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#1 (permalink) Old 02-03-2010, 12:15 AM
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cold hard start

93 325i 2.5l auto
can a bad cam sensor cause a cold hard start?
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#2 (permalink) Old 02-06-2010, 05:41 PM
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maybe. (does that answer your question?? no?? then please continue...)

when was the last time the sparkplugs were replaced?? fuel filter?? air filter?? check the simple things first, replace as necessary since these are 'wear items' and are expected to be replaced at routine intervals.

if all of the above are ok and you are still experiencing a cold start issue, then you can check further into things like idle speed control motor gumming, throttle plate gumming, and fuel pressure/volume tests. or, if you wish, check the cam sensor.

regardless, it's rather difficult to assess a proper diagnosis with just 1 line, which is why i asked the above questions. you wouldn't go to a doctor and say 'i don't feel good' and expect a prescription to be written based on that statement, so please do not expect the same from an online forum.

i am on several forums and have had 15 years in the auto repair field. while i may not have everything 'bmw' under my belt, i can tell you that many things are very similar in regards to symptoms whether it is a honda or something from gm.

i hope this helps you from chasing your tail and buying/replacing parts that are not going to fix your particular issues.


df
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#3 (permalink) Old 02-06-2010, 05:50 PM
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thanks for your input. the parts ive replaced thus far:
fuel pump
fuel filter
fuel pressure regulator
crank sensor
coolant temp sensor (dme)
intake boot
cleaned throttle body
cleaned maf
no vacuum leaks
i have the injectors out right now and am going to get them rebuilt
i do a cel 1215 maf.
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#4 (permalink) Old 02-06-2010, 06:22 PM
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so you have a code for maf fault, cleaned it, and *still* have a maf fault?? why haven't you replaced the maf??

as for the other parts, i think that you have spun your wheels. here's why.

let me start by saying that i am not trying to pick apart what you have done, but wish to try to shed some light as to how these engine management systems work.

'cold start' is in open loop, or preset parameters. at this time, the o2 sensor and coolant temp sensor are not affecting the fuel trim, therefore, should not affect the starting parameters. the maf, however, is a heavy hitter, and major input to the dme regardless of whether it is cold or not. the crank sensor is as well, as it lets the dme know the engine is turning over. the cam sensor is classified as an 'identifier' to control sequential firing of the fuel injectors and ignition coils. some vehicles, gm being one of them, can actually run fine with a faulty cam sensor, it may just take a little longer or a few attempts to get it started.

i do not believe that rebuilding your injectors will resolve the issue. however, if you have the money to rebuild the injectors, you probably have enough to buy a maf. is that what you need?? i don't know for certain. it seems to be the one component that *could* produce a cold start issue.

was there any improvement upon replacing the other components, or were they replaced for other reasons??

do you have a dvom (or better yet, a power graphing meter) to verify the maf operation?? is the voltage getting to the dme properly?? sometimes a poor ground can cause issues. did you try doing a voltage drop test on the ground circuit to the maf??

finally, what did you spend on the parts in your attempt to 'fix' this issue?? i believe a simple diagnostic visit would have been cheaper, even if it cost 2 hours 'flat rate' to do so.

again, not trying to bust balls here, just trying to shed some light as to what sorts of things i did as a driveability tech, and why shops (as in the *better* shops) charge a premium for their services (and stand behind them). if i can help the members on this forum in trying to reslove the simple things that they can do with minimum expenditure for maximum results, then i will try to do so. just as i stated before, when you go to a doctor, he will always ask a series of questions in order to narrow down the possible causes of an illness. tests will need to be done sometimes to verify a system or subsystem or component in order to asses if it is, or, is *not* the cause of the symptoms. experience makes this process easier.

also, when you go to a doctor with multiple issues, they have a particular order in which they will address concerns. i like the analogy of the 3 b's, breathing, bleeding, broken bones. (ok, there's a 4th 'b' in there, so what...)
there's no sense in stopping the bleeding in a patient that isn't breathing, so the breathing issue is addressed first. similarly, in a vehicle that has driveability issues, the routine maintenance concerns should be addressed first. these would be filters, fluids, and spark plugs, and the like.

as i stated earlier, if these are all ok, then you proceed further up the diagnostic chain and check the next round of usual suspects.

check engine lights can make things a little easier, but they are in no way absolute. there are variables (like a poor ground) that can interfere with the proper operation of the engine management system and fool it into think ing that a component is defective or otherwise out of spec when in fact, it is a little bit of corrosion throwing the voltages off spec. (this is usually discovered after said component has been replaced, sometimes more than once, and the problem still is present)

so this all being said, i hope this helps you in your quest to repair your vehicle. if you have any questions, or if i am able to help, please feel free to ask.


df
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