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Discussion Starter · #1 ·
I have a 2003 BMW 318i and had issue saying misfire on cylinder 4 only. Replaced spark plugs, coil packs, injectors tested and also compression tests done on cyclinders 1 and 4 and all came back fine. Swapped coil packs as well and issue stays on cylinder 4. Been told it could be caused by timing chain issue possibly being stretched. Is this likely to be causing only an issue with 1 cylinder rather than all of them. Any help appreciated. Thanks
 

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Chain issue affecting just 1 cylinder don't sound right to me.
But i stand to be corrected as we can learn something new every day as they say.
 

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I have a 2003 BMW 318i and had issue saying misfire on cylinder 4 only. Replaced spark plugs, coil packs, injectors tested and also compression tests done on cyclinders 1 and 4 and all came back fine. Swapped coil packs as well and issue stays on cylinder 4. Been told it could be caused by timing chain issue possibly being stretched. Is this likely to be causing only an issue with 1 cylinder rather than all of them. Any help appreciated. Thanks
who the **** told you that 🤣🤣🤣🤣

no mate a stretched chain cannot cause a single cylinder misfire, I hope it wasn’t someone who works on cars for a living that fed you that complete nonsense.

have you scanned the car for codes?

if compression is fine, new plugs installed etc there’s a few things I would be doing.

1) check there’s no corrosionon to the wiring harness pins that go to the coil pack (if there is try and sand them down slightly and see if that rectifies your situation)

2) check the earth wire.

when you say compression is fine, all cylinders should be between 10-11 on your gauge with a max tolerance of 0.5 difference between them. Is this the case?

Is it an auto?

has the misfire code been cleared and the re occurred?
 

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Discussion Starter · #4 ·
who the **** told you that 🤣🤣🤣🤣

no mate a stretched chain cannot cause a single cylinder misfire, I hope it wasn’t someone who works on cars for a living that fed you that complete nonsense.

have you scanned the car for codes?

if compression is fine, new plugs installed etc there’s a few things I would be doing.

1) check there’s no corrosionon to the wiring harness pins that go to the coil pack (if there is try and sand them down slightly and see if that rectifies your situation)

2) check the earth wire.

when you say compression is fine, all cylinders should be between 10-11 on your gauge with a max tolerance of 0.5 difference between them. Is this the case?

Is it an auto?

has the misfire code been cleared and the re occurred?
who the **** told you that 🤣🤣🤣🤣

no mate a stretched chain cannot cause a single cylinder misfire, I hope it wasn’t someone who works on cars for a living that fed you that complete nonsense.

have you scanned the car for codes?

if compression is fine, new plugs installed etc there’s a few things I would be doing.

1) check there’s no corrosionon to the wiring harness pins that go to the coil pack (if there is try and sand them down slightly and see if that rectifies your situation)

2) check the earth wire.

when you say compression is fine, all cylinders should be between 10-11 on your gauge with a max tolerance of 0.5 difference between them. Is this the case?

Is it an auto?

has the misfire code been cleared and the re occurred?
It was actually BMW who told me that's what they think is the cause so glad I told them to not continue doing the work at their prices. Wanted £450 just to check the chain wasn't stretched! My local garage did compression tests on cylinders 1 and 4 and said both came back in normal expected ranges. Engine light comes on and goes at times so code comes and goes once cleared. Its a manual. Now been to 3 different garages and no one can find the cause so a bit stumped. It's a 2003 so not worth loads but great condition and only 58k so desperate to keep it.
 

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It was actually BMW who told me that's what they think is the cause so glad I told them to not continue doing the work at their prices. Wanted £450 just to check the chain wasn't stretched! My local garage did compression tests on cylinders 1 and 4 and said both came back in normal expected ranges. Engine light comes on and goes at times so code comes and goes once cleared. Its a manual. Now been to 3 different garages and no one can find the cause so a bit stumped. It's a 2003 so not worth loads but great condition and only 58k so desperate to keep it.
do you have a code reader? Or are you having garages read the codes?

how familiar are you with these engines?
 

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Discussion Starter · #6 ·
do you have a code reader? Or are you having garages read the codes?

how familiar are you with these engines?
Unfortunately I don't have much knowledge of these engines at all. I have brought a code reader and getting the same as the garages to say misfire on cylinder 4 with fuel cut off. That's why I couldn't get my head round it being the chain and only 1 cylinder being affected, didn't seem logical and still BMW said it may not be that it Could still be something else. Cheers
 

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Unfortunately I don't have much knowledge of these engines at all. I have brought a code reader and getting the same as the garages to say misfire on cylinder 4 with fuel cut off. That's why I couldn't get my head round it being the chain and only 1 cylinder being affected, didn't seem logical and still BMW said it may not be that it Could still be something else. Cheers
clear the codes

disconnect the MAF harness and then start the car and go for a drive.

this won’t hurt the engine, with the MAF unplugged the car runs at a default set of parameters instead of using the airflow to adjust fuel mixtures etc...

see if it throws up the code again. If it doesn’t then that’s a huge bonus.

the MAF can cause a misfire, so can a ripped air intake boot (£12 to fix and 20 mins of your time and a flat head screwdriver)

I’ve had misfires personally from a ripped intake boot.

what happens is the MAF tells the car what air fuel mixture to feed into it, if it tells it the wrong thing then it can run 1 of the cylinders lean and cause a misfire in 1 cylinder.

so by disconnecting the MAF (mass air flow - sorry forgot to mention what it stands for) it no longer tells the engine what mixture to add, and the engine gets a predefined mixtures set by the manufacturer.

wont lie I am getting sick to the back teeth of garages defaulting to timing chains being a problem for everything.

wouldn’t surprise me if I had an issue with my drivers window next week and get told it might be the timing chain
 

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It sounds maybe odd, but I think it is possible to have one cylinder misfire when timing not right.

Maybe cylinder 4 is weakest cylinder and due of timing fault can be worsen.
 
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