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Neil Hawkins

E34 power problems

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Hi.

I have a 1995 E34 520i auto Tourer on 180000 miles and need some help. I am losing engine power, typically when the engine is warm and when trying to go up a steepish hill or pulling away from traffic lights.

The car has just recently had a service so filters have been changed including the fuel filter and have replaced a couple of breather hoses that had splits in them.

When trying to go uphill it seems as if the car does not want to change down to a lower gear and even with foot to the floor there is nothing there, even when selecting 2nd or 3rd gear. From traffic lights there is a delay in pulling away and only then when I put foot to the floor.

If anyone has any advice or ideas they would be appreciated.

Many thanks

Neil

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Hi Neil

Possibly MAF, from what I can tell it's a fairly common issue and can manifest itself in many ways.

Worth checking that your throttle cable hasn't stretched or the adjuster slipped - I had this on my Merc and it puzzled me for ages. Also worth checking your gearbox fluid level but this feels unlikely to be be problem to me.

Good luck.

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Have you checked the vacuum hose to the fuel pressure reg? If that is split it will be giving you full fuel pressure at the injectors all the time. Fine when cold. Not so good when warm - a bit like having the choke out. Conversely, a weak pump wont give you enough fuel. So maybe check your fuel pressure. Does the kickdown switch work on the flat?

PS. If you let your foot off the accelerator, it doesnt feel like somebody put the brakes on does it?

Edited by whiskychaser

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Lost my post in the forum outage last night, it went something like this:

If it is the box, it's pretty easy to narrow it down. Check the stall speed by engaging drive with the handbrake on and your left foot hard on the brakes, open the throttle wide and check engine speed. It should settle between 2200-2400 rpm for yours.

Also, if your engine seems to respond to throttle inputs (revs rise or sound changes, like the load is increasing) it's likely the box rather than the engine.

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Seems my post disappeared too. The FPR vacuum hose is no. 11 here:

http://bmwfans.info/parts/catalog/E34/Sedan/South_Africa/525i-M50/RHD/A/1992/february/browse/fuel_preparation_system/valves_pipes_of_fuel_injection_system/

Good to hear it doesnt feel like someone is putting the brakes on - if it did that is a sign that it is engaging forward as well as reverse gears and is about to self destruct.

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OK did the stall test and could only get 1900 RPM out of it.

The engine is responding to throttle input although the loss of power isn't continuous. For example I drive home from work which involves a short motorway stretch and all is ok. Then when I leave the motorway and stop at the lights when it's time to pull away initially there is no power and I have to floor the accelerator pedal and after a tiny delay it gets going. Then it seems to be ok again until it's time to go up the hill to where I live. Then, 75% of the time I am left trundling up the hill foot down in 2nd doing 15mph. The other 25% it goes up without any problems.

I will check the hose when it finally stops raining.

Thanks for your help so far guys.

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A little excerpt from the Bentley book:

Low stall speed indicates reduced engine performance, or a faulty torque converter or ATF pump if more than 400rpm low. High stall speed indicates low ATF level or slippage in the clutches. So at least eliminates that bit.

What concerns me however is the former - the sporadic nature of your problems seems to indicate box rather than engine, as engine problems will tend to be linked to temperature and running cycles. It might be worth checking the ATF pressure if you can - I'll copy you the pages from the Bentley book. It's probably a good idea to change the ATF and filter as a matter of course as it *might* just fix the problem - if so, happy days and forget about it. It's an easy job to do yourself and not particularly expensive.

Edit: you say in your first post that even when forcing the box down to either 3rd or 2nd you still have no go? Do the gears actually engage? Also, what sort of revs does it sit at when you're full-bore plugging up the hill at 15mph?

Edited by TomGC

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OK thanks for all the info here.

I had 2 journeys up my hill today. The first one I was in 2nd at about 3000rpm doing <15mph. The second time I stayed in D and did 30mph again at 3000rpm. On this second trip at one point it did change down a gear and rpm went to 5000 but then quickly changed back again. It's worth mentioning I do get a short bit of a run up to the hill.

When I'm on the motorway I have a 2 mile stretch of uphill gradient and at 70mph it goes up without any problems and without the need to floor the accelerator

I did a bit of experimenting today too so here is a bit more info for you now. If I pull away "normally" it feels like the engine has to catch up before it gets going. (does that make sense) If I then floor the accelerator it takes a moment and then roars into action, almost as if its in the wrong gear to start with. This happens whether I move from neutral to Drive or if I am already in Drive. Later this evening when the road is quieter I will go out and try a few standing hill starts and see what happens.

Thanks for your time.

Edited by Neil Hawkins

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It must be a dog to drive. The only time mine hits 5k rpm is if I double tap the throttle and it drops two gears instead of one. 3k rpm at 30mph sounds a bit high. Unless its a proper hill, mine changes up at about 2200 rpm. Do you get the impression of a clutch slipping? Cant see where you live but if you are near me I would be happy to run an engine/tranny diagnostic for you

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Thanks whiskeychaser but I am in High Wycombe. The crazy thing is when I drive to work at 4 in the morning it runs fine. It's only when I'm going home the problem seems to start. I did check the hose you mentioned but that appears to be OK.

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This is strange, I'm a bit stumped to tell you the truth... In your latest-but-one post it now seems like a lack of engine power as you initially thought, but that doesn't really explain why the problem comes and goes. It could be an intermittent fuel pump I suppose, something like that.

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Shame you dont live closer. But something just struck me. We havent asked about basics - have you checked the ATF level? Sounds like you live on a hill. So when you go to work you are fine. When you come home up the hill the atf may be too low to be sucked up so you need to take a run at it. If not you rev the b....cks off the engine and go nowhere fast. Sound right? If so, there is a particular procedure to follow and yes, the fill hole IS on the bottom of the pan:

http://akpp-city.ru/pdf/5HP18.pdf

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Thanks for all your help guys but I'm going to have to take it to my nearest indie and get them to run a diagnostics on it. Took it out this morning and it didn't want to go anywhere very fast even down the hill. I fear an expensive bill coming up!

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Garage is going to change the oil and filter in the gearbox once they discover which gearbox it is, they cant find any serial numbers on it! I should know by Wednesday next week hopefully.

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Put your VIN in realoem.com or bmwfans and it will tell you which gearbox you have. My money is on the 5HP18 (aka A5S310Z). Plate is on driver's side just above the gearbox sump joint. Of course, you wont see it if the car is on the ground as the exhaust is in the way.

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Quick update for you. Gearbox oil and filter changed and...

No change, it still lacks power both on hills and pulling away. I'm convinced its a split hose somewhere but my indie couldn't find anything.

Back to the drawing board...

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Probably time to make your mind up if its the engine or the gearbox. But whatever hill you go up to go home, you should be able to kick it down and make decent progress. If the engine is revving and you are going nowhere, look to the box. But IMHO you are not getting enough pull out of the motor. I'd be looking at fault codes, fuel pressure, intake vacuum and compressions for starters though I actually suspect your O2 sensor is stuffed as you seem to get the problem when its warm.

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Hello I hope to find someone who will still reply to this post. I have exactly the same issue as Neil. My ride is a 520i Touring 1995 automatic transmission with 340000 km. The issue started suddenly one day. I felt low power all of a sudden. Replaced spark plugs and valve cover gasket and there was huge improvement but still occasionally not able to make a fast push start for some seconds then goes ok. It always struggles to go uphill on very stiff angles such as garages ramps unless i kick down making a huge roar.

I first though was the tranny that is old and needs a rebuilt soon... but then the huge improvement by replacing the spark plugs made me think otherwise.  The tranny shifts butter smooth and feels ok. I checked transmission oil and filter 20000 miles ago and everything was in order. I think the culprit could be some intermittent failure of the ignition coils. I've made the basic test disconnecting them one by one when the engine was on and they all were working fine. What about you Neils? (If you are still reading ;) could be just a fuel filter? Or some weird valve not working?

 

Thanks everyone in advance for your kind reply.

David

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I forgot to mention... Sometimes when there is loss of power i hear a shutter sound very similar to the recycling air shutter (if you know what i mean) when i press down the accelerator. Could it be linked? Thanks again!

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I would first check the intake gaiter hose to the air flow meter  It might be worth checking the rubber gaiter off the car for splits etc.

  When the air flow meter is failing the signs can be low down power loss/stumbling at low revs . You will not tell by just unplugging the wiring loom

unless the air meter has totally failed. Because the car's ECU will run the engine on safe/get me home mode.

  If the car would not start and you unpluged the MAF and the engine fires up ... It's the MAF sensor.    

  

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