Idle Bounce, Drop & Stall

T

T2FFN

Senior member
 East Yorkshire
So you fix one issue and another appears it seems. Having recently replaced the starter, a few days on and another issue has hit the car.

After driving for 30mins in traffic, stopping for 5mins at the (useless) post office that was open but wouldn't accept outgoing mail after 6pm :headbang: , on getting back into the car and starting, all was not right. The idle kept dropping like it would stall then bouncing back up. It didn't stall, and allowed me to drive home, but the first 30% of accelerator travel seemed to have little input, so pulling away from stationary needed much more throttle to get moving and it seemed very jerky like it was losing power and pulsing even at 30mph. So some cautious driving home on slow roads and I took this video on the driveway.

Note, I am not touching any pedals until 42 seconds in. The idle is all controlled by the car. I have done the throttle reset but made no difference, if anything it seemed worse afterwards.

[youtube]p5ae1yvPb68[/youtube]

So, my thoughts are a broken throttle position sensor, idle control valve or coil pack, but there's no warning lights.

I highly doubt its connected but for the past week the GPS isn't working, in so much as it isn't locking more than 1 satellite so doesn't have a scooby doo where I am.

Anyone had the same symptoms?

I'll check the coil packs tomorrow and get a spare from ECP in case I find one is defective.

Thanks
 
The ICV is the quickest to sort out, so I'd whip it out and give it a clean :|

Not sure it's the problem though, when mine was going funny it didn't affect the performance of the car at all.
 
The strange thing is the immediateness of it. Working, then not. Would this lend itself more to a failure than a dirty maf / sensor?
 
Tough one T2ffn sounds like process of elimination, time consuming so better you than stealer. good luck with her. will be good to hear outcome. cheers Baz :?
 
I had the idle fluctuation for a while without any warning lights, a little hesitation on the throttle pulling away.....It was a split hose on the air intake...Your symptoms seem similar and as youve been at the starter, which sits below this pipe perhaps you have a split. The symptoms are the same as others have had on here with this fault. Look at the big air pipe from the airbox to the manifold. there are either 1 or 2 one inch corrugated pipes come off it. Have a good look at these pipes...might short circuit your fault finding.

My light eventually came on when the idle was drifting big time and almost stalling,
 
scotty597 said:
I had the idle fluctuation for a while without any warning lights, a little hesitation on the throttle pulling away.....It was a split hose on the air intake...Your symptoms seem similar and as youve been at the starter, which sits below this pipe perhaps you have a split. The symptoms are the same as others have had on here with this fault. Look at the big air pipe from the airbox to the manifold. there are either 1 or 2 one inch corrugated pipes come off it. Have a good look at these pipes...might short circuit your fault finding.

My light eventually came on when the idle was drifting big time and almost stalling,
Click to expand...

This would also be my suggestion. It amazes me how an old Rover 25 i used to daily in had rubber intake tubes that well outlasted what BMW can provide.
 
Good advice, I should have said that in getting to the ICV you'll need to have all of the hoses off anyway, so you would be checking and replacing any split ones as you go. Usually it's the small house that branches off to the ICV that is the problem, as it is more flexible/thinner and prone to cracking.

I too had a split hose, but the idle fluctuation was completely different to yours.
 
Thanks guys, I'll prob pick up some carb cleaner and a new coil today, then work through the hoses to get to the ICV, two birds one stone.

I've seen a good video on the net regarding checking coils; have the engine running and disconnect a coil connector at a time. If the idle doesn't change that's the problem coil / cylinder. Seems crazy doing it while running but the guy was claiming he was a BMW mechanic so should be ok.

If its a CPS or TPS it'll have to wait until I can get a code scanner delivered to read any codes. I don't fancy buying a load of sensors just for the sake of it.

Cheers all,
 
I wouldn't have thought it'd be a coil. Bad coils usually die fairly slowly and show themselves as a nasty misfire at high engine load (typically low rpm also). The misfires you cannot miss!

I would also add to the ICV and Air Leak list. Give the MAF a clean while there (only spray in the air flow direction). Thankfully they are all very easy to get to on the E85/6
 
Just ordered this with next day delivery : http://www.amazon.co.uk/gp/product/B00KXWXR5K?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00

Should help identify any sensor issues.

I've had coils die in an instant, on an old E46 and on a TT. I think the remap killed the TT coils but the E46 was like flicking a switch, working to not. They did however drive roughly, you could tell they weren't firing on all cylinders. The Z4 was more like driving through treacle, low throttle response and bogging down even at 30mph.

Hopefully a quick diagnostic in daylight tomorrow will sort it.
 
Well, the fault finding is postponed. I plugged in the Diagnostic Code Reader with the ignition at stage 2, dash on engine not running, and it found no errors logged. None!

I had read some cars need to have the engine running to find the fault codes, so tried to start the engine. The dash did all sorts of clicking and flashing of all the lights, but didn't try to start the engine. Everything then dimmed and became unresponsive to the key.

I tried again a min later and same result, leaving just the yellow traction control light showing.

I removed the battery and took it to a local Bush tyres for a battery check. It was showing <12v so they'll leave it on charge all weekend and test it again on Monday. The battery is new Bosch (<1yr old) high power affair from ECP so if its duff it should be under warranty. I struggle to see how the battery would be causing the death throws of the idle and unresponsive throttle, but you never know with all the new electronics in cars now.

So as this was a non-starter I spent a couple hours cleaning up the inside of the gf's Clio I'll be using until I can get the Z4 going. Cleaned all the glass, applied Rain X and new wipers so its not such a death trap :fuelfire:
 
So, got the battery back all charged up and reported to be fine. Refitted and car started up. It seems the freeview TV module may have been left on, draining the battery. Its hooked up to CD changer power supply which is meant to turn off 15mins after stopping the engine but i'm pretty certain it stays live.

So, it started, a little rough, revs bouncing. Go get the diagnostic code reader, get back in the car and it stalled itself. Tried to read any codes and again none logged, no error lights. In my mind this rules out CPS, Coils, vanos solenoid, as all should have thrown an error code if causing the trouble.

Roll on 24th so i can remove and check the air box ducting and any vacuum tubes, then clean the ICV. (DISA has been replaced with an upgraded bolt to prevent failure so rules that out too)

If that doesn't sort it, a low loader can take it to a garage.
 
As stated could well be your MAF. Simplest way to check is to just unplug it and see if it improves the situation. Car should run ok without the MAF, uses a different tune in its absence.
 
Checked the oil tonight and it was very low. Only had an oil service a couple months (few hundred miles) ago so seemed odd to be so low. Topped it up, and tried starting the car. Ran for about 30 seconds before cutting out. Unplugged the MAF, tried again, ran for about 3 seconds before cutting out.

Headlight has also gone out so indicator bulb is lit up now too :headbang:

After being in a Mk2 Clio, the inside of the Zed feels so nice and well built. Just a shame its a bloody paper weight.

Plan of attack for Christmas eve;

Swap front side CPS (£50) easy access, just a single bolt.
Try again.
Remove airbox, tubes, remove DISA, clean ICV. (seeing as the issue continues beyond simple idle revs I don't think this is the issue but while in the post code...)
With all of that removed, swap exhaust side CPS. (£40) Seems this one is slightly buried.
Refit all.
Try again.
 
T2FFN said:
Checked the oil tonight and it was very low. Only had an oil service a couple months (few hundred miles) ago so seemed odd to be so low. Topped it up, and tried starting the car. Ran for about 30 seconds before cutting out. Unplugged the MAF, tried again, ran for about 3 seconds before cutting out.

Headlight has also gone out so indicator bulb is lit up now too :headbang:

After being in a Mk2 Clio, the inside of the Zed feels so nice and well built. Just a shame its a bloody paper weight.

Plan of attack for Christmas eve;

Swap front side CPS (£50) easy access, just a single bolt.
Try again.
Remove airbox, tubes, remove DISA, clean ICV. (seeing as the issue continues beyond simple idle revs I don't think this is the issue but while in the post code...)
With all of that removed, swap exhaust side CPS. (£40) Seems this one is slightly buried.
Refit all.
Try again.
Click to expand...

GOOD LUCK and hope you can fix it :thumbsup:
 
No joy.

Changed front cam sensor. No change.

Removed air box and pipes, no splits.

Removed ICV. It was very sooty and stuck partially open (2mm). Gave it a clean with carb cleaner and it closed up as normal. Refitted along with cleaned MAF and air box bits. No change.

Replaced 4 coils. They only had 4 Bosch ones. Swapped the remaining 2 coils between 6 originals. No change with any of them.

Checked fuel system fuses. All fine.

After starting the car, if it doesnt immediately stall and i can apply some revs it certainly feels rough, like its not running all cylinders all the time, and the car shakes.

Even after all of this, no error codes, no engine lights.

WTF?!
 
Yep, made no appreciable difference. Sometimes it will start then immediately revs drop to a stall. Same happened with maf disconnected.
 
Had home start recovery out this morning. He had to hook the car up to his truck as the battery was dead again (reads 11.5v) so either something is draining it or its bad. With the car hooked up so we could start it, his scanner picked up a misfire on cylinder 6. Advised i change the plugs as the coils are new. Changed all 6 but unable to start as the battery is flat. The odd thing is the way the car behaves with a flat battery. Lots of clicking and odd things like interior light flashing.

Hooked the battery up to my motorbike battery charger to see if i can get some life into it so i can refit and close the drivers window as it auto dropped a few inches.

I'll admit defeat and have it recovered to a garage tomorrow.
 
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