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Bad sensor??

3K views 32 replies 6 participants last post by  burbankE34 
#1 ·
I have a bad sensor in the car somewhere it started acting up rite after my grille fell out and drug under the car the exaust smells like its burning really rich, the car is idling really rough what kind of. Sensor could this be the car is idling so poorly the power steering pump is not wanting to function properly! The car wont die but when it idles it tends to shake the car pretty bad! Any suggestions?

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#3 ·
Again, do the stomp test.

However, since it happened when the grill went under the car, then it may have cut the wires to one of your O2 sensors. This would cuase the symptoms you are having.

The grill going under may also have bent or messed up the belt tensioner pulley thereby causing the belt squeal.

Get under the car and look for the O2 sensor wires and check the tensioner pulley.

Good luck.
 
#5 ·
I look at both o2 sensors and they seamed to be fine and I have a plastic shield under the car covering the belt tensioner so idk what it could be how could I tell if the o2s are bad?

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By doing the stomp test or having the codes read.

Just curious, how does the car run when stone cold? The reason I ask is that the O2 sensors don't come into play until they have reached a certain temperature.
 
#7 ·
Unfortunately, Autozone and the like don't have the scanners for the OBS I cars, especially BMW. You may be able to find a local independent mechanic that will read the codes for you. Sometimes they will do it for free if you give them business.

We have had others in the past have difficulty with the stomp test. I usually ask them to shoot a video of their efforts and we have been able to help them determine what they are doing wrong.

If you are willing, would you shoot a video of your efforts and we will review it to see if there is anything we can suggest to get it to work?
 
#8 ·
I turned the key on and the check engine light didn't come on when it should have the bulb is blown I wouldn't know about putting another one in. My old 91 525i as soon as I turned the key on all the instrument cluster lights would turn on then go off when I start the car! I believe the man unplugged the light to cover something up, when I bought the car it was running alright , Ohh and my mass air flow senser, when I unpluged it it didn't make one bit of difference it might be were the car is running really crappy and it is making a difference and you can't tell but I did unhook It when I bought the car and when I unscrewed it the engine started running different like it was about to bog down so I knew it was working at the time the car isn't in running condition to even get to a BMW shop so I don't know what I'm going to do, is their a cheap fault code reader I can buy to let me read the codes?

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#14 ·
I did that and I couldn't tell a difference were the car is running like crap lol u really can't tell well I didn't anyways

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See my friend when you send a reply like this, please ask yourself how someone else might read it. A part of your mind must 'listen' to what you are saying, as if it was a second person. This helps you cut down on miscommunication. Doesn't eliminate it entirely, of course but it helps bigtime.

Those reading your post here would probably wonder if you pulled all the 5 sensors, or just the maf since you've been talking about the maf, etc, and how you did it. So you might as well put in that information with your reply post. It would be faster and more focused for everyone yourself included.

I'm telling you this now because sometimes it takes a lonng time to methodically figure things out, which means alot of interaction over here, so we need to get a good protocol in from the beginning. Don't sweat, its usually just a few extra lines you'll have to type. :)

Secondly, it is normal for your M50 engine to start and idle fine after about a minute, with the maf disconnected. It will not run rough at all. Sometimes, when you do this live (i.e. with the engine running), the engine stumbles a little but will recover and return to normal idling within a minute or so.

Now, this information strictly pertains to the M50 engine. It does not apply to the m20 engine, which dies when the maf's wire is pulled live, and the m52 engine, which idles rough if 2 sensors are disconnected at the same time (or one sensor is disconnected and another, bad sensor, is left connected at the same time).

IOW the disconnect test for drivability sensors works differently for different engines. You need to check your baseline first before deciding if a certain observation is good or bad for your engine.
 
#15 ·
I'm sorry about your miss understanding! Okay from the top, I have an 01 of 95 BMW 540i 6speed (m60) engine, This is how I got into this situation I was driving to the store and on my way my whole grille fell out including the center grille piece the kidneys and the nose panel, I completely ran over the grille didn't notice any damage to the car except for the grille, drove the car home it seamed to be driving fine. Went out side about 2 hours later started the car to do some more running and the engine was shaking and then I turned the wheel and it started squealing really bad and was bogging down as I turned the wheel. I get out and pop the Hood to look at what's making this car run so bad I checked the intake climbed under the car to take a look at the o2 sensers to make sure the nose panel didn't snag a the wires running to the o2s but they seamed just fine! I got up and started looking at my MAF I unscrewed it the car still ran the same! So that's how I'm in this situation I figured it was a bad senser but I don't have a clue of witch one. It could be as simple as a relay who knows! I never did pull any relays, do you have any ideas?

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#18 ·
Take a second look at your engine bay and its belts, both with the engine off and one. With a strong flashlight. Take your time.

Confirm that nothing is leaking onto the driveway. Just your engine oil level, coolant level, power steering fluid level, brake fluid too.

And since there is squealing, get someone to turn the wheel while at idle, and try to localise the squealing.

Just to be scrupulous about this. :)
 
#16 ·
Thank you.

It doesn't seem like this incident is related to the engine problem. I recall you saying that your engine bay has an undercover. Further, you've eyeballed your car from the top and from underneath and nothing is cut.

So I'm going to ignore all that for now.

1. Please download the bentley manual.

2. Find out where your o2 sensor relay, engine coolant temperature sensor, afm, idle control valve, and air temperature sensor, are located on your M60 engine. Google will help you there.

3. Disconnect each sensor and start the engine. Give it 3 minutes. See if it settles and behaves normally. If it doesn't, shut off the engine, reconnect the sensor you just disconnected, disconnect another sensor, then start over again.

4. When you unplug the bad sensor, your engine will behave normally. You can drive with that sensor unplugged, but your fuel economy generally tanks, so its a good idea to get it fixed fast.

5. The above test works if you're dealing with a drivability sensor problem. When the bad sensor is disconnected, the ecu ignores its inputs and substitutes working standard values in its place. Those values are not live precise, but they will not cause problems.

6. It is a good idea for you to fix the busted lightbulb in your instrument cluster for info about how to remove it and change bulbs. There are good DIYs out there. Just swap in a good bulb from elsewhere in your cluster, if you don't have a spare handy.

7. Read the error codes via the stomp test. Then proceed from there.

8. Alternatively purchase the code reader, especially if it will work with the bluetooth /torque thing.
 
#19 ·
I bought this car about 4 months ago and I don't know when the last time the previous owner changed the spark plugs! Can a bad spark plug make the car miss and stutter and have a loss of power and shake and run really bad lol sorry I got carried away!

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#20 · (Edited)
All misfire, rough running and similar problems would generally benefit by you inspecting the plugs and the plug wells for oil. Along with coils each one checked for spark, and replacement of the dizzy cap and rotor combo as a too commonly neglected item. This is after everything else has been tested and ruled out.

M60 and m50 engines dont have dizzy caps, they have direct coil on plug setups.

Oh yeah. Lol.
 
#21 ·
I didn't think about that till just now do you think that could be my problem? The spark plugs! I bet money it is, When I start the car up at a cold start it starts up pretty rough and half the time it takes a send turn over to start it up!

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#23 ·
Well I replaced my plugs took the old ones out, one of the plugs had oil all over it, I wiped it out as good as possible. The old ones were no good worn out put the new ones in and it didn't fix my problem! I'm just gonna have to manage to take it to the BMW shop and let them figure it out!

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#24 ·
Did you should complete the drivability disconnect test with all 5 of your sensors? Did you check your stomp codes? Perhaps you should do that fully before you take your car to the dealer, since they are easily DIYed. They are not going to do anything different. But hey, its your money. :)
 
#25 ·
Good news! I got off work last night and as soon as I got home I pulled the back seat and unhooked my battery and left it sit like that all night, I woke up this morning reconnected my battery and started the car, It ran like a charm!!!! I let it idle for a while and I could feel a slight shaking and the idle getting worse but not much soo this tells me the o2 sensers are bad cause they kick in when the car starts to heat up am I correct?

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#26 · (Edited)
You are indeed correct that the O2 sensors don't affect the engine until they reach a certain temperature. Your symptoms do seem to point in that direction, but it's kind of like the wind blowing in a direction without gettng the proper diagnosis. It's pretty likely that replacing the O2 sensor will fix the problem, but there's a pretty decent chance that it won't.

Anyway, your car may be in need of a new O2 sensor anyway, I'd just hate to see you replace it and that not be the problem. IIRC, you are the one that has the CEL bulb not functioning, correct? I would encourage you to get that replaced as well because the stomp test tells us so much when a problem like yours comes up and ..... it FREE :bigpimp:
 
#27 ·
I hope that's my problem also cause oxygen sensers isn't cheap lol But I'm 90% sure that's my problem and yes my bub went out of my check engine light how would you replece the bulb? I never had to go about doing that before.

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#28 ·
I hope that's my problem also cause oxygen sensers isn't cheap lol But I'm 90% sure that's my problem and yes my bub went out of my check engine light how would you replece the bulb? I never had to go about doing that before.

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You would have to remove the instrument cluster. I have never done it, but from what I read, it can be frustrating getting the cluster beyond the steering wheel without removing the wheel, but it can be done. It is possible that, due to the location of the CEL on the cluster, perhaps the bulb can be replaced without fully removing the cluster :dunno:
 
#30 ·
Do you have an air bag? If so, make sure to disconnect your battery before you take the wheel off or you will get an SRS light and it has to be reset with a special tool.
 
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