power falling off in my 96 BMW

RodneyWright · **Posted:** Mon Jun 27, 2011 9:12 am

So what the heck is wrong w/ my car? The car is dying on course. Here’s what’s been done and the symptoms of the car.

Base car information….

> 96 BMW 328
> 197k miles
> recently replaced the spark plugs and fuel filter
> original injectors
> K&N filter recently cleaned.
> vanios repaired at 190k
> original catalytic converter
> big bore M3 exhaust

Symptoms of the car.
> Car runs fine w/ normal driving and during the first few runs of an autox
> in normal street driving, car will always accelerate when you hit the gas pedal
> As the car starts to heat soak from hard driving, power simply falls off. You can mat the go pedal to the floor and nothing, just keeps station speed and will not accelerate. When it does start to accelerate, is does so VERY gradually even w/ the gas pedal planted to the floor.
> There are no codes being thrown and there is no stutter or skip, just no power, like it’s fuel starved.

I can really use some advice here and quickly as the next event is right around the corner and I’d like to give Lee a run for his money.

I thinking about it and this car has the original catalytic converter, I'm willing to put my money here as the car is being choked off by the cat heating up from hard driving.

Thoughts?

MarcusMcRae · **Posted:** Mon Jun 27, 2011 9:43 am

Sounds like it would be something effected by heat. O2 sensor?

steve remchak · **Posted:** Mon Jun 27, 2011 10:08 am

vacuum leak? i'd swear i gained 10hp after replacing all of the air lines.

RodneyWright · **Posted:** Mon Jun 27, 2011 11:04 am

Just spoke to Dave Davis and I related everything I had mentioned here. His thoughts are leaning towards the fuel pump. As he explained it, there are 2 pumps in the bimmer, one is the primary pump to the injectors and the other is simply a transfer pump to move fuel from the drivers side of the tank saddle to the passenger side where the primary pump is. He had several thoughts on this in regard to this lean condition.

First was the transfer pump may have a leak in the line. If the primary pump is trying to keep pressure for the injectors and there is a crack in the transfer tube, it can't keep the pressure up.

Second, there may be a break in the primary line or the pump itself is simply getting weak and causing cavitation of the fuel, turning the gas into foam and sending the foam to the injectors causing the lean condition.

He also suggested that that a catalytic converter is either plugged or it isn't. They don't cycle in and out causing this condition.

I'm going to pull the transfer pump and check it for cracks in the line and go from there.

steve remchak · **Posted:** Mon Jun 27, 2011 11:16 am

Rodney if you are going to go to the trouble of F'n around with the pumps just spend the bucks and get the dual pick-up / pump set-up. the track guy that buys that car from you someday will appreciate your efforts. :twisted:

http://store.bimmerworld.com/e36-fuel-s ... s-p39.aspx

Chuck Branscomb · **Posted:** Mon Jun 27, 2011 12:56 pm

Rodney,

This on-line BMW TIS is very useful. I'm not sure how long it will remain live, but it can be nice to refer to for stuff like you're attempting.

http://tis.spaghetticoder.org/

BretLuter · **Posted:** Mon Jun 27, 2011 8:26 pm

Rodney,

I've got a couple of OBDII M3 parts cars if you want to swap out pumps to see if that makes a difference.

Bret.

RodneyWright · **Posted:** Mon Jun 27, 2011 8:35 pm

BretLuter wrote:

Rodney,

I've got a couple of OBDII M3 parts cars if you want to swap out pumps to see if that makes a difference.

Bret.

yes please..... any idea how many miles on the cars? Would the fuel pumps hook and wire up the same? What's you asking price for these? Might as well get both the transfer pump and primary pump if they will fit my 328

Sean O'Connell · **Posted:** Mon Jun 27, 2011 9:58 pm

Any idea what the fuel trims look like?

BretLuter · **Posted:** Mon Jun 27, 2011 10:17 pm

RodneyWright wrote:

BretLuter wrote:

Rodney,

I've got a couple of OBDII M3 parts cars if you want to swap out pumps to see if that makes a difference.

Bret.

yes please..... any idea how many miles on the cars? Would the fuel pumps hook and wire up the same? What's you asking price for these? Might as well get both the transfer pump and primary pump if they will fit my 328

according to realoem.com they're the same.

I don't know of a transfer pump though, there's a funky little "V" fitting that shows up in the diagram as some sort of transfer thing, but it's not a pump- more like a little venturi setup.

I'll be glad for you to try one out and see if it fixes the problem, no need to buy unless it helps.

I'll make you a fair deal if you end up needing it.

:thumbsup:

RodneyWright · **Posted:** Tue Jun 28, 2011 10:05 am

Sean O'Connell wrote:

Any idea what the fuel trims look like?

Fuel "trims"? Not sure what you're asking....

RodneyWright · **Posted:** Tue Jun 28, 2011 10:06 am

BretLuter wrote:

RodneyWright wrote:

BretLuter wrote:

Rodney,

I've got a couple of OBDII M3 parts cars if you want to swap out pumps to see if that makes a difference.

Bret.

yes please..... any idea how many miles on the cars? Would the fuel pumps hook and wire up the same? What's you asking price for these? Might as well get both the transfer pump and primary pump if they will fit my 328

according to realoem.com they're the same.

I don't know of a transfer pump though, there's a funky little "V" fitting that shows up in the diagram as some sort of transfer thing, but it's not a pump- more like a little venturi setup.

I'll be glad for you to try one out and see if it fixes the problem, no need to buy unless it helps.

I'll make you a fair deal if you end up needing it.

:thumbsup:

can I pick it up this evening?

BretLuter · **Posted:** Tue Jun 28, 2011 10:51 am

RodneyWright wrote:

can I pick it up this evening?

Sure. Give me a call later today, I should be home by 6pm or so.

As to Sean's question about the fuel trim(s), I think he's referring to the readouts from the O2 sensor(s) to the ECU/DME that determine injector cycle, etc. The way I understand it, the readings are available with an OBDII code reader (I have one we can use) and they are expressed in %, showing how much the system is trying to adjust the amount of fuel supplied based on the sensor inputs (O2 sensor mostly, I think).

If the fuel trim is very high or very low, this tells you that the car is trying to overcome a running problem, but it can't do so within programmed limits- so there's something else wrong. Basically the car is trying to increase or decrease the amount of fuel being shot into the engine to get the sensor readings within spec, but it's not working. A very useful tool once you get a basic understanding of what the numbers mean.

RodneyWright · **Posted:** Tue Jun 28, 2011 12:36 pm

BretLuter wrote:

RodneyWright wrote:

can I pick it up this evening?

Sure. Give me a call later today, I should be home by 6pm or so.

As to Sean's question about the fuel trim(s), I think he's referring to the readouts from the O2 sensor(s) to the ECU/DME that determine injector cycle, etc. The way I understand it, the readings are available with an OBDII code reader (I have one we can use) and they are expressed in %, showing how much the system is trying to adjust the amount of fuel supplied based on the sensor inputs (O2 sensor mostly, I think).

If the fuel trim is very high or very low, this tells you that the car is trying to overcome a running problem, but it can't do so within programmed limits- so there's something else wrong. Basically the car is trying to increase or decrease the amount of fuel being shot into the engine to get the sensor readings within spec, but it's not working. A very useful tool once you get a basic understanding of what the numbers mean.

As always, looks like I need further educating....assuming that's possible. PM sent on the parts....

BretLuter · **Posted:** Tue Jun 28, 2011 1:39 pm

RodneyWright wrote:

As always, looks like I need further educating....assuming that's possible. PM sent on the parts....

A pretty good write-up on fuel trim:
http://www.stealth316.com/misc/obdii_fuel_trim.pdf

Most OBDII code readers will have a "freezeframe" function that records several different readings at the time a code was set- I know Fuel trim is one of them (long term and short term)- others are things like coolant temp, RPM, etc etc.

THSCC Forums

power falling off in my 96 BMW

Who is online