Yet another issue - M60

I only experience this minor issue when the car is cold. I crank and it idles fine but when I put it in gear and start to move it starts stumbling but not to the point where it's gonna stall, just about to 500rpm (idle afaik is 650) it only happens when I first move it, doesn't happen after that until I have another cold start (sorry if it doesn't make that much sense)

I think I have a vacuum leak coming from one of the intake gaskets because they're old and have never been changed. What else could it be?

Originally Posted by Costa

I only experience this minor issue when the car is cold. I crank and it idles fine but when I put it in gear and start to move it starts stumbling but not to the point where it's gonna stall, just about to 500rpm (idle afaik is 650) it only happens when I first move it, doesn't happen after that until I have another cold start (sorry if it doesn't make that much sense)

I think I have a vacuum leak coming from one of the intake gaskets because they're old and have never been changed. What else could it be?

Your gaskets expand when they are heated up, I suspect unmeasured air.

Originally Posted by Costa

I only experience this minor issue when the car is cold. I crank and it idles fine but when I put it in gear and start to move it starts stumbling but not to the point where it's gonna stall, just about to 500rpm (idle afaik is 650) it only happens when I first move it, doesn't happen after that until I have another cold start (sorry if it doesn't make that much sense)

I think I have a vacuum leak coming from one of the intake gaskets because they're old and have never been changed. What else could it be?

Can you replicate this behaviour while at idle, standing over your engine and pressing the throttle cable ?

Then spray carb cleaner at all intake and vacuum ports and see and redo the test to see if the engine behaves better.

Inspect everything in your intake that you can get your hands on without major disassembly, such are the main air hose. Make sure connections are tightened.

I doubt rubber gaskets expand when heated. They are not made of metal.

Your cold start problems could well be a defective crankshaft sensor. The resistance when cold could be falling outside its rated specs. Check the resistances, when cold, and when hot, and anyway, you know the drill sir, if you intend to keep the car and haven't changed it out in the past few years, do so to avoid the inevitable no-start situation.

Rubber expands when it is heated.

Anyways, I can't replicate it any other way. It only happens when there is stress from the driveline on the motor ie. shifting into gear and starting to move. It can't be the CPS because the engine still starts no problem and idles fine. I also think it might be the ICV gasket. It looks like it's not sitting properly in it's space.

Originally Posted by Costa

Rubber expands when it is heated.

Anyways, I can't replicate it any other way. It only happens when there is stress from the driveline on the motor ie. shifting into gear and starting to move. It can't be the CPS because the engine still starts no problem and idles fine. I also think it might be the ICV gasket. It looks like it's not sitting properly in it's space.

Oops. Misread your op.

I've read more than one article that suggests that rubber shrinks when heated.

http://www.ehow.com/how_7902518_shri...ber-seals.html

http://www.ehow.com/about_6544441_te...bber-band.html

http://www.physlink.com/education/askexperts/ae478.cfm

So i would treat that theory with caution.

Clearly too, gaskets not sitting properly, or being too old and brittle, can only lead to trouble eventually. The ICV gasket really screws with idling and the engine when its not fixed properly, so you're probably spot on there.

The difficulties occuring while shifting, and when cold, invoke the possibility of low tranny fluid. Tranny fluid expands when heated and may be too low when cold.

Thirdly, you might want to clean your throttle position sensor and its switch, with contact cleaner, and then apply dielectric grease before fixing it back. That can occasionally cause problems as well.

Are there any relevant error codes ?

Originally Posted by robertobaggio20

I doubt rubber gaskets expand when heated. They are not made of metal.

More basics for you bobby.... http://en.wikipedia.org/wiki/Thermal_expansion

Also consider that the metals that are seperated by the gasket expand, sealing gaps. This really is quite common bobby.

Originally Posted by snowsled7

More basics for you bobby.... http://en.wikipedia.org/wiki/Thermal_expansion

" This article needs attention from an expert in Physics. Please add a reason or a talk parameter to this template to explain the issue with the article. WikiProject Physics or the Physics Portal may be able to help recruit an expert. (August 2009)

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (March 2010) "

The portal I referred to earlier is a physic portal. Here's one from a university's lecture material :

http://www2.le.ac.uk/Members/mr6/lec...s-students.pdf

To quote " The properties of elastomers are remarkable and very different to almost any other solids. For example, ideal rubber does not expand when heated. In fact, loaded rubber will actually contract if heat is applied. "

Applying a layman's "things expand when heated" understanding is quite clearly unsafe when it comes to elastomers, which react differently to changes in entropy from undisordered solids.


rgds,
Roberto

Your point that metal expands when heated is well taken and I'm sure the op took note of it accordingly. I didn't refer to it simply because it had nothing to do with my points about rubber and so was not directly relevant to your response to that.

Aside from that, metal expands when heated, but usually extremely little....unlikely to cover up a hole sizable enough to cause the problems the op has mentioned.

Op, please check everything, tighten everything, inspect everything for cracks, maybe even look in the air box, etc. I think you need to check everything from scratch...wouldn't take you more than 15 minutes. And clean out that tps (throttle position sensor), it could be responsible. I assume you don't have any useful error codes. I don't think its your intake manifold gaskets, they usually stay put and stay that way unless you have done something in that area recently. Unmetered air usually does not lead to near-stall situations, just poor running, fuel economy and poor idling, maybe o2 sensor codes as well.

Double check that you don't have any leaks from your transmission. Double check your cps's resistance when cold. I've cable tied my cps connection to the oil dipstick to make it easy to access for any reason, I suggest you do the same for as long as its not a new unit in there.

Lets wait to hear back from him after this weekend (hopefully).

Originally Posted by robertobaggio20

Aside from that, metal expands when heated, but usually extremely little....unlikely to cover up a hole sizable enough to cause the problems the op has mentioned.

REALLY?

MY posts are being deleted yet advice like this is allowed to stand?

It is COMMON knowledge that expansion and contraction of engine parts causes leaks that cause running issues.

Since my last response was removed, even though it contained further advice for the OP, actual good advice, I will try once again.

Check the coolant temp sensor at the back of the engine, in the crossover tube. It could cause a cold/hot drivability issue, and is reportedly a common failure.

Actually, the post that was removed was not flagged by me. In fact, it was very mild, by your standards.

Bimmerfest does not remove posts for bad advice. Their acceptable use policy makes no reference to this.

I'm driving a 20 year old and I've never heard of a situation that expansion and contraction of engine parts leads to running issues, at least not in a general sense. I've never seen it on these forums either, except for one member's case which my mechanic suggested could be a head gasket issue. He had a cold start problem, which disappeared when the engine warmed up. The head gasket could expand and fix this.

So its certainly not common snowsled7 and therefore it is unlikely to be common knowledge either. That being said, I just came back from an.....intervention, shall we say, where the problem concerned (the story is too long) was traced to a buggy coolant temperature sensor. It caused major engine problems and emptied half the gas tank by the time we figured it out (we had many red herrings to work through). So snowsled may well be right about that.

OP, the way to check it is to disconnect the sensor he refers to and start the car and drive off when its cold and see if the problem recurs. If it doesn't, then its the problem, change that out and you're done. If the problem recurs then its something else, reconnect the sensor and delete the error code that disconnecting it would have generated.

Originally Posted by snowsled7

REALLY?

Since my last response was removed, even though it contained further advice for the OP, actual good advice, I will try once again.

All your actual advice is actually quite good, snowsled7. Really.



rgds,
Roberto

Originally Posted by Costa

I only experience this minor issue when the car is cold. I crank and it idles fine but when I put it in gear and start to move it starts stumbling but not to the point where it's gonna stall, just about to 500rpm (idle afaik is 650) it only happens when I first move it, doesn't happen after that until I have another cold start (sorry if it doesn't make that much sense)

I think I have a vacuum leak coming from one of the intake gaskets because they're old and have never been changed. What else could it be?

I have a similar issue with my 1990 BMW 525i, it idles pretty normal, but when I put it in gear and let off the clutch to move there is excessive engine vibration feeling almost like a misfire but as the car gets to operating temperature it runs perfectly. I suspect an O2 sensor or ECT sensor is to blame. A vacuum leak is also a possibility but I just replaced all my intake gaskets. I'm going to test for my O2 sensor, ECT sensor, and vacuum line. I'll post my findings later today.

-Finished testing-
No vacuum leaks
ECT fine
O2 sensor works

Now I don't know where else to look.

Originally Posted by snowsled7

Check the coolant temp sensor at the back of the engine, in the crossover tube. It could cause a cold/hot drivability issue, and is reportedly a common failure.

I have no record of it ever being replaced. It will probably be swapped out within the next two weeks. I am barely driving my car because I got my exploder running properly again. I am in no rush to fix this but I will update this thread as soon as I find a fix for my issue.

Originally Posted by Microtesties

I have a similar issue with my 1990 BMW 525i, it idles pretty normal, but when I put it in gear and let off the clutch to move there is excessive engine vibration feeling almost like a misfire but as the car gets to operating temperature it runs perfectly. I suspect an O2 sensor or ECT sensor is to blame. A vacuum leak is also a possibility but I just replaced all my intake gaskets. I'm going to test for my O2 sensor, ECT sensor, and vacuum line. I'll post my findings later today.

-Finished testing-
No vacuum leaks
ECT fine
O2 sensor works

Now I don't know where else to look.

Unplug your engine coolant temperature sensor. It should be the blue one next to the fuel pressure regulator. There is a brown one next to it, I believe that connects to the dashboard's temp gauge and that should remain plugged. If you unplug the wrong one, your dashboard temp gauge wont move, that's how you know.

If this solves the problems, then you'll just have to replace the coolant temp sensor.

Oh and of course, please do the stomp test if it works on your car and see if there are any useful error codes there.

OP. we'll hold you to your promise to update your thread. Too many people fail to do that after posting an interesting issue that invites contributions.


rgds,
Roberto

Check voltage of the car running and when It's off. A healthy battery should be somewhere around 12.6 dead I think 12.1. Running should be around 14.4, I havnt checked my car but i would be worried with anything lower than 13.5 volts.


And it is common sense that when heat is applied molecules expand, air metal, and yes rubber, expand with heat.

Originally Posted by Josh429er

Check voltage of the car running and when It's off. A healthy battery should be somewhere around 12.6 dead I think 12.1. Running should be around 14.4, I havnt checked my car but i would be worried with anything lower than 13.5 volts.

How would this be responsible for weird running when cold ?

Originally Posted by Josh429er

And it is common sense that when heat is applied molecules expand, air metal, and yes rubber, expand with heat.

Not according to Dr Werner Kuhn's paper on rubber published 82 years ago.

Originally Posted by robertobaggio20

How would this be responsible for weird running when cold ?

Less power to the coils?

Originally Posted by Costa

Dude, seriously. Rubber expands when it is heated. I can't believe people are actually discussing this OBVIOUS fact.

Costa, love ya man but...

Rubber and water are two common substances that differ from most others in their response to heat. Rubber contracts when heated

HSW "Expansion"

Originally Posted by 95 E34

Costa, love ya man but...

HSW "Expansion"

Oh my, disregard that then. Lol

Originally Posted by Costa

Oh my, disregard that then. Lol

I think this was the padre's missing link....

http://science.howstuffworks.com/dic...nsion-info.htm

Originally Posted by Costa

Less power to the coils?

Well....i've not seen this happen in practice, so I wouldn't go for this when tracing the suspects for your situation here.

I've seen low voltage cause many running issues. When the car is cold its obviously been sitting for awhile without the battery being charged by the alternator. When It's warm It's the exact opposite. The Car os Either charging or has residual voltage in the system.


So that's why it would happen when It's cold. And yes with low voltage everything is starved for power. You can have such a weak spark that It's actually off timing.

And after thinking about yeah rubber shrinks with heat. Like shrink wraping lol. But most gaskets aren't rubber.

My M60 didn't do that but it was moody when cold too. I put royal purple 20w-50 in it, dinan chip, New o2 sensors, and replaced the resonator with an X-pipe and it was much happier in general and especially when cold. I also did a tune up and changed the fuel filter and added a K&N stock replacement filter. It ran like night and day after all these changes. Just make sure the throttle body is clean and your intake snorkel doesn't have a hole in it. Also check your throttle position sensor.

All those changes should fix the issue, each of them decrease the work and load on the engine. But it almost sounds like an intake leak. Smoke tested?

Sent from my PH44100 using Bimmer App

I think I figured out my problem by accident today lol. I was playing around with my ICV and I noticed the little rubber boot going into the intake manifold wasn't seated properly. I took it out and properly put it back together and voila already better response and no hesitation. Hopefully this is the fix. Not too sure because I haven't experienced a cold start yet. That will be left for tomorrow morning.

Originally Posted by Costa

I think I figured out my problem by accident today lol. I was playing around with my ICV and I noticed the little rubber boot going into the intake manifold wasn't seated properly. I took it out and properly put it back together and voila already better response and no hesitation. Hopefully this is the fix. Not too sure because I haven't experienced a cold start yet. That will be left for tomorrow morning.

There are a fair bit of issues that are either caused or could be avoided through better care and observation during work done or eyeball checks. I have certainly created my own share of unforced errors, the latest (probably) being a stripped radiator bleed socket threads. This is inevitable, as we are not trained mechanics and even then we are human. However, Bentley's ghost's dictum, found in the maintenance thread, serves us very well here : always take the time to double check your work.

Glad you found the issue Costa.