Help! Intermittent dying, CEL comes on all power loss.

[driftxsequence]

So today was our longest trip ever since purchasing the car. A 2 hour drive each way. About 10 minutes from our destination the CEL would come on and the RPM gauge would drop like the key was turned off. Speedometer and everything else operated normally.

When the CEL came on and rpm gauge died there was total power loss like someone turned the key off, then turned it back on and you resumed driving as you were. This creates some nasty bucking and happens 3-5 times for about 20 seconds and then it will drive fine for a few minutes.

Any ideas or input would be great....i dont want to pay for a 2 hour tow home. Haha

Car is a 1989 325ix

[peterman]

Rpm is based off yhe coil i think so that means no spark. Could be your crank positioning sensor, but i think that cuts fuel, not spark. Try the stomp test and write down the code. The cel will blink the code

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[driftxsequence]

Came back clear with no codes 1444

I did tighten the positive terminal a LITTLE...hoping thats all it was.

[driftxsequence]

Positive terminal did not resolve the issue. Thinking it may be grounding. The water temp gauge was flopping around when the car would act up. Then when it was finethe gauge would hold steady. I know those sensors are very basic so it must be a ground issue. I will start with the shock tower and go from there.

[peterman]

Check the strap that connects to the oil pan... oil level sender area.


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[TobyB]

crank positioning sensor

was my thought, too.

Also relays- just because at this point in their life,
they're way beyond their expected life.
Main and fuel pump...
http://www.wedophones.com/BMWManualsLead.htm is a lifesaver here.

Grounds on everything, too, of course.

Also, this is less likely, but there is a big fusible link in the trunk, on the smaller
of the 2 wires coming off the battery. They can get damaged, but usually that
is a total power loss.


t

[redlightpete]

Check the circular connector below the intake manifold, C191 if I remember correctly. The injector harness and temp gauge sensor go through it.

[nando]

Mine did the exact same thing and it was confusing as heck to diagnose. I replaced the CPS, fuel pump, checked wiring, etc. Chased it for almost 2 years.

It's most likely your main relay. If your relays are original - replace all 3 (Main, FP, O2 heater). The main relay turns on the DME, which is why the engine just "dies" (the car's power comes from a different wire, so it's not obvious). the tachometer drop is also because the DME is powered down.

[jlevie]

If the DME was loosing power, the CEL would not come on. That tends to exonerate the main relay, fusible link, and DME ground. The tach signal is generated by the DME from timing data from the CPS. The tach going to zero and the CEL coming on usually means that the DME isn't seeing the CPS signal. The first thing to try is to replace the CPS with an OE or OEM part.

[driftxsequence]

https://youtu.be/BQh3NikuE9c

Sometimes it'll only do it for a moment like in the video, and others it'll be for a good 10 consecutive seconds....sorry its pretty poor but...its hard to capture.

[Kershaw]

Does the car not lose power when that happens?

And yeah, try replacing the CPS. And maybe swap in a spare DME if you or a friend has one.

[supermansocks95]

Same thing was happening to me a while back. I'll bet it's your main relay. I went through the fuel system and replaced the DME with one from my old car and still didn't work. The main relay finally did it. I honestly didn't think that was the problem, but it was...

At first, it was giving me the complete loss of power issue, then it started cutting fuel and leaning out. I replaced the fuel pump after the filter and checking everything else out and still no start. I then replaced that relay and BOOM. Haven't had an issue since.

[nando]

even if the relays aren't the culprit (CPS can cause this as well), I would still replace them if they are original.

[supermansocks95]

even if the relays aren't the culprit (CPS can cause this as well), I would still replace them if they are original.

+1
Even though they're easy to replace, there's no need to tackle this issue again. Do it the right way sir. Don't be like some of us (me) and skip preventative maintenance. Lost an output flange and almost lost a driveshaft that way

[TobyB]

If the DME was loosing power, the CEL would not come on.

This fooled me before, too- mine would 'blink'- the relay would interrupt DME power
for just long enough to reset it, and then it'd go through the startup diagnostic,
which illuminates the CEL.

fwiw.

t