odd running for an 1981 SC 3.0

[rockryno]

Well, it happened again tonight. Cold start, about 3-5 min into the drive, give it some gas at a stop sign, and nothing happens. The RPMs stay about 1200 and no acceleration. Finally after keeping the throttle down (not full, but where it should be doing something), something catches and the car roars to life and the RPMs jump to 4k.

This has happened several times before in the month Ive owned it. Ive been trying to associate any other diagnostics with it but I have found none! It is completely random. It could be on a 15 degree morning, or a 60 degree afternoon.

The only coincidences I have noticed are the fuel tank is between half and full everytime (does not do it under half tank), and its always a cold start (sitting for more than 4 hours). It always happens within the first 5 minutes of starting the car. The car runs completely normal after its done it once or twice.

This evening something new happened though. Cold start, Engine running for about 2 minutes. Clutch in, giving it gas and letting up on the clutch simotaneously, like a normal acceleration. RPMS about 1200 before it stops winding up. Clutch back in and coasting about 5 mph and lightly pumping the gas pedal. A few audible pops ( sound like a soft backfire) and the RPMS jump to 4k before I can get my foot off the pedal. The little pops were the new part, and I swear it sounded like they came from the front of the car.

After that, car ran just fine the rest of the drive.

Anyone have any clue? I know the fuel pump is up front, but Ive never heard of them making pops like that? Pressure relief maybe? Like I said I swear it was from the front, but I could always be wrong. PLease help!

[RDM]

My new-to-me SC was doing something similar, right down to the popping (in the muffler, though). Once warmed up, no acceleration to the point the car had to be parked until the end of the day. Once the engine was cold again, it would run normally.

This came and went three times over the course of months before it became permanent.

Cause: oxygen sensor relay under the passenger seat. It's a common relay that you should be able to get locally, or buy it here for ~$12. If you know the terminals, you can even pull the relay and test it.

I hope that's your problem! It was definitely a relief for me.

[Bob Kontak]

Originally Posted by RDM

I hope that's your problem! It was definitely a relief for me.

+1

Another related thing to look at is the 12 pin connector on the back firewall. The juice from the relay to the frequency valve routes through this.

One user in Houston had the connection break every time he drove the car in hot weather. When cooled down it would work.

Hopefully, just the relay.

[RDM]

Rockryno,

What's the word? Success, or still looking for a solution?

[everforward]

I'm with RDM. I just posted less than 2 days ago with a similar problem. Replace your oxygen sensor relay first (<$15.00). If that does not solve your problem diagnosis further. Good luck.

[rockryno]

I'm out of town until mon. I'm going to dive in when I return. I'll post results!

[iiXii]

Hello,
i have the same probleme with this relay. How i can locate the pin 12 on the outlet ?

Originally Posted by Bob Kontak

+1

Another related thing to look at is the 12 pin connector on the back firewall. The juice from the relay to the frequency valve routes through this.

One user in Houston had the connection break every time he drove the car in hot weather. When cooled down it would work.

Hopefully, just the relay.