Intermittent Running...
Discussion
Odd problem - Sometimes she runs fine, othertimes she won't idle, just dies. In this state when driving I think its massively overfuelling. The exhaust is BLACK, and there is plenty of smoke. When you accelerate there's a hesitation (like its missing) up to about 4000rpm then it picks up like normal. Then just like that it retuns to normal driving. I can tell you, it makes for intersting braking techniques when you can't take your foot of the accelerator!
It doesn't seem to make a difference whether hot or cold, absoulutely random. So far I have checked all hoses/ joints etc for air leaks, tried disconnecting cold start inj, and that made no difference. Having read some other posts I wondered what the likely hood of it being ECU solder joints was. When it happened earlier I think it was just after a speed hump, and the ECU fell to the floor?!
If anybody can recommend any more tests it would be greatly appreciated.
Thanks
It doesn't seem to make a difference whether hot or cold, absoulutely random. So far I have checked all hoses/ joints etc for air leaks, tried disconnecting cold start inj, and that made no difference. Having read some other posts I wondered what the likely hood of it being ECU solder joints was. When it happened earlier I think it was just after a speed hump, and the ECU fell to the floor?!
If anybody can recommend any more tests it would be greatly appreciated.
Thanks
Idling problems could indicate a throttle pot problem.
Coolant temperature sensor gave me problems with running, but wouldn't run in the end at all. And when I had fine idling (and nothing else - engine would die), there was and ECU problem. Soldering solved the ECU and it is back in with no problems.
Ignition seems to be able to create problems like this as well (amplifier on its way out, coil not ok anymore, plugs not ok, etc....)
Good luck with the search. It can be fixed!
Rob
Coolant temperature sensor gave me problems with running, but wouldn't run in the end at all. And when I had fine idling (and nothing else - engine would die), there was and ECU problem. Soldering solved the ECU and it is back in with no problems.
Ignition seems to be able to create problems like this as well (amplifier on its way out, coil not ok anymore, plugs not ok, etc....)
Good luck with the search. It can be fixed!
Rob
ISTR when my ECU started playing up, massive overfuelling was the exact symptom. It used almost a tank of juice in 95 miles and actually ran better with half the injectors unplugged!
Sudden impact to the ECU could certainly account for a solder joint problem. You could try getting someone to clout the ECU with a screwdriver handle with the engine running and see if it sporadically improves. It might not, but then again it might...
Sudden impact to the ECU could certainly account for a solder joint problem. You could try getting someone to clout the ECU with a screwdriver handle with the engine running and see if it sporadically improves. It might not, but then again it might...
Sounds exactly like my 350i when the ECU was playing up. Bad solder joint on one of the power transistors wiped out one of the banks, intermittently....
Could actually see the faulty joint when I opened the ECU up, quick warm up with the soldering iron and it was soon back to normal though!
Stu
Could actually see the faulty joint when I opened the ECU up, quick warm up with the soldering iron and it was soon back to normal though!
Stu
phart said:
...When it happened earlier I think it was just after a speed hump, and the ECU fell to the floor?!...
Try un/re-plugging the ECU main plug. When properly mated it makes a satisfyingly positive click into position. If not that then most probably a dry joint on the PCB.
HTH
Leo
After taking the unstructured approach to fault finding, and not getting anywhere 
, I sat down and went through the fuel injection guide on the wedge pages in a systematic fashion. Thankyou to the clever person who wrote a simple manual that I managed to get my head around!
Firstly I found that the fuel pressure regulator had stuck closed, a bit of fiddling and prodding and thats now ok, but just to be safe i've ordered a rising rate regulator.
All of the ecu sensors have tested good, with the exception of the EAV, which I haven't yet got to, and the ecu internals look like it was made yesterday. I now believe the EAV is the problem. By accident I have found that I can run the engine at idle with the air hose disconnected from the AFM, but it dies as soon as you move the flap, of open the throttle butterfly. This got my a bit confused, so I put the hose back and disconnected the EAV hose from the plenum, and once again she started, but this time being able to accellerate, all be it a bit lumpy. Am I correct in thinking that from a completely cold start the EAV should be open, because it is'nt on mine, and as soon as that hose goes back, the engine dies. I haven't yet left the engine to warm up and see what happens then?
Does this sound about right before I go butchering the EAV and having to buy a new one anyway?
, I sat down and went through the fuel injection guide on the wedge pages in a systematic fashion. Thankyou to the clever person who wrote a simple manual that I managed to get my head around! Firstly I found that the fuel pressure regulator had stuck closed, a bit of fiddling and prodding and thats now ok, but just to be safe i've ordered a rising rate regulator.
All of the ecu sensors have tested good, with the exception of the EAV, which I haven't yet got to, and the ecu internals look like it was made yesterday. I now believe the EAV is the problem. By accident I have found that I can run the engine at idle with the air hose disconnected from the AFM, but it dies as soon as you move the flap, of open the throttle butterfly. This got my a bit confused, so I put the hose back and disconnected the EAV hose from the plenum, and once again she started, but this time being able to accellerate, all be it a bit lumpy. Am I correct in thinking that from a completely cold start the EAV should be open, because it is'nt on mine, and as soon as that hose goes back, the engine dies. I haven't yet left the engine to warm up and see what happens then?
Does this sound about right before I go butchering the EAV and having to buy a new one anyway?
Yep, EAV valve should be open when the engine is cold, bi-metal strip progressively closes the disc as the engine warms up, try disconnecting the hose from the other side of the EAV when the engine is cold and see how it runs.
You could always try closing the end of the tube a little at a time to simulate the valve closing as the engine warms up....hope this helps
You could always try closing the end of the tube a little at a time to simulate the valve closing as the engine warms up....hope this helps
Edited by chedder on Friday 16th March 18:31
phart said:
Thankyou to the clever person who wrote a simple manual that I managed to get my head around!
I now believe the EAV is the problem.
I now believe the EAV is the problem.
Thankyou!
If rogue air enters the plenum via the extra air valve which is only supposed to supply metered air during warm-up, then this may be faulty or the pipes connecting it may leak air. The valve is an aperture in a rotating disc turned by a bimetal strip which is heated from two sources: - (i) a 12 volt supply to the heating coil under control of the ECU. & (ii) the hot inlet manifold at about 60-70C. Note that one heat source alone provides insufficient rotation to the disc to shut off the extra air, so check the electrical connections to the valve and that the coil resistance is 30-40 ohms. Its awkward, but the valve can be tested off the car in a shallow pan of very hot water whilst applying a 12V battery to the coil and observe that the aperture rotates completely out of sight of the airway, visible through the output pipe connection.
The extra air valve might also stick in the open position which will raise the slow idle speed much too high, but because the "extra air" is all metered by the AFM the system should still run with correct mixture control by the ECU.
Edited by honestjohntoo on Friday 16th March 20:24
Edited by honestjohntoo on Friday 16th March 20:25
Edited by honestjohntoo on Friday 16th March 20:26
honestjohntoo said:
phart said:
Thankyou to the clever person who wrote a simple manual that I managed to get my head around!
I now believe the EAV is the problem.
I now believe the EAV is the problem.
Thankyou!
If rogue air enters the plenum via the extra air valve which is only supposed to supply metered air during warm-up, then this may be faulty or the pipes connecting it may leak air. The valve is an aperture in a rotating disc turned by a bimetal strip which is heated from two sources: - (i) a 12 volt supply to the heating coil under control of the ECU. & (ii) the hot inlet manifold at about 60-70C. Note that one heat source alone provides insufficient rotation to the disc to shut off the extra air, so check the electrical connections to the valve and that the coil resistance is 30-40 ohms. Its awkward, but the valve can be tested off the car in a shallow pan of very hot water whilst applying a 12V battery to the coil and observe that the aperture rotates completely out of sight of the airway, visible through the output pipe connection.
The extra air valve might also stick in the open position which will raise the slow idle speed much too high, but because the "extra air" is all metered by the AFM the system should still run with correct mixture control by the ECU.
Edited by honestjohntoo on Friday 16th March 20:24
Edited by honestjohntoo on Friday 16th March 20:25
Edited by honestjohntoo on Friday 16th March 20:26
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