Boatman

I have an '81 Auto that I've brought back to life. It was a non-runner when I got it. I had to make a new front engine wiring harness, replace all the vacuum hoses, replace lots of sensors, ignition parts, fuel pump, relays, and a lot of other projects. I passed CA smog testing. It idles fine and pulls well from a start but the power starts to disappear about 3500rpm and just goes flat at about 4000rpm and the rpm won't go any higher. After researching here I figured it was a plugged cat. I did the vacuum test suggested at Nichols' site and it passed with a steady 20 inHg at 3000rpm. Anyone have any ideas about what else I should check?

WallyP

Some random possibilities...
- Ignition timing way off. Sounds unlikely, because it should be down on power even at low RPM.
- Running out of fuel. Plugged tank filter, faulty in-tank pump, low fuel pressure, bent fuel line, etc.
- Running out of air. Intake air flap not opening all the way, rag in the intake, faulty air filter.
- Choked exhaust. As you assumed, the manifold vacuum should drop off as the RPM go up. You really need to have the engine under load for a definitive test. You can run a hose into a side window to a vacuum gauge. Unlikely to be the problem, as I would expect the vacuum to have dropped by 3000 RPM.
- Cam timing way off.

Any symptoms, such as running rough when it loses power?

Boatman

Timing is good - that is part of the smog test. Plenty of fuel in the tank. I don't believe my model has an in-tank pump. Fuel lines are good, but I haven't checked fuel pressure. I had the intake system all apart and everything looked good. New air filter. It doesn't run rough it just seems to run out of power. If I'm up around 400rpm and I stab the throttle in downshifts but the engine just won't spin any faster. The linkage is all good and the wot switch is working.
I haven't checked the cam timing though. Could it be that far off and still run fine at lower rpm? Well enough to pass the CA smog police?

Boatman

The distributer set a little clockwise past the center of the adjustment range.
The firing order is good (the distributer cap is numbered.)
I'll have to get a gauge and attachments to check fuel pressure, but how would I check for sufficient flow?

Landseer

Center of range makes sense, so not a tooth off on distrib install.


Basically with a catch can, but with safety precautions.

Pull the cam gear covers and #1 plug to check harmonic balancer for rotation and to check cam gear back notches match covers which in turn match the harmonic balancer.

BTW, makes sense to confirm the cap matches firing order, at one point there were mislabled caps and a batch of wrongly printed firing order stickers, though I don't think it was for the 81.

Boatman

I wanted to update those who were nice enough to try and help me. I found a few problems that were relatively easy to fix and it is now a whole new car. The main one was a small burn spot on the wires leading to the coil. It looked like it was arcing though the old, stiff insulation. At high rpm it must not have been getting enough spark. Fixing this gave me power and rpm but pointed out how poorly the car was shifting. New transmission oil and filter (a messy job) brought back crisp shifts. That showed up the fact that it was not downshifting. The PO's carpet kit was glued over the kickdown switch. A razor blade fixed that. After I had taken the little ball joint apart under the peddle and adjusted things she purrs, or really growls. Hitting the throttle at speed makes a great sound as she jumps down a gear and launches forward. She is sure a lot more fun to drive. Of course there are other things to do. The speedo was on and off for a few days and now shows no life. Oh well, it's a project.

Maleficio

Very cool. Congrats on figuring it out.

kelanel

ground point under gauge cluster might help with that funny speedo Helped me out. Great job figuring it out!

Boatman

Thanks, I'll check the ground point out. I already check the wires in the spare tire well and I'm getting a pulse so I know the sending unit is working.

rdisney

I’ve had trouble in my 80 US 5-speed with the connector just behind the left rear seat, in the spare tire area. One of the wires goes to the differential for the speed sensor. Re-seat or clean the connections and see if that fixes it.

Ron.

soontobered84

I do love all the yellow 928's. There is just something about that color on the car that looks good to me.

SeanR

Amen to that. The car I learned to drive a stick in was a yellow 928. I will own one someday.

OP, Congrats on getting it running right. Need more pictures.

Boatman

It's unfortunately about a 15 foot paint job. I think the PO did it in his garage. But it came with a very 80's license plate frame (which my wife made me take off.)

tveltman

Oh wow! Paint on the rubber grommet around the trunk release and the between-panel gasketing on the bumper. It is a 15-footer, but I agree, the 928 is beautiful in yellow. Do you know if that is enamel or is there clear over the top? Are there runs in the paint, or just poor surface quality?. Some compound and a buffer and a crapload of time will fix those issues. You might even be able to replace the rubber seals (if you are very careful and lucky) without needing to respray. Of course someone here will say that you need to pull the whole thing apart and redo it frame-up, but I'm guessing that touch-up paint + TLC will considerably "shorten" that paint job distance. GL and great find!

James Bailey

I saw it going down Harbor Blvd a couple weeks ago......it looked fine Nice to see it running.