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Intermittent engine fault |
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John Orme 
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Joined: 25 Oct 2008 Location: United Kingdom Status: Offline Points: 14 |
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 Topic: Intermittent engine faultPosted: 25 Oct 2008 at 8:41pm |
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I have a 1990 320i se. The problem occurs when the engine is warming up from cold usually after about 2 miles. Today at the traffic lights it started to misfire I just limped into a car park. The car was left on returning it started OK and has run fine all day. This has occured many times in the past 5 years usually once in about every two months. I have had all the injectors cleaned this year, as on occasions I could not start it when hot { It flooded } The airflow meter has been cleaned out many times . I feel its now unreliable any suggestions please. Thanks John
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MICK
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Joined: 29 Mar 2007 Location: United Kingdom Status: Offline Points: 181 |
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Posted: 05 Nov 2008 at 9:38pm |
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Hi John,
I have an e30 1984 1.8i with the m10 engine.It's a different engine to yours but I have similar problems. During warm up, the engine can suddenly loose power in town in top gear.(1100 to 1200 revs.)This has only recently started to happen.A new ecu was fitted about 18 months ago for a different fault and I recently changed the air flow meter as I suspected that this might be the cause of the latest fault.(the car being 24 yrs.old ,Ithought it deserved a new one.)I changed the gaitor between this and the throttle body for good measure. The fault is still occurring.It then occurred to me that the bypass valve may be faulty as it is used during warmup,or the cold start valve may be supplying fuel when it should only supply at initial start up.This might be richening the mixture and choking the engine.When the new bypass valve arrives ,I will let you know if it fixes the problem ,meanwhile,my thoughts are you should hold fire on changing either ecu or air flow meter as mine are nearly new. They are quite expensive.If it's not the bypass valve, I might try the thermo timeswitch which controls the cold start valve. Watch this space.
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MICK
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Joined: 29 Mar 2007 Location: United Kingdom Status: Offline Points: 181 |
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Posted: 08 Nov 2008 at 6:06pm |
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Hi john,
Have changed the slide valve ( bypass valve ) and the hoses that connect to it , including the hose that connect to the cold start valve and the hose that connects to the rubber gaitor between the air flow meter and the throttle body( they are 24 yrs old ) with no success.The car starts fine and runs up to temperature,but if left to cool for 30 mins. it starts but ticks over slowly and irratically until it warms up again. I'm not sure what to do next but am hoping for a flash of inspiration to get me interested again.
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Cabrio
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E30 Register & Competition Secretary Joined: 24 Aug 2006 Location: United Kingdom Status: Offline Points: 6625 |
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Posted: 08 Nov 2008 at 10:21pm |
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There are a number of items that can gives similar symptons therefore depending on your location a garage that carries used speare they can check on the car so not to cost you money...checking ecu, ICV, AFM etc but also DME and wiring....also sounds like its when it goes off choke worth checking that also...sorry but need to look at those first...but dont buy new items unless you are 100% know you need to hence why worth trying used items
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E30 Register joint coordinator - Competition Secretary - Contact name Neil for PM and Email - cabrio_e30@yahoo.co.uk - be aware addicted to E numbers
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John Orme
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Joined: 25 Oct 2008 Location: United Kingdom Status: Offline Points: 14 |
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Posted: 10 Nov 2008 at 11:48am |
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Hi Guys thanks for the replies. Mick I have also changed the Bi- Pass valve and fitted a new rubber intake pipe. I am now going to look at the sensors on the thermostat housing pipe which I suspected at first but they checked out okay at the time. As my fault is intermittent I will proberly replace it anyway. There are two sensors one brown with 1 wire and a blue one with 2 wires. I assume one is for the temperature guage and the other sends information to adjust the mixture during warm up and may even send info when the engine is at running temperature? I dont know which sensor does what. CAN ANYONE help with more info on what these sensors do and which is which. I dont want to take my car to a garage if possible as I now try to keep costs down since retirement. Thank John.
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Cabrio
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E30 Register & Competition Secretary Joined: 24 Aug 2006 Location: United Kingdom Status: Offline Points: 6625 |
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Posted: 10 Nov 2008 at 12:59pm |
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John...if you had a wrong signal from temp sender the vehicle is unlikely to run at all...the can go wrong (but if they do send a signal thats its too hot sometimes) but you need to check the other items first...appreciate you want to save money hence why I suggested visiting someone known who will not rip you off and would swap items eg AFM, DME and ICV without charge and first confirm if those items work correctly...or find someone with the same car yourself who is willing for you to swap and test....thats your cheapest bet
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E30 Register joint coordinator - Competition Secretary - Contact name Neil for PM and Email - cabrio_e30@yahoo.co.uk - be aware addicted to E numbers
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Stonesie
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Joined: 19 Aug 2008 Location: United Kingdom Status: Offline Points: 15 |
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Posted: 10 Nov 2008 at 3:03pm |
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The brown 1 wire sensor is for the gauge and the blue one is for the ECU, another thing to check is the round multi-plug under the inlet manifold. It's a known water trap, especially the lower section so peal the rubber boots back and check for rotten wires.
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MICK
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Joined: 29 Mar 2007 Location: United Kingdom Status: Offline Points: 181 |
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Posted: 10 Nov 2008 at 3:08pm |
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Hi John,
If you start the car and unplug the temperature sensor for the fuel injection,the car will stop running(at least thats what mine does ) The temperature guage sensor is the one with the single connector,(the guage stops working if this is unplugged)the fuel injection sensor has two connectors (on my car).
I take the attitude that I will be keeping the car for a long time and so anything that I change will not be a waste of money because even if it doesn't clear the fault, I now have a working spare on the shelf and if you swop them about regularly ,you know that they are good in an emergency.I know it's a luxury but it's one way of justifying the expence.I don't spend on tarting up my car, but I like it to run reliably.
I have changed the temperature sensor in the past, and recently changed back to the old sensor with no luck. I thiink I'll try messing about with the idle mixture ,as my car seems to go wrong at low speed.( making sure that I record the original setting. )
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MICK
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Joined: 29 Mar 2007 Location: United Kingdom Status: Offline Points: 181 |
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Posted: 15 Nov 2008 at 6:19pm |
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John,I don't know if you have cleared your problem but I have checked the cold start valve on my car and it doesn't leak any fuel into the inlet manifold (or inlet plenum as they call it in the manual).Checking the thermal time switch,I have found that the earth condition on the tag which should only be there when the engine is cold and should disappear completely when warm or hot , still reads 500 ohms resistance when hot. I have two workshop manuals, each describing different test results (the second test states that when reading across the two terminals for continuity,there should be an open circuit ) but my thermal switch fails both electrical tests. so I think it must be faulty.In the meantime I have found that,when the engine is cold, the car starts well without the cold start valve plug connected,so I think I will run the car without it for a while and see what happens. |
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John Orme
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Joined: 25 Oct 2008 Location: United Kingdom Status: Offline Points: 14 |
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Posted: 16 Nov 2008 at 1:26pm |
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Hi Mick No I havent had chance yet, the car is in my garage, I am just fitting a new o/s front wing. The tin worm had got at the other one, but as usual I have had to weld in some new metal to the floor footwell first. I am going to change the temp sensor which I dint know I had, it was with my Morris Minor spares ? yes I also have two Minors that also take up quite a bit of my time. Hope your car is sorted soon I will let you know how mine is as soon as it is back on the road.
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MICK
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Joined: 29 Mar 2007 Location: United Kingdom Status: Offline Points: 181 |
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Posted: 17 Nov 2008 at 12:22pm |
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Hi John,I am having to backtrack on my assumption that the thermal time switch is faulty.Having found a circuit diagram of the thermal time switch ,it appears that neither of the tests described in the manual are valid .It looks like the 500 ohms reading that I am reading is correct. I have had my floorpan welded at that point as well,and the bottom of the wing.The rust had only affected the bottom 4 inches,the rest was still good. I have done a fair amount of work on my brother -in-law's mgb 1980 model (repacking the front seats ,renewing door hinges,new prop. universal joints,front shock absorbers,carb.jets,new brakes.) They seem easier to work on than moder cars. I have tried lately to reproduce the fault on the 318 but it has behaved itself.I can't believe that it has gone away so will keep at it. |
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MICK
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Posted: 20 Nov 2008 at 4:41pm |
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Hi john,
It might be too early to say ,but today the fault came back,so I used an exhaust gas analyser and found that the idle mixture was too rich.Iam not confident that this is the problem ,it seems trivial and unlikely. It read around 2% when according to the manual it should be 0.5-1.5% at 850 plus or minus 50 rpm. I have set it to 0.8%.My workshop manual only ranges models up to 1986 but quotes 320i with L- jetronic 82-86 ,1.5%maximum if that's any help.My theory,for what it is worth,is that when the engine starts to warm up ,the fuel injection reduces the mixture to a point where the idle mixture is too rich due to the setting of the idle control screw.and the engine runs rough. As it comes up to running temperature,the fuel injection further reduces the mixture that it supplies and the car then runs fine.Don't quote me though John,it's only a theory.Only time will tell whether I'm right or not.
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MICK
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Joined: 29 Mar 2007 Location: United Kingdom Status: Offline Points: 181 |
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Posted: 03 Jan 2009 at 6:06pm |
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John,
I have changed the temperature sensor today on the E30 and run it up to normal temperature.It seems fine but I,ve been caught before and it might be too soon to be sure.It occurred to me to check the bottom hose and found that the fault occurred at the same time as the engine thermostat opened and the hose started to get warm. Maybe the sensor didn't like being cooled by the inrush of cold water from the radiator.I had already changed it once, using what I thought was a good spare so was reluctant to buy a new one (£30),but after three attempts to get the right spare due to inaccurate information, have got a Bosch part the same as the original.Will let you know if it sorts the problem. Edited by MICK - 03 Jan 2009 at 6:07pm |
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Mike Fishwick
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Joined: 04 Aug 2006 Location: France Status: Offline Points: 2753 |
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Posted: 04 Jan 2009 at 2:12pm |
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At low speeds (below about 1000 rpm or so) when the signal from the vane-type airflow sensor is insignificant, the L-Jetronic unit controls fuel delivery in proportion to the output of the temperature sensor, so you are on the right track by replacing it. According to Haynes motorcycle electrical manual, at temperatures of 0 to 10 degrees C, expect a resistance of about 10,500 ohms.
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John Orme
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Joined: 25 Oct 2008 Location: United Kingdom Status: Offline Points: 14 |
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Posted: 14 Jan 2009 at 9:36pm |
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Hi Mick I have had the car on the road now for a couple of months all seems to be okay at the moment. I changed the water temp sensor and also cleaned out the airflow meter and internal resistor track inside the air flowmeter. I have checked the resistance of the old sensor at different temperatures and they are the same as quoted in the manual, so time will tell. Hope your car is running okay. John
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MICK
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Joined: 29 Mar 2007 Location: United Kingdom Status: Offline Points: 181 |
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Posted: 15 Jan 2009 at 6:32pm |
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John mine is still faulty. Glad yours is better |
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MICK
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Posted: 18 Jan 2009 at 8:55pm |
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Hello John,
Sorry about the quick reply,Internet trouble. Can you tell me which manual you refer to? I have an Autodata and Haynes manual but I cant find any reference to this information. I have measured the resistance of both the sensor with the blue cap and with the light colour cap ( both old )and they measure approx.3000 ohms at room temp.When put into boiling water they respond similarly.When put into the freezer they behave very differently.The white one drops to 6000 ohms but the blue one remains at approx.3000.The new one is About 3,500 ohms.Both the white and blue sensors have worked o.k. in the past. I am thinking of changing the thermostat next as it might be opening at the wrong temperature but after that I'm stuck again.  There's not much left but the throttle switch and the fuel regulator that I think might affect the fault. The cold start valve and the thermal time switch are only used whilst the starter is operated. Edited by MICK - 18 Jan 2009 at 8:58pm |
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John Orme
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Joined: 25 Oct 2008 Location: United Kingdom Status: Offline Points: 14 |
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Posted: 24 Jan 2009 at 8:16pm |
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Hi Mick I tested my coolant temp sensor( blue one) in a jug of water with a digital multimeter conneted and a digital thermometer. Starting off at 20deg C then finally 90deg C. Haynes manual chapter 6.2 states cold 2100 to 2900 ohms and 270 to 400ohms hot. I also have the Bently service manual in that one it states the same readings Taken at 20degC and 80degC. I also found out that the air flow temp sensor situated in the air flow meter should be within 10% of the water temp sensor at 20degC. Hope this answers your query. John
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Cabrio
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E30 Register & Competition Secretary Joined: 24 Aug 2006 Location: United Kingdom Status: Offline Points: 6625 |
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Posted: 24 Jan 2009 at 9:07pm |
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If you believe it has nothing to do with AFM, ICV or ECU or a wiring issue and think the sensors are an issue why not get hold of some from a working car from a specialist or breaker and then no need for testing as you know it should work...or can check against yours if of interest....I dont understand how this problem has taken so long to sort...where are you located so can suggest a used parts supplier if cost is the issue...let me know Neil
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E30 Register joint coordinator - Competition Secretary - Contact name Neil for PM and Email - cabrio_e30@yahoo.co.uk - be aware addicted to E numbers
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MICK
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Posted: 25 Jan 2009 at 8:30pm |
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Hi John,
Thanks for your prompt reply. I fell into the trap of not looking in the engine management section of the Haynes Manual as my car hasn't got engine management.Its a poor excuse. . The figures seem to be approx. what mine registers. Also,found the info. on the throttle position switch interesting.
Have renewed my engine thermostat as it was the original with 84 (year I assume ) stamped on it ( it has been used before as a test spare and left in situe last time ) it's about time it had a new one. I tried it yesterday and it behaved itself but as you mentioned before,the fault is of an intermittent nature and thus it takes time to be sure that it has been cured.Here's hoping that this is the end of the saga.
Thanks again for your interest and the input from Neil. Edited by MICK - 25 Jan 2009 at 8:56pm |
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Mike Fishwick
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Posted: 31 Jan 2009 at 11:16am |
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The usual cause of misfiring and refusal to start when hot is that of low fuel pressure - often due to a failing fuel pressure regulator, or non-return valve in the fuel pump.
Always check the fuel pressure before spending any money on bits and pieces.
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Cabrio
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E30 Register & Competition Secretary Joined: 24 Aug 2006 Location: United Kingdom Status: Offline Points: 6625 |
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Posted: 31 Jan 2009 at 11:26am |
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or the pump...the list can get very long
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E30 Register joint coordinator - Competition Secretary - Contact name Neil for PM and Email - cabrio_e30@yahoo.co.uk - be aware addicted to E numbers
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Mike Fishwick
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Posted: 31 Jan 2009 at 11:39am |
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Yes - that's why I always suggest checking the fuel pressure first! If the pressure is reducing, clamp the return hose frmo the regulator, and if it holds, the regulator is leaking internally. If not, the pump is leaking back into the tank.
I've recently written an article on L-Jetronic injection for the magazine, and have another, on K-Jetronic, awaiting a trip to the UK for pictures to be taken.
Neither system is exactly white man's magic, being capable of DIY work, but it's essential to be logical, and not replace expensive bits in the hope that they will cure things.
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hennabm
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Posted: 01 Feb 2009 at 2:32pm |
I have just read the article and looked at the pictures - and wondered why the pictures were not of an L Jetronic system
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82 323i Henna
90 320iSE - died Apr 21 10 116d Sport 12 1.4 Punto Easy 89 240DL est 11 X3 3.0d SE |
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Cabrio
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Posted: 01 Feb 2009 at 2:43pm |
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Mike W - I did wonder about that - but thought maybe the office made a mistake rather than Mike F
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E30 Register joint coordinator - Competition Secretary - Contact name Neil for PM and Email - cabrio_e30@yahoo.co.uk - be aware addicted to E numbers
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Mike Fishwick
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Posted: 01 Feb 2009 at 5:07pm |
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I have not received my copy of the February magazine yet, but the pictures I sent in were taken on a Z1 - which uses the same airflow sensor and fuel pressure regulator etc. as the L-Jet system on the earlier E30 models.
I'll report back when my copy arrives next week!
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hennabm
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Posted: 02 Feb 2009 at 1:29pm |
A Z1 may run the same as a 325 but they do not run early L Jetronic systems. On all L Jetronic cars I've seen there is not an Idle Control Valve to be seen as shown in the photos.
The pics of the sensors also show the blue and brown multi connectors - again something that came on later cars.
On early L Jetronic there are three sensors on the thermostat housing and all wired with the traditional female push fit ends.The pressure regulator is the same but again the fuel rail is different on early cars being of solid construction rather than a pressed metal construction found on later cars.
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82 323i Henna
90 320iSE - died Apr 21 10 116d Sport 12 1.4 Punto Easy 89 240DL est 11 X3 3.0d SE |
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Mike Fishwick
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Posted: 02 Feb 2009 at 4:00pm |
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My magazine arrived this morning, including the pictures I sent with the article - taken on a Z1.
I did not claim in the article that the pics were of a particular year or model, the Z1 I used for photographs being an early Motronic engine - Motronic 3.1 I would think.
However, all the main bits and pieces - throttle body, airflow sesnor, pressure regulator etc look the same, and they were clean, which is more than I would say for any of the E30 engine bays I looked at when I needed the pictures! Hence the use of a Z1.
As BMW would put it, the pictures are for 'product appreciation purposes' only! While I referred to the E30 at the beginning of the article, I was not trying to write a definitive E30 workshop manual, as the article was not intended to only cover the E30.
What I did hope was that it would help people to understand how their L-Jet system works, and what is likely to go wrong with it. If even one member gains something from it, then it was worthwhile.
I have seen an L-Jet engine on a 5 Series with an idle valve in this position, where at least it can be photographed clearly - again, the article was about L-Jet, not the E30.
The type of sensor plugs vary with model and year - for example, the brown and blue rectangular connectors were used from about 1983 on BMW's K-Series motorcycles, and on some later cars.
While the push-on connectors can be seen on L-Jet engines, they are usually reserved for non-injection associated applications. In the same way, the fuel rail can vary from model to model
Hope no-one is offended when my K-Jetronic article is published, for most of the pictures will probably show the main components fitted to a Golf GTI engine - on an E21 for example, it is impossible to see most of them, let alone get decent pictures of them. Edited by Mike Fishwick - 02 Feb 2009 at 4:13pm |
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Cabrio
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Posted: 02 Feb 2009 at 6:34pm |
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Mike - thanks for writing the article as it was good - but if you need pics in future just ask away - know Mike W would have taken pics of his for you also
Sure it was found useful for some people if they understood as there was some good detail
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E30 Register joint coordinator - Competition Secretary - Contact name Neil for PM and Email - cabrio_e30@yahoo.co.uk - be aware addicted to E numbers
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hennabm
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Posted: 06 Feb 2009 at 4:38pm |
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Mike
A tip then for the E21 article.
Pop a post on the E21 part of the forum asking for photos of various bits and see if you get a response. Nothing to lose.
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82 323i Henna
90 320iSE - died Apr 21 10 116d Sport 12 1.4 Punto Easy 89 240DL est 11 X3 3.0d SE |
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Mike Fishwick wrote: