Diagnose this Scenario

81SCRosewood · 81SCRosewood's Garage

Please diagnose this scenario ...

I recently took a long trip up and down California, to Vegas and back, etc. The 81 911SC ran flawlessly. In fact, it seemed like it had never run so well.

I got a friends house in Northern California and parked it. Two days later, I started it up and it ran like ***t. Real rough like running on 4-5 cylinders.

I pulled the plugs and things looked fine. I replaced them just in case. Started it up and it still runs horribly. Spark plug wires are one year old and still look new.

Could it be the coil? Possibly a clogged injector or fuel distributor?

Anyway, I'm hoping someone has experienced this same scenario and discovered what it was and could share it please!

RSTarga · 05-18-2016, 03:11 PM

Fuel filter at bottom of tank? Coil? Cyl head temp sensor?

GothingNC · 05-18-2016, 03:36 PM

O2 sensor relay under the padsanger seat.

I just had a similar problem. Bad gas and then the relay failed.

Uncle Enzo · Uncle Enzo's Garage

Pull the distributer cap and check for moisture.

81SCRosewood · 81SCRosewood's Garage

Thanks for the replies. I shall check into all of your suggestions. I appreciate the help!!!

DRACO A5OG · DRACO A5OG's Garage

Check for vacuum leak too

T77911S · 05-20-2016, 04:03 AM

did it backfire when starting. if so check the pop off valve to see if it is seated/closed
fuse 18 good

drive it and see if it clears up

Porchdog · 05-20-2016, 04:24 AM

We had the weather clear a bit here and I've been driving my 81 the last three days.

It was glorious Wednesday and yesterday. This morning on the way in to work ( a twisty, hilly two lane for 14 miles) I had a hesitation / miss after warm up. Idle also seemed a bit high. Checked under the hood when I arrived and nothing is obviously amiss.

I'm suspecting a vacuum leak somehow, but I just got all of those fixed!

81SCRosewood · 81SCRosewood's Garage

Quote:

Originally Posted by T77911S

did it backfire when starting. if so check the pop off valve to see if it is seated/closed
fuse 18 good

drive it and see if it clears up

No backfire. Still trying to find out what has gone wrong

gazzerr · 06-15-2016, 03:46 PM

If the OXS relay and control box is good you might have a vacuum leak close to the intakes, like the rubber connectors on the runners or the injector seats and o-rings. Perhaps a big airbox leak?

81SCRosewood · 81SCRosewood's Garage

Quote:

Originally Posted by gazzerr

If the OXS relay and control box is good you might have a vacuum leak close to the intakes, like the rubber connectors on the runners or the injector seats and o-rings. Perhaps a big airbox leak?

Thanks gazzerr, I've ordered a new oxs relay. If that doesn't straighten things out ... I will look for those vacuum leaks. Thanks for your input!

gazzerr · 06:51 AM

I remember a couple of guys complaining about symptoms similar to what you describe. One guy found a big hole in a rubber connector between the aluminum runner and the airbox. You can pull your relay when the engine and is running and if there is no change then the relay/box or wiring is bad. Also check continuity to your control box and relay too. Does your cabin light work? It runs off the same fuse.