2002 S60 Misfire diagnosis, not ignition coils

butthole · Post by **butthole** » 21 Dec 2014, 04:57

Hi

I've had a cylinder misfire on 4 and 5 for quite a while. One can actually feel terrible misfires when it's starting up most of the time (even if hot). One can also feel the misfires when idling as well, it's almost as if the more throttle I give, the less I feel it misfire (but still sh*t fuel economy)

I've replaced the ignition coils 4,5 that fault codes reported as misfiring. (first took it to a mechanic who mistakenly changed 2,3). Seemed to work well for a bit, but alas the codes returned and it's still misfiring. Sparkies are all changed. (Actually after replacing the spark plugs, cylinder 3 was added to the fault codes)

draser · Post by **draser** » 21 Dec 2014, 08:01

If you have a scanner that reads fuel trims look at short term to be around zero and long term in single digits. If long term is 2-digits negative the ecu is trying to supply less gas to compensate for some fuel supply problem, hence bad mpg. Also look at AFR number indicating if engine run lean or rich. If no scanner look at plugs to see if they're smoked. Try a strong injector cleaner to see if it makes a diff. Are you losing any antifreeze? Hopefully not, that may indicate a leaky head gasket, but you'll see evidence of it looking at the plugs.

Post by **oragex** » 21 Dec 2014, 10:13

The thing you can easily check and fix would be indeed a fuel injector clogged. For the injectors, either get used ones off ebay, or have them cleaned off ebay as well for about $100 all of them - best option so you know all will work like new

Note that in car injector cleaning is not useful at this stage. You need to have them removed and put on an ultrasonic cleaning machine. Have a look on Youtube.

Also, check the wires that go to the ignition coils, might get crushed and break. Lastly, could be burned valve or a head gasket, as mentioned

butthole · Post by **butthole** » 22 Dec 2014, 02:17

Yes I do actually have a coolant leak lol. A rather bad one. The only thing is, the gauge has never gone past the middle and I've never seen white smoke nor does the oil show signs of coolant contamination.

Apparently it's the waterpump but the mechanic that told me that has been wrong before.

butthole · Post by **butthole** » 22 Dec 2014, 02:26

Forgot to add, sometimes when starting the car it will start then die instantly. (But also sometimes struggles to start)

The long term fuel trim is -7.03%

draser · Post by **draser** » 22 Dec 2014, 12:55

I'd focus on that then. I'd do a compression test to confirm. Not the best of the news.

Post by **abscate** » 22 Dec 2014, 18:51

butthole wrote:Yes I do actually have a coolant leak lol. A rather bad one. The only thing is, the gauge has never gone past the middle and I've never seen white smoke nor does the oil show signs of coolant contamination.

Apparently it's the waterpump but the mechanic that told me that has been wrong before.

This isn't relevant to the misfire directly, but if the water pump does seize it takes out the timing belt and then the cylinder head, to the tune of 2000 usd repairs.

Post by **FLXC90** » 23 Dec 2014, 14:01

And remember, compression check is not the only way to verify leaking head gasket on a whiteblock, they will pass compression test, but pressurize the coolant system. Search Block check tests; it checks for exhaust gasses in the coolant.

Also, since the misfire is still in 4 and 5, check the ground wire for those coils. Maybe you'll get lucky!!

2008XC70 · Post by **2008XC70** » 01 Jan 2015, 22:55

Whoah there, slow down. Head replacement is a last resort!

First, pull the coil packs and make sure none of them have cracks anywhere (slide the rubber boots down too). Make sure plugs are gapped appropriately.

Check and make sure all vacuum lines are tight.

Pull injector connectors one by one and see if you notice a difference in idle. If you notice a particular injector makes little or no difference in idle, that is suspect. You can do the same with coil packs.

Have you done tbelt or pcv recently? Sometimes timing will be off or a vacuum line was disturbed.

Check compression and do a leak-down test. This would be a last resort indicating its time for a head job. A leak down test will tell you if there are issues in the top end or bottom end.