540i stalling - ideas please

[Etwenty1 45]

Have been doing some of the deferred maintenance on the old 1993 540i i picked up as a non-runner. Had a rough idle, noisy chain and oil leaks.

Replaced rocker cover gaskets, the pcv plate gasket and associated o rings, oil pan gasket, oil pump bolts, chain tensioner, oil fliter, oil, air filter. I now have a car that is running better, quiet and leak free but has a new tendency to stall if you brake hard to a stop. Not sure if its a new problem because i was nursing it along everywhere.

I had it scanned at Shersons (indie BMW workshop) and they said the TPS was faulty. I have replaced this and again its running even better, but still stalling. Have checked for vacuum hose leaks and the workshop gave it a good spray with some solvent but no leaks found.

I picked up a full set of coils from a known good runner so i unplugged each coil while running, each made a very slight difference to the idle especially the plug at the front pass side that nearly stalled it when un plugged. swapped all the coils over and it seems smoother but you guessed it, still stalling.

I have cleaned the AFM and the ICV what was a bit gummed up but now moving freely. The scan test also cleared the AFM. Both crank and cam position sensors are on spec for resistance.

The only other things i can think of are fuel pump and battery. I had to replace the fuel pump and one filter to get the car running, i should replace the other filter too.... The battery was dead flat after sitting for months but came up ok. It goes a bit flat if the car sits for a week requiring a quick jump. Voltage at idle is 14v.

The car accelerates verrrry well and drives good, no cutting out under load etc.

I'm tempted to replace the cam and crank sensors based on the amount of online forum threads pointing at these but hate doing that when no fault is showing. Am thinking ICV but.............any ideas?

[_Matt_ 42]

had exact same problem with the e28, annoying thing was i never figured out what i did to fix it. It kind of stopped eventually after I did all the things you've listed. Only thing I can think of that's not on your list is the throttle valve switch and fuel pressure regulator, I swapped mine out (had a spare engine luckily)

[BM WORLD 1283]

they will run without the cam sensor , but will die if the crank sensor fails.

what rpm does it idle at , and is it smooth or lumpy?

i sell a few crank sensors for these , comon failing part.

when it dies is it instant(crank sensor ,ecu etc ) or spluters and dies (fuel pump )

also check the ecu for corrision inside etc have seen a few fail that way or dry joints etc

[Etwenty1 45]

they will run without the cam sensor , but will die if the crank sensor fails.

what rpm does it idle at , and is it smooth or lumpy?

i sell a few crank sensors for these , comon failing part.

when it dies is it instant(crank sensor ,ecu etc ) or spluters and dies (fuel pump )

also check the ecu for corrision inside etc have seen a few fail that way or dry joints etc

idle is stable between 500-600, idle is smooth with just a hint that one cylinder might be dropping out.... hard to explain. Have checked all pluds and put stethescope on each injector to check.

If i slow down slowly the the idle dips to just under 500 then recovers. If i brake hard it dips under 500 then stops. Like there is too much load... or the ICV is not kicking in.

Will check ECU, cheers Brent.

[Etwenty1 45]

had exact same problem with the e28, annoying thing was i never figured out what i did to fix it. It kind of stopped eventually after I did all the things you've listed. Only thing I can think of that's not on your list is the throttle valve switch and fuel pressure regulator, I swapped mine out (had a spare engine luckily)

Cheers, throttle valve switch would be the TPS that i replaced..... Will think about the FPR, but i can't see how that would be related to RPM, i think it would stall anytime with a dodgy FPR not just on brakes. Might check brake booster line......Thanks for those suggestions.

[BM WORLD 1283]

e34 540i have hydrolic brake booster system so no vac brake booster .

sounds like the icv is not working properly, but may have a vac leak .

also afm can go bad

[_Matt_ 42]

Does the rpm drop badly when you steer the wheel back and forth while stationary? That could indicate a leak somewhere in the hydrolic system. My hydrolic servo unit was leaking quite badly between it and the brake master cylinder. Loosing presure causing a problem Brent?

I remember if I slammed on the brake and held my foot down it would stall but if I slammed on the brakes and released my foot it wouldn't stall so I assume that's strain on the engine...trying to keep the pressure correct in the brake cylinder...and a leak meant it couldn't. I'm just taking a stab in the dark.

Edited October 27, 2013 by _Matt_

[Etwenty1 45]

Does the rpm drop badly when you steer the wheel back and forth while stationary? That could indicate a leak somewhere in the hydrolic system. My hydrolic servo unit was leaking quite badly between it and the brake master cylinder. Loosing presure causing a problem Brent?

I remember if I slammed on the brake and held my foot down it would stall but if I slammed on the brakes and released my foot it wouldn't stall so I assume that's strain on the engine...trying to keep the pressure correct in the brake cylinder...and a leak meant it couldn't. I'm just taking a stab in the dark.

Yeah engaging the power steering does drop the revs, ive tried to check the ps fluid but my cap unscrews to reveal the end of a thread. Where is the ps dipstick typically?

[yng_750 247]

PS dipstick extends out of the cap.

I believe you cant use standard p/s fluid, i got differing opinions when i needed a top up so ended up playing it safe with some fully synthetic stuff for $32 a litre.

[Phil-540i 166]

Awesome. You'll be looking forward to actually getting to drive it for a bit now............

[Etwenty1 45]

Well the old bitch was just tricking, after a longer drive the stall is back.

It seems to be the last downshift of the trans that causes the stall On medium throttle the car shifts normally, on light throttle the up shifts are a bit laboured, like the handbrake is being lightly applied as the shift occurs.

I took it to a trans shop for a round the block diagnosis but the guy said it was ok and the stall was an engine issue.

Suggestions still wanted........

[yng_750 247]

possibly not a good idea but i have seen it work on another breed of car.

tighten the throttle cable up just enough that its slightly holding the throttle open, enough that the engine can idle under 1000, and that the icv should be ignored or irrelevent. if it still stalls then the icv or circuit that controls it will be good. if the stall problem goes away then it would likely be the icv system.

take that advice at your own risk.

other than that could it be fuel pressure? if the vac hose to the regulator is blocked or leaking it could be dumping excessive fuel in when under vacuum.

hold it in 2nd gear and from about 5k let it slow down with engine overrun. if its over fueling on the overrun you will likely hear a good amount of popping and crackling in the exhaust.

last idea. what if it is the crank sensor but a fault elsewhere has already killed the new one like it did the last one? not sure if possible in bmws

Edited November 2, 2013 by jason H

[*Glenn* 854]

Get the fault diagnosed by someone that knows what they are doing and stop doing all this hit & miss fault diagnosis which probly won't get you anyehere. You have probably introduced more faults, these will need to be cleared, then drive the car till the fault occurs again and see what the fault is. The fault registered in the DME could also be the result of something else, so I would suggest getting a person with BMW knowledge to do this.

[Etwenty1 45]

Took it to dealer for trans service and scan. No faults in computer but likely has broken chain guide

good to eliminate other issues i suppose but not a nice looking DIY.....

[Etwenty1 45]

...have finished the teardown and keen for some advice - I found where a chunk of alloy in the pan came from - has broken off the lower timing cover.

The main chain appeared quite loose with the trestle tool fitted and so did the drivers side chain between the cams.

Now working out what to replace, the teeth on the crank sproket are very sharp (worn?) compared to the cam sprockets. The guides are in sound condition with very shallow chain tracks and no chipping or cracks. The OSV seems ok too. Am wondering if these have been replaced once already.

Appears i have a stretched chain worn sprocket but guides are fine...?

I am planning to keep this car so will be doing; new chain, sprockets, guides, waterpump, coolant pipes, intake gaskets, valley pan, o-rings along the way etc.

Struggling to find clear info on the cam timing. To get the cam locks on i had to rotate the cams counterclockwise about 45 degrees.

see before and after;

Drivers side

passenger side

Is that normal? The slotted sprocket holes allow for some adjustment but i would be good to know the factory setting ?

[jeffbebe 1560]

Interested to see how you go with this... I have been considering options to change the lower timing cover gaskets and chain guides and not sure I've enough skill for a DIY (will most likely be calling on Ray for this).

Edited March 11, 2014 by jeffbebe

[Etwenty1 45]

I've been following a DIY on another site but its for the later model M62 ? with the vanos. A few differences...mine has head gaskets that run through the timing covers. Good potential there for trouble.

I have a couple of weeks to work out the cam timing while parts arrive.

[Etwenty1 45]

waiting patently for parts to arrive, especially the new chain so i can see if the old one was stretched.

Decided to full the intake and do the valley pan, intake gaskets and check a bolt on the PCV plate i did last year. Messy job, cable sheath turned to dust and lots of crap in the valley to clean out...

While the intake was off i thought i would pull the dodgy wiper mechanism that is slowly grinding the edge of the bonnet away. Has anyone sourced the brass bushes to do this repair? alternatively anyone have a good arm lying around let me know.

All my knock sensor are badly cracked so adding them to the list.

Edited March 23, 2014 by etwenty1

[Etwenty1 45]

Back together with new crank sprocket, deflection wheel, cam chains, main chain, timed and ready for covers to go back on.

[Etwenty1 45]

had a break from this project but tonight i was ready to refit the intake;

Shortly after this was taken i had broken the vacuum nipple off the pcv plate and realised the knock sensors that i bought are 2 pin and my loom is 3 pin.

There is a blanked of nipple that i can use on the PCV but the knock sensors - is it possible to modify these ?

[Etwenty1 45]

back together and started up on second attempt. Hell noisy while the oil gets back into everything.

Turned it off for a couple of minutes and now can't get it to start again. Suspect stale gas (5 months old)

Can anyone tell me exactly where the fuel pump relay is on these? have jumped all the likely suspects with no joy.

Looking better on my group buy H&R springs, have some Bugatti rims to add.

[BM WORLD 1283]

fuel pump relay lives in the ecu box

rhs(drivers side) engine bay

its the 4 pin relay

[Etwenty1 45]

Thanks Brent found it blue one under top layer of plugs.

Fresh gas and still no go.

I added a drop of oil to each cylinder first time around so might try that again.....

[kiwi328i 118]

Has this been sorted?

I had idle issues also, and looking at your engine all apart was a very recent memory for me. I was lucky I had 2 of everything so I just went through every combo I had. In the end I don't know what fixed it other than, I took the battery off for a bit and it got better instantly then let it run for a bit and it runs well now, but I looked for leaks that didn't exist and whilst I didn't do any resistor testing, I swapped every bloody cam/crank sensor I had, every TPS and ICV I had, and triple cleaned everything. It will come right.

Of the other possibles, it could be anything but under brakes tells me possibly that it cant figure out the load which must be a TPS or ICV issue? All other things being equal. When I was turning the wheels whilst being stationary mine would cough and splutter, so it wasn't figuring in the additional load and it did turn out to be TPS and ICV related.

I dunno, good luck

[Etwenty1 45]

No not sorted. Local dealer confirmed noisy chain. Which has been replaced. Unfortunately after first start I have a cylinder full of valve pieces. Was turning over fine by hand, had checked reference marks, used flywheel land cam locks so pretty baffling and gutting. Am just leaving taupo now after buying another engine off a bloke. Will strip the other one over Xmas and try to work out what went wrong. Anyone got an engine crane for hire?