E21 316 (82) running problem woes!

[Steely]

Hi, my 316 with the Bosch electric distributor, coil and ignition module is playing up!
It starts ok, idles ok, runs ok until warm, then it starts to miss, it feels like an electrical problem.
Eventually after a short while, any revs will result in the engine dying.. I have to floor it to stop it from stalling.
Then when idle, I can rev to around 2000-2500 rpm and hold it there, no probs, a bit more gas and it starts to die, unless I floor it. Whilst it's like this, driving is like an on/off switch, bucking down the road!
No other symptoms, everything electrical appears to work.

On the odd occasion I can switch it off/on a few times and it will sort itself out, but usually I need to leave it for a while.
In my possession I had a replacement Bosch ignition module, distributor and coil, they have all been replaced already.

Any ideas?

I have not replaced the ht leads, dizzy cap or plugs yet, but they were all replaced within 2000 miles, and a while before this issue started, all look ok.

It's been like this for about 2 weeks and I really need to sort it out now, it's my daily

Thanks.

[E21-driver]

Hi, has it the original 2B4 carb ? Check the pulldown function. The choke flap should open when engine is warmed up. If not, check the pulldown diaphragm, it may be leak. Then check the electrical starter. It should help to open the choke flap. If faulty, then change it. It gets 12V from the two-pole water sensor in front of the head. Check also this function. If these items are not working properly, the carb will not get enough air and it runs too rich, this may make it die when warmed up.
Always change the ignition trigger against a new one, used ones maybe crap. They are really not expensive.
And check also the replacement coil, it MUST be one for transistor ignition, not for point ignition.
Greets
M.

[Steely]

Hi, I should have said, it has a weber 32/36 with manual choke, everything seems fine there, no leaks that I can determine.
I am using the correct Bosch coil and a new ignition trigger module, I will check a few more things, thanks.

[Jeroen]

My money would be on ignition parts but you swapped those all out already, and with correct P/N's I guess. Did the issue start all of a sudden? No work was done or parts replaced? Ignition advance working correctly?

[Steely]

I have replaced everything ignition with the correct parts, including plugs, leads and distributor cap now too, it still has a problem but it's not as bad! Idles fine, runs ok for a short while, then starts to hesitate under acceleration, seems ok at about 2k rpm and it doesn't cut out now. I wonder if it could be a fueling problem, I haven't replaced the mechanical pump yet, having difficulty finding the right pump with the lever, ordered one but its type with a pin and spring, the one on the car is sealed and I think from a 5 series.
Advance seems to work. It did just start all of a sudden.
I'm running out of ideas, anyone?

My money would be on ignition parts but you swapped those all out already, and with correct P/N's I guess. Did the issue start all of a sudden? No work was done or parts replaced? Ignition advance working correctly?

[Jeroen]

If its rather predictable when and how it will hamper I don't expect a fuel pump that's on its way out, then behaviour should be more unpredictable or getting worse. Issues are at a certain point during warm up or under specific loads/situations?

[Steely]

Hi, well heat must be a factor, it is ok until it warms up, for how long is not so predictable, and the symptoms are not as bad after above mentioned work. Also now I can't replicate any symptoms at idle which is making it hard to diagnose.
I'm considering taking to a rolling road for a diagnosis, but that is going to cost!
Any suggestions appreciated.

[Steely]

It turns out heat isn't a factor after all, went for a little run earlier and it was playing up from the off, it was ok at idle before I set off, but as soon as I hit the road it was missing, give it a bit of gas over 2k rpm and it loses power momentarily before taking off, foot to the floor and it's ok! Where else to check?

[E21-driver]

When engine warms up, does the choke flap open?
If not, check the pull down diaphragm. The Weber should also have one.
Then, check the acceleration diaphragm. Both should be in excellent condition.
M.

[Steely]

I checked and double checked everything, re-inserted the distributor, checked advance is working, re-set timing etc. actually followed the book
So engine at normal temp after running for a while on the drive, I went for a test run, I went some 20 miles without a problem.
Came back, let it cool down for an hour or so, went for another run, this time I got approx 6 miles down the road and it started to play up again, missing, losing power, getting worse until it stalled, still moving I switch it off/on still missing, switch off/on again, backfire and its running ok again! made the same journey back home no problems, it might be my imagination, but it seemed a bit down on power on the way home.
I just don't know where to go next with this! Any more ideas please?

[Jeroen]

I think our carb expert Peter is back on line within a few days, hope he can be of help!

[Peter V.]

If I read it right you have the weber with manual choke so that is a big worry less. If you have the chokeflaps open then they stay open.

What the biggest issue is is that you can run it now sometimes good and sometimes bad. That makes trouble search difficult.

Higher revs then 2000 makes trouble and less and idle are OK.

You say that the ignition is OK. Did you check the vacuumadvance and the centrifugal advance? Can you check the colour of your sparkplugs?

[Steely]

Hi Peter, I decided to remove all ignition components and put it all back together again, plugs were clean and the vacuum advance seems ok, I put it back together and set the timing again, slight advance on the stock settings according to the worshop manual, 20 miles and all was fine (it needs a bit of tweaking but runs ok) then it started missing again to the point that within about a minuet it stalled, switched engine off/on twice and it was running fine again!
I have since adjusted the mixture slightly and changed the fuel filter, now I don't have a smooth idle, and it feels down on power, but I have covered 50 miles or so without the main issue, but I get a strong smell of fuel in the cabin at times.
I am considering taking it to my local rolling road to set the timing and mixture precisely, but I don't know about the fuel smell. Any ideas welcome.

[Peter V.]

The fuelsmell could be that you have set your mixture to rich or that you are flooding the carb. A leak is possible also offcourse.

What the most strange part is that sometimes it goes good and then it stalls again. At the moment that it stalls you must remove a spark plug and see how it looks. If it is very wet and black you have a rich mixture.

[Steely]

I don't think its the mixture, I have slowly adjusted it, it might be a little bit rich, but not much now, I am looking at tank breather for that smell now.
Today (after about 60miles without an issue this week) I had a problem again, this time I had to pull out quickly from a difficult junction, so gave it some revs and it immediately started to play up, spluttering and hesitating, it was fine to that point! it was near my work place, and made it without cutting out, its been sitting outside all day now, I will see how it goes on my journey home in a short while.
I should say that in those 60 or so miles I probably never got over about 50-55mph, so low revs.

Edit: on leaving work it was playing up straight away from cold, hesitating and spluttering all the way home, same old problem. Pulling away from standstill, over 2000rpm it starts to die unless I floor it, it's ok when foots planted to the floor!
so got home and left it running, could replicate it at idle, holds 2000rpm no probs, any more gas and it starts to die, pulled the filter off, gave it some gas and sprayed with carb cleaner, did it a few times and it started running ok again!
Crap in the carb somewhere maybe? I took the jets out and sprayed them through, no evidence of crap there!