I just boughth a 91 Coupe DeVille with a 4.9 for my son. The car has 168K and looks great.

We bought the car and started to drive it home. Just when we were starting to feel good about our purchase the car shut off.

We were traveling down the highway at 65 MPH with the cruise on. The car died, all the dash lights came on and the speedodometer needle started bouncing.

We coasted to a stop and restarted the car. It started right away. If I drove it with light throttle it seemed to run fine. If I went beyond 1/4 throttle it would fall on its face.

We made it home and while idling it would surge. I shut it off and let it sit for about 5 minutes. I started it back up and it ran fine. I have not driven it sense.

I hope someone can help. I am pretty handy at troubleshooting, I just need to know where to start. Maybe this is a common problem?

Thanks in advance,

Jim

 

That shutting off and surge points to a faulty fuel pump in my opinion or at least inconsistent fuel delivery, maybe even fuel filter issues,

 

I will check the fuel pressure. What should it be? I would suspect 30-40 psi?

This seems more electrical than fuel related to me. When it shut off it was sudden. The speedometer bouncing from 0-85 a couple of times would lead me to believe it is a PCM/ECM issue or a ground issue. Maybe a CSPS (Crank Shaft Position Sensor)?

I have a Snap-on scanner. Will that tell me anything? There is not a CEL indication.

 

ECM could be faulty, have you checked connections at coil , alternator ?

 

I checked the coil but not the alternator. I will take a look at that connection too.

If it is an ECM where would I find a replacement? How much do they run?

 

http://cgi.ebay.com/ebaymotors/16132...Q5fAccessories

Try any parts store or slavage dealer.