94 SC400 196K miles, Orig owner, no accidents, completely stock, Arizona car

Here is what I've done so far: Replaced battery, replaced alternator, and thoroughly cleaned (wire wheel using a drill) the battery cables at the battery as well as the connection to the block. Every time I do something, it seems to help for about a couple weeks, then the problem comes back. Unfortunately, it doesn't happen consistently (each day) so I'm thoroughly confused.

The problem is that I have an electrical problem that is sporadic. Symptoms are that the gauge cluster flickers and can go blank, engine skips a beat and can stall. It seems there are different levels of the problem. On the light side, I get a gauge flicker, on the severe side, the engine stalls. No issues starting and no issues with anything else on the car.

The condition that causes the cluster flicker or engine stall is a temporary spike load. For example, no issues until I use a turn signal, or use the brakes (brake lights come on), or turn on the headlights. After the load is applied, then no issue. For example, turning on the headlights causes the condition but after that quick moment, then everything is fine (headlights now on).

An additional symptom is that on the more severe side, the clock gets reset to 1:00, but the trip odo does not get reset, nor do I lose the preset radio stations. I thought of an electrical short (or a ground issue), but seeing that the odo doesn't get reset or the preset radio stations don't, then I'm questioning it.

If you've read this far, thank you. Any ideas would be welcomed. I can supply any additional info that may help.

 

check all the stupid stuff too to rule it all out like the fuses get a real close look at them and look at the wires in the fuse box. Im no electrical expert but most electrical problems I've ran into just took time and troubleshooting. Look over any questionable wires and meter them too. Try to recreate problem while checking everything, if you find a wire in question wiggle it and see if it causes the problem.

 

Sounds like ground issues brotha!

 

I've definitely done the obvious stuff and even tried pulling every fuse out, inspecting them, and reinserting.

I figure it's got to be something major to kill the engine. I thought about the ignition switch but seeing the clock reseting seems to rule that out.

I'm also thinking about ground issues but can't figure out why I would lose the engine/clock, yet keep the trip odo and the preset radio stations.

Nothing seems to be making sense on this one.

 

chk under driver side wheel well make sure your engine wire harness is still intact

 

those battery terminal connecters are pos! I've cleaned mine and thought i tighten the crap out of them so that they don't budge... As soon as I replaced them, no problems after that...

 

Thanks for the ideas. I've got a used neg batt terminal cable coming for $10 and I'll use it to troubleshoot. They're ~$100 new but the Pos side is about $400 new - expensive cables.

 

Just in case anyone else runs into this issue, I believe I solved it by swapping out the ECU. I had a spare from another diagnosis nightmare and I put in it. No issues yet. Will report back after a month or so to confirm if that really solved it.

 

Thats good news, report back. Hopefully with still good news.

 

I'd also suspect ecu and grounding

 

Sorry for the delay in posting ... finally found the solution: Negative battery cable.

I learned a bit that may help anyone with symptoms similar to mine. First, I learned the car will run without the battery hooked up. Amazing to me because I thought removing the battery cable would kill the engine - not so. What does happen though is the alternator can't keep up with spike type loads. So when you turn on headlights, try to move the seat back when it's already back as far as it goes, etc, the electrical load is too quick for the alternator to adjust and therefore you get a cutout of the engine for a split second.

I realize most reading this will think identifying the negative battery cable as the issue should have been easy. Well, I thoroughly cleaned (with a wire wheel) the connector to the battery (it looked like new after I was done), and also the connector to the block. I fully checked/tightened the bolts on both ends and made sure everything was solid. However, in-between the connectors is another connector that clamps to the body. The clamp wasn't the issue, rather some corrosion under the tape that seals the rubber sheathing. I've attached a picture that may help. It was very elusive especially given it's an Arizona car and corrosion isn't typically an issue as dry as it is out here.

The car has run about six months with no issues and replacing the battery cable (thanks Gazi for the part) was done independently of any other repairs (ECU, Alternator, etc). So I'm positive the issue was the cable.

Happy Holidays to all.

 

I'm glad you found it. I've preached about the inner cables for years on here.

 

Hmm, interesting post. I'm curious if this is the cause for my sporadic battery issues..

I'm getting my oil changed in a few days so I'll get the mechanic to look at these cables and see what he says. Where exactly are the cables located?

 

This is the negative battery cable. On my 94 SC400, the cable goes from the negative battery terminal, down to a metal connector by the battery tray, then on to the block on the driver's side of the engine. The picture I posted has the metal connector that bolts to the frame and is located by the battery tray. Hope it helps.

 

Great info, 94SC4 --- my 94SC3 is having electical quirks --- so it may help me. Thanks