92 325 intermitant starting problem - BMW Forum

frankinbarnes · 04-20-2008, 02:42 PM

I just purchased a 92 325. I really like the car however it has become a pain in the butt the last couple days... test drove the car....it ran fine and stated several times with no issue....i bought the car....it started and ran fine back to my house (20 mins)....shut the car off went inside came back out about an hour later started and drove fine. the next day it would not start. .... then about an hour later it started ran for about 30 seconds and shut itself off. did not have time to mess with it... saturday came and it still would not start ( it rolls over but no fire) so i started looking for loose conections etc.... found a couple vacume hoses to be loose but still did not help then i put a new battery in because i had killed this one trying to start the car(maby i reset the computer by doing so ) car fired right up.... ran awesome all the way down to the post office... went inside came back out car wouldnt start.... you get the idea... now it seems very intermitant. it will start ten times in a row.... then nothing. found the gas pedal trick for the codes and i got a intake air temp sensor code... so i located that(fun) and found it was unplugged... plugged it in.. car started but idles irratically... not terible but noticable...drove car for 30 mins... no check engine light.. shut it off and startd it about a half a dozen times... went inside came out an hour later car wont start (WTF) check engine light reappears same code... I can get a sensor but will this thing actually keep my car from starting? Am i getting lucky every once and while with a limp home mode? Does this car have a limp home mode? i can disconect battery and restart computer doesnt help any more. i would hate to go buy a sensor and it not be the problem.. .this is the only code it flashes though. anyone had a similar problem before?? thanks for your help and sorry for the longwinded post.

frankinbarnes · 04-20-2008, 07:28 PM

So i started looking into the problem a little more..... it appears as though the car does not have any spark.... or fuel(the fuel pump isnt coming on when i hit the key) Couple questions. Is the fuel pump controlled by the ecm or dtm or whatever they call it.... and how is the spark controlled... im assuming the computer is telling the coils when to fire... but is there anything between the coils and the computer..... which sensor controls how the computer is told to spark Crankshaft or camshaft sensor or combo? I can hotwire the fuel pump at the relay and it will kick on... therefore i thought that it wasnt getting signal to turn on....when my friend hits the key to run i do no hear it under the car... next question does the key switch turn it on or is it controlled by a fuel pump relay... or maby the brain tells the rely to kick.... dtm is getting power through the relay..... hmmmmmmmmm

AlpineSixAndSeven · 04-20-2008, 08:11 PM

hmmm main relay? just a thought....

frankinbarnes · 04-20-2008, 09:11 PM

Quote:

Originally Posted by AlpineSixAndSeven

hmmm main relay? just a thought....

appologize for calling a dtm it is a dme. is that the main relay??? if it is i have checked it out and it is good.... thanks for the input
ryan

AlpineSixAndSeven · 04-20-2008, 10:09 PM

The DME is the computer Right?

The main relay is just a relay the provides power when you turn the ignition if it goes dead then there is no power on certian circuits.... thus no spark or fuel....

bimmerguy82 · 04-21-2008, 12:30 AM

Quote:

Originally Posted by frankinbarnes

So i started looking into the problem a little more..... it appears as though the car does not have any spark.... or fuel(the fuel pump isnt coming on when i hit the key) Couple questions. Is the fuel pump controlled by the ecm or dtm or whatever they call it.... and how is the spark controlled... im assuming the computer is telling the coils when to fire... but is there anything between the coils and the computer..... which sensor controls how the computer is told to spark Crankshaft or camshaft sensor or combo? I can hotwire the fuel pump at the relay and it will kick on... therefore i thought that it wasnt getting signal to turn on....when my friend hits the key to run i do no hear it under the car... next question does the key switch turn it on or is it controlled by a fuel pump relay... or maby the brain tells the rely to kick.... dtm is getting power through the relay..... hmmmmmmmmm

It sounds like your intermitent issues might be electrical problems. I would spend some time looking into relays and fuses and such to narrow it down.

frankinbarnes · 04-21-2008, 05:47 PM

the relay i am checking is the dme relay which i believe is the main relay that you are speaking of.... it checks out ok. i have not checked power at the dme because i dont have the proper wiring diagram....waiting on the bentley book in the mail. does it have quality diagrams? i want to purchase a real factory engine control diagram for this car. because i am sure i will have wiring problems in the future.
Is the fuel pump controlled by the computer? Is my vehicle equiped with an inertia switch? Like many late model cars it is a switch that will kill the computer (engine and fuel pump) if the car is in an accident so it wont burn to the ground... bmw may call it something other than an inertia switch.... do all of these cars come with a factory alarm.. there is no stereo in the car and i know on the vw's if you take the stereo outit is tied into the alarm and it can kill the electronics i.e. car still cranks but no fire. Is this computer smart enough to kill everything if the car is running out side of its likeable perameters..... it has custom straight exhaust(must go sounds terrible) So it goes back to my first question is it possible that the burn ratio is so bad that the electronics will put the car in "limp home" untill shut off.. and then not start untill it can reset and the issue is resolved. Would the intake air temperature sensor shut this car down? because that is the only code i get off the car. where can i buy a plug in diagnostic machine fore this car? is it worth it. will it tell me more than the car codes itself? thanks for all your help... oh yeah if there is a main relay other than the dme relay. i would much appreciate a location so i could check it. thank you again

landy · 04-23-2008, 05:06 AM

HI, Just had the same prob for a while, on my '98 328is, took lots of tries to start and then seemed to run ok once it was started, occasionally conked out but that was very rare. I was lucky enough to borrow a OBD comp from my local garage and it showed up camshaft sensor, we replaced that today, quite an easy job and starts first time, runs perfect and no cutting out. I would recommend borrowing OBD tool before carrying out any repairs theres quite a few things it could be and you dont want to go to the expense of replacing parts that are fine. Good Luck