I finally got the 3.4L in and running. I had all sorts of problems, mainly my own making. I did the 4.3L tbi conversion at the same time.
The motor is running but I'm not satisfied with it yet. It seems to be basically sound but it still idles too high, surges from 1000 to 1500 especially when cold and runs a little rough while accelerating. And I don't think I'm getting the power out of it that I should. I suspect the TPS or a vacuum leak. I had to replace the TPS and I've tried to adjust it but it didn't seem to make any difference. I searched for a vacuum leak (I even used the propane trick) but can't find one. I also set the timing to 10 degrees BTDC per the instructions for the 2.8L.
If anyone out there has any thoughts about what may be causing these problems I'd love to hear from you.
Jim

Did you reset the Idle Air Control motor? I believe when changing TBs or making other mods it is a reccommended step.





Maybe that can get your idle down.

I'll give it a try.
Thanks, Jim

I'm making some progress.
I found that the IAC from the 2.8L, wasn't closing all the way and causing a massive vacuum leak. I replaced it with the 4.3L IAC which helped tremendously but now I have other problems.
The idle seems pretty steady at about 800 rpms but surges up to 900 irregularly. The motor seems to lack power as I accelerate from 2000 to 2500 rpm as if the plugs were fuel fouled (too rich). It takes off at about 3000 rpms and runs steady.
The biggest problem is that it stalls when I come to a stop. It doesn't stall all the time, only once in a while and after it has warmed up.
Any thoughts?
Jim

Jim,

When you set the timing did you disconnect the electronic spark control first, and then reconnect it after you were done?

I remember doing that; I just don't remember the location of the connector - maybe the console where the ODB code jumper is.

How did you remove/install the balancer? Could the timing marks have shifted?



Ed

Yup, I disconnected the timing advance. The computer is under the center console and there are two plugs (one for the code reader and another square one, I don't know what it's for), one wire for the 4X4 dash light and one other wire. By the process of elimination, I assumed that this last one must be the advance so I disconnected it. I reconnected it when I was done.
When I put the balancer back on I set the #1 cylinder to top dead center on the compression stroke (I used a straw in the sparkplug hole to determine TDC). The mark on the balancer lined up with 0 degrees on the timing belt cover. Since the mark lined up where I expected it to, I assumed I got it right. I static timed the ignition to 10 BTDC before I started it. After I got it running I checked the timing with a light and it showed 10 degrees. The balancer is keyed so I think that it can only go on one way.
I have been wondering if I got something wrong regarding the timing. Any suggestions how I might double check it? It doesn't backfire or diesel, and it starts right up.

Disconnect the plug you think disables EST, does the timing light show the timing mark PERFECTLY STEADY on the crank pulley?

Reconnect the plug, the light should make the timing mark jump around to the point it MAY SEEM BLURRY.

If you can't tell the difference EASILY between having the connector connected or not, than you got the wrong one.

I hope this has not already been covered--it seems like you weren't positive about the EST connector.

Yes, I tried that just recently and the timing was steady at 10 BTDC. So, I must have gotten the right one. When I connect it the timing goes to the top of the scale (14 BTDC I think). So, the computer is compensating for something but I don't know what it is yet.
I'm slowly eliminating the possible problems. Tomorrow I'm going to test the O2 sensor, check for vacuum leaks (haven't found any yet) and try to adjust the TPS as best I can.
I'm beginning to think it may be a leaky manifold gasket, but I sure hate to have to take all that stuff off to fix it.
Jim