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equalie 11-17-2012 09:43 PM

e34 lost power
first of all thank u guys for replying to posts, I have reviewed multiple posts and u guys have helped me multiple times. I have been having a major issue with my 1990 525i BMW.

1990 525i e34
228 k miles

I just had refilled my car with gas, pulled out of parking lot and got 100 yards, I was in third gear probably around 2800 rpms when all of a sudden my rpms dropped down to 500 and acted as if it had stalled. Down shifted and again no dice, I pulled off the side of the road and when I stopped the car stalled. Took a minute and tried starting it and it wouldn't it sounded different as well like there was a loss of pressure or something. Took awhile and a lot of pumping of the gas to get it started again. Once it did start, it was running really rough and had a very loud continual clicking that followed the rpms. I was too far away from home to get it towed, and it was at least running, so I took my chances and drove it home. Noticing that the power had dropped dramatically. When I got home I noticed that the ticking was less, but the power loss was still very significant.
I took the car into a mechanic and they said that they had to adjust the tps in the car and added fuel injection cleaner and said that it should improve with time. Still no improvement after a month and one refill of gas. Also the loss of power remains, especially going up hills....ex is one hill I used to be able to get up in 5th gear now I have to down shift into third and rev to about 5000 rpms just to maintain speed. Also the lack of acceleration with the car where the car doesn't get up and go until u hit 4500 rpms.
Side note:
months prior, I replaced the spark plugs, spark plug wires, ignition coil, and clutch. And it had run perfectly fine for those three or four months. So I figured it wasn't that.

Sorry for the lengthy message but any help or suggestions would be greatly appreciated. This has been driving me insane. This has never happened before and I know the car is seasoned, but I love this car too much tho get rid of it.

robertobaggio20 11-17-2012 10:03 PM

Don't worry. This is probably an easy problem to solve.

1. Please read through the maintenance sticky and download and read through the bentley manual's engine troubleshooting page, located at the end of the relevant chapter.

2. Perform the stomp test if it works on your car. Details in the sticky and demos on youtube, and code descriptions on google.

3. As a quick test (chances of it working are poor), delete all the error codes on your car by unclamping your ecu. Sometimes old codes will hold a system back until they are deleted, or they go through 60 startups without incident (self-deletion). The ecu is in the black box behind the right shock absorber tower. Leave it unclamped for a few minutes, and key2 the car meanwhile to discharge all internal capacitors (Key0=insertion, key1=first click, key2=second click plus lights, key3=ignition). Then key0 and reclamp the ecu. Start the car and let it idle for 10 minutes (5 if you have an o2 sensor).

4. If the stomp test works, use the stomp test to extract and note all error codes on your car, before using it to delete all stored codes and performing the test outlined in #4. After one week of regular driving, pull the codes again and decide if you need to take action on those which are repeated.

5. You might have an o2 sensor issue. You can disable the o2 sensor temporarily by removing the appropriate relay in the ecu box's compartment. Please check bentley for exact position, can't remember offhand. Then start and test drive the car. If it works, you'll probably just need to replace the o2 sensor.

6. Did the workshop you went to previously scan your car's computer ?If they did, what did they find ?

7. The sudden loss of power that you describe is not consistent with vcg (valve cover gasket) failure, which leaks oil into your spark plug wells and affects charge delivery. However, if its not difficult, pull a few leads out and look down the wells. If you can't crane your neck down properly, use your phone's video camera with the flash activated. Make sure the leads are tightly affixed when you replace them.

8. You might as well double check to see if your spark plugs themselves are tight in the cylinder head.

9. You might have a bad ect (engine coolant temp sensor). It can lead to funny engine problems. I'm only suggesting it here because its so easy to test again. Just disconnect the blue coolant temperature sensor fitting on your engine, located right next to the fuel pressure regulator. Then test drive the car. If the problem goes away, this is it. $25 to replace and a diy as well.

10. There might also be an air flow meter issue. If your engine runs with the afm disconnected, then disconnect it and go for a test drive as well.

11. Driving with the o2 sensor, afm, and ect disabled is not dangerous to the car. It is not optimal in terms of power and fuel economy, but this can only be seen when driving for half a tanks' worth and when the engine is pushed. Since the process of disabling them and reactivating them is effortless, I would suggest that you try this.

12. Only try this after you've read (if possible) and deleted the error codes from your ecu and that does not fix the problem. If it does, keep driving the car and if the problem recurs a few weeks later, then start disabling components in turn to isolate the culprit.

13. As mentioned, I'm going to bet that this is a simple problem to fix. I'm going to wager that you sort it out within 90 minutes max. :)


p.s. Disabling components generates error codes, so at the end of your test cycle, read and clear the error codes once again.

equalie 11-21-2012 09:16 PM

engine coolant temp sensor??? is this the same as the thermostat. Cause I drove the car today and noticed that the temp gauge went from normal warm to cold. So is it possible that the choke is continually on causing the loss of power in normal driving. And also could a spike of a faulty thermostat cause the car to stall as it did in the beginning of this mess.
Thanks for the help,

1995i540 11-21-2012 10:50 PM

Don't listen to him unless you want to spend $$$$ on throwing parts on your car. ECT has nothing to do with your symptoms.

paperplane94 11-22-2012 03:56 PM

Original fuel pump?

That's probably what it is.
If not that then its sounds like a fueling problem. You could change out the fuel filter since they are cheap.
After that you need to T in a fuel pressure gauge into the fuel feed line.

robertobaggio20 11-22-2012 04:52 PM


Originally Posted by equalie (Post 7208247)
engine coolant temp sensor??? is this the same as the thermostat. Cause I drove the car today and noticed that the temp gauge went from normal warm to cold. So is it possible that the choke is continually on causing the loss of power in normal driving. And also could a spike of a faulty thermostat cause the car to stall as it did in the beginning of this mess.
Thanks for the help,

No the engine coolant temperature sensor is not the same as the sensor that connects to the temp gauge in your dashboard. Another sensor is dedicated for this task. Both of these sensors are fixed into the cylinder head. I believe the ect is the one closest to the front of the car. In any case, if you disconnect the wrong one, your dash gauge will not work so that's how you'll know.

What you have indicated above might be a buggy thermostat. That itself could lead to big problems if it gets buggy the wrong way.

There is no choke in our cars. :)

Disconnect the ect and see if your car's behaviour changes. Its a 5 minute job. Bad ects are not always deactivated by the ecu, and can thus lead to strange engine symptoms. It is not likely at all, but since its so easy to test it why not ?


p.s. Please follow the steps I outlined in my first response to you as well.

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