 4 because the spark lead is connected to a 'dead' coil as well?

Have to source an Voltage meter to try the ohm test.

Are second hand coils/leads from a wrecker a bad idea?

[Taz]

Considering the price off the shelf from a store, its definitely best to just buy them off the shelf - it will also eliminate the possibility of buying faulty leads. If you also switch everything out and it still isnt fixed youll probably assume the leads again and end up buying more - best to get new so you know theyre not the problem.

[shadowarrior]

Considering the price off the shelf from a store, its definitely best to just buy them off the shelf - it will also eliminate the possibility of buying faulty leads. If you also switch everything out and it still isnt fixed youll probably assume the leads again and end up buying more - best to get new so you know theyre not the problem.

Cheers Taz. Good point. They are $150 each though! Damn!

[Taz]

wow really 150 a lead? dayum! which stores were they?
maybe payaya or someone else in the industry can get em trade price for ya

[shadowarrior]

wow really 150 a lead? dayum! which stores were they?
maybe payaya or someone else in the industry can get em trade price for ya

Cheapest price I got so far: $150 per coil. And $70 for a set of (2) leads. (Coils from Repco and Leads from Supercheap)
I tried disconnecting the plugs from each of the coils, but engine ran crap in both the cases. Which makes me think the coils are weak instead of completely dead? I'll spend some more time testing it after 5.

[shadowarrior]

I have a feeling that I have managed to fix it

[Technikhaus]

explain.....

[Bennoz]

Fully! What a prick tease.

[shadowarrior]

lol

First I opened the sparkies to check anything odd there. Didn't see anything wrong, brush cleaned them and put them back in. Miss-fire still present. Then picked up a set of new leads. NGK leads for $72. Swapped them with the old leads. Now I can't feel the miss-fire. Drove around for an hour yesterday with the AC on. No miss-fire. RPM needle is steady when idling, acceleration feels way smooth and more responsive.

Mrs drove the car and could feel the difference straight away. Its her car, so she would know better I guess. It wouldn't hurt to get an expert's 'OK' on it though, but I don't want to take it back to my mechanic. He quoted me $400 with a shotgun approach to the problem.

Which reminds me...I wanted to get my engine mounts and rear trailing arm bush of the FTO replaced through him... Benz? Couple of Johnny Walker Black Labels your way will intoxicate you enough to help me install them?

If the miss-fire fix stays like this...awesome..else am going to buy 1 coil instead of 2 and swap them around.

That's the story so far. Oh and I need to buy a multi-meter/volt meter and learn how to use it!