intermittent idle and driveability issues suck
Discussion
I'm about ready to drive the 350i off a cliff. I drove from home over to Virginia this past weekend (410 miles). It popped and sputtered and used 6 gal of fuel in 99 miles. The back of the car is covered in black soot. When I stopped to refill, it started up fine and drove 235 miles on less than 8 gal. and then blew a rad hose due to garbage getting stuck in the grill which over heated the car enough to do it. My mistake. But made it to Virginia and replaced the bad hose with a new hose on Monday afternoon.
Going to the office in the morning on Monday (25 miles) the car ran beautiful. Idled correct and ran great. On the way home, about 5 minutes from home it started popping and sputtering and had little to no power with anything more than very light application of the gas. limped home, changed the hose, cleaned a few things up which took about an hour or so and it started up great. Shut it down for the night. Tuesday morning ran supper all the way to work again. On the way home it ran great. At a stop light while idling perfectly is just stopped. Like it was shut off. Restarted with no problem and drove nearly all the way home until it started sputtering again but only during no acceleration. On the gas good, totally off the gas good but would also not idle. And when I held it at about 900 to 1000 rpm it would hunt like crazy, up and down. Got it home, let the car cool off a bit and was going to take it over to the car was to clean it up for the show this weekend. Started it and it was still stumbling and wouldn't run right. Parked it.
This morning, started up perfect and drove fine all the way to work. A little less than perfect at idle but didn't require additional gas to keep it from stalling. Mornings here are in the high 50's to low 60's and afternoons have been in the mid to high 70's but today will be mid 90's. Not looking forward to the drive home.
Since I can't test while on the road, I'll fight it up to Woodwork, about 2.5 hours Friday morning and back to Ohio another 5 hours on Sunday. Not a clue what to do next.
I had the ECU re-soldered last fall and it ran good but now I think its other stuff. Might have to just replace all the stuff that normally go bad plus all the hoses. Since the problems seem to come and go it doesn't sound like basic tune up things though. And with the over fueling only being one issue that also comes and goes. Not sure what to do next.
Any ideas?
Going to the office in the morning on Monday (25 miles) the car ran beautiful. Idled correct and ran great. On the way home, about 5 minutes from home it started popping and sputtering and had little to no power with anything more than very light application of the gas. limped home, changed the hose, cleaned a few things up which took about an hour or so and it started up great. Shut it down for the night. Tuesday morning ran supper all the way to work again. On the way home it ran great. At a stop light while idling perfectly is just stopped. Like it was shut off. Restarted with no problem and drove nearly all the way home until it started sputtering again but only during no acceleration. On the gas good, totally off the gas good but would also not idle. And when I held it at about 900 to 1000 rpm it would hunt like crazy, up and down. Got it home, let the car cool off a bit and was going to take it over to the car was to clean it up for the show this weekend. Started it and it was still stumbling and wouldn't run right. Parked it.
This morning, started up perfect and drove fine all the way to work. A little less than perfect at idle but didn't require additional gas to keep it from stalling. Mornings here are in the high 50's to low 60's and afternoons have been in the mid to high 70's but today will be mid 90's. Not looking forward to the drive home.
Since I can't test while on the road, I'll fight it up to Woodwork, about 2.5 hours Friday morning and back to Ohio another 5 hours on Sunday. Not a clue what to do next.
I had the ECU re-soldered last fall and it ran good but now I think its other stuff. Might have to just replace all the stuff that normally go bad plus all the hoses. Since the problems seem to come and go it doesn't sound like basic tune up things though. And with the over fueling only being one issue that also comes and goes. Not sure what to do next.
Any ideas?
Change the ignition module. It's usually the culprit and if it's not at least you've eliminated it. Make sure you buy a good quality unit and not a rubbish one, otherwise you'll think you've eliminated it and lead to other problems by further unnecessary fettling. Don't forget to use a heat paste when mounting the unit. If it doesn't improve then change the coil to eliminate that. Then, the temprature sensor etc. From then on it could really be anything from timing to fuel pressure, afm etc. Good luck.
Tony. TCB.
Tony. TCB.
Edited by ElvisWedgeman on Thursday 18th May 10:13
A slightly different view, but you could pull the EFI and just stick a good 4 barrel carb on there and a good electronic ignition setup.
If I'm reading your profile correctly you are in the USA. So suspect doing this would be pretty cheap. Or maybe even one of the self programmable TBI EFI kits if you can find something suitable.
Either that or look to something like a Megasquirt setup.
The main problem is, you are chasing fault likely after fault and intermittent ones. You might get lucky and solve it, but in two answers above I think you've been given different things it "could" be. So it might just be worth cutting your loses and going to something to truly solve it.
Plus the original setup wasn't exactly the best thing in the world either. And if you want originality, well just chuck all the old bits in a box in the corner of the garage. At least you could in theory chuck it all back on again.
If I'm reading your profile correctly you are in the USA. So suspect doing this would be pretty cheap. Or maybe even one of the self programmable TBI EFI kits if you can find something suitable.
Either that or look to something like a Megasquirt setup.
The main problem is, you are chasing fault likely after fault and intermittent ones. You might get lucky and solve it, but in two answers above I think you've been given different things it "could" be. So it might just be worth cutting your loses and going to something to truly solve it.
Plus the original setup wasn't exactly the best thing in the world either. And if you want originality, well just chuck all the old bits in a box in the corner of the garage. At least you could in theory chuck it all back on again.
Hi Charlie
Check that the ECU connector is pushed firmly home, They can become loose and give that symptom ...Give it a good firm push...And if this is the problem then use some cable ties to pull the connector on.
Also check the rectangular silver resistor connector plug on the inner wing, this can also give similar symptoms...again a cable tie is your friend indeed..
.
Ziga
Check that the ECU connector is pushed firmly home, They can become loose and give that symptom ...Give it a good firm push...And if this is the problem then use some cable ties to pull the connector on.
Also check the rectangular silver resistor connector plug on the inner wing, this can also give similar symptoms...again a cable tie is your friend indeed..
.Ziga
300bhp/ton said:
A slightly different view, but you could pull the EFI and just stick a good 4 barrel carb on there and a good electronic ignition setup.
If I'm reading your profile correctly you are in the USA. So suspect doing this would be pretty cheap. Or maybe even one of the self programmable TBI EFI kits if you can find something suitable.
Either that or look to something like a Megasquirt setup.
The main problem is, you are chasing fault likely after fault and intermittent ones. You might get lucky and solve it, but in two answers above I think you've been given different things it "could" be. So it might just be worth cutting your loses and going to something to truly solve it.
Plus the original setup wasn't exactly the best thing in the world either. And if you want originality, well just chuck all the old bits in a box in the corner of the garage. At least you could in theory chuck it all back on again.
This is a bit extreme. If I'm reading your profile correctly you are in the USA. So suspect doing this would be pretty cheap. Or maybe even one of the self programmable TBI EFI kits if you can find something suitable.
Either that or look to something like a Megasquirt setup.
The main problem is, you are chasing fault likely after fault and intermittent ones. You might get lucky and solve it, but in two answers above I think you've been given different things it "could" be. So it might just be worth cutting your loses and going to something to truly solve it.
Plus the original setup wasn't exactly the best thing in the world either. And if you want originality, well just chuck all the old bits in a box in the corner of the garage. At least you could in theory chuck it all back on again.
Classic signs of engine temp sensor I reckon, as it's cheaper than the ignition module I would try replacing that first.
When that fails open circuit the engine runs really rich and spits out black soot. Power is down, with intermittent cutting out too.
I had one a long time ago that was good hot, good cold, but failed during warm--up, and took a while to track down.
When that fails open circuit the engine runs really rich and spits out black soot. Power is down, with intermittent cutting out too.
I had one a long time ago that was good hot, good cold, but failed during warm--up, and took a while to track down.
Yes im with adam try temp sensor first , the one that send a resistance value depending on temp to adjust fuel delivery to the ecu.
Should be about 300 ohms at working temp and 2000 cold , if it checks out ok still change it and check wires are not rubbed through some where.
Let us know how you get on
Should be about 300 ohms at working temp and 2000 cold , if it checks out ok still change it and check wires are not rubbed through some where.
Let us know how you get on
Edited by celcius on Wednesday 17th May 20:30
Also check your efi / AFM ground points. If screwed only slightly it will tell the ecu to go open circuit and cause poor running / over fuelling etc. Even cheaper to fix lol as it's just checking wires
Had this on my old 420 and it was a few broken strands on the AFM ground where it bolts to the back of the engine. Literally a few broken strands. Still had 90% but was enough to freak out
Had this on my old 420 and it was a few broken strands on the AFM ground where it bolts to the back of the engine. Literally a few broken strands. Still had 90% but was enough to freak out
The temp sensor is one of a pair on top of the plenum, it's next to and partly obscured by the thermotime switch and they both have similar automotive plugs on them. It's the smaller one and harder to get to (as I recall 13/16" spanner?)
Try and get one with a brass hex "nut" rather than the cheap plastic ones.
Best photo I could find online, it's where the yellow circle is:
Try and get one with a brass hex "nut" rather than the cheap plastic ones.
Best photo I could find online, it's where the yellow circle is:
Edited by adam quantrill on Thursday 18th May 08:21
When I had these symptoms again for the third time recently it seemed to be dodgy connections rather than a dodgy sensor. I had a loose wire remote from the CTS and a little debris in the ecu connection. Rectifying these was easier and cheaper than replacing the sensor. And actually fixed the problem!
This may help...
https://www.pistonheads.com/gassing/topic.asp?t=15...
P:S Please be aware that if you are testing the CTS with a multi-meter then do not hold the probes on there too long as this can burn out the sensor.....
https://www.pistonheads.com/gassing/topic.asp?t=15...
P:S Please be aware that if you are testing the CTS with a multi-meter then do not hold the probes on there too long as this can burn out the sensor.....
Edited by mrzigazaga on Thursday 18th May 09:40
Car ran like crap on the way to work today so I'm going out and changing the CTS at lunch in the parking lot. That way I'll have the drive home to determine if it did anything major or it I move on to the next item on the list.
I appreciate everyone chiming in and all your past experiences.
I appreciate everyone chiming in and all your past experiences.
General Zod said:
This is a bit extreme.
Extreme yes, but ultimately pretty easy.I only suggest it, as a frustrating car is not an enjoyable one. And if it's the fact age is causing problems such as bad connectors, duff wires, dodgy solder joints. Then you might well fix bit, for another to fail a day later. Or end up chasing your own tail fault finding.
Not saying you shouldn't do this, and obviously if it turns out to be something cheap and simple. Then jobs a good'un!
And I suspect in the USA not all that costly to do either.
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