‘95 325i rough idle and intermittent stalling?

[jaegre36]

Hey all. Been having some trouble with this new project car. Picked it up a couple weeks ago. It’s a 1995 325i. I have so far went from the car being dead and not running at all to being able to drive it up and down the road. I have replaced the idle control valve, intake boot and hoses, along with the mass airflow sensor. I have put in a new fuel pump. I also just installed a new camshaft position sensor. Before anyone instantly replies telling me how to spend my money like on other sites please don’t. All of these parts I replace, I do so acknowledging it may not fix my issues but needs to be done at some point anyway. As of right now, I’m leaning toward it being fuel pressure regulator or filter issue. It could also be a crankshaft position sensor issue. I have recorded a video of what it’s doing and how it runs. I can drive it down the road but it will stall intermittently and sometimes after dying, will not start again until it sits for anywhere from 2-24 hours. Some days the car will fire up after a day of sitting and run like a champ idling around 1k rpms for around 5 minutes and even runs down the road and back. Other days I go out and she will barely idle for a minute. If anyone has a recommendation or a path I’m better off working toward, it would be helpful. Thanks and I hope your night is well! - J

https://youtu.be/dKgneJqepI4

[dominator293]

Check everywhere around the intake for vacuum leaks. A lot of idling and running issues can be attributed to that. Considering you've replaced a lot of the parts hanging off the intake, i'd be checking for leaks on the intake side of the MAF. Maybe you haven't reconnected one of the vacuum hoses or the like. Possible a smoke test would reveal if there are any leaks. Anyway it's a cost free inspection that could help identify the problem.

[jaegre36]

Alrighty, I will surely look over everything again. I’ve tried the old starting fluid trick and nowhere I could spray seemed to change the idle. Guess it doesn’t help it’s not steady to begin with. I read someone talking about a smoke test. How would I go about doing that if you don’t mind pointing me in a direction? Thanks!

[dominator293]

Here's a handy vid that shows you one method of smoke testing. It should give you a general idea of how to do it. https://www.youtube.com/watch?v=L9CDZ9lu6Rs

Goodluck!

[jaegre36]

Thanks Dominator, I will get this done tomorrow hopefully! It’s still racking my brain though. How come the car won’t start after it’s been driven up and down the road stalling out during the drive? Like yesterday for example. Got about a mile down and after about the 4th time stalling, stopped at a stop sign and shut it off. It wouldn’t start back up after that. Had to tow it home.

[dominator293]

No worries. Probably not much help with the rest of it unfortunately. For a car to fire the basics you need are fuel, air and spark. Could be an issue with ignition, coil harness? Fuel filter (as you mentioned)? Maybe ECU fault? Not sure hey. But you need to start somewhere and may as well tick off the 'air' side of things with vacuum leaks. Then maybe check fuel pressure somehow, and if that all turns out ok, check into the spark side of things.

I'm not a huge help here as i'm just going off common sense, i've never experienced the issues you have personally so can't give to many suggestions other than general advise.

[B320i]

Does the old "stomp test" to pull any lurking fault codes from the DME work on a 1995 325i? That'd be worth a look in to see if anything is logged in the ECU that hasn't triggered a CEL. While we're on the topic of the DME, remove it from it's little nook and inspect for any signs of water ingress. Whilst it is removed, check the gutter drains for correct function (they're quite easy to block with leaf litter). A water-damaged DME can cause all sorts of erratic behaviour, but they can sometimes be salvaged.

Given the vehicle's age, I wouldn't be surprised if a Crankshaft sensor was beginning to fail electrically but wasn't logging a code. Not only would that potentially explain the stalling, but also the inability for a successful restart for a long time. Inspect the sensor for any visual damage, or damage to the wiring, and for correct positioning. Would even go as far as to say give it a look over to see that it is the genuine part, someone may have swapped in one of those dud Chinese knock-off parts that rarely (if ever) last more than a few weeks or months. I'm not sure if the Bosch Motronic DME would allow the engine to run with the sensor disconnected, but it could be worth a shot once the engine reaches a point where it will fail to restart.

[Eric93se]

Pull the DME, get access to both sides of the board and take good pictures. Start running injector cleaner, use a different cleaner each tank of gas.

[jaegre36]

Thanks B320i for the very detailed reply. I have done stomp test multiple times. As of right now, I’m getting no codes. I will pull the DME today after work and take pictures for you guys! I was curious about it as well, but figured that should be a last resort. I am also going to replace the crank sensor regardless this weekend.

[klaas]

Sounds a lot like the symptoms i had and replacing the crankshaft sensor fixed it. Try measure the resistance of the crankshaft sensor with a multimeter.

https://www.bimmerforums.com/forum/s...ng-for-2-weeks


If the RPM needle is behaving erratic (ive watched your video, cant really tell), that is a sign.

I assume you dont have stuff to read out the ECU or dashboard. And im not sure what codes the stomp test give, probs not the dashboard codes (KOMBI).
The dashboard can give some rpm error, the ecu a cranshaft error.

Though, that there are no errors does not at all have to mean the sensor is good, i only got them a few times, when my car wouldnt start i didnt get one at all.

To avoid replacing stuff that is not necessary try reach under the intake manifold and take of the crankshaft connector (might have to remove the oil filter cap to be able to reach). Then measure the resistance between terminal 1 and 2, they probably read in the 100.0000 or even 1000.000's of ohms if its broken. Anything above 1000ohm would be bad.

[spyderg0d]

You can check the crankshaft sensor with a multimeter for whatever ohms its supposed to be btwn pins 2 and 3.
You can put 12v directly to the fuel pump and hear if its running or not. You can also do that to check fuel pressure.
If its obd2 i suggest you get a scan tool and make sure the 02 sensor voltage is oscilating appropriatly.
After that, theres only vacuum leaks, maybe ground strap connection, or bad coil packs. 1 bad pack will dull the engine considerably. 2 bad packs will make it stall while attempting to idle. A bad maf, paired with vacuum leaks will also do it, but not with just a bad maf.

- - - Updated - - -

Tjeres also bad fuel or a blown head as a extreme possability.

[klaas]

Im no authority on this at all... but .. would vacuum leaks not be present all the time and cause problems all the time. Something electronic would make more sense right..

[jaegre36]

So to everyone on the topic of testing the crankshaft sensor. It was difficult but I finally managed to pull the plug without taking anything out from under the hood. It tested it at least 20 times to be sure lmao. A certain pair of pins read 1 meaning infinite resistance, I’m assuming. The other pair, the one I should be testing, was a little tricky to get a reading. Actually I didn’t get a solid stable number. I made sure the last few times I tested it that I touched only the pins themselves and not the casing. Watching the multimeter reading from 20k ohms. It would instantly jump to 10.90-10.95 and somewhat rapidly fall all the way down to 0, never stopping at or around 540-580 +/- 10. I watched a couple videos to ensure I was testing it correctly. Does it sound like a faulty sensor? This was done without the car running/cranking and the battery disconnected? Maybe that’s my error? Thanks. I would really appreciate some feedback! Have a good night folks.

[Eric93se]

No the car should not be running and the battery doesn't matter .

Is your meter auto ranging ? The blinking 1 might be that your in the wrong range.

[jaegre36]

Okay so I did my test correctly. Hmm, not sure on the auto ranging you speak of and it didn’t blink the number 1. The 2 and 3 pin I’m guessing are supposed to read 1 or infinite. The 1 and 2 are supposed to show a reading or maybe I have it flip flopped but anywho. Yeah. The connection I did make, with my mm set to 20k, (the only range on my meter that would get a reading), instantly read 10.90ish and then rapidly dropped through the numbers all the way down to nothing and I kept retrying with the same results. It won’t hold a steady reading and or number.

[klaas]

You have to measure between 1 and 2... so thats good. So you are reading 10Kohm, that would be to much and maybe the dropping of the resistance also means the sensor is bad, that would mean its providing (to much) resistance after which it short circuits. It still sound weird, i would test my multimeter on a resistor to be sure. If all good then would replace the sensor. Is the current sensor original? Does it have a metal or plastic housing?
Another explanation would be that the wiring to the sensor is broken and short circuiting while you are handling the wire and multimeter.

[scooper]

check your battery for strength and alternator to see if it's working properly. Without both working well your car will not run smoothly if at all.

[jaegre36]

Everyone that doesn’t still mind helping me out. New crank sensor is in just a few minutes ago. Car fires right up and is idling nice at 1kish? Like instant start which seems a bit quicker now. Only problem is if I give it any throttle it bogs the idle down and wants to stall out. If I let go in time it will keep trying to idle from a stall? If you guys have any ideas I would very much appreciate it.

[B320i]

The Crank sensor is supposedly quite sensitive to variations in the distance between it and what it monitors (harmonic balancer?). Double-check you have it seated properly. Unfortunately I don't have any measurements for how far away/close it needs to be to function properly.

[jaegre36]

So I have now completed a smoke test on the car. The car is solid vacuum wise. No leaks anywhere in the entire system? Car still starts and idles for a bit but if I touch the gas it drops rpms and dies. Do you think this could be the throttle position sensor?

[spyderg0d]

Maf.

[jaegre36]

I have replaced the maf. It’s new.

[scooper]

try driving it awhile...maybe the system needs some time to reset

[jaegre36]

try driving it awhile...maybe the system needs some time to reset

That’s not possible right now, lol. If I step on the gas the car dies.

[jaegre36]

Replaced the throttle position sensor today. Disconnected the battery to reset. Car fired right up but idle was surging. 500 to 1000, 500-1000, 500-1000... over and over. Car doesn’t stall out anymore when I give it throttle. Drove it up and down the road. Car ran and felt great. It did stall once on my way back after a mile drive, other than all was well. Pulled it back in the driveway and let it cool a few. Smoke is coming out from under my oil cap for maybe 3-5 mins? Started the car again after a bit and the throttle is so touchy almost laggy if you will. You press down and a second later I get response and it revs really high on its own. Like from a 500-1000rpm idle, it’s jumping to 1k-2k on its own and slowly back down to its surge. Did a stomp test and for some reason maf code is back. Unplugged maf and nothing changes? I’m a little lost at this point. At one point when I was playing with the pedal, it started revving by itself all the way to 5k range and I got scared and shut the car off. Someone please give any input lol.

So far...

- ICV replaced
- Intake boot and hoses replaced
- Camshaft, Crankshaft and Throttle position sensors replaced
- Fuel pump replaced
- Mass Airflow sensor replaced
- New relays

Car has been smoke tested for vacuum leaks and fuel pressure has been tested. Car has literally ran and drove well other than one stall. Thanks, J