Check Engine Light. Cutting on and off.

[tcc91]

I will be going along at highway speeds when my car shudders briefly, the red check engine light comes on, the revs drop, and the car loses speed like I am braking hard. This goes on for a few seconds then the revs pick right back to where they were and the problem goes away. This keeps happening on and off with no pattern. Towards the end of my trip it got worse, the revs did not pick back up and the engine completely cut off a few times. The problem does not seem to happen as much at low speed, but it could be just because the car is not on long enough for this to pop up. This started not too long after I put the engine back in my car after resealing and repainting it. Does anyone have an idea what the problem could be? Any ideas would be appreciated.

[paperplane94]

Doesn't the E30 have a stomp test feature?.

[jlevie]

If the tach takes a drop greater that the loss of road speed would require, the DME is loosing power/ground or START signal, or the DME is loosing timing data. If the tach doesn't react but the econometer drives towards zero there is a problme with the fuel system.

[tcc91]

The tach reacts. Engine speed drops quickly, causing the car to shudder and slow down. Most of the time it picks back up to where it was quickly, a few times the engine speed failed to pick back up and the engine died.

[Ryann]

Most likely your AFM. Stomp test should blink a 1215 code. You can fix it as in the video below.

http://m.youtube.com/watch?v=-11J8XawQtc

[tcc91]

How exactly do you do a stomp test?

[ButtJuice]

I believe you do this: While in neutral, turn on the ignition and stomp on the gas pedal 3 times, a light will blink with a sequence. For example, it will blink once, then pause, then twice, then pause, ect.... For a number result of 12ect.... If that doesn't make sense, fucking google it.

[ButtJuice]

I think I was a little off

http://www.e30performance.info/viewtopic.php?f=35&t=1528

[Drive Old Cars]

I had a similar problem, still not sure exactly what it was. it seemed to be a few issues, all fuel related. My car would stall out mid drive.

clogged fuel filter or faulty fpr. i replaced my filter and it would stall less frequently.

check the connections at the fuel pump under your back seat to see if it is getting proper power, also the are two relays by the air-box that i believe are fuel related, unplugging and replugging them worked for a while to start my car back up after it would stall.

fuse #11 is for your fuel pump as well, that blew one time and replacing it solved the problem for me. it hasn't died in a couple months now.

get a fuel pressure gauge

Hope that helps

[Gregs///M]

Classic signs of a failed AFM. Check my thread on the topic for more details on why this happens. (AFM signal drops to zero volts while driving)

[tcc91]

I replaced my AFM with a known working unit and I replaced the fuel filter, but the problem persists. Anyone have some thoughts?

[dnguyen1963]

Have you done the stomp test as suggested?

[tcc91]

I can't get the stomp test to work. I have read the instructions and tried, but nothing happens.

[jlevie]

The tach reacts. Engine speed drops quickly, causing the car to shudder and slow down. Most of the time it picks back up to where it was quickly, a few times the engine speed failed to pick back up and the engine died.

If the tachometer drops faster than the loss of speed would require, go back and read post #3 again. Then eliminate the possibilities I mentioned.

You don't say what car this is. The stomp test only works on 325i/is/ic cars produced after 9/87 if the original DME is present. It will work on a 325is/ic produced from 9/86-8/87 only if the DME has been changed to a 173 or later. It will never work on a ETA or early 318. Even on the cars where it is supported the TPS must be fully functional and proper adjusted.

[tcc91]

It's a 1990 325is, but I imagine that my TPS must not be functioning properly.