problem before and after chip

[flatfoot56]

So I installed a chip (ebay special) in my 87' 325i, and it ran like shit. threw CEL, bogging down, studdering in low rpms. wasnt happy, so i re-installed the old one that never had a problem and now its doing the samething. CEL, bogging down/studdering in low RPMS. What happened? and how do I get the car back to normal?

[Sagaris]

Try disconnecting the battery for 30 min to an hour to reset the ECU. Take a drive and give it a couple miles to relearn the fuel trim. Report back.

If it still sucks, ditch the ebay chip for something legit

[flatfoot56]

appreaciate it, one other thing to add, while i had the ebay special chip in, the tach was completely dead. odd

[Sagaris]

before resetting the ecu, check the DME fault codes that are stored.

http://e30world.com/fuel/BMW-E30-DME-Motronic-fault-codes

The issue may be unrelated to the chip and could just be a coincidental problem that happened to pop up at the same time, but most likely it is something to do with the chip. re-installing the stock chip could easily determine if that is the case. Hopefully a reset of the ECU is all you need

[flatfoot56]

I re-installed the stock chip, battery unhooked for 30 mins or so, then drove it about 10+ miles, still same problems. Fault code I got was 12? thats it. blink once, pause, blink twice, then just stays on.

[flatfoot56]

just went back out to check fault codes again. key on, 5 stomps, then it blinks once, pause, then stays on.???wtf

[flatfoot56]

Is there a set amount of time or mileage that it takes before the ECU re-learns and stops running like shit?

[Sagaris]

It seems to me that it takes about 5 miles of driving for the ecu to establish whatever fuel trim and other initial things it may need to determine. I just reset mine today and that is about how long it took for the car to feel as powerful and sharp as it normally does in closed loop / to feel normal again

[flatfoot56]

I drove 10 miles or so and still runs like shit

[flatfoot56]

any other ideas?

[flatfoot56]

drove it 20 miles today, seems that it studders if i try to push past 3/4 throttle, the tach isnt reading accurately, and my MPG gauge stopped working, but it worked before. WTF?? and my CEL is on, but isnt givng a code

[Sagaris]

The crank position sensor could be causing the bad tach. and poor running.
The tach. and mpg meter could just be a wonky gauge cluster though too.


Take a look at the toothed wheel on the crank pulley to see if it wobbles when the engine is on + revved. It is bonded to the crank pulley by a piece of rubber which will allow the wheel to wobble out of sight of the crank position sensor if it becomes unbonded.

Take a look at the wiring for the crank position sensor and make sure it is intact, especially if whoever previously did the timing belt on the car didnt run the wiring through the belt/pulley area properly, there is a plastic shield and some clips that tend to break, you may find that the wires are zip tied into place or just kinda chillin there where they are vulnerable to damage from the water pump pulley and drive belts. There should be some sort of resistance measurement you can take of the sensor itself to see if it is within spec and if the sensor is good or not, check the Bentley manual for such a test/spec.

Also take a look at the tip of the sensor to make sure it isnt coated in road grime and that it is not too far from the toothed wheel. I believe there is a spec in the Bentley manual which calls for something like a ~1 to 2 mm air gap for the sensor and the wheel.

Check the main ground to the ECU located on the passenger strut tower. make sure it is in good shape, clean, and if you can locate an ECU pinout, measure the resistance between the main ground on the ECU harness and the chassis ground on the strut tower.

Check your battery terminals to make sure they are clean, corrosion free, and snug.

Also take a look at your C191 harness

http://forums.bimmerforums.com/forum/showthread.php?t=1597051

You will need to be a member of bimmerforums to view the pictures

Last but not least, if you have a spare ECU to try or dont mind spending $35 for a known good one then give that a shot. A bad ECU can do a number of things that don't make sense and cause a lot of grief.

I hope you find the culprit

[Kershaw]

you fried the DME by not wearing a static strap when swapping chips?

[flatfoot56]

i didnt use static straps, but there wasnt any built up static that i had noticed during the chip swapping.

well, looks like i'll have to swap DME. Can i put a 173 in, instead of a 153? do DME's have to be specific? (vert, diff, auto/manual trans. etc.)?

[E30_fiend]

the 173 will work better than the 153 actually. Swap it out and see if it fixes the problem. I personally think your problem is the AFM but swap the ecu first.


Taylor