I did search the forum and found and read the stuff that matched, but either I didn't understand the answers, or I felt they didn't apply. If you know of a thread that directly answers this, please post it here and I'll read/reread it, and hopefully will understand it. I'm tech savvy, and have worked on all of my previous cars except the last two, which were under warranty. I have rebuilt a couple of engines and a manual 5 speed transmission. I'm not an electronics guy at all, but can solder pretty well, and if you tell me how to use my digital meter, I can do it - just use plain language, not electronics technician terms. That should give you an understanding where I'm at.

OK, now to the question/problem. I just bought my shiny, beautiful '92 SC400 3 days ago. I got a slightly better than fair deal on it, so I didn't worry about the needs that weren't lit on the gauges. Actually, not all of them aren't lit. Anyway, what I didn't notice, was that the speedometer needle was bouncing around. I had this on an old car of mine, and if I remember right, I simply replaced the cable, but I'm guessing this isn't so simple. After reading some of the other threads, I saw that there is some relationship to the cruise control, so I tested that. I was surprised to find out that the cruise control is following the needle! LOL So, I'm guessing they both get their speed information from the same place. Would that be the VSS (Vehicle Speed Sensor?)? So, if I replace the VSS it will fix this?

I'm SUPER tight on cash right now because I was laid off... which is why I'm in this car now instead of the '09 Audi A4 I just sold. So I reeeeaaaly don't want to go on a parts buying spree to try to find the problem. I want to be as sure as possible before dropping a dime!

Thanks in advance!

BTW, I checked out several SC300/400 forums and this one beats the rest by a long shot. You guys obviously love your cars, and don't mind geeking out over them. My kinda people!

 

Nobody? Please? This is really annoying!

 

what do you mean your cruise follows your needle? im not sure about the jumping.

someone here will chime in. you may just need to consolidate your words and state your problem right off for those passing through.

 

It is a common problem (from what I've read) that the speedo needle sort of bounces. The slower you go the less accurate it is, and by around 50 it gets relatively stable. What I mean by the cruise control following the needle is that whatever is telling the needle (gauge) what your speed is, is also telling the cruise control (they listen to the same sensor apparently). So, if you set the cruise control when you're at 45, even though your speed hasn't actually changed, when the needle drops, the cruise control gives the engine more throttle. When the needle goes up, it lets off the gas. Essentially, the cruise control is working correctly, its just being given misinformation.

I read about a guy who disconnected one speed sensor at a time to figure out which one it was, and replaced that one. His issue was different and it didn't end up fixing his issue anyway, but it makes sense in my case. But I would prefer to hear about someone's success with this issue.

 

have you tried replacing the speed sensor in the tranny? driftmotion sells them. it might help you out.

 

Is there a check engine code on or light? A VSS will cause a code to come on. Maybe DTC 30,31.32,33? That's what mine was but the cruise still worked and I had no jumpy needle.

 

Not yet, I'm super strapped for cash right now, but I'm pretty sure it is one of the VSSs that is the cause of the bouncing needle. I'll disconnect them one at a time, testing in between to see which one is controlling the needle and cruise control. Actually, I have the shop manual, I should see if that has that info.

Thanks for tipping me off to driftmotion though.

 

I wish I knew. I have equipment and software (for laptop use) for OBDII, but not OBDI, which is what this car is, I believe. I probably need to get that stuff if I plan to keep this car. I did get a check engine light for a few days, but it went away. I was guessing it was due to the tanny/OD issues.

Hey, so you're in SoCal? Anywhere near the SFV?

 

The one in the tail shaft housing actually drives the speedo. I might have one I could sell you for cheap if I can find it. The other 2 are trans input speed and output speed.

I don't know about the quality of the cluser in these cars, but that could be it also?

 

where did u see that? i was just on driftmotion last week looking for a tranny speed sensor myself, and i didnt see that on their site for the 2J anywhere.

 

Send me an email if you find it! shawn at satoveillon dot com

I hear ya about the cluster though. With the needles gone dark it does make me wonder about the guage itself, but as far as my research has shown, replacing the cluster doesn't fix this issue. The dark needles is a whole other issue though. You can replace the needles, or "fix" them with LEDs from Radio Shack (and possibly more solutions). I'll get around to that once I get the big items resolved. The sticky OD/tranny issues and speedo issues first.

 

I didn't see it either.

 

Really it is only going to be the VSS, or the cluster. Only way to know without buying parts is to test vss with o-scope.

 

If you need a speed sensor, and its the right front, I have one, 30 shipped. LMK.. Good luck.. I would try and find someone to read the OBD I for you, if the lights come back one again, and try not to start replacing parts, not sure it will fix the problem.