My turn for cold start issues

[Silverti]

Hi guys,

I've been reading a lot of the threads on here about cold start problems, but i thought it may be an idea to have a new thread now the weathers turning (in the UK). It may be helpful to others.

My cars always been a little lumpy for around 30 secs after starting when theres been a chill in the air but the low temps the last few days have seen it taking a turn for the worse.

Yesterday on starting from cold it fired first turn as always but was running like a bag of bolts, probably on 2 or 3 cylinders for about 1 minute and then it settled down. It still seems to rev ok though and didn't throw a CEL. After that it was fine for the rest of the day.

Today similar temp, fired first turn again but then stalled, and then continued like above on the 2nd start.

I've only had the car a few months and the garage assure me they gave it a service before i had it but i'm doubting they did as i had to fill the oil up the day i got it (oil was below dipstick level!!) and it hasn't lost a drop since. Millage is coming up to 90K so its due a service but i was going to do that with the MOT in a couple of months.

Is a 1999 318ti with the M44 lump.

So list to check / change

Going to get the codes read tomorrow (i assume not all codes will throw a CEL?)
Change spark plugs
Check / change ignition leads
Check vacuum pipes

Thats probably about the extent of my knowledge as far as working on a car goes.

From reading the other threads i'm seeing cam sensor and crank sensor coming up a few times, though hopefully that would show up when i get the codes read? Also the secondary air pump, but wouldn't have a clue where to start with that.

It just seems strange that it only happens for the first 30 sec - 1 min, not really enough time for the engine to warm up, but the problem seems temperature related.

Anyone have any ideas?

Cheers
Rob

[xxxJohnBoyxxx]

Read the codes and you might find something. SAP will throw a code if it is not working correctly so you might be able to cross that off your list. Upstream O2 sensor with a lame heating element might cause this issue since the car exhaust would have to heat the O2 sensor, it will not throw a code if the sensor heating element is not broken but it could not be heating the O2 up to the correct temp quickly. Other issues that might show up as PD errors or could be the issue would be intake air sensor not reading correct temp, coolant temp sender not reading correct (reading hotter then temp is), vacuum leaks, boot leak after MAF.

There are a lot of things that can throw off the air fuel ratio since the engine is not running in Lambda when it first starts and relies on specific sensors to calculate AFR for the first 30 seconds to 1 minute. fter that it goes into Lambda control which sounds like it is working good in your situation.

Good luck, John Smith

[Bluebimma]

If you checked the oil level and added oil, make sure you closed the cap completely and it has sealed, it will bog the engine out.

[Silverti]

Thanks John, some really useful information there. I learn something new every day.

Bluebimma, cheers, will check the oil cap.

Just had the codes read and it was giving:

Misfire
Misfire 2
Misfire 3
Camshaft Sensor

Also the mech doing the code reading noticed the coil pack was loose and he reckoned that it may be faulty and may be the cause even though no fault codes for it. He also reckoned that the cam sensor fault code was probably due to the misfiring during starting.

Does that sound reasonable?

Got some new NGK's to fit today and the guy said he'll do another code read for free tomorrow to see if any of the codes come back again.

Rob

[Bluebimma]

Did he check for a valve cover leak as well?

[Silverti]

No he didn't but while i was just out there changing the plugs i had a look and can't see it leaking anywhere.

Leads seem fine as well, rubbers still soft on the outside and couldn't see any brakes anywhere along them.

Plugs had definately done a few miles so could have done with being changed anyway.

[bmvw]

Does your car use any coolant?

[Silverti]

Hi bmvw,

Doesn't seem to, i'll go and check it again this morning before i head out.

Am i right in thinking that that could point to the head gasket, causing coolant to leak into the head overnight?

[Silverti]

Just had a look at the coolant before going to get the codes read again and....

Looks like shes losing coolant. I topped it up about a month ago and it seems to have gone down a couple of inches since then. I've never seen any coolant on the road where i park so i guess it could be going into the head.

Also reading the codes again the camshaft sensor came up again since he cleared them yesterday.

It was slightly warmer today than the last couple and the car started ok, a bit lumpy but didn't misfire. So the fault definately seems temp related.

So the next thing to change is the cam sensor.

Edit: Cam sensor and new o ring ordered, should be here friday or monday.

[xxxJohnBoyxxx]

I think you are ok with the head gasket. If you were leaking on all plugs you would have major issues since during a firing stroke the combustion would pump a bunch of gasses in your cooling system. Go with the plugs and cam sensor for now and see how it runs. You don't want to get in there and start changing a bunch of parts. If the plug eletrodes where all worn down then it could very well cause a mis-fire when the plugs were cold, also the coils could be weak. Change that bad camshaft sensor, erase all codes and see how it runs. Hopefully that takes care of the issue and if not then we start trouble shooting deeper into the car but only change parts that are obviously damaged.

John Smith

Originally Posted by Silverti

Just had a look at the coolant before going to get the codes read again and....

Looks like shes losing coolant. I topped it up about a month ago and it seems to have gone down a couple of inches since then. I've never seen any coolant on the road where i park so i guess it could be going into the head.

Also reading the codes again the camshaft sensor came up again since he cleared them yesterday.

It was slightly warmer today than the last couple and the car started ok, a bit lumpy but didn't misfire. So the fault definately seems temp related.

So the next thing to change is the cam sensor.

Edit: Cam sensor and new o ring ordered, should be here friday or monday.

[Silverti]

Thanks John,

Thats the plan i was going with, as the cam sensor code returned again thats definately the next thing to change and should be done by early next week.

When i changed the plugs the old ones weren't in that bad a condition. Was thinking about the coil pack, but wouldn't that cause more of a problem while the car was running as well?

Either way hopefully the cam sensor will cure it but will keep everyone informed.

[bmvw]

I'm not liking the symptoms here. Was the car ever overheated? I did mine, and drove with a cracked head for about 10,000 miles. It would use 1-2" of coolant a week. Finally it got to the point where bars-leak wouldn't stop it any more and I got similar cold start misfire symptoms with misfire CELs.

See if there is white water vapor coming from your tailpipe (after it is fully warmed up - 20 minutes of driving).

[Silverti]

Well i've only had the car for a few months so no idea if it was overheated before hand.

Always runs with the temp needle in the 12 o clock position now.

Will have a look for some vapour next time i'm out and about.

Cheers again bmvw.

[Silverti]

Right,

Changed the cam sensor yesterday and....

Started her up today and still the same. Sounded and felt like she was running on 2 cylinders for 30 secs or so until i revved it and then was fine.

Went for a long drive and got her nice and warm then parked up and looked for any sign of vapour from the exhaust and couldn't see anything. Never seen any sign of anything from the exhaust when shes warm.

But while i was round the back looking for vapour, every time the engine dropped in revs slightly (100rpm or so) there was a ppfffttt sound from the exhaust. Well the sound is hard to explain but like a surge of air through the exhaust if that helps.

[bmvw]

It's probably something else then. Just to eliminate the possibility, pull the plugs and look for one that is suspiciously clean looking. Also check the antifreeze and see if it is oily or darker than normal.