Author Topic: Power cuts off at high revs (Read 4381 times)

SamuthNBS · « **on:** December 28, 2007, 08:43:38 AM »

Hi guys, first post - I'm new here!
I've read through all of the topics here and can't seem to find anyone with a similar problem so here goes.

When I first start the car, things are fine. Starts nicely, idles nicely, drives nicely. Warm it up nice and slowly and things seem okay. After a while though, usually about 5-10 mins but sometimes less) the engine just loses power. It usually just seems like it's got no power but sometimes it seems to hit a hard rev. limiter at about 4krpm (although as the problem goes on, this number gets lower).
If I stop the car, it idles fine and it drives as normal at low revs (unless I keep driving for a long time in which case it just won't rev above 2krpm. If I put it in neutral and put the accelerator pedal flat to the floor it still won't exceed wherever the 'rev. limiter' has moved to. Very annoying if you suddenly can't rev above 2k!

If I turn the car off then straight back on again, with no delay, it starts fine and the problem disappears for 5 minutes or so.
If I turn it off and wait half an hour, it won't start without ticking over for a good minute or so. (Possibly battery/unrelated?) There is combustion just not enough to start the engine, apparently.

The fuel pump has gotten slightly noisier.

The problem is worse with a small amount of fuel in the tank. MUCH worse.
The problem is MUCH better with a full tank of petrol.

All of these problems started at the same time so in my eyes they are all related although it may be coincidence.

I took it to many mechanics and they've all said it's the air flow meter.

I have:
Replaced the fuel filter and checked the lines are unclogged.
Had the air flow meter checked my the BMW mechanics and they say it seems fine.
Replaced sparks.
Replaced leaky idle hose.
Tried driving with no fuel cap on (in case a vacuum was forming).
Replaced rocker cover gaskets (Oil on plugs 1+2).

Recently replaced water pump too since my old one spat bearings all over the road but that was unrelated. But due to this I've replaced all of the coolant and oil recently and given the whole engine a thorough check and it all seems fine. No funny noises (just the usual chain rattle).

Any thoughts? I might replace the AFM but they're *really* expensive and/or hard to find (in the UK at least) and I don't want to do that unless I *know* it's the problem. Shelling out �250 isn't something I do randomly.
I did get the ECU fault checked and it has no faults listed. No warning lights come on either.

I've checked the connections on the fuel pump and they all seem fine.
My fuel gauge has never worked but the low fuel warning light stopped working at the same time as the problem started. I hoped it meant the cables had been shaken loose but apparently not.

Could it just be the fuel pump getting knackered and starting to slow down so that it can't pressurise the fuel enough?

SamuthNBS · « **Reply #1 on:** December 28, 2007, 08:44:17 AM »

Crap, forgot to mention what car it is. Dumbass.

1990 E30 318iS.

Febi Guibo · « **Reply #2 on:** December 28, 2007, 09:32:14 PM »

see if you can borrow someone's AFM (a known working AFM) and swap it in...

charlie (asubimmer) had a similar problem awhile ago... I think it was the crank reference sensor...

SamuthNBS · « **Reply #3 on:** December 29, 2007, 05:59:43 AM »

Problem is, I don't know anyone with a 0280202203. I don't even know anyone with an M42 engine, there are only around 1500 in the UK, apparently.

The crank position sensor on my car is very dirty, could that be it?

nicknikolovski · « **Reply #4 on:** December 29, 2007, 08:41:35 PM »

Could be injectors, maybe? Not spraying enough fuel to start the car and also the car maybe running to lean during normal operation. The CPS will cause the engine not to start if it is faulty.

Try testing the resistances of the AFM and the CPS.

But the strange thing is that no faults come up.

SamuthNBS · « **Reply #5 on:** January 22, 2008, 02:36:18 AM »

Replaced AFM and no change.
Will clean and test CPS tomorrow morning.

RED IS 91 · « **Reply #6 on:** January 22, 2008, 07:13:32 AM »

When you say it's worse when fuel is low and the pump is starting to make noise makes me think you should do a fuel pressure test at the pump. You should have around 42 PSI .I had similar problems and after replacing every sensor it ended up being one of my coils.

haledj · « **Reply #7 on:** January 22, 2008, 09:20:19 AM »

I would guess coils or plugwires.

I had a similar problem.

HarrisonS · « **Reply #8 on:** January 22, 2008, 11:00:14 AM »

I had this same exact problem. I was only able to rev to about 4.5k and then it would act like a rev limiter was in place. Once i brought the throttle down it would run fine. Strangely, like 2 months later, over the course of a couple weeks, i was able to rev higher and higher, until one day, the problem just went away.

SamuthNBS · « **Reply #9 on:** January 22, 2008, 03:44:19 PM »

Dirty injectors, HarrisonS?

HarrisonS · « **Reply #10 on:** January 23, 2008, 11:43:50 AM »

Possibly. I added a fuel injector cleaner, but it didn't seem to remedy the problem..

SamuthNBS · « **Reply #11 on:** January 27, 2008, 08:52:47 PM »

Same here

I nearly emptied my fuel tank once by mistake (due to a shit fuel sender unit) and after that it's been doing this so I thought filter or injectors but alas it seems to be the pump. Which are fucking hard to find around here, for some reason.
Are they all the same for late type E30 saloons?