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E36 (1991 - 1999)
The E36 chassis 3-Series BMW was a huge hit among driving enthusiasts from the first moment the car hit the pavement. The E36 won numerous awards over the years it was produced and is still a favorite of many BMW enthusiasts to this day! -- View the E36 Wiki

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  #1  
Old 05-15-2012, 07:14 PM
andrew320i andrew320i is offline
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'94 320i starting issues - unstable revs

My car has unfortunately been having some very intermittent starting issues. It's happened twice during the last half year I've owned it, and I drive it most days. It has about 200,000 km on the clock.

What happens is that I turn the ignition on, and it sparks and all, but then the the RPM drops badly below idle randomly, like every few seconds or so.

First time was at the end of a long day late at night, and the air was a bit cool - maybe 20 C. I thought it may had been bad for the car so I didn't try drive. Tried it again the next morning, was worse, so got the mechanic to tow it. Once it was at the mechanics, it worked fine

Second time was yesterday morning - air was a fair bit cooler, maybe 10 C. This time I didn't feel like having a car get in the way of my plans for the day, so I just floored it. It was a little unstable for the first 1 km, stalled while I was reversing out of my driveway, but once I got going it seemed fine. Power felt fine, if not good.

So I'm quite sure that a cold start combined with some other problem is causing it. That "other problem" is obviously something very random, so maybe an electrical or fuel problem.

I guess I may as well describe how the car has been performing overall. Fuel efficiency hasn't been great, it's about 10 L / 100km, when it supposedly should be like 7.5 L/100km when new. It doesn't fluctuate much, regardless of how I drive. Performance is great for 3k+ RPM, but below that it's very sluggish. To start fast off the line, it takes a high rev with the clutch in. Completely opposite to an ~'03 Corolla I used to drive - that had heaps of torque at low RPM, if you wanted to you could easily get wheel spin, but after that it didn't have much at all.

Any thoughts?

EDIT: Thought it would be good to mention that I had the engine rebreather hose replaced about two months before the first time this was an issue. The engine rebreather hose had collapsed.

Last edited by andrew320i; 05-15-2012 at 07:23 PM.
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  #2  
Old 05-15-2012, 07:30 PM
tchavera tchavera is offline
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sounds like idle control valve. it's probably like a level 3 on a DIY. since your there replace the CCV and the air temp sensor. however, i wouldn't throw money into guessing. others might contribute but in the end you will get mixed answers. i really hope you figure this out from the forum though. however, IMO these situations need to be seen first hand by a mechanic who can go through different testing methods. at a bare minimum you could pull out the idle control valve and clean it up. plenty of DIYs out there. good luck
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  #3  
Old 05-15-2012, 08:17 PM
andrew320i andrew320i is offline
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Quote:
Originally Posted by tchavera View Post
sounds like idle control valve. it's probably like a level 3 on a DIY. since your there replace the CCV and the air temp sensor. however, i wouldn't throw money into guessing. others might contribute but in the end you will get mixed answers. i really hope you figure this out from the forum though. however, IMO these situations need to be seen first hand by a mechanic who can go through different testing methods. at a bare minimum you could pull out the idle control valve and clean it up. plenty of DIYs out there. good luck
Thanks for the response. Mechanic had no idea, so might need to do this one myself I guess!
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  #4  
Old 06-18-2012, 12:09 AM
andrew320i andrew320i is offline
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I thought I'd post an update about what's been happening.

I didn't get around to doing any work on it, sort of put it off as I thought that I could get the car to work whenever I needed it to.

Well, apparently not - last week I tried to start it, and it didn't spark much at all, only very occasionally. So it was dead. I had run the petrol very low, but had refilled it. Long story short; the breakdown assistance guy said it seemed like it was still starved of fuel, so he suspected the fuel pump. However when he hit the fuel tank with a rubber mallet he wasn't able to get it going, which is supposedly a common way to temporarily fix a broken fuel pump.

So I had it towed to my mechanic, and he thought it was the fuel pump so I had him replace it ($515). It started fine, but when I drove off and gave it a good run in first gear, the revs cut down badly when I was above 4k rpm. Seemed fine for the rest of the day though, so thought it may had just been air bubbles in the fuel line.

However yesterday and today it performed really badly. I was able to get it started, but still very unstable at high revs, backfires a fair bit, seemed a bit weak on the power front, and just generally rough and bad. Also it didn't go away after a bit of driving like before.

Can the ICV really cause all those issues, particularly issues at high revs? I'd think not.. though I'm going to try give it a clean this weekend.

EDIT: Drove it after getting home tonight, running better but still a bit of backfiring, also just sounding rough (may need to give the chain some attention or some of the belts). The cold definitely seems to exaggerate the issues.

Last edited by andrew320i; 06-18-2012 at 12:55 AM.
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  #5  
Old 06-25-2012, 02:14 AM
andrew320i andrew320i is offline
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To update, I cleaned the ICV - my first ever proper DIY job on a car! Was a bit challenging, I have quite long arms and big hands, so getting into that small space is not easy. The ICV was a bit dirty, but it still moved ok before cleaning. We cleaned it anyway, but afterwards we are still having starting issues. Also I tried starting it with the MAF detached, but that made no difference.

To describe it, at the moment often when I turn the car on in the morning, the engine struggles massively, with the revs dropping down heaps (and also kicking up at times), and the throttle seems to do nothing. So more or less, the engine is really rough and violent but going, but you have no control (and negligible power). However we realised this morning though that if you open the throttle just a little bit (not a lot), it starts after 5 or 10 seconds.

We're getting an instrument to measure error codes, and also a new o2 sensor. We know it's probably not it, but we're hoping the new o2 sensor will improve the currently terrible fuel efficiency.

I'm wondering whether the ICV has actually failed, but that wouldn't explain failures while the revs are above idle. Maybe the crankshaft sensor? Hopefully we can get some useful error codes.

If anyone has any thoughts, I'm keen to hear them!
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  #6  
Old 06-26-2012, 09:16 AM
bmw-mania bmw-mania is offline
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Ok.. before you go spending money on a code reader.. STOMP TEST.

http://www.pelicanparts.com/BMW/tech...de_Reading.htm

Clean, Clean, Clean the MAF.. remove screens on MAF, use spray FIRST, (and LIGHTLY with q-tip if necessary) clean the element.
Clean Throttle body
Clean Throttle position sensor
Check for vacuum leaks
Check the hoses that are plumbed into the boot on intake

Disconnect, clean, lube, and reconnect all associated electrical connections.

And whatever work the mechanic did.. cover your butt.. keep your old parts..
Your fuel pump was probably fine.
Find a more experienced technician to help you with your vehicle in the future.
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Last edited by bmw-mania; 06-26-2012 at 09:17 AM.
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  #7  
Old 06-26-2012, 03:52 PM
andrew320i andrew320i is offline
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Quote:
Originally Posted by bmw-mania View Post
Ok.. before you go spending money on a code reader.. STOMP TEST.

http://www.pelicanparts.com/BMW/tech...de_Reading.htm

Clean, Clean, Clean the MAF.. remove screens on MAF, use spray FIRST, (and LIGHTLY with q-tip if necessary) clean the element.
Clean Throttle body
Clean Throttle position sensor
Check for vacuum leaks
Check the hoses that are plumbed into the boot on intake

Disconnect, clean, lube, and reconnect all associated electrical connections.

And whatever work the mechanic did.. cover your butt.. keep your old parts..
Your fuel pump was probably fine.
Find a more experienced technician to help you with your vehicle in the future.
Yeah that stomp test.. need to give that a go. My dad has already ordered a code reader though.

Thanks for the tips though, I'll try work through them. Hopefully I can get the fuel pump back.

Three questions:
1. My understanding is that normal CRC contact cleaner is no good for MAFs, must I get the MAF CRC cleaner?
2. Is normal contact cleaner fine for the rest of the parts?
3. How far do I go with checking my vacuum leaks? Just air intake is enough right, not exhaust?
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  #8  
Old 06-27-2012, 09:29 AM
bmw-mania bmw-mania is offline
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Quote:
Originally Posted by andrew320i View Post
Yeah that stomp test.. need to give that a go.
My dad has already ordered a code reader though.
You're hyped.

Quote:
Originally Posted by andrew320i View Post
Thanks for the tips though, I'll try work through them. Hopefully I can get the fuel pump back.
Dont "ask" for it back..
say "hey you forgot to give me my old parts (fuel pump) I thought you put it in the trunk."
said as a statement.. not a question.

Quote:
Originally Posted by andrew320i View Post
Three questions:
1. My understanding is that normal CRC contact cleaner is no good for MAFs, must I get the MAF CRC cleaner?
2. Is normal contact cleaner fine for the rest of the parts?
3. How far do I go with checking my vacuum leaks? Just air intake is enough right, not exhaust?
  1. Might as well. Short bursts, or soak a q-tip. You can use anything that isnt abrasive that has high evap, and leaves no residue. Alcohol?
  2. Normal electrical contact cleaner should be fine. But use the MAF if you bought it. Clean as you go, lube contact points.
  3. Anything that is rubber needs to be checked. dry, cracked, LEAKING hoses WILL KILL. (your car) Check anything that is rubber. Inspect, Clean, and Replace as Necessary
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Bmw-Mania, Ladies and Gentlemen.

Last edited by bmw-mania; 06-27-2012 at 09:36 AM.
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  #9  
Old 06-27-2012, 03:27 PM
andrew320i andrew320i is offline
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Cool, thanks for all the info. One last question - what do I use to lube the contact points?
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  #10  
Old 06-27-2012, 03:47 PM
bmw-mania bmw-mania is offline
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this stuff seems to work..
or anything like it.

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I don't have to read the username on these posts to know who wrote it.

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  #11  
Old 06-27-2012, 07:18 PM
andrew320i andrew320i is offline
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Thanks, I'll post when I've got some more work done on it.
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  #12  
Old 06-28-2012, 07:34 AM
bmw-mania bmw-mania is offline
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Coo'!

Ill standby.
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I don't have to read the username on these posts to know who wrote it.

Bmw-Mania, Ladies and Gentlemen.
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  #13  
Old 07-08-2012, 03:16 PM
andrew320i andrew320i is offline
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I thought it would be good to post an update:

About a week ago, the car wasn't starting, but I really needed the car to work for me, and I happened to be parked on a hill. So, I decided to clutch start it - the first time I had ever clutch started a car. I was able to get it going, and then opened the throttle a fair bit as I've found that I need to get the engine heated up otherwise it fails again. So I got to the bottom of the hill (a very short hill, maybe 15 m vertical distance), then went up a slope. At the top I had to do a sharp turn, so I had to slow down.. but then it stalled. Thankfully I was still on a bit of a slope, so I intentionally rolled backwards (no power -> no power steering and no power on the breaks ) back through the turn, then rolled backwards up a bit of a driveway, pointed the car downhill again, got the speed up and clutch started it again!! So I managed to get up the other side successfully, turned onto another road that sloped downhill, then drove down that. But then it stalled on the way down! So I clutch started it again!!! Poor car!

TL;DR: Clutch started it 3 times as it first didn't start, then stalled twice while moving (once fast, the other slow

After that I did some "spirited driving" to help get up hill and warm the engine up fast. A couple things I noticed from it all:
1. Stalling while moving (as mentioned)
2. The engine struggles to get past ~3.3k RPM when going up a hill. Feels like it hits a wall in terms of acceleration, and the revs are a bit unstable then.
3. Something like misfiring, knocking etc.

From this I've concluded that the key issue isn't an idle issue, and timing seems like a bit of a concern given the harsh sounds coming from the engine.


Now we got the error code reader (had trouble getting the pump test to work.. I'll need to try again some time) and we ran that this morning. One error came up - crankshaft sensor. This was one of the possibilities I was considering, and would explain the instability even while moving, and also the apparent timing issues (correct me if I'm wrong). So now we'll look into the crankshaft sensor.
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  #14  
Old 07-27-2012, 01:30 AM
andrew320i andrew320i is offline
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Update:

My car has now been having trouble starting each time I turn it on when the engine is cold. Also gets close to stalling at low revs when going off from the lights. I've taken it to my local BMW dealership/service centre for a proper diagnostic (the code reader and pump test didn't work on my car - supposedly doesn't work on my car and other 320i's made around my year).

They've concluded that my front crank pulley is distorted and needs replacing. They said that had I not replaced the crankshaft sensor, they probably would have gone with that, so I suppose we were on the right track.

Unfortunately the front crank pulley will cost AUD $1,555 to replace. $390 for the labour and the rest for the part. Which is really is quite bad news considering the car is worth $5,000 at best.

I suppose this leaves me with three options:
1. Bite the bullet and get the dealer to do the service
2. Replace it myself using a part from an old BMW
3. Sell it

I guess there's a fourth option of just ignoring the problem, but that seems very unwise.

In the end, I'm probably thinking to sell it, as I can't afford a car like this right now. It's a shame because it's a seriously nice car to drive, and probably the nicest car I'll drive for a long time. However considering the age of the car, the cost of parts, and the bad fuel economy, I'm thinking that this isn't a financially wise car to own.

Time to start looking at lame Japanese 4 cyl hatchbacks, like a Mitsubishi Mirage...


For those interested in more details of the mechanics:

My car takes roughly 5 seconds of cranking before it gets going. Then often once it's going, it has trouble getting above a specific RPM near 3k. Once it warms up it's fine. The BMW guy explains that the crankshaft sensor isn't reading, so after 5 seconds of cranking the ECU takes the reading from the camshaft sensor. Once it takes that reading, it gets going, but when it's purely relying on that the ECU doesn't let it get above 3k. He said that relying on the camshaft sensor will put an excessive burden on it.

As for the temperature relationship, he said that the crankshaft sensor is used the most when the engine is cold and needs larger injections of fuel. I suppose that explains why it seems that my engine was fuel starved when cranking.
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  #15  
Old 07-27-2012, 10:11 AM
bmw-mania bmw-mania is offline
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uh.. That is recockulously expensive.
You might want to check around.

I thought you already changed the CPS(?)


relevent:
check fuel pump signal by checking main fuel line.
you should have a squirt.. not an ON..
Take off the main fuel supply line direct into gascan and briefly switch to No. II on the ignition, if there is no squirt, try cranking.
record result

Any strange electrical occurrences happen recently?
Are all the injectors normal/good? Youve switched/swapped them around at this point.. yes?

Pull DME look for condensation/waterlines..

if you're 100% sure you have fuel and a spark on all four cylinders you can rule out the DME relay which is fairly common.
The problem occurs when you start the car cold and then stop the engine again very quickly, for example when you move it a few yards nearer to your house as I did. The engine management system senes a cold start and dumps lots of fuel into the engine flooding it. The result is it won't start up again next time!
proceed with caution..
You remove the fuel pump fuse and then turn the engine over with the starter motor as long as you dare battery permitting.
You can hear the engine turning over quickly to start with and then slow down as oil is drawn up re-sealing the piston rings and increasing the compression.
You then pop the fuel pump fuse back in and it should start after a few turns.

And are you sure the COP wires are going to the correct cyl..? A cable didnt get swapped around accidentally?
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  #16  
Old 07-27-2012, 11:50 PM
andrew320i andrew320i is offline
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Sorry I'm not exactly sure about all your post. We did replace the crankshaft position sensor. BMW is confident that it's a crankshaft sensing issue (I'd agree), so they're saying it must be the front crankshaft pulley. As in the metal cog itself.

I tried starting it then turning it off immediately, then starting it again. Works fine.

I'm sure I got sparks and fuel in all four cylinders, at least once it gets going. Runs great once it's warm. When it's having trouble, it really seems like a timing issue. I.e. crankshaft.

So to be specific, what alternative parts do you think it could be?
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  #17  
Old 07-30-2012, 09:09 AM
bmw-mania bmw-mania is offline
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have you tried cleaning the sensor, and "cogs" first?

Maybe these will help.


http://www.m42club.com/forums/showthread.php?t=11106

http://www.ebay.com/itm/E36-93-94-95...c5d65d&vxp=mtr
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I don't have to read the username on these posts to know who wrote it.

Bmw-Mania, Ladies and Gentlemen.

Last edited by bmw-mania; 07-31-2012 at 09:46 AM.
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  #18  
Old 07-30-2012, 04:19 PM
andrew320i andrew320i is offline
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Awesome thanks for the links. Probably a lot wiser getting a second hand part for $100 rather than a new part for $1,000.

I think we'll be doing some diagnostics ourselves this weekend, we'll try hook up an oscilloscope and see if we're getting a signal. While we're doing that we'll probably be checking gap size and cleanliness and such. I'll post afterwards.
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  #19  
Old 07-31-2012, 09:47 AM
bmw-mania bmw-mania is offline
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holla.

Looking to see your update..
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  #20  
Old 11-26-2012, 02:40 PM
andrew320i andrew320i is offline
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Quote:
Originally Posted by bmw-mania View Post
holla.

Looking to see your update..
Sorry for the huge delay - we hadn't had any success until now! It turns out that the dealer service guy got it correct - you can see the wobble in the crankshaft pulley as it spins. So now it's just a question of how to get it done. We'll probably look at a used part, as I'm not putting $1,000 into a part when the car is only worth around four times that. May do the replacement ourselves, may pay a mechanic to do it.

It's good to see that BMW indeed are the experts. Gives me comfort, as if I one day have a much more expensive BMW, I can feel ok about taking it to them and just throwing money at them to get it fixed.
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  #21  
Old 11-29-2012, 10:09 AM
bmw-mania bmw-mania is offline
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Damn..
glad to hear you got it sorted.

If you need anyone to relay shipping a part to you down under.. let me know.
Cheers!
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  #22  
Old 11-29-2012, 08:34 PM
kemalzepppy kemalzepppy is offline
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I had the same problems, lik hard starting long time ago, we found out 2 of the 6 sparks plugs were flooded with water, after i replaced it i ran fine,
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  #23  
Old 01-24-2013, 06:48 PM
andrew320i andrew320i is offline
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I've finally got it fixed!

It indeed was the crankshaft pulley (vibration damper) as BMW diagnosed. I bought the part used for $25, paid $217 for install, and it's now running like a dream! Don't think I'll be selling this car any time soon.

Still have some other work to do, namely the roof lining is drooping, panel on my door is loose, then rear brakes and shocks, but hey - it starts and runs well!
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