Rough Idle, Check Engine Light Intermittent

I have a 1994 530i that has been running quite well in the three years I've had it. However, recently I've been having a bit of a problem. The car idles rough and almost dies. Then it speeds up (ostensibly the
computer is giving it gas to prevent the engine from dying) and then the check engine light comes on. After a short period of time the light goes out and everything seems fine. This seems to happen only in the morning and only when the engine is about 3/4 the way to its normal operating temperature. It doesn't seem to happen in the afternoon even if the engine starts out cold. Perhaps outside air temperature has something to do with it. I don't have a tool to check the fault code, so I'm in the dark as to what this might be. Any ideas?
--
Rule of Acquisition number 284: Deep down, everyone's a Ferengi.

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Could be a problem with the cold-temp idle stuff. Could be a leaking intake hose/plenum/manifold. Or, it could be the dreaded Nikasil problem (Google on the koalamotorsport website.)
FloydR
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On 11/13/2007 4:49 PM, Floyd Rogers went clickity clack on the keyboard and produced this interesting bit of text:

Fortunately, it's not the Nikasil problem. The engine was replaced at 88K for that reason.
--
The last thing he said to me, doc, he said, "Sometime when the crew is
up against it, the breaks are beating the boys, tell them to get out
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Air mass meter?
wrote

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Won't this car tell the trouble code by mashing the gas pedal 5 times while holding your tongue against the roof of your mouth? Turn the ignition to ON but not START, fully depress the gas pedal 5 times within 3 seconds and the code is displayed by the Check light flashing.
I'm not sure of the timing on the depressing-the-gas-pedal stuff, so I expect somebody will jump in here and dial that in for us ... (I am pretty sure you have to hold your tongue in the right position though, or none of this works ;-) )

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It's probably the mass air flow sensor.
I have a similar problem with the same model.
My son probably can help me with this. Hee hee
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The E30's had a test for this. With the air flow sensor feed disconnected, slowly opening the trap door should reflect a consistently changing resistance on a meter. The door should swing with no rough spots or binding. You can look for something stuck in there maybe. Good luck, that's an expensive part for some reason.
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On 11/14/2007 11:54 PM, cosmo went clickity clack on the keyboard and produced this interesting bit of text:

Yeah, tell me about it. $230 is the best price I've seen. I did some research on how mass sensor works and apparently there are about four different ways of doing it, each having a different accuracy. I think that there is some data processing chip involved and that's probably what drives the price up.
--
I gave my cat a bath the other day. He just sat there. Actually, I think
he enjoyed it. It wasn't very fun for me, though. The fur kind of stuck
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No, in the case of the E30, it's just a vane with a pot. There are two variants of the thing, one with five pins and one with six, but the pot inside is pretty much the same.
It is possible to disassemble the thing, clean and lubricate the bronze bearings, and clean the pot element with Cailube or Cramolin. Most of the problems with these are caused either by the bearings causing the vane to hang up, or with the pot developing dead spots.
If the pot wiper is worn out, you buy a new sensor box. --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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On 11/15/2007 11:31 AM, Scott Dorsey went clickity clack on the keyboard and produced this interesting bit of text:

Interesting. I like the idea of being able to save some bucks by repairing it. I'll have to make time for it sometime soon.
But "Cramolin"? That sounds almost obscene!
--
"Pinky, are you pondering what I'm pondering?"
"Whuh... I think so, Brain, but... but if Charlton Heston doesn't eat
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On Thu, 15 Nov 2007 11:52:17 -0800, Vernon Balbert

I (knock on wood...) fixed mine with one drop of oil on the vane hinge, cleaning the rheostat track with a pencil eraser, and running some 400 grit under the wiper arm.
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Get the codes. Borrow a tool from someone. Pay someone. Just get the codes. Without seeing the codes, you are working completely blind. --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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