1993 SC Tach dead, Check Engine light on


Registered User

I recently purchased a 93 SC 5-speed and have been chasing down most of its issues. One that I’m having a lot of trouble with is that when I start the car, the tach will be dead and the check engine light will be on; but not every time I start the car. Last time it happened, I did the OBD-1 paperclip trick, I did Key On Engine off and got no bad codes. I did Key On Engine On and it passed (on my third try of “goosing” the gas ;) ). During the tests and immediately after, the tach was fine and the Check Engine light was off (except when it was flashing codes). I didn’t have a problem again until today right before taking it for a test drive. I thought I could just turn off the car and turn it on again and it would work fine (I turned it off and on 3 times) but the problem remained. I decided not to drive the car anywhere until I address this issue.

The only thing I can think of that I did the same last week and now was that the car was warmed up for about 5 minutes, allowed to sit for 10 minutes, started again for 5 minutes, then allowed to sit another 20-30 minutes before being started again. Maybe if I waited another 15 minutes (which was how long it took us to find a paperclip and to do the KOEO tests) the tach would have been normal and the check engine light would have turned off, but I didn’t want to take a chance the problem reoccurs while I’m on a public roadway. Could this be signs of a bad cam sensor? The idle was not rough but it was getting harder and harder to start the car every time I turned it off then back on.

Edit: I just did a little research (looking at old forum posts) it seems some people who had a bad DIS and/or bad Cam sensor did not get any codes and they had a hard time starting too. It also seems that the rough idle/bucking happens after the car gets hot (I didn’t let my car run long with a dead tach). I am planning on replacing my Cam sensor and maybe cleaning off then applying fresh heat transfer computer paste to my DIS module (if that’s not enough, I’ll then replace the DIS module).
Last edited:

sam jones

Registered User
Good evening

+1 on replacing the CAM sensor and reapplying DIS heat sink first.

I would also inspect the DIS harness connection for corrosion and apply die-electric compound.