Engine cutting out...im at the end of my rope!!

[FLG]

Spoke too soon.

Been fine for days...came back yesterday for no rhyme or reason.

What's this obc disable relay?

What's a good resistance reading for the fusable link on the wire that goes to the dme? I'm gonna grab some led bulbs today and do some testing.

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[FLG]

Fusable link in trunk for dme. Was broken in such a way (just barely separated) that it worked most of the time but I guess when I got that right harmonic tone from exhaust it would be enough to wiggle and separate..my conclusion anyways...going to replace and keep fingers crossed

Oh and for future ref, according to RealOEM its 50a link..i would not use an inline fuse due to the characteristics of each...a fuse is meant to protect electronics, a fusible link is used to protect wiring and thus is "slow" at actually blowing, it can take momentary spikes where as a fuse would just blow.


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[jlevie]

Oh and for future ref, according to RealOEM its 50a link..i would not use an inline fuse due to the characteristics of each...a fuse is meant to protect electronics, a fusible link is used to protect wiring and thus is "slow" at actually blowing, it can take momentary spikes where as a fuse would just blow.

In the general case there is no difference between a fuse and a fusible link. Technically the fusible link is a fuse. There are special "fast blow" fuses for protection of electronics, but ordinary automotive fuses are all "slow blow".

An easy fix for a bad fusible link is to splice out the link and interpose a lug type 60A fuse between the small cable from the battery and where that cable connects to the power block in the engine bay. That is the first thing I do with any E30 as I have yet to see a fusible link that didn't have corrosion from acid vapors.

[FLG]

Thanks.

I just wound up getting a new link and soldering the connections back on...so far so good. If it blows again (which it shouldnt) ill just go with an inline fuse or a breaker.

[FLG]

I spoke to damn soon!!!

Problem has returned.

I connected 2 led's to the dme harness, one to the constant 12v signal, one to the switched (start) 12v signal. During an event, neither of the 12v wires loose signal.

I cannot replicate this when just revving the engine, i cannot replicate the issue when flogging the living crap out of it...she pulls like a bat out of hell with NO hesitation or issues.

EDIT Spoke to soon again LOL I was just able to replicate the issue when I revved the engine. Again, no loss of power to the DME.

The ONLY time i can replicate the issue is either

A) Cruising along sometimes will happen during shifts or right above 2500 rpm
B) (this is when it happens the most) 5th gear cruising on the highway right at the 2500ish rpm mark not loading up the engine just gentle throttle moving along

What the HELL is going on...

All the grounds are good
CPS air gap is good
CPS sensor Ohm's good (it is used but had same issue with other brand new sensor which dosnt Ohm out good)

One thing i didnt try which i will right now is with the LED lights i had them on the positive wires and the negative on a screw, i will switch the negative to the negative going to the DME to see if its loosing ground somewhere

No stored errors in dme

Is it possible 2 crank sensors are bad? Also when I had car on the lift today I inspected the sprocket on the harmonic and it seemed fine and tight.

Edit: Drove around more tonight, ground checks out as well so the DME is not loosing power. Also happened for the first time under 2k RPM though probably the only time it did. And after leaving a friends house, the whole ride home it did not have an issue. Im at a loss here.

Im also assuming the AFM i have is also good...if a AFM had an issue would i also have this drop from the tach? Or is this strictly related to a CPS sensor/harness issue?

[FLG]

Bump

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[blueapplesoda]

Check the missing tooth wheel..I once had a motor in an e30 that was from a front accident car, and the crankshaft (or balancer) was ever so slightly bent just enough to cause the tooth wheel to wobble, causing rpm sync loss with the ECU.

Derek

[FLG]

Thanks Derek

I inspected the wheel its tight with no obvious issues. Looks straight when its spinning.

I've checked everything. Even switched back to the new crank sensor...same issue.

Tried shuffling the dme harness...car didn't miss a beat... moved around every damn harness I could think of.

Dme isn't loosing power as previously tested.

Anyone got a portable o scope I can borrow? Lol

This is so aggravating

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[SpecM]

check the harness very very closely

my 325i has been doing the same thing, I was repalceing some cooling system parts last night and there is a spot on the harness that is rubbed through. many of the wires on the inside are exposed and likey were shorting. I have to find a way to repair it, and I obviously haven't tried to drive it yet.

[FLG]

Thanks Bud,

I rechecked and checked everything, wiggled as many harness as i can..the car is completely unmolested so i have faith in a lot of the wiring, every wire cover and sheath is still on it like it rolled out of the factory, all the connectors are clean, and i couldnt get it to stall again from wiggling wiring.

Is it possible i have 2 bad crank sensors?? The new one (ohm's bad) and when i installed it things got A LOT worse it becomes embarrassing, goes from the occasional shut down to almost constant. Im switching back to the old one and seeing if things improve, if they do im going to buy ANOTHER crank sensor and see what happens.

Again, the DME is NOT loosing power, and the toothed wheel on the crank is tight and not wobbly at all. WTF is going on! I wish the damn thing had a carburetor on it and no computer!

Switched to old cps sensor..seems better. Getting another sensor from a member in a bit...just for testing purposes since 100+ for a new sensor isn't cheap..

Edit: Wasnt able to get it tonight, will try to get it tomorrow. Drove around with the new (used) sensor on, was fine from my buddies house around town..than after i dropped him off it started up again...i dont get it, seems to be no rhyme or reason to the issue. Sometimes its fine, other times its horrible..lately though it seems to have gotten worse.

Also, i forgot to mention...lately cold starts have taken extra long..ive read this can also be due to a bad CPS sensor?

(all parts of fuel and ignition system are new, wires, plugs, cap, rotor, FPR, injectors, fuel filter, ignition coil)

Warm starts, she turns over and fires right up...cold starts leaves me cranking for awhile

[FLG]

Tried another cps sensor...same issue. Guess I'm down to a wiring issue...unless someone has another idea. Trying to find a o scope to borrow.

Also something I noticed...when it happens while on the highway cruising sometimes I'll get a nasty backfire out of the exhaust like it might still be dumping fuel but loosing spark.

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[jlevie]

Been there done that. A backfire can be the result of a loss of timing data.

My advice at this point is for you to get and install another engine harness.

[FLG]

OK...will see if i can find another engine harness.

What a effing pain in the ass!

[jlevie]

Well yeah, but these cars are all +20 years old. For a tale of troubles see http://www.r3vlimited.com/board/showthread.php?t=237141

My new harness will hopefully show up late this week.

[FLG]

Sounds like fun. I pmed blunt just to see the prices on new' though my other project takes priority over this one (73 charger) so might need to settle for used.

This is why I like carburetors lol


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