Z3 Cold engine RPM

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kingy1
Joined: Tue 08 Sep, 2009 20:44
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  Z3 roadster 1.9
Location: Worksop

Z3 Cold engine RPM

Post by kingy1 » Tue 12 Dec, 2017 03:42

After the wonderful warm months driving the Z generally with the roof down. The cold weather has highlighted its weakness to start in the cold.
The reason for this post is to hopefully diagnose the issue that causing this.
Ive noticed when i do eventually get it started the revs are only about 700rpm even while its cold, im sure this is not normal !
Also ( dont know if this is the issue ) what measures the engine temp when its cold and obviously aids start up, by increasing the revs ?

Ive looked at post after post but cant seem to pinpoint the problem, and not sure going on a reader will solve it because when its eventually warm she runs like a beauty.
Any ideas please ?

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colb
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  Z3 roadster 1.8 TU
Location: Newport South Wales UK

Re: Z3 Cold engine RPM

Post by colb » Tue 12 Dec, 2017 10:10

Some advice on this previous post regarding this issue unfortunately he didn't get back with any results.
viewtopic.php?f=5&t=43652&p=403320&hili ... rt#p403320

Revs from cold start worked out by water temperature sensor and exhaust lambda sensor being compared by the ecu. Maf will have some effect on this as well telling the ecu how much flow there is and temp of the air.
If you have access to a live data type of diagnostics then you would be able to monitor both these sensors from a cold start to see what they are doing.

Check for any split rubbers from the Maf to the intake side of the engine and replace if any found as leaks will cause mixture problems by leaning out the mixture with the unmetered air getting in. Also give the idle control valve a wash out with carb cleaner they can get a little sticky with age.
Colb
1999 BMW 1.8 Z3
1998 Honda Deauville NT650V

kingy1
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  Z3 roadster 1.9
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Re: Z3 Cold engine RPM

Post by kingy1 » Tue 12 Dec, 2017 22:15

Thanks colb, thats great advice and exactly what ive been looking for. Ive already put a new icv valve on, and cleaned the Maf sensor, (but not with the correct maf cleaner though). Water temp seems fine though according to the guage and recently ive had a new thermostat and water pump, so would i be wrong in assuming its prob the sensor because its been very difficult to get through emissions since i purchased the car.
When you start your car from cold what RPM does it run at ? Mine is very low at about 700 !
Thanks

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colb
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  Z3 roadster 1.8 TU
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Re: Z3 Cold engine RPM

Post by colb » Tue 12 Dec, 2017 23:49

From what you have replaced so far it looks like the water temp sensor is functioning ok, cleaning the Maf with the wrong stuff is not recommended it will often destroy it as would touching the sensor itself with anything. A bad Maf may well be the cause of your problems as you have already changed the ICV. The exhaust Lambda sensors could also be suspect. Best check what they are doing by plugging in a live diagnostic system, you should see the sensors voltages rising and falling.
I chased a rough running problem which turned out to be a bad Maf, replaced it with an oem make Bosch or Siemens and that corrected the rough running immediately. You could try a known working used one which would be a cheaper option but don't buy a cheap pattern part they seldom work correctly, been there done that.
Will have a look at what mine revs at on cold start and post back.
If you have had emission issues for the MOT and your sure you have no air leaks in the rubber pipework then it may well be the Maf or the exhaust sensors causing the problem in misreporting what they see to the ecu.
A bad Maf will not always set codes.
Colb
1999 BMW 1.8 Z3
1998 Honda Deauville NT650V

kingy1
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  Z3 roadster 1.9
Location: Worksop

Re: Z3 Cold engine RPM

Post by kingy1 » Wed 13 Dec, 2017 04:35

I think firstly colb im going to look at the maf and rubber pipework. Then the exhaust sensor, and hopefully your advice will get me to the problem, fingers crossed !
Thanks again

therealdb1
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  Z3 roadster 2.0

Re: Z3 Cold engine RPM

Post by therealdb1 » Wed 13 Dec, 2017 11:25

Colb has offered sensible advice but one other simple thing you could try, if you haven't already, is disconnect the electrical connection to the MAF and start up.
This will force the engine management to select a fixed value for intake air rather than taking the real time value from the MAF.
I had an issue with my car a couple of years back where it would fire on every turn of the key but would not continue to run at all. Disconnected the MAF and it started and ran so that I could at least drive the car. A new (OEM) MAF sorted the problem.
I'm not saying your MAF is faulty but for a cost of nothing it is worth a try as MAF's notoriously do not throw fault codes when they go partially wrong!
If doing this makes no difference you have probably ruled out an MAF issue.

kingy1
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  Z3 roadster 1.9
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Re: Z3 Cold engine RPM

Post by kingy1 » Thu 14 Dec, 2017 14:51

After all the great advice, today I did a bit of further investigative work.
Checked all the rubbers and couldn't find any leaks.
When plugged into the code reader the MAF gave a reading of 2.63, I then cleaned the maf, it went up to 3.1, then dropped back down to 2.6.
Any ideas if the running measurement of 2.6 is low ?

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colb
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Re: Z3 Cold engine RPM

Post by colb » Thu 14 Dec, 2017 15:56

Did a cold start on my 1.9 M43 engine today, on starting it revs at 1000rpm idling as it warms up revs decrease to 750-800rpm at idle.

The maf should be reporting the amount of air passing through it, your readings are very low, if your viewing live data what is it showing when you rev it up it should show high figures of gallons per second in teens and twenties.

Really sonds like the Maf is at the root of your problems, get a replacement and put it in without doing anything else and see what a difference it makes.

As mentioned earlier have you ried to disconnect the maf plug and running the car as with it disconnected the ecu will go into default mode, car should start and run better than with a duff maf connected.
Colb
1999 BMW 1.8 Z3
1998 Honda Deauville NT650V

kingy1
Joined: Tue 08 Sep, 2009 20:44
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  Z3 roadster 1.9
Location: Worksop

Re: Z3 Cold engine RPM

Post by kingy1 » Thu 14 Dec, 2017 20:34

Thanks colb,
In respect of the measurement it didn't really move above 3.5.
yep I'm going to do exactly as you recommended, just doing my research for best quality and price maf sensor.
I rang BMW up today £308 + vat 😂😂😂😂
You can buy a car for that !!
Just want a Bosch one for £40 but not looking like it's gonna happen :head:

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colb
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Re: Z3 Cold engine RPM

Post by colb » Thu 14 Dec, 2017 21:16

Might be best to go for a known good used part from one of the guys who breaks Z's on here.
What engine is in yours M43 or M44? Need to get the right one as they are different. M43 has a plug in socket on the Maf M44 has a screw in socket for the connector.
Mine is a 1.9 M43, when I had to replace mine I got a Bosch one from Carparts4less in October 2012, it cost me £131.10.
Current price from them is £155.28 for Bosch, alternative make by Hass is £88.44 not sure of the Hass brand.
https://www.carparts4less.co.uk/engine- ... ent-sensor

Keep us updated on what you end up doing and if you solve the issue with a replacement Maf
Colb
1999 BMW 1.8 Z3
1998 Honda Deauville NT650V

kingy1
Joined: Tue 08 Sep, 2009 20:44
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  Z3 roadster 1.9
Location: Worksop

Re: Z3 Cold engine RPM

Post by kingy1 » Tue 19 Dec, 2017 21:56

Well after all the advice and not listening regarding the aftermarket MAF sensor :head: , i replaced and reset everything.
The next morning i started the car in a very heavy frost and everything was brilliant, the revs were a lot higher, and it seemed very smooth.
The only problem is after two days everything seems to have reverted back to before the new MAF, and its becoming difficult to start again. Its as if something else is overiding the new MAF.
We plugged the car into the code reader today and got these readings;-

SHRTFT1 6.3%
LONGFT1 -21.9 %
MAF 2.36
RPM 802

im not a mechanic but this long term fuel figure dosent look right,
A because it wasnt moving
B It seems high
Any ideas again ?

gookah
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Re: Z3 Cold engine RPM

Post by gookah » Tue 19 Dec, 2017 22:09

did you ever try disconnecting the MAF as posted above? I cannot see anywhere that you mentioned you had done this?
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colb
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Re: Z3 Cold engine RPM

Post by colb » Tue 19 Dec, 2017 22:19

Try it with the Maf disconnected to see if it runs better with the default settings as gookha said.

If you bought a cheap pattern Maf you were warned of the folly in doing that!!

Wonder if anyone is near you with a working oem Maf you could try before shelling out on an oem one just to prove it is bad.

What engine do you have in yours M43 or M44 as the Maf's have different connectors.
Colb
1999 BMW 1.8 Z3
1998 Honda Deauville NT650V

Del
Joined: Sat 19 Nov, 2011 18:35
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  Z3 roadster 1.9

Re: Z3 Cold engine RPM

Post by Del » Tue 19 Dec, 2017 23:05

I notice you must have the 1.9 twin cam M44 engine as your car is circa 1997. These engines are tough reliable and bullet-proof but were renowned for a slightly rough idle – one solution used by the BMW technicians was to manually tweak the ignition timing.

The later M43 MAFs and M44 MAFs are different. The latter are expensive and I would suggest, initially a second-hand spare as you do not know for sure that yours is faulty. The M44 has a lot of vacuum pipework which can cause starting problems – 1) the small pipe at the front of the ICV valve, 2) the MAF bellows and from the MAF bellows 3) a tree of four small pipes running to each injector under the inlet manifold top section. All will be perished on your car – I have replaced mine.

I’m not clear whether you are having starting problems in colder weather? The M44 engine seems to have narrower oil feed ways around the valve lifters and on some cars additional “varnish deposits” seem to restrict initial, start-up oil feed to the lifters resulting in a difficult start and initial “ticking” noise. This can be eradicated (as I did) by use of a 0W-40 oil. There are several old threads on this, I can provide links if you wish.

Unlike most modern cars, the idle speed on the M44 does not seem to be much higher on a cold engine, the ECU seems to maintain a more constant idle speed rather than a noticeably faster one which reduces after a minute of so.

kingy1
Joined: Tue 08 Sep, 2009 20:44
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  Z3 roadster 1.9
Location: Worksop

Re: Z3 Cold engine RPM

Post by kingy1 » Wed 20 Dec, 2017 00:41

Thanks for the quick response.
To reply to your questions, Yes its the M44 1.9 engine, and its the start up when cold problem.
With the previous MAF i did disconnect but it made no difference, but ive not done it with this new MAF sensor ( ill try tomorrow ).
Ive checked all the bellows ( ok ) and also replaced the little pipe on the ICV valve.
The MAF reading ( 2.36 )seems very low, which i interpret as running very lean.
The long term fuel reading of -21.9 % is also out of its tolerances, and not moving up or down.

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colb
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Re: Z3 Cold engine RPM

Post by colb » Wed 20 Dec, 2017 08:52

Your diagnostic results do point towards the Maf being bad, the exhaust lambda sensors are controlling the fuel mixture using the Maf readings it could of course be that the exhaust sensors are past their best as well. Its going to be expensive throwing new sensors at it just to see if they are working or not.
What diagnostic code reader are you using the Maf figure you quote is a little confusing to me.


If you can get a code reader that will show live running data you should be able to watch what the Maf and the lambda sensors are doing to see if they are suspect or not. The Maf on live data will show up as gallons per second and will go up with increased throttle openings, you should see somewhere in the 20's increasing with wider throttle openings.
The lambda sensors in live data should be seen to rise and fall through their voltages as they scan the exhaust, increase in throttle will show up as movement of the voltage which the ecu will determine as a richer mixture and adjust the injection to suit what it sees using the data it holds in its programming.

Wonder if anyone with BMW Inpa diagnostics is near you that could plug in and see what that will tell you, its better than generic code readers for tracing problems.
Colb
1999 BMW 1.8 Z3
1998 Honda Deauville NT650V

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colb
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Re: Z3 Cold engine RPM

Post by colb » Wed 20 Dec, 2017 09:55

Just found this posted on another forum regarding cold start issues, worth a look
https://www.youtube.com/watch?v=3r7jvpf ... e=youtu.be
Colb
1999 BMW 1.8 Z3
1998 Honda Deauville NT650V

kingy1
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  Z3 roadster 1.9
Location: Worksop

Re: Z3 Cold engine RPM

Post by kingy1 » Wed 20 Dec, 2017 21:33

Code reader is an Autel maxidiag elite, not a Chinese copy.
The 02 reading ok and fluctuating as it should on live readings
Stft seams to work ok, disconnect a vac line and it goes positive adding fuel to compensate.
Ltft seems to be stuck at -21%, even when a vac line unplugged.
Just seems weird long term fueling is not reacting even after a fair time of running.

ps i'm not kingy, brother n law lol.
Anyone in Chesterfield /Worksop area that is prepared to let us try a maf that works?

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colb
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Re: Z3 Cold engine RPM

Post by colb » Wed 20 Dec, 2017 22:24

As it seems frozen at that reading might be worth pulling the Disa valve out and checking it is intact as per that video link I posted, could be thats the source of the problem. If a known good Maf fails to solve it then the Disa Valve would be the next place to check.
If that checks out ok then one of the exhaust sensors needs further investigation as its not reacting.

Will your scanner allow you to reset the fuel trims? If it can try that and see what happens.
Colb
1999 BMW 1.8 Z3
1998 Honda Deauville NT650V

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