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[RileyRomius]

So changed the MAF sensor today as I was not getting any info on the live diagnostics. Recently serviced the car and cleaned the breather system with carb cleaner (including the carb itself). I now have the problem of the car miss firing in cylinder 3... Some of the coil pack boots are worn and number 3 was significantly worn but I swapped the boots around and it's still number 3 miss firing. I haven't checked the plugs but they were changed a matter of 3 weeks ago, I have also thrown some injector cleaner down its neck a few weeks back. The fault codes have been frequent but only once did I get a fault code about the coil pack. This was before I changed the boots around, yet cylinder 3 is still miss firing. The miss fire is infrequent. Could it be the coil pack? Or would that provide a consistent misfire?

[RileyRomius]

Oh I should also mention that when we were fitting the carburettor back in, the fuel line wasn't fitting snugly onto the carb. It was throwing up the fault code P0170 which ended up being the fuel trim and seen as that was the only part of the fuel system we touched we assumed it was that. I tightened the pipe with a jubilee clip and the fault code went away but the pipe itself is slightly worn... Don't know if that would contribute to the miss fire?

[Nick W]

I'm slightly confused by you fiddling around with the carburetor on a fuel-injected engine?


As for your misfire, the coil pack is by far the likeliest  cause if the plugs are new.

[RileyRomius]

I followed the guide to cleaning the breather system on this site and it explained cleaning and checking the carburettor. Didn't think it could hurt, could it?

Yeah that was my worry, is there anyway I can prove for definite that it is the coil pack and not an injector/fuel problem?

[RobG]

I followed the guide to cleaning the breather system on this site and it explained cleaning and checking the carburettor. Didn't think it could hurt, could it?

Yeah that was my worry, is there anyway I can prove for definite that it is the coil pack and not an injector/fuel problem?

Throttle body

[biggriffin]

Cam sensor.

[RileyRomius]

Ah yes throttle body! Don't know why I kept calling it a carburettor! I've just drove her this morning and it's occurring far less than it was yesterday, it's still inconsistent though. I'm going to check the spark plugs later. Will keep you posted

[minifreek]

Would have thought if it was coilpack/dispac it would misfire on 2 cylinders and not just 1 as the ignition system works on a 'lost spark' type ignition... it's what happened with mine, misfired on 2 cylinders and not just the 1... was always number 1 that misfired on mine though...?


Have you tried swapping plug leads...?

it wouldn't hurt to check the plugs....?

[RileyRomius]

Hmm, I really wouldn't have thought it would have been the spark plugs though, recently had new ones put in but I'll check them. The engine was running rich until I changed the MAF. Could that have damaged the plugs? How would I go about accessing the leads? Does the coil pack just pop open?

[tunnie]

The coil pack is a sealed unit 

Got any other codes?

[RileyRomius]

No other codes just the P0303

I haven't had it in a while though but the engine is still miss firing, not as frequent as before but it's still there.

[baggers]

Definitely check the plugs and see if there is any damp on them, if so smell it, does it have a petrol odour or not?

Even though the ignition runs a waste spark each cylinder has it's own trigger so it's not always the case that two cylinders would misfire.  You could test this by removing the coil pack inserting a spark plug in to the coil (each one in turn and earthing the plug) get someone to crank the car over whist you check for a good spark, it would be worth removing the fuel pump fuse before you carry out this test.

(P0303 misfire on number 3 cylinder) cylinders 3 & 4 are prone to gasket failure.  Compression test? you can still have good well balanced compression even if the gasket has started to seep. With the engine warm/hot disconnect & remove coil pack crank the engine for a good 10 seconds, remove spark plugs (number 3 first) look down in to the bore with torch, can you see liquid?

[RileyRomius]

Right changed the plugs! But while I was changing them I noticed that one of my rubber boots for the coil pack had split and was revealing the spring... Could this be causing an infrequent miss fire? Would it be worth changing the entire coil pack or just the rubber boots?

[Diamond Black Geezer]

Coil packs can be had used for very little money, or about £40-80 for brand new, and leads can be sourced from Keith ABS off here (member of the Autobahnstormers Club) via their club shop for about £55 for top quality leads. Also Bosch brand new can be sourced for similar money.

Check your wiring that goes to the DIS pack, too just in case there's an issue/split wire there. That was the cause of my misfire (down to a previous bodge failing, not poor design)

[plym ian]

I found that i had a misfire after changing my worn boots. Took me ages to find the problem, it was on of the plastic bits that the boot sat on had snapped of exposing the metal underneath thus causing the mis fire