M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => Engine + Driveline => Topic started by: shiver on June 26, 2006, 01:20:45 PM
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hey guys,
i would just like your help in diagnosing two problems that my car has, i am probably going to take it to the shop, but i would just like input from the M42 guys. i know it is hard to diagnose problems over the internet, i will try to make it as descriptive as possible, so bare with me.
problem # 1:
sometimes when i start the car it will idle funny- going up and down between 800 and 500 rpm and then die. i can prevent it from stalling if i give it some gas. also, when i do get the car rolling, it seems to hesitate. when i push down on the gas pedal, the car will slowly accelerate, it almost feels like there is a slight resistance. then suddenly, the problem wears away and the car accelerates normally. this problem occurs at different times, sometimes when the car is parked for a long time, and other times when the car has just been restarted after a drive.
problem # 2:
i was out for a drive last night and i noticed when accelerating in first, at about 4500-6000 rpm, a vibration occurs. it also happens in second gear at around the same rpms, but is less noticeable. the vibration almost feels like it comes from the rear end of the car, but i'm not 100% sure. i checked the wheels and they were all torqued properly, and all the weights were still there. also, the there is not vibration at high speeds when i'm coasting, so i am almost certain it is not wheel related. i have no clue what this might be, if anyone has experienced anything similar and has diagnosed it, i would appreciate your input.
thanks for reading all of that, your help is much appreciated.
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Well, #1 could be your idle control valve, although unlikely if it causes problems on-throttle. Your oxygen sensor could also be going out, or there might be a really bad vacuum leak somewhere in there. It is fuel-control system related most likely. The air flow meter might even be the culprit. There are a lot of things it could be.
#2 I would say check your driveshaft's center support bearing, tranny mounts, and guibo (flex disc...sits between tranny's output shaft & the driveshaft). Look for cracks...the guibo is a little harder to check on-car, it might been to be removed. I'd just replace it anyway if it has never been done. The support bearing is an item that dies very frequently as well, but it easier to see if the rubber webbing has torn.
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Are you running aftermarket wheels? If you are, and you don't have hubcentric rings on them, you can still have vibration even if they're balanced properly and they're torqued correctly.
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i'm rolling on stock weaves. the vibration occured recently, and i've been running my wheel/tire setup for a while now. i think i'll check out the things bmwman91 pointed out.
thanks guys.
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your problem #1 could be a lot of things, but I would very carefully check your AFM unit; take it out and check the seal around the top black plastic cover to see if its been opened and/or fiddled with; while it's out, clean the inside with carb cleaner very carefully.
Take it from me, don't open the electronic part up and mess with the sensor itself, just make sure the barn door is clean and works smoothly.
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just a quick update.
i haven't had time to bring the car to a shop, so i'm still in the dark with regards to what the problems are.
anyway, last night, after going out for dinner, i started the car (1-2 hrs of sitting), and problem #1 occured again. it was really bad, and the car was sputtering/stalling. but this time, while accelerating (i was still getting the hesitation/resistance), the car was really sputtering and the check engine light went on. i shut car off for about a minute, and when i restarted the check engine light disapeared, but the car continued to run rough.
this morning, the car ran without the sputtering/fluctuating idle, but i'm not convinced that the car is running too well. it feels like (maybe its my imagination), that the car is down a few ponies.
i'm really anxious to get it into the shop and all sorted out. i'll update my findings re: the problems/solutions.
thanks
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I have problem #1 to a lesser extent I guess. I'm going to replace the O2 sensor and try to clean the AFM some way...keep me posted on what the shop says/does.
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Well, from my experience messing with the air flow metering system, issues like that come from the sensor not working at all. Check the connector and wiring for breaks...something may be coming loose. O2 is unlikely. When my wide-band died I was running with NO sensor at all for a week until the replacement arrived. The car ran fine...just VERY VERY rich. When the o2 dies the car goes into emergency-enrichments to ensure that the motor does not run lean.
On the other hand, if the AFM dies, it is a different story. The idle will likely be very unsteady, and the engine will cease all power production under 2 conditions: 1)you try to rev it over ~3500RPM and 2)you open the throttle more than say ~20%. If this sounds familiar, then I would put money on the AFM.
The carbon-track inside the AFM could be worn out. It is repairable (I cannot remember where the writeups are...someone help him ou with that) without spending any $.
OH, and problem #2, I almost forgot.
There is a common problem where the muffler hanger will come in contact with the spare tire well. At some RPM's the harmonics of the engine vibration will displace it enough to cause a lot of commotion back there. Check to see if the PVC coating has been work away on the spare tire well around the front hanger. If so, you can try bending the straps with a hammer, LARGE screwdriver, and some big pliers.
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engine will cease all power production under 2 conditions: 1)you try to rev it over ~3500RPM and 2)you open the throttle more than say ~20%
by ceasing all power, do you mean it will die, or not accelerate too well? i've taken the car to about 6k rpms with no problem, and have gone WOT a couple of times. its just that the car doesn't seem to have the same pick-up as before.
i think the o2 sensor is on its way out, i am smelling unburnt gas when the car is idling. i don't know if that's whats causing the problem, but i think i'll replace it anyway- hopefully my mpg will improve.
with regards to the AFM dying, i don't think its completely dead. the funny idling only occurs intermittently, and as i mentioned before, i was able to rev to 6000+k rpm no problem at WOT.
can't wait to get this all sorted out :confused:
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You were able to rev to 6k when this problem was in its full effect? If so, then yeah, I doubt it is the AFM. The O2 dying will cause a little sluggishness, but nothing horrendous like it sounded like. I guess it is probably the O2 that is the culprit.
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actually, i was able to rev to 6k, but not as it was happening. i never really got it to 6k when the problem was actually occuring. but right after, when it would go away, the car could go to 6k.
well, there is a strange new development. just some background info before i get into the whole story. the PO had a mark D chip in the car. when i purchased it, the owner removed it.
anyways.. today i left my lights on. this obivously caused the battery to drain, and the car not being able to start. but, i noticed when i jumped the car and got it running again, the time/date was reset. does this mean that other things in the car reset as well?
when replacing chips, does the car have to be reset in anyway? this might have caused the problem of intermittent rough idle and bad acceleration... i'm not really too sure if this even has anything to do with the battery dying, but ever since this morning, the car seems to be running better and no idling/accelerating problems have occured. i'll wait a couple of days before i draw any conclusions.
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Hmmmmm.
If a sensor goes south and you replace it without resetting teh ECU then yeah, all the self-adaptations will make it run poorly. Any time you unlpug the battery or remove the ECU it is reset.
I was asking about the 6000RPM DURING the problem. It still could be comethign AFM related (bad connector or something). I know on mine, every time I reset the ECU it idles like garbage for a good 10 minutes. I think it has issues running the ICV and it has to re-learn. After that it is fine, although it never affected my on-throttle performance. It could be that the EC is resetting for some reason intermittently, forgetting all its adaptive programming.
This is a tough one. I have a spare AFM if you want to borrow it and see what happens, although I would do a thorough check for damaged connectors & wires.
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It happens to me too. The car will idle very poorly, threatening to die at times, and I find that's when I'm in a parking lot, and running very slowly...I WOT it and nothing happens...until bam! it's back and it revs again. Then the problem won't occur until I shut the car dow and leave it there for a while. I also think it's more prone to happen when it's hot and humid outside. My wires, spark plugs etc. are all new. It doesn't do it everytime.
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Wow, that is really weird. This is definitely a problem with one of the EFI's input systems. I wonder what it is. For once, I am totally stumped on a control-system problem.
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silverblades, that is exactly what happens to me! oh, and the problem did come back, bringing it into the shop this week, so we'll see.
thanks for all the pointers.
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This could be a good time to get a Bentley manual and learn how to tune the car and check fuel injection components. You could also replace all the vacuum and rubber hoses. If you want to get into real rocket science, spray the hoses with WD-40 to check for vacuum leaks. This is the method of choice if you more time than money.
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All my vaccum hoses are new, replaced when I did my head gasket. ICV is clean, throttle is clean, spark plugs, wires both new. Used injector cleaner aswell. Only thing I can think of now is faulty AFM, O2 sensor or partly clogged catalyser.
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This may sound wacky, but check the attachment at the throttle cable to the top of the intake manifold. When I first got my car I drove for a week with the little black plastic threaded end totaly out of the metal part that holds it. Amazing that the car would go at all i think, but it would start and idle really low (and consequently rough) until the ICV responded by cranking the throttle up. I think it is unlikely to be your problem, but it might be easy to overlook.
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Hey, just signed up, mainly because Im having this same issue (or very close). Im sure its fuel control related. Reason you notice the hesitation is because the engine is getting too much gas, and you need the throttle open for a couple secs to burn it off, then you get normal performance again, if you didn't realize (at least thats my problem). Engine sounds exactly like it did when I flooded my engine with gas for the time when its not accelerating properly. Though I do believe that its that the car is getting too little air, not too much gas - ive had a couple problems in the past with my air system (ICV/AFM/O2sensor), so Im sure its one of those acting up on me. Think thats why the revs are dieing as well (my car isn't stalling, but the idle goes from 800-500 at lights) - too little, air suffocating the engine, revs drop, ICV realizes and brings revs back up, etc...
Im getting a new muffler installed on tuesday and letting my mechanic take a look at the problem before I rip stuff apart myself :P
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This may sound wacky, but check the attachment at the throttle cable to the top of the intake manifold. When I first got my car I drove for a week with the little black plastic threaded end totaly out of the metal part that holds it. Amazing that the car would go at all i think, but it would start and idle really low (and consequently rough) until the ICV responded by cranking the throttle up. I think it is unlikely to be your problem, but it might be easy to overlook.
That just might be the answer for me. The little black plastic jammy is also totaly out of the metal part that holds it. I guess if i can get a new throttle cable, i'll give it a try.
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how did you make out with your rough idle and accelleration ???
I'm having the same problem .
Before the rough idle and accelleration I installed a new fuel pump ,gas filter and spark plugs .I too am leaning toward the co 2 sensor but will unplug the tps tomorrow to see if that makes a difference.
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I had a HUGE MISS from 2000-4500 rpm that new coils from BMA solved when I got my 318is 3+ years ago. Might want to look there...
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Just adding to the moral support and encouraging input b/c I have similar symptoms (thoough not as severe). Mine seems more related to cold engine... but we're not diagnosing me (yet). Please keep us posted as I too am curious if your solution(s) are applicable to me.
Cheers and GOOD LUCK!
Henry
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I did a fault code check and it came back as no faults .
code # 1444
I will continue to keep checking different items cause I don't want to just start changing parts .
This rough idle and crappy accelleration is very irritating .But it's not a daily driver so I have time .
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UPDATE
this evening I
1) disconnected the tps - this made the car run worse
2)took off the mas and cleaned it - this made no difference
3) disconnected the oxygen sensor in the exhaust pipe - this didn't make it run any worse ???? HMMM
4) I checked for vacumn leaks on everything I could see - none that i could detect
This is the question
Should there be a difference while running when I disconnect the oxygen sensor ????
Or is it to minimal to notice .It does look old but I didn't get that code fault .
I will solve this mystery
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You should get a CEL with the EGO sensor off, and the car should run really rich. I was stuck for a week with a crapped one that I disconnected and had to drive to work. It did not behave as you are describing with the stalling idle and lumpy acceleration...it just ran extremely rich.
Inspect the crank position sensor and main pulley/toothed wheel. Check to see if they are damaged.
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I just disconnected the o2 sensor and my check engine light did not come on .
What does that mean ????
It does come on when I turn the key to the on position .
I'll check the cps tomorrow and I think I'll put in some injector cleaner and see if that helps anything.
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I just disconnected the o2 sensor and my check engine light did not come on .
What does that mean ????
It does come on when I turn the key to the on position .
I'll check the cps tomorrow and I think I'll put in some injector cleaner and see if that helps anything.
i do appreciate all the help I'm getting
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My daughters e30 had a similar intermittant rough running issue that turned out to be a bad connection to the coolant temp sensor. I found it by accident when I brushed the wire while tapping the FPR. She doesn't have an m42 but the problem does sound similar. I cleaned the connection and it's been fine since.
I just got through rebuilding the front end on her car after she put it into a telephone pole. Everything from the waterpump forward had to be replaced. Anyway, when I took it for a test drive I had severe vibration that would come and go dependant on speed or direction I was turning. Back home I looked under the car and she had hit the pole hard enoght to knock one side of the tranny cross member loose. Anyway, point is to check your motor and tranny mounts. I had the same issue a year after I bought that car and had a motor and tranny mount that had gone bad. I thought I'd spun a bearing or something. New mounts and it was smoothe as silk again.
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I just disconnected the o2 sensor and my check engine light did not come on .
What does that mean ????
It does come on when I turn the key to the on position .
I'll check the cps tomorrow and I think I'll put in some injector cleaner and see if that helps anything.
i do appreciate all the help I'm getting
I just replaced my bad o2 sensor and here is my experience. The car will run fine without an O2 sensor. You won't necessarily get a check engine light right away if you disconnect the O2 sensor. You will only get it from time to time when you're in open loop mode while cruising at a steady speed. My o2 sensor did cause erratic idle. The rough running, I'm still trying to sort out.
While the motor is running, try disconnecting your big vaccum breather hose going to the valve cover towards the front and see if there is any difference.
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Thanks Alpine
I did disconnect the big vacuum line before and the motor immediately died .
I still need to check a bunch of sensors using the bentley manual .
I was wondering if anyone had any experience with the coolant temp sensor.
I've read on numerous threads that that sensor if faulty leads to rough idle and poor accelleration .I just don't want to start replacing parts ,I'd like to find the problem by analysis ,not by parts changing.
Like anything,work :( gets in the way of working on the car .
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Update
I changed out the thermostat ( The one I removed said China on it :mad: )
I flushed the cooling system and installed new antifreeze with distilled water.
I changed out the oxygen sensor .
After all this car still ran like it was running rich.
I did another code check and this time I got back mas code .
I removed it and sprayed carb cleaner on it
VOILA ,,the car seems to be running good now but I'm keeping my fingers crossed .
PS I worked my ass off trying to get that old oxygen sensor out .
torches and everything .
Then I squirted some PB Blaster on it and 15 minutes later it came right off .
I am now a believer in PB Blaster.:)
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I am now a believer in PB Blaster.:)
Glad you found the problem.
All you have to do is spray WD40 into a styrofoam cup and PB Blaster into a separate cup and watch as the PB Blaster eat through the cup. Just like their ad campaign. haha.