1.8T 190 intermittent Missfire on Number 1 cylinder

[rickc]

Hi All,

My 2004 A4 1.8T, BEX engine, has developed a missfire on cylinder 1 (as confirmed last night by the AA) with the engine management light flashing. It happens typically when driving up a hill under load. The car has had new coilpacks (courtest of Audi) and new spark plugs in the last 200 miles approx.

While the AA chap was out, we swapped first the coil pack and then the spark plug from number 1 cylinder with some spare ones I've got, cleared the fault and went for a drive to find that the fault was still there both times. So that seemed to rule out the plug & coil pack.

As a further check, we swapped the plug & coil from cylinder 4 to cylinder 1 and put the original cylinder 1 coil & plug in cylinder 4. We expected the fault to still be present but it didn't re-occur and no fault codes were logged on the test drive.

There's no reason for it to be fixed so I'm expecting it to re-occur.

Does anyone have any suggestion as to what else it might be, please?

The same thing did happen last year but I thought then that a faulty spark plug had caused it as it went away when a plug was swapped out. Maybe that was coincidental and there is an underlying fault?

Thanks in advance and sorry for the lengthy post!

Rick.

 

[Az]

Have you checked the wiring leading to the coil pack? If a wire has a split in the insulating sleeve it can ark causing a misfire.

 

[rickc]

Hi and thanks.

No, I haven't. Presumably I'll need to strip back the sleeve and check the wire all the way back as far as I can? Or is it likely to be under the rubber grommet part near to the plug where it enters the coil pack?

My car has only done 34000 miles so I wouldn't expect too much wear and tear .

 

[Az]

It's not really mileage dependant, it could be a case that the wiring loom to the coil pack is rubbing against a part in the engine bay. I've recently repaired a load of severed wires in both my front door looms, I had no central locking, passenger electric window, door illumination, or drivers door speaker, all down to damaged or completely severed wires that were in the loom, I was shocked at how much protection the wiring loom had, yet it still managed to do that damage through the harness protective shroud.

I'd look for obvious kinks in the wiring loom that could indicate a break in the wires, or look for any signs of rubbing on the loom protective shroud. Check to see if it runs close to any other parts in the engine bay that could rub against it under load when the engine flexes on it's mounts.

 

[rickc]

Right-ho. I'll have a look and report back. Thanks

 

[Jasdent]

This is weird, this exactly what I was about to post. My car is 163 hp 1.8t and I was driving the other day when I got a missfire and the engine management started flashing. I hooked up the timing lights and it showed the coilpack nearest the cabin wasn't firing.

I fitted a new coil pack and the car started and idled fine. it cruised fine but as soon as I tried to accelerate or went up a hill, the engine management light came on again. I can't work it out but was wondering if the ecu needs reset or some kind of reset procedure needs to be carried out for the new coil pack to be accepted ?

I'll monitor the thread as this is of interest to me also.

 

[rickc]

No obvious signs of a wiring problem on mine - I ckecked the wires to number 1 cylinder as well as I could without stripping the whole lot back to bare wires.

It does sound like you have a similar problem, Jasdent. I don't think coilpacks need any kind of reset to be accepted, only to get rid of fault codes.

 

[Jasdent]

well, my freind has vagcom so I will see if he can pop up and give me a diagnosis of what comes back. seems a hell of a coincedance that we both have the same problem. surely we can't be the only one's this is happening to. I've also seen a 'safety-mode' before so I don't know if maybe that is applicable ?

 

[rickc]

Mine's running fine this morning *touches wood*. I really don't know what to think.

As you say, we can't be the only ones.

People have been scaring me with things like sticking valves but if that was the case, wouldn't it be sticking all the time and not intermittently?

 

[Az]

I very much doubt it has anything to do with sticking valves, they normally relate to subtle or irratic power loss, not misfires.

I dont know if audi's use crank sensors as not all manufactures do, but if your car does have a crank sensor it might be worth checking that. I had an old car a few years back that had a misfire under load (hard acceleration or driving up hill) and it turned out to be a dodgy crank sensor which also had bad wiring because of where it was positioned under the engine. The crank sensor tells the ecu when pistons 1 and 3 (on a 4 cylinder engine for example) are at TDC (top dead centre) so it knows when to send a signal to fire the relevant cylinders. If the crank sensor is faulty or it's not picking up a good enough signal from the crank then it will be sending the wrong signals to the ecu which in turn will make the ecu send a wrong signal to the coil packs causing a misfire.

These are just thoughts in my head for what I'd look for if I were in your position, I could be completely wrong of course!

 

[rickc]

Thanks Az. Something else for us to think about and potentially investigate if and when the fault re-appears.

 

[mjsulliva]

Blimey - make that 3 people. I've got an 04 1.8T 190, and I've logged in to see if anyone can help with my misfire.

I'm getting an intermittent misfire on cyl 1 which seems to be getting more frequent - it only happens under load. At first I thought it was dodgy fuel. I've had new coil packs and plugs in the last 2000 miles. This problem has started in the last week (200 miles or so)

I do occasionally get a P0420 which I've read is either a Catalytic convertor gone, or an O2 sensor gone, but the car seemed to be running reasonably well so I've ignored them. However, I found a posting somewhere that said a dodgy O2 sensor could cause the misfire, so I'm thinking about replacing it to see if it sorts it.

I too can't see anything untoward with my wiring.

 

[mjsulliva]

Re: above, here's the link, but it could be a long shot ...

HELP!! 2003 Audi A4 1.8t misfire problem.

 

[marktdisport]

try some forte fuel cleaner ??? for a £10 a tub well worth a go might help un carbon bits and bobs

 

[Az]

Yep, o2 sensor is a good call as well! Definately sounds like a sensor or electrical related.

 

[Jasdent]

I have to say, the O2 sensor is favoured choice now, the one before the cat. These can be damaged due to unspent fuel from the dodgey cylinder igniting in the exhaust from the heat. also I sometimes have a slight smell of fuel which could back this up, probably change it anyway !

 

[rickc]

Mine's still running fine at the moment. if and when it starts playing up again, the O2 sensor could be a good starting point - thanks.

Jasdent - please let us know what happens if you change yours.

 

[poggz]

When was the fuel filter last changed try that if it hasn't been done within the last 30k miles.

 

[Audi Doodah]

Uber thread resurrection for a first post!

Welcome!