Fuel pump out?

[87E30is]

I think my fuel pump is out, but I'm not 100% sure.

Here's what happened:

2 days ago I was driving when I noticed my water temp gauge was acting funny. It was steady most of the time, but then would just randomly bounce back and forth. I just let it go hoping it would be better the next day. I'm not sure if this has anything to do with the problem or not.

Yesterday, while in traffic, I downshifted and noticed a significant drop in power, followed by roughness in the engine and jerkiness. It steadily got worse. It was idling pretty rough, and when I got around 2500RPM the engine would jerk around. Above that it was fine until about 3500RPM when it did the same thing. It was pretty violent shaking. It finally quit on me and I coasted into a parking lot and had it towed to my house later that night.

Today, I went to start it and it fired right up. I'm not quite sure what the deal is. I let it get up to temperature, then went around the block, and it started getting really rough again. I just decided to part it.

Does anyone know what's wrong with it? Any help is appreciated. Thanks!

Nick

1987 325is 132k

 

[epj3]

Sounds like a combination of things - if not just a bad ECU.

The engine software has a few different ways to interpret the information it is getting from the various sensors. When the car is cold in the morning, it won't rely on the oxygen sensor for it's voltage. During the phase the ECU runs in an open mode (which is aka warm-up). It only listens to a few sensors at this point - one being the engine temperature sensor. When the oxygen sensor itself is warmed up, it will listen to it's voltage.

Once the engine is warmed up it will listen to all sensors, and run in whatever you want to call the "normal mode".

I think you might have a bad thermostat, sounds like it's stuck closed, or stuck partly open. Does your water temp gauge stay straight up most of the time? It should hang at the middle hash all the time.

 

[87E30is]

I changed the thermostat about 3000 miles ago. It usually does stay straight up though. When I say bounced back and forth, I mean similar to a spring or something.

I've also heard that the oxygen sensor can sometimes not read correctly when it's at a certain spot. I can't really think of how to word this.. like when the air's coming in I'm pretty sure it pushes on a dial of some sort in the air box, and I think this dial may have some dead spots in it. Does this sound like a possibility?

Thanks for your help.

 

[epj3]

I changed the thermostat about 3000 miles ago. It usually does stay straight up though. When I say bounced back and forth, I mean similar to a spring or something.

I've also heard that the oxygen sensor can sometimes not read correctly when it's at a certain spot. I can't really think of how to word this.. like when the air's coming in I'm pretty sure it pushes on a dial of some sort in the air box, and I think this dial may have some dead spots in it. Does this sound like a possibility?

Thanks for your help.

The oxygen sensor is in the exhaust. You're talking about the air flow meter (that sits on top of the air box). Your problems also sound an awful lot like a vacuume leak... I'd take a part the entire intake system (from the throttle body to the airbox...) and replace anything that looks cracked. Clean out the throttle body, air flow meter, and idle control valve (little thing sticking out of the boot between the throttle body and air flow meter).

 

[jrt67ss350]

Once the engine is warmed up it will listen to all sensors, and run in whatever you want to call the "normal mode".

That "normal mode" is called "closed loop." When the engine is cold and the ECU is ignoring the O2 sensor, the ECU is running in "open loop." Definitely sounds to me like this is related to the open loop/closed loop transition. Something is wrong when the computer switches to closed loop. Is the check engine light on?

 

[87E30is]

Check engine light isn't on...

 

[ldzpstnr]

I wonder if the thermo time switch is going out. Not sure if the later motronic 1.1 system has one like my older E30 does. This sensor tells the computer how warm the engine is. Not the same sensor as the tempuature guagte though.

In late 1987 the updated the fuel injection so your car may call the sensor something else. I havent owned a 325is yet so I cannot say for certain.

 

[87E30is]

here's some more info

With some help from my friend's dad, we found some more symptoms.

Today it started up and ran just fine. We let it get up to temperature and drove it around the block a couple of times. What we noticed was around 3600RPMs the temperature gauge would begin to swing back and forth from red to blue, and the car would start "bucking." When I would depress the clutch to shift, the temp gauge would go crazy once again. It did this several times. We parked it and let it continue to run for a few minutes before driving it again. This second time we went out, the temperature gauge would still swing, but the car wasn't bucking and jerking like it did the time before. The gauge would also swing when I would clutch to shift.

My friend's dad knows way more about this than I do, but I think what I need to ask is: is there any connection between the temp gauge and the ECU that would cause the car to buck like it was?

Also, is there any kind of diagnostic tool that uses the check engine light to flash a code telling what's wrong? To be honest, I'm not sure that my check engine light even works. All the warning lights to the right of the steering wheel come on when the key is on "run" but the engine isn't on, and the lights on the left don't come on.


I'm stumped

 

[87E30is]

my car was made in March of 87 if that helps..

 

[ldzpstnr]

Your car should have the ability to do a self diagnosis. Um I think you gotta turn the engine to run, and press the accelorater 5 times to the floor and then the check engine light will start flashing. It will flash in sequences. If you have your owners manual look in it, that should tell you how to do it exactly. Otherwise search the forums here, I am sure someone has posted the directions before. My car does not have the self-diagnostic ability, so I dont know to much about it.

 

[epj3]

If the temperature sensor was bad, it wouldn't cause the engine to not run - it would just run in the open loop mode justin and I talked about (probably not smooth, but not bucking...)