Ethan5150

Hi all, over the last couple of weeks my car has been intermittently running rough ('93 SC 400) but now it's all the time. It feels like it's missing on a cylinder but I'm no mechanic so I could be totally off. Also, the check engine light has been coming on intermittently and it too, is now on solid. Over the past couple of weeks, when it did come on, it would sometimes come on really dim, get brighter, get dimmer, go off... strange behavior. But now its solid on.

So I tried to pull diagnostics by jumping T1 and E1 in the engine compartment, but all I get is a solid CEL and a flashing OD/OFF light - no codes from the CEL.

Also, if it's any help - my Air Bag light came on around the same time. Solid on. The wire dance fix doesn't clear it after MANY tries (I've done this before without issue) - it just flashes 3-1 and comes back on. I don't know if this is related or not...

What am I missing here? Any help would be greatly appreciated.

Tallyhoe

My first question would be, if it's lowered? check underneath the driver side splash guard and check for damaged wires. If your CEL was flashing, while you were driving, maybe a misfire. Check ignitors on both banks, spark plugs and wires. Look up wiring diagrams for the airbags, and check to see if the plugs are fully seated, if they're not damaged. On the transmission, is it the original transmission? Other possibilities a rat probably got to the wiring and feasted on them.

Ethan5150

Thanks a bunch Tallyhoe, I really appreciate your insight. I went out this morning and checked the driver's side splash guard area. It looks totally clean. I didn't actually pull it off to check "under" (above) it, but it's completely intact and looks like if the tires have ever rubbed, it was minimal. The car is lowered, but only a little. But that got me to thinking about rats because, yeah, here in Hawaii they're a constant nuisance. I immediately found the remains of a rats nest in the very center of the engine under what I believe is the intake manifold. I did my best to use a coat hanger and pull the detritus out and I noticed two visible plugs in there. I wish I could fit my hand in there but it appears that a LOT of the top of the engine must be dismantled to really get in there. That said, I took some pictures. Looking from the driver's side down into the center, here's what I see:


A closer zoom shows this:

So my first question is; that plug on the bottom left - how many wires should be going into it? I only see one. I would expect two, but perhaps I'm mistaken? Is that an injector?

As far as troubleshooting the plugs and wires, the wires LOOK good from what I've seen but I know that's not a valid way to test. Is there an "easy" way to test if a plug or injector is failing? I'm happy to do some troubleshooting on my own but I'm no mechanic so my skills (and time) are limited.

Also, I don't believe the CEL light ever flashed while I was driving. It would sometimes come on slowly/dimly, sometimes stay on for a while, then go back out. Currently it's off. I don't think I've ever seen it flash though.

I still haven't figured out the airbag situation; you mentioned "Look up wiring diagrams for the airbags, and check to see if the plugs are fully seated" - are you referring to the plugs for the airbag connectors? I don't have a wiring diagram, nor do I know where I would find those plugs...

I really appreciate your help.

Oh, and yes, the tranny is original. I recently had the kickdown cable replaced and ever since then, occasionally when I step on the gas it fails to "give 'er power" - It's hard to describe. The pedal feels like it's not providing normal resistance (if anything, more) and doesn't go down smoothly - it sort of provides more resistance before it's fully depressed, and the car accelerates at like 10% of normal power - it doesn't "kick into gear" like normal. If I let off the gas fully, then try again it will frequently engage normally. Sometimes I have to do this two or three times. Other times, it works fine the first time I step on the gas. I don't know if this is related to the above issues but you asked about the tranny so that's the backstory. To be clear, this issue, at least in terms of my ability to discern from symptoms, is separate from the more recent running rough/CEL light issue. It's been having this acceleration issue for a couple months. This new issue that feels like it's missing on a cylinder just started and is constant from the moment I start the car.

Tallyhoe

I would check your driver side kick panel under the dash forward of the door. There is a thread about rerouting the harness, and one of these plugs is the airbag plug. You can start your search there. From your picture, it doesn't seem like any wire was damaged, but it is hard to tell like you said. I do believe deep towards the rear of the engine resides the starter, so in case the pictures wires were not damage, what are the odds other wires were damaged that are unseen. Your transmission issue reminds me of my misfire and how the transmission responded, it was intermittent at 10% and it was a lack of power that would suddenly surge. My idle was randomized and sometimes would die, but the car would still be on. If rats were nesting in there, may have gotten to your transmission wires as well. You may need to do some digging on that though since it may be a 50/50 shot.

Ethan5150

Ok, I still haven't figured this out. The check engine light SLOWLY comes on when I start driving. When I first start the car, it's off. Then, over the course of several minutes of driving it gets brighter and brighter. But then, if I turn the car off and jump the diag connectors under the hood, I don't get ANY flash codes - NADA. I've checked all the areas where wiring harness might have been damaged and everything seems good. Incidentally, the car seems to be running just fine lately too.

I don't know if it's related but the airbag light is still on. I tried the wire dance with no luck. Perhaps I didn't get the timing right but I've done it before without trouble and this time I tried like a dozen times and the light stays on.

Any ideas here? I'm trying to sell the car and the check engine light and airbag light being on doesn't help my cause...