Good to be back....

[Guest]

Hey everyone, how's it going?  It's been awhile since I've been on here, and I've missed reading and posting.  I lost internet for several months, but I'm back in business-- just in time to have the strangest problem with my '88 GT since I've owned her.  It's a manual trans, and this problem has got me stumped.

It all started one day a couple months ago when I was driving to work.  I was cruising down the road around 55 mph, and all of the sudden a big lurch, and it died completely.  Still coasting, it started running again fine (clutch was up, and it bump-started)... and then it was fine for several more days.  Then, it did it again, but at a lower speed.  And then it started happening every few minutes.  Well, it never did set a code in the ECM, and by the way it acts, I realized quickly it was something electrical.  It runs great, and idles real smooth, just about (everything under the hood is brand new GM parts)-- as long as it's sitting still.  As SOON as I put it in gear and let out the clutch and move a little, whether it's first gear or reverse-  it dies abruptly.  After replacing the ignition module and coil packs (again), and a ton of other sensors and wires, relays, etc... I still have the same problem.  Well, yesterday I finally found the problem:  the VSS (vehicle speed sensor)... but I don't understand WHY.  If I disconnect the VSS, I have no miles-per-hour, but she runs perfect, no matter what speed I'm at.  If I reconnect the VSS, I have MPH but it will die at random speeds, or won't even let me get out of the driveway.  I don't have a lot of info on the VSS, except my electrical diagrams.  I know the VSS goes right into the ECM, and that it controls the operation of the TCC solenoid on the automatic transmission.  But I have a manual!!  All the VSS does for me (I thought) was provide MPH and tell the "Shift Now" light to come on periodically.  Correct me if I'm wrong, but from looking at the wiring, does the VSS control the Integrated electronic EGR valve signal as well?  Obviously the VSS has a close relationship with cruise control, too-- but it still does the same thing even with the cruise fuse pulled.  So, to some up, until I figure this weird situation out, I have to drive with no idea what speed I'm at, and that's going to cost me a ticket soon, I just know it.  Please help!

[96BlackRoseZ26]

For the heck of it, with the car running and in neutral, start wiggling the wiring harness that sits between the engin and the firewall and see if the engine dies when you move a certain area.  My sister's 95 was doing something really similiar to what you are describing.  As it turns out, she had a wire that had broken inside the insulation from the engine/harness movement over time, and when the car was put into gear, it caused the engine to rock just enough to put pressure on the wire to interrupt the connection.  Took a little bit of wiggling but I was able to find the one wire in a mess of about 40 that had the break in it.  Took the break out and spliced the wire back together and was good as new.  Not sure if it's your problem or not, but definitely sounds like it is something electrical that is getting worse with movement.  Couldn't hurt to check.

[Guest]

Thanks for the suggestion.  I've done the "wiggle test" on just about everything.  But, just in case, I tried the harness on the firewall anyway.  No luck.  It didn't do anything different.  Just to make sure it was the VSS thing again, I reconnected it and hopped in the car, put in reverse, and got about 10 feet out of the driveway and it died.  I jumped out, disconnected the VSS, and took off like a bat out of hell, went around the block, with no problem, and parked it again.  I wonder if this an ECM problem.... I hate to spend 75 bucks on a new VSS if it doesn't need it.  I still find this very hard to believe that a speed sensor would affect so much.  The DIS system doesn't use it in any way to control fuel delivery or timing... or does it?  dunno yet

[Guest]

Just an update on this odd VSS situation...

I picked up a used ECM out of an '88 Beretta from the junkyard, and installed it.  I re-connected the VSS and put it in reverse, and couldn't even move 3 feet backwards before it lurched and died.  Disconnected the VSS, started her up, and went 10 miles.  So, I have now ruled out the ECM having anything to do with this.  Now, I have an extra '88 ECM.  (sigh)....  Guess it's time to buy that expensive replacement VSS and see it that's gonna do it.  Now, I have to figure out to remove the old one from the trans.  I've taken the hold-down clip and bolt off, but can't get the sensor to come up and out.  Does anyone know anything about replacing this?  Is it threaded in, or does it just sit in there with a seal or something?

[1988GTU]

Depending how hard they are to get off, I can probably get you a used one from the yard for really cheap.

Just PM with details.

[Guest]

Well, I got the new Borg-Warner VSS today.  I still can't get the old one out of the manual trans.  It's easy to get to, sits right on top of the trans.  Pull the connector off, and there it is.  However, it will NOT come out.  I've tried every tool I have.  I have even tried the good 'ol Vise-grips, pull up hard, twist slightly... nothing.  From looking at the new VSS, it just goes down into the trans, it has a rubber gasket built into it.  I'm thinking that the old gasket on the existing VSS is rotted, and therefore it won't pull out.  I hope there isn't some "special" GM tool necessary to take this thing out!  Has ~anyone~ replaced this on their GT?  If so, any tricks you might share with me on removal?

[Guest]

The old VSS was very hard to remove- turns out it was bad-- VERY bad.  Once I finally got it out, I quickly realized what had happened.  At some point, probably when it was well below zero, the plastic part of the sensor cracked, allowing manual trans. fluid, etc. to seep into the sensor, mixing with tiny metal fragments and slivers... the magnet inside the sensor attracted all this junk, and created a closed loop, a short circuit of sorts... this confused the hell out of my ECM, and was causing all kinds of weird things to happen.  I have posted a picture of the old VSS.  With the new one installed, and having flushed out the tranny, and refilled with new Syncromesh, I have no problems at all...
This is definately an unexpected problem, as even my factory manual doesn't offer any possibilities of such havoc being caused by a VSS.  I'm so glad to finally be done with this, as it has caused months of scratching my head and lots of unnecesary diagnoses, etc...

Wow, man.... time for a beer