Chugging water and rough idle

[hickatew]

Hey all, I just got a SES light recently, a few days after I noticed my car had drank all the water/coolant. It's also rough idling at RPMs lower than usual (500 vs 1k), needs a bit more gas at lower RPMs, and MPG took a slight hit.

Passed by Autozone (my obd2 reader shipment got delayed) and they gave me the following codes: P0305, P2240

Any ideas? Was going to take a 3.5 hour trip to Killington this weekend but not sure whether to trust it

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[slater]

weird. P0305 is a misfire code... that would explain the rough idle. it's either a bad plug or a bad coil pack. without the scanner it's tough to troubleshoot, because with it you could see what cylinder is misfiring and then move that coilpack to another cylinder and see if the misfire follows.

the coolant loss is another issue though. based on that, i would not take the car on a road trip until you get it sorted out.

[hickatew]

I got a print out from autozone, it says cylinder 5. I just had never heard of having to replace an ignition coil in one of these cars so wanted a second opinion.

I'd guess the coolant loss is from running lean because of code P2240 (oxygen sensor malfunction) but it's not burning oil at all. To be fair it only ran down on coolant once, I've managed to keep it at a decent level since I noticed the problem

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[slater]

I got a print out from autozone, it says cylinder 5. I just had never heard of having to replace an ignition coil in one of these cars so wanted a second opinion.

I'd guess the coolant loss is from running lean because of code P2240 (oxygen sensor malfunction) but it's not burning oil at all. To be fair it only ran down on coolant once, I've managed to keep it at a decent level since I noticed the problem

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coolant loss will be from a leak; you should see traces underhood.

coils do go bad, i've had to replace two over the years. since you know it's cyl #5, move that ignition coil to, say, #1.... run the car, scan it, and see if the misfire follows to #1. if you haven't replaced your spark plugs, that would also be a good thing to do.

[ELCID86]

I got a print out from autozone, it says cylinder 5. I just had never heard of having to replace an ignition coil in one of these cars so wanted a second opinion.



Definitely go bad. I’d recommend doing the set. Go OEM.

[Newjack]

coolant loss will be from a leak; you should see traces underhood.

coils do go bad, i've had to replace two over the years. since you know it's cyl #5, move that ignition coil to, say, #1.... run the car, scan it, and see if the misfire follows to #1. if you haven't replaced your spark plugs, that would also be a good thing to do.

Yeah this is a good way to check if its the coil pack vs the spark plug.

As for the coolant leak, the most common failure point on these cars is the expansion tank which tends to crack and leak. Really hard to tell without looking or knowing anything about your car/car history.

[hickatew]

Alright awesome, this gives me some things to try - thanks guys!

Car history: bought it at 76k miles about a year ago from Denver, CO. It was previously an EAG car, modded to a DINAN 3 (intake, exhaust, strut bar, engine software), that had a full cooling system refresh done before I got it. While I've had it, I've replaced the fuel pump and relay as it died, and an autobody replaced the front bumper and horn because somebody hit me. Now at about 89k miles in Boston, MA

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[Newjack]

I'm not going to sit here and try to guess where the coolant leak is. I just went through a hunt for a coolant leak and it could be coming from anywhere. If you get under the car or pop the hood and take a look let us know what you find. Could be something as simple as a gasket on your temp sensor, or could be the radiator.

[SaltyNC]

Since a lot of these are higher mileage cars, it's not a bad idea to always keep a spare coil on hand even if you have someone else swap it out for you. It can mean getting back on the road in minutes. On long road trips, I often put one in the trunk with my spare bottle of oil, especially if the trip is to an area far from any BMW shops/dealers.

Salty

[ZHPizza]

Since a lot of these are higher mileage cars, it's not a bad idea to always keep a spare coil on hand even if you have someone else swap it out for you. It can mean getting back on the road in minutes. On long road trips, I often put one in the trunk with my spare bottle of oil, especially if the trip is to an area far from any BMW shops/dealers.

SaltyYou can get duralast coils for these cars from any Autozone or whatever. I had a lean condition (likely vacuum leak) on my last zhp that was killing could packs once a month.

[hickatew]

So when I left Autozone this morning I'm almost positive the SES light was still on. When I left work a few hours ago, it was mysteriously gone. Do these things just clear themselves after a some miles? Might have just missed when the Autozone guy cleared it but I don't think so

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[az3579]

Check your oil and make sure it's not milky. Disappearing coolant (with no trace of coolant loss externally) sounds like a bad head gasket to me.

[SaltyNC]

You can get duralast coils for these cars from any Autozone or whatever. I had a lean condition (likely vacuum leak) on my last zhp that was killing could packs once a month.

Cool. I didn't know they carried them for BMWs.

Salty

[ELCID86]

So when I left Autozone this morning I'm almost positive the SES light was still on. When I left work a few hours ago, it was mysteriously gone. Do these things just clear themselves after a some miles? Might have just missed when the Autozone guy cleared it but I don't think so

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Yes. I have a SES that pops on/off intermittently. I think it’s a misfire.

[Sockethead]

If you can't find the leak and your oil isn't milky, take the cap off the coolant tank and take a whiff. If it smells like exhaust, it a bad head gasket. This is how I ID'd a bad head gasket on my first bimmer : low coolant light, no trace of leaks, no milky oil, no smoke out the tail pipe

Also if the SES light is a hard code, they remain even after the light goes off so you should still be able to read it. Soft codes may reset after a period of driving