3.2 shutting down -Reference Sensor?

[Blade1055]

Ok, I've got a great 1989 3.2 targa with 84K miles on it all stock, driving home from WA state to Walnut Creek, CA. 11 / 12 hours of HWY 5. 2 hours into the trip (only 5 A.M. so it was cool outside) @ 65 / 70 MPH it starts "bucking", just like the key was being turned on and off.

No change in lights or instruments This would go on for two or three minutes and then would be fine for 15 minutes to 1/2 hour Sometimes an hour. When it got light I threw in my spare DME relay under the drivers seat but that changed nothing.

What started out as "bucking" later became "Shutting off" 5, 10, 30 seconds. This gets scary when the 18 wheelers are behind you. Once I was on the shoulder down to 35 MPH before it turned back on and was able to get right back up to 65. Probably needs a new set of motor mounts after all that bucking.

Did stop at an indie shop is Ashland but they found nothing.

When much closer to home I discovered that shifting down to 4th gear solved the problem, not sure if it just coincidence or if it was the answer, but it worked the last two time the problem showed up.

I read the threads from others on the reference sensors but the symptom's are not exactly the same.

Plan - Upgrade to the two wire temp sensor. I thought about the RPM sensor, but wouldn'the tach have gone to zero if it quit reading?

No problem in the last 400 miles since home. In the last two years I've driven 1400 miles back from Denver, CO and two trips up and back to Northern WA with out a problem. The only Tune-up type maintence Item I haven't done is change the fuel filter,

Suggestions?
Thanks for all the help, this forum is Awesome! Picture is from the Golden Gate Autocross in March

[Wil Ferch]

Hmmm....89's should already have the 2 wire cyl head sensor...you can pull it easily enough to check the plug...if one "spade" of the dual-looking connector looks metallic and the other side looks to be white plastic as the plug...you have a one-wire sensor. But by 89 all the 3.2's should have the 2 wire sensor.

Bucking that is solved bu running higher RPM's is typically a bad ignition wire....but I don't think this is what you have for the many seconds it is "out"...and then back "on".

First order of business for any of these shenanigans is checking all grounds....then go thru a systematic DME function check as decribed by the factory manuals or Bentley. I would then look at hairline cracks on the soldered connections of the printed circuit board on the DME....then go thru the checks.

[L8Brakr]

I experienced a similar bucking issue a couple of years ago while driving home 400 miles from a DE. The problem began as a hesitation/stutter when running on and off of part throttle in interstate traffic. Let of the accelerator in traffic...return to partial throttle and stutter, buck, and eventually re-fire. After about half an hour of frustration I discovered that at full throttle, everything ran normally. I spent 200 miles running flat to the floor til 85, coast til 65, and then do it again.

Jump ahead to the solution.....after many headaches and much electrical diagnosis I gave up and started randomly replacing switches. Turns out the idle microswitch was intermittently bad. It tested fine on the bench, but when hot and under vibration it would cut out and shut off the fuel flow. Revs never fell to idle because I was in gear, thus the idle control circuits wouldn't fire and restart fuel flow and I was left watching for traffic approaching in the rear-view. As I understand the DME logic, by flooring the throttle I would trigger the WOT switch thus restarting fuel flow.

The microswitch is a $70 item from our host last time I checked. I suggest starting there and hopefully solving your problem.

As usual the advice above is worth exactly what you paid for it. Good Luck!!

[Zeke]

My post won't help solve the problem, but it might address another issue. SCWDP folks are always telling us how great the 3.0 SC cars are. Given the number of 3.2 no start and poorly running threads we have in the last 2 months, you wonder if they are actually correct.

[Blade1055]

All,
Thanks for the responses, L8Brakr sounds like he had the same problem as me, For $70 I'll give that a try. That and going through the DME function check in my Bentley manual.
Thanks for the help