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whitey 
Really Senior Member I
Joined: 15-May-2004
Location: United Kingdom
Status: Offline
Points: 450
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 Topic: Testing Airflow Meters?
Posted: 02-January-2006 at 04:42 |
Hi. Still got this uneven tickover on my '89 325 convertible. I've done all the usual like the dis cap,rotor, plugs and even the pressure regulator. Before I go looking for air leaks and stripping down the inlet side, my next plan was to meter the airflow meter and the ICV. It had a new ICV a couple of years ago but I'll check it out anyway.
Anyone ever checked the airflow meter with a digital multi meter. I have a bentleys manual but any tips would be handy. I've heard that the readings should show a gradual change with few or no steps / jumps.
Basically the idle is uneven and low (although it never stall's) and it's worse in drive. Smells rich too although the c02 readings are spot on. Flew through it's MOT but nearly choked all the mechanics working in there with the fumes.
Cheers in advance and a happy new year to you all.
Trevor
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2000 e39 523i with full factory sport kit.
1989 e30 325i Convertible
1999 Golf GTI 1.8T
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BeemaBoy
Really Senior Member II
Starting a Collection
Joined: 25-October-2004
Location: Johannesburg, South Africa
Status: Offline
Points: 927
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Posted: 04-January-2006 at 07:10 |
Hi
I have had many issues with the AFM on my 87 320i and Iam convinced that without really expensive workshop equipment, you cannot accurately test or set a Bosch AFM. The only way I eventually got around to getting it right was just trial and error. The vane type AFM's are horrible pieces of equipment to do anything to. I did try moving the little wiper onto a new piece of electronic track and all that did was cause massive flat spots all over the rev range. I eventually got a compramise of putting one contact on a new track and the other on the old worn bit. Seems that setting the spring to a little richer setting (eg: a click or two - NO MORE) sorted out most problems.
My advice, if you even suspect that the AFM is at fault open it up and have a look. If the track is worn enought that you can see the little silver wires in the black resistance material, buy another new AFM from BMW or Bosch - not even worth getting a secondhand one in my opinion. But then again, I was burnt twice on this matter!
But anyway to get back to you're point, eventhough the Haynes and Bentley manuals say that sticking a Multi meter across the two most right terminals and moving the flap will tell you a correct reading, in my opinion is flawed! You can only use this method to check if the resistance drops to zero - which is very bad and will cause your car to missfire and judder violently. Even on a brand new AFM from BMW, the readings were jumping all over the place and not increasing smoothly as the Haynes and Bentley manuals state. Have not yet come across an AFM where this is the case!
BeemaBoy
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87 E30 320I
95 E34 525I Auto, Executive Package, Arctic Silver
98 E38 740I Steptronic, Silver
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whitey
Really Senior Member I
Joined: 15-May-2004
Location: United Kingdom
Status: Offline
Points: 450
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Posted: 04-January-2006 at 15:31 |
I figured that may be the case. I'm shooting over to where the cars stored in the winter to meter out a few things tomorrow.
I'll see how I get on. I wouldn't by a second hand AFM purely because there aint that many e30's about now with less miles on it than mine. Common sense tells me the chances are that the AFM would be in a similar state (or at least getting close) as mine. At the same time I don't want to blow £200 for nothing. Plus I'm not convinced it's the cause. The fault is ONLY at tickover. It never hesitates, has no flat spots and pulls like a f****** train when told to.
What do you reckon on my other theory? Temp sensor? If this was faulty and the ecu was thinking the coolant was colder than it was, it would run richer surely?
Regards
trevor
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2000 e39 523i with full factory sport kit.
1989 e30 325i Convertible
1999 Golf GTI 1.8T
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BeemaBoy
Really Senior Member II
Starting a Collection
Joined: 25-October-2004
Location: Johannesburg, South Africa
Status: Offline
Points: 927
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Posted: 05-January-2006 at 04:00 |
Could be the temp sensor. As I see you're car is an 89 model it is probably a motronic system. The blue temp sensor plays a large part in the motronic system, so by all means take it out and check the condition. I did this to mine and it was all covered in rust and other muck! I simply took some fine sandpaper and sanded it back to a shiny brass finish. Did not make much difference - bought a new one from the dealers - still no differrence.
Don't forget aswell, the AFM also has a temp sensor in it which works in conjuction with the signals from the wiper track. Try checking that and see what reading you get. On a normal summer morning the resistance should be about 2200ohms. This little thing plays a big part in running conditions by getting the temp of air to determine it's mass (temp+amount of air = mass).
But I don't know. Reading you're post, I might be going too deep into this. Have you simply tried getting a garage to reset the CO's and idle speed and maybe clean out the idle stabilizer valve? Remember with cars, always start at the cheapest thing first and work you're way up.
My advice though, try to clean out the Idle Control Valve first and then post the results. This can cause a lumpy idle on Motronic cars.
BeemaBoy
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87 E30 320I
95 E34 525I Auto, Executive Package, Arctic Silver
98 E38 740I Steptronic, Silver
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whitey
Really Senior Member I
Joined: 15-May-2004
Location: United Kingdom
Status: Offline
Points: 450
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Posted: 05-January-2006 at 14:48 |
Well I changed the temp sensor and it made a slight difference so i figure for £13 it's well changed anyway. ICV is spotless and checks out okay.
I checked out the AFM as well and strangely, the readings were pretty stable with little fluctuation and no big jumps in the readings. One thing I did do was fire it up with just the airflow meter connected to the inlet bellows with no air box. With the engine running and up to temp, if i operated the airlfow meter flap VERY slightly, i.e. just take it off it's stop, it ran much better. The trouble is I have nothing to compare the readings I got to. So tomorrow I'm off to the breakers to check out some others. I'm taking mine with me so I can check them side by side at the same temperature. I took my AFM indoors today and got very different readings as the temp rose so I figure the temp sensor in it is okay. I'll check out the resistance on that as well.
I reckon you could be right though. It needs to go and be set up properly. However, a 2.7 conversion could be on the cards. I'll be selling the five soon due to a firms car and I'll take some doh out of that and source a 525eta lump for it.
The frustrating thing is it drives fine, it's just the damn tickover.
Thanks again and I'll let you know how I get on.
Trevor
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2000 e39 523i with full factory sport kit.
1989 e30 325i Convertible
1999 Golf GTI 1.8T
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whitey
Really Senior Member I
Joined: 15-May-2004
Location: United Kingdom
Status: Offline
Points: 450
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Posted: 07-January-2006 at 04:41 |
Spent yesterday down the breakers with little luck it appears. I did pick up one AFM for £20 but from a 320, same year but a tourer. Part numbers from the black covers as follows:
My Original 325: 0280202082 followed by 13621286615.9 Made in Germany
The 320: 0280202083 followed by 13621710539.9. Made in France.
They look identical in venturi sizes, the only physical difference being a slight variation in the internal sidewalls. Would it be worth plugging this one in on my car to see what happens or am I wastung my time?
Cheers
Trevor
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2000 e39 523i with full factory sport kit.
1989 e30 325i Convertible
1999 Golf GTI 1.8T
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whitey
Really Senior Member I
Joined: 15-May-2004
Location: United Kingdom
Status: Offline
Points: 450
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Posted: 09-January-2006 at 13:23 |
Today I bit the bullet and decided on a major stripdown on the inlet side. Decided it wasnt worth trying the 320 AFM. Considering approx 2500 miles ago the head was off (before I bought it so not sure who or what! did the work) I was shocked at what I found.
First, I removed the throttle body and underneath there is a short pipe (similar to what a fuel hose would connect to), not connected to anything. It is capped off by a black rubber cap. This is so perished that you can blow through it!
2 of the 12 inlet manifold nuts were missing and none had the wave washers fitted.
The gaskets looked very cheap and nasty although I need to compare them to the gen ones I've ordered today.
The triangular plate where the vacum pipe for the pressure regulator comes from has no gasket fitted at all!
With all of the above I reckon it was breathing air in from everywhere. I've ordered today, the manifold gaskets, The rubber cap, gasket for the pressure regulator vacum take off plate, 12 new nuts with the washers to go with them, a new rocker cover gasket and the o rings for the vertical brether tube (manifold to crankcase).
Hopefully this will sort the idle problem once and for all. I'll report on the outcome soon.
Edited by whitey
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2000 e39 523i with full factory sport kit.
1989 e30 325i Convertible
1999 Golf GTI 1.8T
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Testing Airflow Meters?