CEL light but no codes...? [Archive]

tim eh?

04-09-2009, 01:45 PM

'check engine' came on today.

I've done the stomp test before on this car and it gave me codes, but now when i do it it flashes off for half a second then goes back on and just stays on.

Suspected bad fuel pressure regulator, I've been getting lousy mileage lately - there is a new one on the way, but wouldn't it at least give me a code? Otherwise I don't notice anything and it idles fine. Hope it's not the cat... Ideas?

JD525IA

04-09-2009, 02:12 PM

tim eh?

04-09-2009, 02:28 PM

I at least got a code for the MAF. Check your voltage. Do you have a OBC to do this easily. Check you battery as well.

JD

I keep a pretty good eye on my new battery with the obc, almost daily... I will check but I'm 99% sure battery is good and that I run on 13.5+V. Thanks for the suggestion. I will check fuses then if it could be electrical, but all the codes that are listed here (http://www.bmwe34.net/Wiki/tiki-index.php?page=Engine+codes) seem to have more to do with the ignition system and various sensors to the engine.... (?)

JD525IA

04-09-2009, 04:46 PM

I keep a pretty good eye on my new battery with the obc, almost daily... I will check but I'm 99% sure battery is good and that I run on 13.5+V. Thanks for the suggestion. I will check fuses then if it could be electrical, but all the codes that are listed here (http://www.bmwe34.net/Wiki/tiki-index.php?page=Engine+codes) seem to have more to do with the ignition system and various sensors to the engine.... (?)

YEP - That was the code I got when my cat was going bad - 1215 - AFM/MAF.

Made me say MF out loud.

tim eh?

04-09-2009, 05:25 PM

ok so I just changed the plugs... cel gone (off). :)

They are pretty filthy for 6 months I think. I am not a good plug reader, maybe there is something obvious to someone, maybe that is normal?

I'm hoping it looks like lousy spark (I recently replaced the ignition coil, cap and rotor 1 year old, wires ? yrs) or low fuel pressure (changing FPR next week probably, fuel pump is good). Anyway, maybe the bad mileage is from dirty plugs too. Good excuse for a long, motorized egg hunt this weekend...

whiskychaser

04-10-2009, 04:02 AM

maybe the bad mileage is from dirty plugs too. ...
Dirty plugs and bad mileage are both symptoms. The plugs do look a bit sooty which means you are getting more fuel in the engine than it needs. Full set of trouble codes is here: http://www.e38.org/e32/bmw%20code%20defaut.pdf
If you cant read the codes with the stomp test I'd suggest having them read with an interface or similar. The ECU cant 'know' you have changed the plugs or the FPR. So I think that CEL is going to come back again

tim eh?

04-10-2009, 07:22 AM

Dirty plugs and bad mileage are both symptoms. The plugs do look a bit sooty which means you are getting more fuel in the engine than it needs. Full set of trouble codes is here: http://www.e38.org/e32/bmw%20code%20defaut.pdf
If you cant read the codes with the stomp test I'd suggest having them read with an interface or similar. The ECU cant 'know' you have changed the plugs or the FPR. So I think that CEL is going to come back again

thanks wc... yeah I wasn't expecting the cel to go off when I changed the plugs but it did wtf. I was going to change them anyway and thought the old ones might have a clue. i should try to get a 1444 silly me i didn't think.

So... too much fuel.... that can't mean weak spark also? If it was weak spark that would explain it, as the ignition coil was bad for most of the time these plugs were in there.

whiskychaser

04-10-2009, 07:47 AM

So... too much fuel.... that can't mean weak spark also? If it was weak spark that would explain it, as the ignition coil was bad for most of the time these plugs were in there.
The electrodes look very 'white'. I'd expect them to look more yellow - like the tip of the one on the left. This is going to sound a bit silly, but it looks to me like they are not running hot enough. But if you had a weak spark I suppose that tallies. I'd want to know what the CEL meant. I'd run it in the dark to see if I could see any arcs that would drop the HT voltage and check the HT leads are in spec.

tim eh?

04-10-2009, 07:54 AM

The electrodes look very 'white'. I'd expect them to look more yellow - like the tip of the one on the left. This is going to sound a bit silly, but it looks to me like they are not running hot enough. But if you had a weak spark I suppose that tallies. I'd want to know what the CEL meant. I'd run it in the dark to see if I could see any arcs that would drop the HT voltage and check the HT leads are in spec.

sorry... HT=?

Yes I suppose it would be smart to check the wires (or dumb not to). I know for sure the coil was bad for a while.

Will check resistance - silly question how dark does it have to be to see arcing?

*- the plugs actually look more yellow than white... flash brightens things. That seems to check out then, thanks for that wc... will see about cel maybe it is unrelated.

Bill R.

04-10-2009, 08:32 AM

The plugs look perfectly fine for an m20, You may have had one of you new plug wires not clipped on solidly causing a random misfire that triggered the code and after changing the plugs you now have the boots pushed down all the way... any number of possibilities, if it doesn't come back on don't worry about it.

sorry... HT=?

Yes I suppose it would be smart to check the wires (or dumb not to). I know for sure the coil was bad for a while.

Will check resistance - silly question how dark does it have to be to see arcing?

*- the plugs actually look more yellow than white... flash brightens things. That seems to check out then, thanks for that wc... will see about cel maybe it is unrelated.

whiskychaser

04-10-2009, 11:59 AM

sorry... HT=?

Will check resistance - silly question how dark does it have to be to see arcing?

HT= High Tension - the high voltage side between the coil output and the plugs. As long as its not broad daylight you will see the flash. You may well hear it too as a repeated clicking.

tim eh?

04-10-2009, 02:27 PM

JD525IA

04-10-2009, 03:35 PM

Thanks very much guys- well the cel is staying off for now and I am getting 1444 when I do the stomp test again. Still lousy mileage - I remain hopeful the new fpr will fix that. Much appreciated JD, WC, Bill.

Change plugs.
Change air filter.
Change 02 sensor.
Change fuel filter and check fuel pressure.
Do a Shogun reset - disconnect battery for enough time to reset ECU.
Wash your car - this is therotical.
Drive down hills most of the time.
Roll windows up and turn off A/C - not a popular choice in the summer.
Get an alignment?
Don't be like old ladies and drive with feet on both pedals at the same time.

Hope something helps.

JD

tim eh?

04-11-2009, 06:39 AM

Change plugs.
Change air filter.
Change 02 sensor.
Change fuel filter and check fuel pressure.
Do a Shogun reset - disconnect battery for enough time to reset ECU.
Wash your car - this is therotical.
Drive down hills most of the time.
Roll windows up and turn off A/C - not a popular choice in the summer.
Get an alignment?
Don't be like old ladies and drive with feet on both pedals at the same time.

Hope something helps.

JD

haha not much I can do about being like old ladies but as for the rest... check, (all hills here go down, you seriously think i've had time to fix the a/c?) except 2 things - I haven't checked fuel pressure but the fpr needs to be replaced. if that doesn't fix it then i'll wash the car :D.

whiskychaser

04-11-2009, 07:04 AM

if that doesn't fix it then i'll wash the car :D.
Funny how they seem to run better when they have been washed. Reckon its something to do with moisture. Might have had a go with steam on the Cortina I had at the same time as this guy but maybe not now:D :
http://www.trent.karoo.net/steam-injection.html