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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 3 Series / 4 Series > E30 (1982 - 1993)

E30 (1982 - 1993)
God's Chariot. The E30 was produced primarily from 1982 through 1991. The cabriolet was the one exception which was produced through 1993.

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  #1  
Old 05-07-2013, 08:54 AM
510man 510man is offline
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Help with Erratic Ignition & Check Engine Light

I'm driving the '87 E30 Vert in the rain last night. It's running fine. Suddenly, it starts to buck. The gauge needles bounce. It runs like the ignition is cutting in and out. Idles poorly and won't accelerate without tremendous missing and cut out. Check Engine light comes on.

I limped the car about two blocks to a parking lot and left it over night given the rain. The next day, I started the car. It started easily. Same problem. Idles poorly, won't rev up and the Check Engine light is on. Tried multiple times to pull the codes but the car will not go into the fault code reader program. I've had this problem before.

After checking a bunch of connections, especially the CPS since I recently replaced it, I disconnected the battery to clear the codes. I put the battery cable back on and started the car. Runs perfectly!!!! No Check Engine light. No misfire. Remember, it would hardly run moments ago.

I'm stumped but need the car to be reliable. DMEs in these cars are a weak point. Mine is likely 7-8 years old with a Conforti chip. Should I replace it? Anybody used ecudoctors.com? Need to confirm this is the correct ECU number for my car.

http://www.ecudoctors.com/bmw-325-ecu-0261200173a.html.

Suggestions on what to try?
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  #2  
Old 05-07-2013, 10:15 AM
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Newman271 Newman271 is offline
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Honestly sounds like: A) need ignition wires---water on the enginecould cause arc's and misfire. B) ignition coil getting wet or on its way to being bad... C) water in distributor cap?

I'd check this before I go replacing an ecu. I had the same issues with my M30 when I first swapped it in plus randomally it would backfire, turned out my coil was loose and moving around causing the cut out and inability to rev.
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  #3  
Old 05-07-2013, 02:36 PM
510man 510man is offline
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Great suggestion. I thought about that as well. However, if the problem was in the ignition components (i.e cap, rotor, wires, etc.) then why would clearing the codes fix the problem? Remember, it ran poorly until I cleared the codes and then it ran fine leading me to consider the DME. I'm still not convinced it's the DME but it's my $#1 suspect at the moment.
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  #4  
Old 05-08-2013, 02:35 AM
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Nick323 Nick323 is offline
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Post

If you have the Motronic then they do it
This ECU is self learning & detecting to a small extent.
So your problem gets the system conused and disconnecting or clearing the system helps this.
The ignition getting wet can easily cause this
Water getting into the ECU will definitely cause issues
The HT from the ignition can also harm the CMOS in your ECU.

I would not replace the ECU until you fix the actual fault first.
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  #5  
Old 05-11-2013, 07:49 PM
510man 510man is offline
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Did it again today in the dry. Disconnected the battery to clear the codes.............it runs perfectly.
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  #6  
Old 05-14-2013, 03:47 PM
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BMWFatherFigure BMWFatherFigure is offline
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Have you checked all the other stuff yet?
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  #7  
Old 05-14-2013, 06:12 PM
510man 510man is offline
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Weather was dry. Replaced cap and rotor. New doesn't mean good in the world electronics. Ignition coil is dry. I don't have a spare to test. I bought a used ECU for $25 so we'll see. That's less then a coil replacement.
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  #8  
Old 05-17-2013, 04:36 PM
510man 510man is offline
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Sent the ECU to ecudoctors.com for troubleshooting and repair, if needed. We'll see what they fine.
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  #9  
Old 06-17-2013, 07:58 AM
510man 510man is offline
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ECU checked out okay. Used a loaner ECU and the same problem occurred.

Disconnected the MAF sensor and the car ran well. Replaced the MAF. Progress but not fixed. In general, the car runs well. Has an occasional misfire. I believe it is ignition related given how erratic the remaining problem is and how it feels like a temporary ignition failure. The tach bounces when it misses too, further leading me to ignition. I would think a vacuum leak wouldn't cause the tach to bounce. No check engine light now.

What are the signs of a faulty CPS? I replaced mine but a new part doesn't mean it's good. I also used an aftermarket part. I've since seen some posts from others having problems with aftermarket CPS they replaced with a Bosch, as I recall, and problems where resolved. There's also the sensor on the ignition wire. Not sure what it does but it's clearly sensing timing for something.

Comments and thoughts on what to try next?
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  #10  
Old 06-17-2013, 10:48 AM
7pilot 7pilot is offline
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I would suspect a weak coil, then possibly inconsistent power supply to the DME.
So:
1, visual inspection of ignition cap, rotor and wires.
2, electrical tests of the wires, the primary and secondary resistance of the coil.
3, inspect the power supply from the battery.
4, pull the instrument cluster and check the grounding of the gauges. tighten the screws if necessary (Past experience to cure a misfire/back fire issue).

m
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  #11  
Old 07-14-2013, 02:15 PM
510man 510man is offline
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Quote:
Originally Posted by 7pilot View Post
I would suspect a weak coil, then possibly inconsistent power supply to the DME.
So:
1, visual inspection of ignition cap, rotor and wires. m
These are new and look fine

Quote:
Originally Posted by 7pilot View Post
2, electrical tests of the wires, the primary and secondary resistance of the coil. m
These test fine.

Quote:
Originally Posted by 7pilot View Post
3, inspect the power supply from the battery. m
Done by me and the shop.

Quote:
Originally Posted by 7pilot View Post
4, pull the instrument cluster and check the grounding of the gauges. tighten the screws if necessary (Past experience to cure a misfire/back fire issue). m
Not sure what I'm checking here. Is there a grounding strap or anything that makes the grounding point obvious?


Since my last post, I replaced the CPS again since "new" doesn't mean "good". I used a BMW OEM CPS this time. Cleaned the connection and the DME connections with electronic cleaner. And...............I still have the problem.

Took it to a local shop that has E30s all over the parking lot, including a few racecars. They spent two hours on it and couldn't reproduce the problem. They pulled a code 33 using an OBD-I code reader, which is a general timing intervention code. They checked the fuel pressure, which is fine and all the ground and positive connections at the battery, DME, fusebox, etc. and tightened them to be sure. The main power relay is original. They recommended I change it. Being a vert, they said there's no fuse link in the trunk (?) so that's not an issue. They said they could continue at an hourly rate but until the car exhibited the problem, they were making educated guesses like I was. I picked up the car with no progress made. I'm just poorer for the two hours labor.

I picked that car up Friday at 6:00pm. It is now Sunday at 4:30PM. Since then, the car had the problem three more times in about 40 miles of driving. What have noticed now that I'm paying closer attention?

The gauge bounce is now the MPG gauge and the temp gauge. The other gauges do not move. Tach is no longer bouncing. The third time it acted up, it threw a CEL and continued to miss. The other two times it missed a split second and continued to run well. On the third incident, I was two miles from the shop so I limped to their parking lot with the CEL on with the intent of leaving the car and calling them Monday morning now that car exhibited the problem on restart. I literally pulled in a parking space in their lot and the CEL clears. Car runs fine. What?!!! However, driving the car that short distance I noticed some things I had not noticed before.

The second incident was while idling at a light. Car missed a split second and cut off. Started right back up. Driving after the third incident with the CEL on, the car will run fine up to about 1800 RPM. Then it misses like it's in some kind of rev limiter or valet mode. I was able to drive the car fine provided I stayed under 1800 RPM. The moment I exceeded 1800 RPM, rev limiter time. It coughed and missed terribly. MPG gauge jumps to 40 and the Temp gauge needle moves back and forth a 1/4" or so. The other gauges do not move.

Does the E30 have a rev limiter or some kind of "limp mode"? My Mercruiser boat engine has a limp mode and I have an Electromotive TEC II system on a Datsun that acts exactly like this when the rev limiter is enabled or it is in valet mode and the RPM threshold is exceeded. If so, what invokes it on an E30? A faulty knock sensor maybe?

Nice car but I'm ready to roll this thing off a cliff!

Last edited by 510man; 07-14-2013 at 02:18 PM.
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  #12  
Old 07-14-2013, 03:57 PM
dirtx dirtx is offline
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you tryed a lot of stuff. Have you looked at the connector and or checked the resitance of the Coolant Temp Sender? The cars run like crap when you disconnect it. The thermostat housing has 4 coolant switches in it. Its the seconed from the top on of the larger connectors not the small yellow one with two loose connectors.
Just a thought, good luck.
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  #13  
Old 07-15-2013, 05:47 AM
7pilot 7pilot is offline
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on the back of the gauges, there are brass colored screws. If one or more happens to loosen, the cluster develops grounding issues. This causes the cluster to send incomplete or faulty signals to the ECU. This can result in aberrant gauge behavior...Temp gauge reads high, fuel gauge becomes inaccurate, and the ECU send crappy info to the OBC, plus mismanages the engine causing hesitation, stalling, misfiring, and the dumping of raw gas into the hot exhaust...in my experience.

If the tach needle is bouncing very quickly like flicking/slamming sweeps, it points to an ignition issue.
The the tach needle is simply dropping and catching but not slamming around, then the problem may be in the fuel delivery.

m
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  #14  
Old 07-17-2013, 08:06 PM
510man 510man is offline
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Quote:
Originally Posted by 7pilot View Post
on the back of the gauges, there are brass colored screws. If one or more happens to loosen, the cluster develops grounding issues. This causes the cluster to send incomplete or faulty signals to the ECU. This can result in aberrant gauge behavior...Temp gauge reads high, fuel gauge becomes inaccurate, and the ECU send crappy info to the OBC, plus mismanages the engine causing hesitation, stalling, misfiring, and the dumping of raw gas into the hot exhaust...in my experience. m
Hmmm.....I'll check this out. Sounds like a "no way" kinda thing but I'll try most anything at this point. I would think the ECU would send info to the gauges and not the other way around. However, electricity is bidirectional unless diodes stop it from flowing backwards. I guess it could make a mess. Would have never looked to the gauges as a possible problem. However, after reading your post, I've noticed the fuel gauge wanders. It never did that before and I assumed the sending unit may be going bad after 26 years. Fuel gauge moves around an 1/8 of a tank or so. Temp gauge runs about a needle width past straight up.

Haven't replaced the temp sensor. I think mine are original. Looks like I have two. Can't imagine why you'd need four. Will look into this too. I need to change one thing at a time though or I'll never know what actually fixed the problem.

Last edited by 510man; 07-17-2013 at 08:09 PM.
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  #15  
Old 09-07-2013, 08:40 PM
510man 510man is offline
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Sorry for the reporting delay. I don't have a lot of time to stay on this project. I'm back to it for now.

Repaired the ODO gears. I cleaned the electrical connectors on the cluster and ensured all the screws are tight. Mine all appear to tighten into plastic (early VDO cluster) so I'm not sure how that ties to a possible grounding problem. Regardless, it's been checked.

I removed the negative battery terminal to remove the gauge cluster. That will reset the OBDI codes. We'll see if the problem comes back.

Separately, I ordered new main, fuel and O2 relays. Mine are all original stamped 2/87. the shop that looked at the car recommended I change them. Will snap those in when they arrive. It would be nice if it was the main relay getting quirky!!

Removed and cleaned the ECU ground post. I looked clean but I removed, cleaned and re-tightened it anyway.

I found the fuselink. It's in the harness covered with some shrinkwarp-like loom. If the problem comes back, I'll remove the insulation to where I can see if the link is corroded. I read elsewhere that some people bypass the link using a 50A car stereo fuse holder. Carry an extra fuse and this potential problem is solved.

Will drive the car for the next few days to see if it has a reoccurrence and report back. Sometimes it will act up within 10 minutes while other times it will drive fine for days before having a problem.
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Old 09-14-2013, 12:49 PM
510man 510man is offline
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Relays replaced and SI batteries replaced. Gauge screws are all tight. Drove six miles and had the same problem. Disconnected the battery to reset the codes and the car drove home fine. Had one significant miss while sitting at a traffic light but it recovered with no CEL.

I'm off to the fuse link and temp senders now. If it's neither of those, I'm to the engine harness.
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  #17  
Old 09-15-2013, 12:21 AM
7pilot 7pilot is offline
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I still think that your suspicion of a dodgy ignition system is founded.

How old are the plug Wires?
There are resistance checks for the wires and the connectors in the Bentley Manual.
If the wires are hard, or have any cracks in the insulation, or have discolored/corroded contacts, change them.

m
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  #18  
Old 09-28-2013, 01:41 PM
510man 510man is offline
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Ding, ding ding!!! I think we may have a winner courtesy of DIRTX. Replaced the blue temp sensor that feeds the DME. Car runs great. I drove it 40 miles without issue. Previously it would fail in six miles. Progress!! We'll see what happens over the next few days.

If this ends up being the problem, it would have been discovered long ago if BMW didn't out engineer itself by using multiple water temp sensors. If they only used one, the temp gauge would read incorrectly, I'd replace the sensor to fix the gauge, and I'd fix the DME data issue at the same time. Lots of time and money wasted if this is it.

Thanks for the suggestion DIRTX. I would have never checked the temp sensor if the gauge was working correctly.
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  #19  
Old 10-03-2013, 07:04 AM
dirtx dirtx is offline
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glad it helped .hope that was it. Ya 4 temp sensors is a little overkill. I knew this cause my sensor retaining clip is broken and I have it safety wired on. Ive seen replacement connectors but dont feel like spliceing them in. safety wire works so far. keep driving it an hope that was it!
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  #20  
Old 10-10-2013, 04:48 AM
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Nick323 Nick323 is offline
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I have yet to see a EFi vehicle that uses the same temp sensor for the ECU & temperature gauge
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  #21  
Old 02-28-2014, 06:10 AM
510man 510man is offline
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Following up on this lengthy thread.

I replaced the TPS in this car and it seems to have resolved the problem. I've been here before only for it to come back so I'm hesitant to say it's fixed.

The TPS tested good with an ohm meter. However, the car would not go into stomp mode. I replaced the switch in my pursuit to fix this problem. Really just another guess trying to find what's wrong. Since replacing the TPS, the car now goes into stomp mode and the problem has not come back in several hundred miles of driving.

I also replaced the ignition wires. They were aged but I'm not sure they were bad. It did, however, smooth the idle out a bit so probably worth doing. I replaced the wires several weeks after the TPS in an effort to isolate the fix.

It's a very intermittent problem so it could still come back. Time will tell. If I don't post further, assume it is finally resolved by replacing the TPS.
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