Tac & Power Issue

[Black91SHO]

I have a '91 SHO. I was doing about 75mph in 5th gear today when my RPMs drop from around 3,000 to 2,000, even though my speed and gear didn't change. Also, the power output dropped quite a bit. I didn't hear anything out of the ordinary. I smelled something hot, so I pulled over. Saw no signs of burning. The smell could've been another car. I drove it another 230 miles and this happened maybe 3 times, if that. It occurs randomly.

I'm sure I caused this, because I went to jump start the car the other day and mindlessly put the jumper cables on the wrong posts. A wire from the starter solenoid started smoking, so I pilled the jumper cables off ASAP. The next day, after I started it, the car's idle dropped and bobbed for about 15-20 seconds, then went back to normal. And now, a few days later, this tac and power problem.

Any ideas what might have been damaged to cause these strange symptoms?

I think I may have damaged the ECU.

 

[rubydist]

most likely either the cam sensor is sick, or the pcm is.

 

[Black91SHO]

Yeah, that was my conclusion. I'll start by replacing the cam sensors. That makes the most sense. Then we'll try another ECU.

Thanks.

 

[Slo-Sho]

The tachometer in my 95 started to show incorrect readings as well as stay at 1k rpm's while driving normally. I had to get another cluster and swap the tachometer head with mine, year doesn't matter except the gen I's had more hash marks but it will interchange. Welcome to old electronics.

 

[Black91SHO]

The tachometer in my 95 started to show incorrect readings as well as stay at 1k rpm's while driving normally. I had to get another cluster and swap the tachometer head with mine, year doesn't matter except the gen I's had more hash marks but it will interchange. Welcome to old electronics.

I considered one of the tach cables or the cluster going bad, but I'm hoping that's not the case...

 

[rubydist]

the tach doesn't have "cables" - it just reads the frequency from the cam sensor and displays accordingly. it could be the cluster going bad, but I have seen more cam sensors and pcms bad than tachs.

 

[Black91SHO]

I was thinking of the speedometer cables, not the tach. Not sure where my mind is lately.

Yeah, in all my 15 years of owning SHOs, I've only heard of one gauge cluster going bad.

Thanks.

 

[Racer X]

The DIS and ECU are the most sensitive to something like that, followed by the alternator diodes.

Good luck.

 

[Black91SHO]

Thanks, man. I appreciate it.