M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => Engine management => Topic started by: Hunsbergring on April 27, 2012, 12:00:48 PM
-
Greetings, M42ers!
First-time poster, here, though some of you will recognize me from Bimmerforums, where I've been hanging out for five years or so (I also have an Eta). I've posted about this problem on there, but no one has seemed to have many ideas, except advice to post on here...
Anyway, my '91 318i sedan (329,000kms) has started misbehaving. It won't rev past 3000rpm--just feels like it's running up against a limiter, with a clean cut. Seems to be an ignition cut, since it looks like there's unburned fuel in the exhaust. Originally, it started doing this only when warm (after 15-20mins of running). I pulled the crank and cam sensors, and found that the crank sensor was caked in gunk. Cleaned it, reinstalled it, and the car ran perfectly for a month. Then, it started doing it again, and after a couple days began doing it even when cold. Now, it won't rev past 3k under any circumstances.
Stomp test says 1244, which is cam sensor. Replaced the cam sensor from my parts car to no avail. I've also swapped out a bunch of other stuff from the parts car (which ran perfectly when parked), such as coils, AFM, DME, plug wires and TPS. No effect. Resistance on crank and cam sensors is spot on.
Any ideas?
-
if revs good just after cold start for 20s it could be lambda sensor.
-
I dunno, that sounds exactly like a cam or a crank sensor failure to me. A clean cutoff is almost always ignition related, and that controls it all. The coils in those sensors are more prone to be noisy when they get hot, I'm betting something is still off there somewhere. Especially if pulling the sensor and reinstalling it fixed the problem for a bit.
-
You swapped the DME and coils, so I'd say you've eliminated them...can't be a dead coil or coil driver.
Since it was originally temperature related, I'd be testing the CTS and IAT sensors too. If the car still thinks it's cold, it'll never switch to closed-loop. You might be stuck in cold start enrichment, and the O2 sensor never get consulted about the mixture.
Cam sensor error could also be a bad wire, ground or EM interference. I'm guessing the sensor itself is OK since you swapped it with no change. I'm not sure how I'd track down a bad wire in the main harness though.
You didn't happen to swap out the main & FP relays, did you? Occasionally those die in odd ways, working when they're cold but cutting out when warm. With that hard rev cut, relays are unlikely but might be worth a shot.
-
New cam sensor is on its way--I'll swap in a known good one and see if it makes any difference. If not, and the code 1244 comes back, it has to be a wiring issue, either in the harness or at a ground somewhere.
I'll try the relays from the parts car, too, cause I guess you never know...
-
New cam sensor swapped in with no change. There must be sadness in my harness. :(
-
Why dont you want tu buy diagnostic cable with INPA and check what is wrong? Or just go to BMW dealer and do diagnostic...
-
INPA...?
I may eventually take it to someone for professional help, but it hasn't seen a mechanic in four years and I don't want to break my streak of self-reliance!
-
INPA is diagnostic software.
For cable and interface search eBay. I am not sure that all cables support old cars E30. Check it with seller. Probably you will need older inpa version. I checked mine INPA V5.0.2 and there is an engine option for motrinic 1.7.
Search for USB obd2 with 20pin adapter.
-
I was thinking about your problem a bit. How far away is the face of that crank sensor from the trigger wheel? It should be very close, like the thickness of a credit card. Is the trigger wheel relatively clean?
Have you taken a look at the cam gears? It's a long shot, but are the sensor pins intact?
Also, the crank & cam sensors don't ground to the chassis. They have "floating" grounds that head over to the DME, to cut down on EMF noise. When you ohm'ed out the sensors, did you check all three wires? 1-2 should be spec (640-ish for the crank sensor), but 1-3 and 2-3 should be a very high value, like 300Kohms.
-
@Romkasponka: Nice! I didn't know that sort of thing existed for these cars. Thanks for the heads-up.
@DesktopDave: The crank sensor clearance is fine--that was one of the first things I checked. The pins for the cam sensor had occurred to me, too, but I haven't checked that yet--figured I'd exhaust all sensor/electrical possibilities before checking for mechanical damage. I also haven't checked the resistance for the cam/crank sensor grounds, but that is an excellent suggestion and I'll try that next.
-
The cam timing pins are cast into the cam gears. Pretty slim chance one has gone missing.
I think testing the sensors for proper impedance is your best bet!
-
I've seen this symptom described 3x now having the end result been a weak fuel pump.
-
^I see how a weak pump could cause low revving, but there's a distinctive "leaning out" feeling to fuel starvation whereas this is a definite, sharp, electronic cut-out. Like I said earlier, it's like a rev limiter at 3k.
I've been focusing on getting my 325e running properly for the last while, but I'm back onto the M42 again. I'll go test the sensor connector pins now and see what I get for resistance.
-
I get proper resistance on the 1-2 test on the cam sensor, but infinite on 1-3 and 2-3. Both other cam sensors in my collection are the same.
Are there any test values for checking the corresponding terminals on the harness side of the connection?
-
check you speed sensor on the diff
-
I too hve a 1991 BMW, 318i with the same problem. It is currently at a shop specializing in european cars and they too, cannot find the problem. They suspect a missing crankcase ventilation hose. Does anyone have a vacuum hose diagram for this car? The dealer is no help, Chiltons is no help and Hanes is no help. Help!
-
Have either of the two of you actually popped in a known good fp to test the theory I've seen solve this issue a few times? Seeing as you all are stumped, why not give it a go?
-
I have a new fuel pump; pressure & flow check per Chilton manual. Also new:
camshaft sensor
vacuum hoses (replaced as they were when I purchased car)
O2 sensor
fuel filter
injectors
spark plugs
plug wires
Coils check ok and am getting spark on all four.
Exhaust has been checked for blockage.
Replaced ECM with another used one.
Nothing has helped. Still suspect hoses and need an accurate diagram for my 1991 318 I.
Hope you all don't mind my adding my problem. (first time user)
-
@Avtovaz (nice handle, btw): Funny you should mention the speed sensor. I finally broke down and took the car in to a local German car specialist (whose daughter I dated in High School...) to have him take a crack at it. He said his diagnostic scan turned up codes for the cam sensor and the speed sensor.
All he did with the cam sensor was fiddle with connections. Didn't do anything with the speed sensor. What would the speed sensor have to do with anything, though? I didn't figure it would have any effect on engine management.
@axisofjustice: If this speed sensor business doesn't lead to any insight I'll swap the fp out of the parts car and give it a try!
-
All he did with the cam sensor was fiddle with connections. Didn't do anything with the speed sensor. What would the speed sensor have to do with anything, though? I didn't figure it would have any effect on engine management.
Doesn't the speed sensor input factor into RPM spark cutout for later e30's? I think the e30 M3 was speed-limited...perhaps the M42 is as well? I mean LOL on BMW if it is, since I'd think a healthy e30 M42 can't see the far side of 135mph. I know this is a cockamamie theory (my favorite types) but if that sender isn't playing nice, maybe you have a doubled speedo count and you're getting kicked out halfway? 3k RPM is really close to being half the M42 redline of 6300rpm...
This thread (http://www.kneb.net/bmw/E30/BMW%20E30%20M3%20Repair%20Manual/12_engine_electrical/motronics_description.htm) has some great details about DME operation, though they seem very general. Load and timing are discussed, that's my theory about a potential speed sensor problem.
I noted a limp mode on this thread (http://www.r3vlimited.com/board/archive/index.php?t-119322.html), but it's only for the later Siemens M52 DME's.
-
I swapped out the speed sensor from the parts car. After putting about 100kms on the car today, it was working fine--no cutout at any point, running reliably to 6500rpm. Then, just as I was almost home, I ran the engine fully out in 2nd gear, and it sputtered at 6k rpm. Did a stomp test and it threw no codes.
I also had in in for an emissions test, today, and it failed the acceleration tests for both carbon monoxide and hydrocarbons, but passed on NOx. Passed everything at idle.
Any thoughts on any of this?
-
Things regarding reving being limited might be the coding plug on the cluster. One, you need to make sure you have the right one for your car and second it might be bad. I dont believe they are expensive to get if not NLA. Also, maybe you can borrow it from a working car so you dont have to order one. Its a long shot but could limit your RPMs.
-
I'm glad you're closer. I never figured the speed sensor could cause troubles like that.
The cam sensor is very important for timing. The speed sensor retards top speed with spark cut-out. A failed emissions test could also point to timing. Odd coincidence, no? I suspect a relation here. I'd be tempted to run continuity tests on the DME plug - make sure it's not plugged into the DME when you do that.
You didn't check those coolant and air temp sensors yet, did you? If the car is getting bad data from those sensors & running open loop it'll cause all sorts of troubles with retarded timing.
-
No, Dave, you're right--I forgot about the air temp and coolant sensors. That'll be job one tomorrow.
-
Does anyone have a quick link for DME pin tests? I've just been through that on my Eta but haven't been able to find a list of tests for an M42. Figure it'd be easier to do that and test a bunch of sensors all in one go rather than yanking stuff out one at a time...
-
Greetings, all-first time posting here, but long time member over on Bimmerforums. I've been having a similar problem w/ my car (95 318i m/t, 215k and counting) for going on a month now. I've just been living with it until I find a solution I can bite my teeth into, but I wanted to share my experience because it's a little different from what's being described here and maybe it'll shine some light on what could fix either or both of our problems...
Similar to what Hunsbergring is describing, my car won't rev past a certain RPM, but where my problem seems to differ from Huns' is that mine is seemingly completely temperature related. I.E., from a cold start (on a cold morning, say 30* ambient), it usually will top out at 2500RPM; however, as the engine warms up, the rev cut will gradually rise until it finally will rev all the way to ~6300 when the engine is at normal temperature, and that will remain the case until the engine cools off again. As w/ Hunsbergring, the "cut" feels very precise and computer-controlled; the engine runs strong all the way up to whatever RPM it cuts out. Other than this, I've noticed absolutely nothing out of the ordinary as far as performance is concerned. The stomp test is clean, haven't ever had a CEL, so I'm kinda stumped...
It all started after I decided to replace my front main seal and the gaskets on the oil filter housing. During that process, I (unfortunately) had to replace my alternator due to one of the studs breaking off my original one. Other than this, every part I put on the car came off the car, and I've triple checked my handiwork and can find no loose ends there. The only thing I can knowingly say may have something to do with this is the fact that I noticed while it was removed that my harmonic balancer is slightly out-of-round due to a crack in the rubber at its' base. I have another balancer out of a junkyard car that appears to be in good shape, but I need to order another crank bolt before I can replace this. My thought there is perhaps the CPS is getting a bad reading due to the balancer wobbling, but I don't understand how this could be anything temperature-related :confused: Unless it's something as crazy far-fetched as the wiring continuity changing w/ engine compartment temperature, or the rubber on the crank pulley becoming more pliable and it wobbling less once the engine is warm. But both of those seem to be so far-out in my mind...I can't imagine the tolerances are close enough for either of those theories to have any merit...
As with this thread, people on Bimmerforums suggested O2 sensors, IT sensor, MAF sensor, fuel issues, etc. etc. But seeing what all Hunsbergring has tried, I'm hesitant to just start throwing money at some pretty expensive sensors. Granted, I haven't changed anything since this problem started and it's been consistent for over a month now.
Any suggestions are appreciated.
-
Has everyone checked the grounding straps from the alternator to the engine block to the chassis as well as battery cables?
-
No, although I did have the battery disconnected for a few days while I was replacing the seals I mentioned before...but I don't understand how a problem like what I'm experiencing would have anything to do w/ a ground strap?
-
No, although I did have the battery disconnected for a few days while I was replacing the seals I mentioned before...but I don't understand how a problem like what I'm experiencing would have anything to do w/ a ground strap?
I recommended checking the ground straps and battery cables because you stated that you replaced your alternator. Those nasty little ground straps are often overlooked and neglected.:p I don't think the harmonic balancer is your problem unless the crank key has sheared and the balancer has rotated on the crank, but that doesn't explain the temperature dependency effect you are experiencing.
Based on everyone's (understandable) hesitancy to throw money into expensive parts you may not need, my mindset is to stop at this point, go back to basics and start with a good, strong electrical system.
Check all emission hoses for proper connections and cracks as well as the intake boot aft of the AFM. If you've already done that...check 'em again!:D
Make sure you have at least a 1/4 tank of fuel so the fuel pump is being properly cooled and not overheating; check fuel pressure. When is the last time the fuel filter was changed?
It's possible for the cat to be blocked and that can easily be checked with a vacuum gauge, however, I think that were the case the car would have driveability issues throughout the entire RPM range. *Has anyone found that the car can be revved past 3K when it's in neutral, but not in gear?
-
All good advice keflaman; and to answer your question, I toyed around with mine a little when I was leaving work yesterday and it did its' usual cut-out at around 2250 in gear, but to my surprise, when clutched it would run up to ~3000 before hitting the cut. But, again, the longer I drove, the better it got. Even hit the actual limiter on the interstate once it was up to temp. So I don't know!
I've got a week off coming up so hopefully I'll get in and poke around some more.
-
_
-
Hey, Eric, just saw this and your PM--haven't been on here in a few weeks.
I haven't thrown any more time at my issue since my last post. I've been focusing on my 325e and my new winter beater, which is a nice, rusty, dented, boring, '99 Civic hatch. Pretty easy to justify 800 bucks on something you know will run through the winter without giving you any guff. Too bad about the complete lack of steering feel, but whatcha gonna do?
I fired up the 318i today for the first time in a few weeks. Got it up to temp and took it for a drive. Didn't misbehave at all, but these days it's going for 30mins or more before acting up.
Next job is going to be grounds. Gonna find every one I can and clean it up. Battery connections are good, so I'll go for the alternator next and proceed from there.
It's hilarious that yours and mine are doing the same thing but under opposite conditions! Mine runs fine cold but sputters when warm, yours sputters when cold but runs fine when warm. I expect we're chasing the same gremlin, here.
-
...sorry for that blank post. It won't seem to let me delete it...
-
I have a new fuel pump; pressure & flow check per Chilton manual. Also new:
camshaft sensor
vacuum hoses (replaced as they were when I purchased car)
O2 sensor
fuel filter
injectors
spark plugs
plug wires
Coils check ok and am getting spark on all four.
Exhaust has been checked for blockage.
Replaced ECM with another used one.
Nothing has helped. Still suspect hoses and need an accurate diagram for my 1991 318 I.
Hope you all don't mind my adding my problem. (first time user)
The M42 Holy Grail for "The Mess Under The Intake". Refer to page 14, post #321 for an excellent picture reference.
-
Does anyone have a quick link for DME pin tests? I've just been through that on my Eta but haven't been able to find a list of tests for an M42. Figure it'd be easier to do that and test a bunch of sensors all in one go rather than yanking stuff out one at a time...
I'm not sure if you're going to be able to download this, but I just tried and it appears to be working: http://bmw.ctcms.net/BMW/Software/E30%20CD%20Repair/Cd%20Repair%20Bmw%20e30.rar
Page 202, section 12-111/4. It's a read only PDF document and a great (if not better IMHO) companion to the Bentley.
-
I fired up the 318i today for the first time in a few weeks. Got it up to temp and took it for a drive. Didn't misbehave at all, but these days it's going for 30mins or more before acting up.
Next job is going to be grounds. Gonna find every one I can and clean it up. Battery connections are good, so I'll go for the alternator next and proceed from there.
It's hilarious that yours and mine are doing the same thing but under opposite conditions! Mine runs fine cold but sputters when warm, yours sputters when cold but runs fine when warm. I expect we're chasing the same gremlin, here.
Here's an idea: Cool down what's hot and heat up what's cool.:cool:
Your problem actually sounds like a coil and I know you swapped them around, but typically when a coil has a cracked case or is breaking down internally it will operate fine when cool but exhibit exactly what is happening as you describe it. So, drive the car until it starts to sputter and then immediately swap out the coils (or another component you suspect) and see what happens. If you don't have a spare, throw that component in the freezer (or snow bank:eek:) for ten or fifteen minutes and reinstall.
318ieric - you could try doing the same thing in reverse: hit a component with a hair dryer or heat gun and see if you can duplicate your problem while the engine is cold.
-
Keflaman--I've actually tried that exactly! It was one of the first things I did when the problem appeared.
For my own peace of mind, I think I've comfortably exhausted all ignition/fuel delivery/DME/sensor possibilities and need to move on to grounds. Since the DME was throwing codes for two completely unrelated components (cam sensor and diff speed sensor), that sounds to me like a bad ground that's causing problems for a few different systems. Will start with alternator ground.
-
Cam sensor is related to that problem. I was not able to rev past 3k. After sensor replacement problem was solved... Quite important is to have correct gap, my friend had missing O-ring and after he installed O-ring fault of the cam sensor was gone.
-
Cam sensor is related to that problem. I was not able to rev past 3k. After sensor replacement problem was solved... Quite important is to have correct gap, my friend had missing O-ring and after he installed O-ring fault of the cam sensor was gone.
And my theory about the coils doesn't stand because it wouldn't be RPM specific.:mad: Sorry about that.:o
I disregarded the cam sensor because two of the cars swapped a total of three sensors (two of them were new) and the problem persisted.
As an act of penance for my misdirection I will pull my cam sensor and remove the O-ring. Standby for results.:D
Edit: Going back to the basics, have you guys tried pulling your sparkplug wires one at a time while it's running rough to see if there's a difference?
-
I haven't pulled the wires one at a time since it's clear that the ignition (or fuel) cut is complete--it's not just one or two cylinders not firing, it's definitely all of them.
-
I hope you don't see my contributions to solving your problem as little more than spamming the thread. Solving the mystery is a bit of a personal issue for me: http://www.m42club.com/forums/showthread.php?t=8981
I never figured out my problem and as I stated in the thread, it occurred only when I drove the vehicle. I even tried several different driving styles; I lived in Italy at the time and it was an '89 Euro-spec car, non-cat.
I looked into the O-ring issue as suggested by romkasponka and I don't see how it could affect the sensor except in regards to a wiring issue.
-
Got a bit of an update; I was able to pin down a buddy of mine who works at an indy Benz shop, but they had a scanner for BMW's so we hooked it up and were able to see a few things the stomp test didn't reveal. The only fault code stored was for the No. 2 knock sensor (replaced both knock sensors w/ new Bosch units earlier this past year, while chasing another issue which turned out to be a dead injector), were able to see the intake temperature reading and it seemed reasonable considering the ambient temperature and the fact that the engine was hot when we scanned it. Coolant temperature readout seemed right as well. Wish I'd written the exact numbers down, but the scanner honestly wasn't the best one around so I was really just looking for a major red flag here.
He reset the knock sensor code, and we need to scan it again now that I've driven it a while to see if it came back. My thoughts at this point are:
-something's causing it to knock when cold (failing plug/wire/coil/fuel injector) and the DME is retarding/advancing timing to try to fix the knock, hence in effect "limiting" the revs
OR
-the knock is due to the "misfire" triggered by the DME when the engine is being "limited"
Since I know the knock sensors are new and I in no way touched them (or anything to do with them) while repairing the seals I mentioned earlier, I'm operating under the assumption that they're working correctly. To me, it's a question of which came first- the knock or the DME reacting to the knock..if that makes sense.
In regards to my first suspicion about a failing component, the plugs have probably less than 10k miles on them, although they aren't the copper plugs I've read so many places that our engines seem to prefer; they're Bosch dual-tipped platinums, whichever ones are outlined in the owner's manual. I checked resistance on the coils back this summer (when the plugs were replaced) and they all checked out just fine, and one injector has been rebuilt; no. 3 I believe.
-
I got mine back from the shop with no resolution and no charge. FYI, my fuel pump has been replaced and my speed sensor, CAE, has been replaced. The car was running hot, so I replaced the thermostat with a cooler one. Now it runs too cool (154 deg. F.) Could the O2 sensor cause this problem because the engine is not actually at operating temp? My reading of the literature indicates that it would simply run in open loop, but it should run.
At one point I thought I had it fixed. The literature indicates that the ABS could throw a code to the ecm if the wheels were slipping. Two of my wheel sensors were bad. Replaced them and it seemed to run fine on short trips, about six miles; just enough to get heated up to operating temp. Then, it started cutting out again at 3500 rpm. on the same six mile test run. I have checked continuity of the sensors and replaced the DME twice. Any new thoughts?
-
Well guys- I can't say w/ 100% certainty that it was any one thing, but something I did last night fixed my rev problem. As I believe I'd mentioned before, my harmonic balancer had a slight crack in the rubber which caused it to "wobble" as it rotated. Well, last night I installed another balancer from a junkyard car and cleaned the crank position sensor and wallah! No more rev problems :o
I discovered, once I removed the old balancer, that it appeared as though perhaps (somehow) the balancer had shifted from center. I'm not sure how this could happen because the woodruff key was intact, and I don't recall having to put any effort at all into installing it when I had it off the first time. Perhaps torquing it down with the crank bolt caused it to rotate?? Still doesn't make sense, though, if the key wasn't broken. So I don't know, but I'm just happy to report that it appears to be back to normal.
Thanks for all the head scratching guys- if not for you guys, I probably would have spent countless hours and money replacing things that didn't need replacing.