View Full Version : DIS, Cam/Crank Sensor? HARD TO START

09-19-2002, 07:07 AM
I've had my car for about 1 1/2 years and the tach has alway been speratic, It seems to have gotten worse over the past 6 months -- (doesn't work about 90% of the time)

Someone on here suggested putting heatsink compound under the DIS months ago, I did it and for about a month the tach worked perfectly. Then it went right back to its current condition.

Also, the hard starting problem that would only show up once every month or so has plaqued me every day this week!! Only when the engine is cold. I have to crank, stop, crank again and again. After a few POP's and stumbles the engine will finally start.

WHAT IS THIS? I have a fealing it is the DIS, CAM sensor or CRANK sensor. Can't afford to replace all three.

Does anyone have any wisdom on this subject?

Les Borda
09-19-2002, 08:19 AM
The next time it does not want to start, keep cranking it and see if the yellow upshift light stays on, if it does this is indicative of bad crank sensor. The flaky tach could be either cam sensor or DIS. The CAM sensor is not very expensive and easy to change.

09-20-2002, 09:55 AM
Yes, the shift light comes on when trying to start. I guess I need to replace CRANK sensor. Are you saying the flaky tach can't be the crank sensor and MUST be the cam sensor or DIS?

Does anyone have any tips on changing the CRANK sensor on a 90 SC?

Thanks in advance

09-20-2002, 11:43 AM
Check the TBSEC FAQ board...look for post by XR7 Dave,"Easy crank sensor replacement"...shows pics and explains...not too hard to do,just follow directions...hope this helps.

09-23-2002, 07:58 AM
Thanks for the advice, but where is the TBSEC FAQ board. I've been looking all over for it.

Also, I was wrong the shift light is NOT coming on when I'm trying to start car. Does this mean it may not be the crank sensor? And ofcourse my tach is still freaking out constantly.

09-23-2002, 12:23 PM
OOOPS!...I didn't give you the full address TBSCEC[Thunderbird Supercoupe Enthusiasists Club.com]..sorry ....jumpy/non-working Tach is usually a DIS/CAM sensor problem...good luck.

09-24-2002, 03:33 PM
If you put new grease on the DIS and it worked well for awhile, then my guess would be the DIS might have a temperature problem. The signal that is sent to the tach (IDM) is a copy of the signal sent to the DIS from the EEC. If the is DIS is flaky (technical term) it may not output this signal properly. I have read that a bad crank or cam sensor can stop this signal from getting to the the tach, but I do not know why. The shift light I believe comes from the EEC so if the IDM signal it receives from the DIS is not correct it probably lights the light. Just my two cents....

09-25-2002, 07:34 AM
Thanks for all the response. I changed the CAM sensor and the starting problem has seemed to go away! The tach is still flaky.

After a week of driving the way it is (to make sure the CAM sensor remedied the starting problem) I will make a aluminum heatsink in our machine shop for the DIS and install it will some heatsink compound. Maybe the tach will start working properly and stay that way!

09-25-2002, 09:24 PM
Will the "easy crank shaft sensor" tutorial by xr7 dave at tbscec.com work with the '89 supercoupe? Thanks.

09-26-2002, 12:01 AM
Yes it will work....that's what I used as reference to replace the CPS in my 90.Good luck.

09-26-2002, 12:20 AM
I just have a couple more questions about this. I heard when replacing the cps you need a special tool to align the crankshaft or something. Is this true or what? Also how much is a crankshaft sensor anyway?

09-26-2002, 11:12 AM
Autozone stk, #SU220,$54.99....I got mine from PEP BOYS,had exactly same stk.# as the oem,but packaged in a WELLS box.You can eyeball the clearance btwn the sensor and the balancer but most suggest using a matchbook cover,just be sure you have equal clearance on both sides of sensor and balancer vanes.Also check crank bolt for tightness,you don't want wobbly pulley.
Good luck,

09-26-2002, 03:51 PM
You can eyeball it if you know what you are looking for.

Dave(XR7 Dave) replaced mine on the side of the I-40 turnpike on the way home from the 2001 MN-12 Nationals. Took us, him, about 45 mins total, and that was with the car sitting on my burnout wheels!

Dave is the man!