Intermittent rough running

[simon-york]

Hi guys
Can I sound you out to see if your thoughts agree with mine? I have a 1989 530i SE here in the UK - this has the M30 engine and is the same as the 535 you know and love just a smaller capacity. The car normally runs very well but increasingly during a run it will suddenly run very roughly (sounds like 4 cylinders), lack all power and feel like it is going to stall. Then it suddenly clears and is fine again for several days at least. Then it will do it again with the same performance. The car has had indifferent servicing over recent years with a cut-corners independent and has yet to have an Inspection I or II with my present guy who is excellent. I am wondering about maybe a blocked fule filter as it comes and goes. Anyone experienced this before and can confirm or suggest an alternative reason for me?
Sincere thanks for any responses and best wishes to all members.
Simon
York
England

[whiskychaser]

Hi guys
Can I sound you out to see if your thoughts agree with mine? I have a 1989 530i SE here in the UK - this has the M30 engine and is the same as the 535 you know and love just a smaller capacity. The car normally runs very well but increasingly during a run it will suddenly run very roughly (sounds like 4 cylinders), lack all power and feel like it is going to stall. Then it suddenly clears and is fine again for several days at least. Then it will do it again with the same performance. The car has had indifferent servicing over recent years with a cut-corners independent and has yet to have an Inspection I or II with my present guy who is excellent. I am wondering about maybe a blocked fule filter as it comes and goes. Anyone experienced this before and can confirm or suggest an alternative reason for me?
Sincere thanks for any responses and best wishes to all members.
Simon
York
England

Hi Simon. Dont think you have had any floods in your area for a while so water in the intake shouldnt be a problem Intermittant faults are always a bugger to sort, especially by remote. I know sfa about the 530 but give us a clue what you done to resolve so far. Are all the plugs the same/clean? Also, does it play up hot or cold? Any fault codes?

[simon-york]

Hi Simon. Dont think you have had any floods in your area for a while so water in the intake shouldnt be a problem Intermittant faults are always a bugger to sort, especially by remote. I know sfa about the 530 but give us a clue what you done to resolve so far. Are all the plugs the same/clean? Also, does it play up hot or cold? Any fault codes?

Luckily I live at the highest point in York so the flooding in the city centre as the river rises never affects me! I have done nothing so far - thought I'd ask you guys first. It tends to happen when the engine is hot rather than cold, although it can happen when it is still warming up. It can also happen when the car has been running perfectly for some miles - and can be there on idle (chug, chug, chug). I haven't tried the plugs yet (alloy heads always worry me!) but it is the poor servicing that made me think of the fuel filter really - when one transmission specialist said that the diff had very little oil in it and hadn't been checked in years alarm bells as to thoroughness began to ring. Where ought I to start?

Many thanks!

[whiskychaser]

Luckily I live at the highest point in York so the flooding in the city centre as the river rises never affects me! I have done nothing so far - thought I'd ask you guys first. It tends to happen when the engine is hot rather than cold, although it can happen when it is still warming up. It can also happen when the car has been running perfectly for some miles - and can be there on idle (chug, chug, chug). I haven't tried the plugs yet (alloy heads always worry me!) but it is the poor servicing that made me think of the fuel filter really - when one transmission specialist said that the diff had very little oil in it and hadn't been checked in years alarm bells as to thoroughness began to ring. Where ought I to start?

Many thanks!

I'd start by having a look at the plugs. If they have a sandy coloured deposit the engine is running OK but sooty or white are too rich/lean. As it runs fine otherwise I doubt its the plugs themselves. Check for any vacuum leaks on the inlet side. If you see any suspect hose connections, spray a bit of wd40 on them and see if the revs pick up. I dont know if your car has a dizzie or not but if so give it and HT leads a good looking at. If its dark you may even see flashes of sparks when the engine is running. My guess is an iffy temp sensor but the 'stomp test' you will read about on here wont work on your car. You need a code reader to see if any fault codes are stored. My son lives in York and is due for a visit so if you cant resolve it soon I will bring my interface and laptop over and you can do your own diagnostic check for nothing.

[simon-york]

I'd start by having a look at the plugs. If they have a sandy coloured deposit the engine is running OK but sooty or white are too rich/lean. As it runs fine otherwise I doubt its the plugs themselves. Check for any vacuum leaks on the inlet side. If you see any suspect hose connections, spray a bit of wd40 on them and see if the revs pick up. I dont know if your car has a dizzie or not but if so give it and HT leads a good looking at. If its dark you may even see flashes of sparks when the engine is running. My guess is an iffy temp sensor but the 'stomp test' you will read about on here wont work on your car. You need a code reader to see if any fault codes are stored. My son lives in York and is due for a visit so if you cant resolve it soon I will bring my interface and laptop over and you can do your own diagnostic check for nothing.

Hello whiskychaser - well many thanks for that - I'll have a look at the plugs if I can get them out and let you know - however as the car runs well most of the time the iffy temp sensor sounds a possibility. If you don't mind bringing your laptop and interface over that would be very welcome and greatly appreciated. Let's keep intouch and I'll let you know if any of your suggestions bear fruit in the meantime.
Many thanks
Simon
01904 345409
07812 080043

[whiskychaser]

Hello whiskychaser - well many thanks for that - I'll have a look at the plugs if I can get them out and let you know - however as the car runs well most of the time the iffy temp sensor sounds a possibility. If you don't mind bringing your laptop and interface over that would be very welcome and greatly appreciated. Let's keep intouch and I'll let you know if any of your suggestions bear fruit in the meantime.
Many thanks
Simon
01904 345409
07812 080043

A duff sensor may not always register a fault in the memory but at least you would know in 5 mins if it has I dont want all sorts of loonies ringing my numbers so as this is an open forum I'm not listing them. You can PM if you need to and there is a wealth of experience on this board you can draw on. To give people a chance to respond its perhaps wise to let them know what you have already eliminated. The offer stands but keep at it and see what you can find out.

[simon-york]

A duff sensor may not always register a fault in the memory but at least you would know in 5 mins if it has I dont want all sorts of loonies ringing my numbers so as this is an open forum I'm not listing them. You can PM if you need to and there is a wealth of experience on this board you can draw on. To give people a chance to respond its perhaps wise to let them know what you have already eliminated. The offer stands but keep at it and see what you can find out.

Thanks once again whiskychaser. Today after a run of 8 miles or so - including afast dash along the A64 - while manoevering the car a friend noticed it smelt very rich. I have noticed this a few times myself too, so maybe even when the car is running fine it is too rich. I have not had a chance today to take any plugs out (doesn't the engine need to be cold?) but I did look for vacuum leaks on the pipes and inlet manifold joints and sprayed WD40 around as you suggested. Nothing showed up and the revs did not alter at all. I'll do my best to look at the plugs next weekend as it is dark by the time I get home from work.
If that rich smell tells you or anyone else something, please do let me know!
Many thanks, Simon

[whiskychaser]

Thanks once again whiskychaser. Today after a run of 8 miles or so - including afast dash along the A64 - while manoevering the car a friend noticed it smelt very rich. I have noticed this a few times myself too, so maybe even when the car is running fine it is too rich. I have not had a chance today to take any plugs out (doesn't the engine need to be cold?) but I did look for vacuum leaks on the pipes and inlet manifold joints and sprayed WD40 around as you suggested. Nothing showed up and the revs did not alter at all. I'll do my best to look at the plugs next weekend as it is dark by the time I get home from work.
If that rich smell tells you or anyone else something, please do let me know!
Many thanks, Simon

I shouldnt be discouraging you from looking at your plugs but clearly they are not your problem: its running rich. Probably starts and runs fine when cold but chugs its head off when warm and exhaust stinks of fuel? You should have 2 temp sensors-one tells the needle what to do and the other tells the OBC how hot the engine is and therefore how much fuel to deliver. Thats the one I'd be checking. My Bentleys isnt here or I would look it up together with how to test it. But I'm sure somebody here will know off the top of their head If thats Ok I'd be thinking O2 sensor but thats where code readers come in

[simon-york]

I shouldnt be discouraging you from looking at your plugs but clearly they are not your problem: its running rich. Probably starts and runs fine when cold but chugs its head off when warm and exhaust stinks of fuel? You should have 2 temp sensors-one tells the needle what to do and the other tells the OBC how hot the engine is and therefore how much fuel to deliver. Thats the one I'd be checking. My Bentleys isnt here or I would look it up together with how to test it. But I'm sure somebody here will know off the top of their head If thats Ok I'd be thinking O2 sensor but thats where code readers come in

Well, when it does chug its head off it is usually warm to hot rather than cold yes. However a lot of the time it runs well on road and gives me about 30mpg when on the motorway at a steady 70 or so. However, if it were possible to be running slightly rich most of the time and really rich when it does start chugging before moving back to slightly rich again as things improve that would describe the situation exactly! Are temp sensors cheap enough to just fit a new one and see whether the problem goes?

[gale]

One of the posters on another 7-series board had that exact problem with his 735iL for more than a year. His mechanic finally diagnosed it as crud in the fuel tank getting sucked up and clogging the pump intake screen while running making it run rougher. The crud would then fall off and settle to the bottom of the tank when parked and would run fine again for a little while and then crap out again a day or 2 later. He had the fuel tank removed and etched and lined, and cleaned the fuel pump, blew out the lines, and replaced the filter, and that finally solved the problem. I'll look for a link and add it to this post. He had replaced/rebuilt just about every air, fuel, ignition and electrical component prior to that.

edit: It was "Windhund" (Neal) who had the problem:

http://www.bimmerboard.com/forums/posts/282417/

I remember many posts of him chasing the problem in the old roadfly days.