Heres another, this is 83 but I'm sure its the same. You need the Morehouse CDs, BTW, from Roger.

Show some pictures of your vac routing and throttle body and we can help.

If not california, you will have one of the front vac connections on the throttle body covered with a red rubber cap

 

Landseer - mucho thanks!

 

Sounds like a vacuum leak if you got a hissing sound. My '83AT would light up the tires in the first 2 gears after I got it running right. Good Luck!

 

Was thinking the same thing--but I can't think of a hose that could be off that wouldn't effect idle or cause it to also run rough(?) Although I'm wondering about the vac line that runs from the front of the spider back to the tranny. Sounds like it's either starved for air or fuel--I'm thinking fuel.

I also agree on the "assometer" factor of the OBs; my 84 is MUCH more responsive at low speeds than my GTS and will also spin the tires on 2nd and 3rd shifts.

 

From the great comments everyone had made, it sounds like the first efforts are with the vacuum, throttle and fuel intake settings. With the known AT vacuum issue, it will pay to go over the entire vacuum system. I am also going to pickup new spark plug cables and the Jim Morehouse CD set from Roger.

Again, thanks to everyone for your insight and expertise!

rob

 

Did you triple check the firing order after you changed the spark plugs?

 

Yes, no issue there.

 

I don't know if '84s still use a MAF sensor like my '85 does, but recalibrating the MAF made a big difference. The previous owner had installed a different one, and resistance was almost double what it needed to be, it wouldn't even idle when I started the car until I put it in gear. Now it's a lot more responsive. I had the benefit of fine tuning with the Blink'r because mine is an '85, but even dialing it down to stock made a huge difference.

 

84 US 928s are Ljet systems that use an AFM, (barn door), there is no adjustement neede, unless soemone has messed with it.

 

I ordered the Morehouse CDs, though seems they are on back order at the moment. Can anyone tell me what the vacuum pressure should be for the AT setting? thanks

 

OK, good news everyone!

I have the shark out of winter storage and sent her to my mechanic to have the new (bad) alternator changed out. As I was headed out of town for two weeks on holiday, I made up a list of items for him to check out based on all of your suggestions in this thread.

Thru previous testing, I was aware that the AT was having a shift point issue, though not sure if it was the bowden cable or a vacuum issue. Well, spoke to the mechanic today and he tells me the cable was loose as all hell, now good and tight with very little play. He has also adjusted the other cable to the throttle plate and WOT. I am excited to feel the changes, can’t wait to drive her.

There are several other items I am having checked out including vacuum tests all around. I have the CD's now and expect to have the shark back early next week and will update changes in her performance.

 

Bump

(sorry to intrude, damn good stuff here, and was thinking about the exact same stuff)

 

So....... I got the shark back today and f'n wow! What a difference there is with the bowden cable to the AT now snug and the shift points at spec. I had the vacuum lines all checked out, the WOT is now full opening and the injectors / fuel pressure worked out. Her speed off the line has about doubled... for the first time since I have owned her; she will lay rubber.

All those kids that use to point and laugh as their school bus blew past me… we will see who has the last laugh now!!!! The same goes for the all the blue heads in their old caddys giving me the finger for getting in their way.

Now there’s a new sheriff in town! Thanks to everyone who has posted here, your insight has been invaluable.

OSP

 

Sweet! I'm off to do the same stuff to mine. Shift points are absurdly close to one another.

 

Lucky for me I have to adjust my Bowden cable at the tranny. It's very loose. I have to put it up in the air yet again.

At least I was able to adjust the throttle cable. It was very loose, too.